IR: add 'byval(<ty>)' variant to 'byval' function parameters

[t.p.northover]

Summary

One of the remaining blocking issues for merging all pointer types is that byval parameters need some way to communicate their size other than the element type of the pointer. This patch addresses the issue by adding a size function attribute, only usable with byval that encodes the information independently.

It's mostly a pretty straightforward copy/paste of the existing align handling, except I decided to allow more than 16-bits of size. It should be very rare, but I have seen people pass ridiculous structs by value and the compiler should probably be able to cope.

The main other thing I found slightly questionable was whether we could reuse the existing dereferencable or alloc_size attributes. In the end I decided the semantic contortion was just slightly too high so implemented a new keyword to be maximally compatible with the align it will sit next to.

[arsenm]

Needs bitcode compatibility tests

llvm/test/Assembler/size-param-attr.ll

17 ↗

(On Diff #200973)

Also a test with 0?

[arsenm]

llvm/test/Assembler/invalid-size2.ll

4 ↗

(On Diff #200973)

Could also use a size > UINT_MAX

[dblaikie]

Hey Tim - thanks for looking into this!

The original discussions for this had centered around adding a parameter to the byval attribute itself, rather than having it dependent on another attribute.

In the typeless pointer future - this size attribute wouldn't be optional, but required when 'byval' is present. So this seems more like a transitionary state - and perhaps we should consider whether the intermediate state is worthwhile compared to what would be the final form.

ie: What about adding an integer parameter to 'byval'?

[t.p.northover]

ie: What about adding an integer parameter to 'byval'?

I do agree that we should prioritize the final state, but I think that final state should somehow include the word "size" so that the number is interpretable without looking at the documentation (at least to some degree). I also quite like the symmetry in this scheme between "size" and "align". Both of those are reasonably mild opinions though.

I have even less strong views on other components, though I'm not sure if you were even talking about those. We could, for example, change ATTR_KIND_SIZE to ATTR_KIND_BYVAL_WITH_SIZE and in the C++ representation drop the separate Attribute::Byval.

OTOH we could do both of those (and change IR, come to that) at some later date without breaking compatibility.

[jyknight]

One of the other suggestions was to pass a _type_ as a parameter to byval. IMO that would be the nicest idea (but I don't know if it's infeasibly difficult?)

In the transitory state, you'd need to specify the exact pointee-type to byval, as is specified in the pointee type of the argument.
E.g.:

define i8 @f({i32, i8}* byval({i32, i8}) %p) ...

In the future, that'd then turn into:

define i8 @f(ptr byval({i32, i8}) %p) ...

[t.p.northover]

One of the other suggestions was to pass a _type_ as a parameter to byval. IMO that would be the nicest idea (but I don't know if it's infeasibly difficult?)

I wouldn't worry about the implementation difficulty, I can see a pretty clear path there. I also like the spelling of that option, it certainly bypasses the ambiguity of a bare number. I wonder if it's promising more than we actually deliver though. SelectionDAG only exposes the size and alignment to backends.

A final point in favour of the type idea is that I think targets where pointers are special (e.g. CHERI where a pointer in memory is only usable if it was stored by a special, blessed instruction) couldn't work with a plain size. They don't work with SelectionDAG either but in future they might want to use byval. I'm not entirely sure how theoretical that argument is though.

[dblaikie]

In D62319#1514029, @jyknight wrote:

One of the other suggestions was to pass a _type_ as a parameter to byval. IMO that would be the nicest idea (but I don't know if it's infeasibly difficult?)

Yeah, sorry, forgot to mention that - one of the justifications for this was consistency with global variables (which, similarly, are really just bytes and alignment - but we use a type to describe those bytes and alignment)

In the transitory state, you'd need to specify the exact pointee-type to byval, as is specified in the pointee type of the argument.
E.g.:

define i8 @f({i32, i8}* byval({i32, i8}) %p) ...

In the future, that'd then turn into:

define i8 @f(ptr byval({i32, i8}) %p) ...

[t.p.northover]

I'm liking the type idea more and more. I'll get started reworking the patch to do that.

[t.p.northover]

Switched to byval(<ty>) syntax, still optional for now but auto-upgraded when reading .bc files.

[arsenm]

llvm/lib/CodeGen/SelectionDAG/FastISel.cpp

1206–1207

Ternary operator

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

9076–9080

Ternary operator

9580–9584

Ternary operator

[t.p.northover]

While modifying Clang to emit this new style attribute, it turned out I'd got the printing incorrect and you could end up with things like byval(%mystruct = type { i32 }). Fixed that and added a unit test for it.

[t.p.northover]

Accidentally included half-done Clang changes in last upload, so this removes them.

[t.p.northover]

Switched to ternary operators as Matt suggested.

[t.p.northover]

llvm/lib/CodeGen/#SwiftErrorValueTracking.cpp#

1

Accidental addition. I'll remove it when I next upload.

llvm/test/Assembler/#invalid-size2.ll#

1

Accidental addition. It'll be gone next time.

[dblaikie]

Generally looking pretty good to me.

llvm/include/llvm/IR/Argument.h

81

Comment looks to be out of date (speaks of returning the size, rather than type)

llvm/lib/IR/Attributes.cpp

394–395

You can roll the declaration into the condition if you like - pretty common in the LLVM codebase, though not a stylistic requirement by any means.

554

This being pointer ordering - that means it'll be unstable across runs (which I assume/think none of the other attributes are?) - is that OK?(I don't know if that's OK - it probably is OK)

llvm/test/Assembler/invalid-size1.ll

1–4

Leftover from the previous version?

[t.p.northover]

Some replies, and I'll upload a new revision tomorrow with the things that definitely need fixing.

llvm/include/llvm/IR/Argument.h

81

Bother, I did a specific "git diff" run to catch those!

llvm/lib/IR/Attributes.cpp

394–395

Yep. No idea why I didn't do that.

554

I did worry about that, but came to the conclusion it doesn't matter unless the same attribute can appear repeatedly. And I don't think that is possible.

Even with IntAttributes, I replaced the corresponding comparison with an llvm_unreachable and the only thing that broke was a unit test specifically exercising this function.

So in summary I have no real preference between status quo and llvm_unreachable, but don't think it's worth implementing a stable order right now.

I should probably add some checks to that unittest myself though.

llvm/test/Assembler/invalid-size1.ll

1–4

Yes. I don't think there's an equivalent (at least not a new one) so I'll remove it.

[dexonsmith]

llvm/lib/IR/Attributes.cpp

554

I would prefer llvm_unreachable or report_fatal_error with a comment saying that comparing on type wouldn't be stable, but is also not possible. Or, sorting it in an unstable way with comment saying it's illegal, and adding a corresponding verifier error. Happy with whatever you and David decide though, if you think it's better as is.

[dblaikie]

llvm/lib/IR/Attributes.cpp

554

Yeah, +1 to that - if the code isn't used, unreachable/assert - then we can discover if it ever gets used and add test coverage for it.

[t.p.northover]

I think I've fixed everything suggested, including making the comparison assert if it ever happens since that seems to be the consensus.

I also noticed some Clang tests will need to be updated because byval now sorts slightly differently, so I've included those in the diff here for completeness.

[dblaikie]

Seems good to me - thanks a bunch (:

(I'd probably suggest making the type parameter to byval non-optional in the IR and builder APIs as soon as it's convenient - that was my general approach in the previous work I did on opaque pointers)

llvm/lib/IR/Attributes.cpp

553–554

Prefer assertion rather than branch-to-unreachable

assert(getKindAsEnum() != AI.getKindAsEnum() ...

[t.p.northover]

Thanks David. I've committed it as r362012 and r362013 with the tweak you suggested.

[jordan_rose]

llvm/lib/IR/Attributes.cpp

553–554

Swift is hitting this assertion on its master-next branch right now when two type attributes are wrapping the same type. Is that supposed to be checked earlier or canonicalized away?

[t.p.northover]

llvm/lib/IR/Attributes.cpp

553–554

Sorry, I was on holiday last week. It should be fixed now. I've made FunctionComparator delve into attributes with types since it's main purpose seems to be going to heroic efforts to compare things stably anyway.

llvm/docs/LangRef.rst

``signext``
     the callee (for a return value).
 ``inreg``
     This indicates that this parameter or return value should be treated
     in a special target-dependent fashion while emitting code for
     a function call or return (usually, by putting it in a register as
     opposed to memory, though some targets use it to distinguish between
     two different kinds of registers). Use of this attribute is
     target-specific.
-``byval``
+``byval`` or ``byval(<ty>)``
     This indicates that the pointer parameter should really be passed by
     value to the function. The attribute implies that a hidden copy of
     the pointee is made between the caller and the callee, so the callee
     is unable to modify the value in the caller. This attribute is only
     valid on LLVM pointer arguments. It is generally used to pass
     structs and arrays by value, but is also valid on pointers to
     scalars. The copy is considered to belong to the caller not the
     callee (for example, ``readonly`` functions should not write to
     ``byval`` parameters). This is not a valid attribute for return
     values.
 
+    The byval attribute also supports an optional type argument, which must be
+    the same as the pointee type of the argument.
+
     The byval attribute also supports specifying an alignment with the
     align attribute. It indicates the alignment of the stack slot to
     form and the known alignment of the pointer specified to the call
     site. If the alignment is not specified, then the code generator
     makes a target-specific assumption.
 
 .. _attr_inalloca:
 

llvm/include/llvm/CodeGen/TargetLowering.h

public:
     bool IsSRet : 1;
     bool IsNest : 1;
     bool IsByVal : 1;
     bool IsInAlloca : 1;
     bool IsReturned : 1;
     bool IsSwiftSelf : 1;
     bool IsSwiftError : 1;
     uint16_t Alignment = 0;
+    Type *ByValType = nullptr;
 
     ArgListEntry()
         : IsSExt(false), IsZExt(false), IsInReg(false), IsSRet(false),
           IsNest(false), IsByVal(false), IsInAlloca(false), IsReturned(false),
           IsSwiftSelf(false), IsSwiftError(false) {}
 
     void setAttributes(const CallBase *Call, unsigned ArgIdx);
 

llvm/include/llvm/IR/Argument.h

public:
 
   /// Return true if this argument has the byval attribute or inalloca
   /// attribute. These attributes represent arguments being passed by value.
   bool hasByValOrInAllocaAttr() const;
 
   /// If this is a byval or inalloca argument, return its alignment.
   unsigned getParamAlignment() const;
 
+  /// If this is a byval argument, return its size.
+  Type *getParamByValType() const;
+
   /// Return true if this argument has the nest attribute.
   bool hasNestAttr() const;
 
   /// Return true if this argument has the noalias attribute.
   bool hasNoAliasAttr() const;
 
   /// Return true if this argument has the nocapture attribute.
   bool hasNoCaptureAttr() const;

llvm/include/llvm/IR/Attributes.h

public:
   //===--------------------------------------------------------------------===//
   // Attribute Construction
   //===--------------------------------------------------------------------===//
 
   /// Return a uniquified Attribute object.
   static Attribute get(LLVMContext &Context, AttrKind Kind, uint64_t Val = 0);
   static Attribute get(LLVMContext &Context, StringRef Kind,
                        StringRef Val = StringRef());
+  static Attribute get(LLVMContext &Context, AttrKind Kind, Type *Ty);
 
   /// Return a uniquified Attribute object that has the specific
   /// alignment set.
   static Attribute getWithAlignment(LLVMContext &Context, uint64_t Align);
   static Attribute getWithStackAlignment(LLVMContext &Context, uint64_t Align);
   static Attribute getWithDereferenceableBytes(LLVMContext &Context,
                                               uint64_t Bytes);
   static Attribute getWithDereferenceableOrNullBytes(LLVMContext &Context,
                                                      uint64_t Bytes);
   static Attribute getWithAllocSizeArgs(LLVMContext &Context,
                                         unsigned ElemSizeArg,
                                         const Optional<unsigned> &NumElemsArg);
+  static Attribute getWithByValType(LLVMContext &Context, Type *Ty);
 
   //===--------------------------------------------------------------------===//
   // Attribute Accessors
   //===--------------------------------------------------------------------===//
 
   /// Return true if the attribute is an Attribute::AttrKind type.
   bool isEnumAttribute() const;
 
   /// Return true if the attribute is an integer attribute.
   bool isIntAttribute() const;
 
   /// Return true if the attribute is a string (target-dependent)
   /// attribute.
   bool isStringAttribute() const;
 
+  /// Return true if the attribute is a type attribute.
+  bool isTypeAttribute() const;
+
   /// Return true if the attribute is present.
   bool hasAttribute(AttrKind Val) const;
 
   /// Return true if the target-dependent attribute is present.
   bool hasAttribute(StringRef Val) const;
 
   /// Return the attribute's kind as an enum (Attribute::AttrKind). This
   /// requires the attribute to be an enum or integer attribute.
   Attribute::AttrKind getKindAsEnum() const;
 
   /// Return the attribute's value as an integer. This requires that the
   /// attribute be an integer attribute.
   uint64_t getValueAsInt() const;
 
   /// Return the attribute's kind as a string. This requires the
   /// attribute to be a string attribute.
   StringRef getKindAsString() const;
 
   /// Return the attribute's value as a string. This requires the
   /// attribute to be a string attribute.
   StringRef getValueAsString() const;
 
+  /// Return the attribute's value as a Type. This requires the attribute to be
+  /// a type attribute.
+  Type *getValueAsType() const;
+
   /// Returns the alignment field of an attribute as a byte alignment
   /// value.
   unsigned getAlignment() const;
 
   /// Returns the stack alignment field of an attribute as a byte
   /// alignment value.
   unsigned getStackAlignment() const;
 
public:
 
   /// Return the target-dependent attribute object.
   Attribute getAttribute(StringRef Kind) const;
 
   unsigned getAlignment() const;
   unsigned getStackAlignment() const;
   uint64_t getDereferenceableBytes() const;
   uint64_t getDereferenceableOrNullBytes() const;
+  Type *getByValType() const;
   std::pair<unsigned, Optional<unsigned>> getAllocSizeArgs() const;
   std::string getAsString(bool InAttrGrp = false) const;
 
   using iterator = const Attribute *;
 
   iterator begin() const;
   iterator end() const;
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
public:
   }
 
   /// Return the alignment of the return value.
   unsigned getRetAlignment() const;
 
   /// Return the alignment for the specified function parameter.
   unsigned getParamAlignment(unsigned ArgNo) const;
 
+  /// Return the byval type for the specified function parameter.
+  Type *getParamByValType(unsigned ArgNo) const;
+
   /// Get the stack alignment.
   unsigned getStackAlignment(unsigned Index) const;
 
   /// Get the number of dereferenceable bytes (or zero if unknown).
   uint64_t getDereferenceableBytes(unsigned Index) const;
 
   /// Get the number of dereferenceable bytes (or zero if unknown) of an
   /// arg.

 class AttrBuilder {
   std::bitset<Attribute::EndAttrKinds> Attrs;
   std::map<std::string, std::string> TargetDepAttrs;
   uint64_t Alignment = 0;
   uint64_t StackAlignment = 0;
   uint64_t DerefBytes = 0;
   uint64_t DerefOrNullBytes = 0;
   uint64_t AllocSizeArgs = 0;
+  Type *ByValType = nullptr;
 
 public:
   AttrBuilder() = default;
 
   AttrBuilder(const Attribute &A) {
     addAttribute(A);
   }
 
public:
   /// Retrieve the number of dereferenceable bytes, if the
   /// dereferenceable attribute exists (zero is returned otherwise).
   uint64_t getDereferenceableBytes() const { return DerefBytes; }
 
   /// Retrieve the number of dereferenceable_or_null bytes, if the
   /// dereferenceable_or_null attribute exists (zero is returned otherwise).
   uint64_t getDereferenceableOrNullBytes() const { return DerefOrNullBytes; }
 
+  /// Retrieve the byval type.
+  Type *getByValType() const { return ByValType; }
+
   /// Retrieve the allocsize args, if the allocsize attribute exists.  If it
   /// doesn't exist, pair(0, 0) is returned.
   std::pair<unsigned, Optional<unsigned>> getAllocSizeArgs() const;
 
   /// This turns an int alignment (which must be a power of 2) into the
   /// form used internally in Attribute.
   AttrBuilder &addAlignmentAttr(unsigned Align);
 
   /// This turns an int stack alignment (which must be a power of 2) into
   /// the form used internally in Attribute.
   AttrBuilder &addStackAlignmentAttr(unsigned Align);
 
   /// This turns the number of dereferenceable bytes into the form used
   /// internally in Attribute.
   AttrBuilder &addDereferenceableAttr(uint64_t Bytes);
 
   /// This turns the number of dereferenceable_or_null bytes into the
   /// form used internally in Attribute.
   AttrBuilder &addDereferenceableOrNullAttr(uint64_t Bytes);
 
   /// This turns one (or two) ints into the form used internally in Attribute.
   AttrBuilder &addAllocSizeAttr(unsigned ElemSizeArg,
                                 const Optional<unsigned> &NumElemsArg);
 
+  /// This turns a byval type into the form used internally in Attribute.
+  AttrBuilder &addByValAttr(Type *Ty);
+
   /// Add an allocsize attribute, using the representation returned by
   /// Attribute.getIntValue().
   AttrBuilder &addAllocSizeAttrFromRawRepr(uint64_t RawAllocSizeRepr);
 
   /// Return true if the builder contains no target-independent
   /// attributes.
   bool empty() const { return Attrs.none(); }
 

llvm/include/llvm/IR/CallSite.h

unsigned getRetAlignment() const {
     CALLSITE_DELEGATE_GETTER(getRetAlignment());
   }
 
   /// Extract the alignment for a call or parameter (0=unknown).
   unsigned getParamAlignment(unsigned ArgNo) const {
     CALLSITE_DELEGATE_GETTER(getParamAlignment(ArgNo));
   }
 
+  /// Extract the byval type for a call or parameter (nullptr=unknown).
+  Type *getParamByValType(unsigned ArgNo) const {
+    CALLSITE_DELEGATE_GETTER(getParamByValType(ArgNo));
+  }
+
   /// Extract the number of dereferenceable bytes for a call or parameter
   /// (0=unknown).
   uint64_t getDereferenceableBytes(unsigned i) const {
     CALLSITE_DELEGATE_GETTER(getDereferenceableBytes(i));
   }
 
   /// Extract the number of dereferenceable_or_null bytes for a call or
   /// parameter (0=unknown).

llvm/include/llvm/IR/Function.h

public:
   /// attributes for the given arg.
   void addDereferenceableOrNullParamAttr(unsigned ArgNo, uint64_t Bytes);
 
   /// Extract the alignment for a call or parameter (0=unknown).
   unsigned getParamAlignment(unsigned ArgNo) const {
     return AttributeSets.getParamAlignment(ArgNo);
   }
 
+  /// Extract the byval type for a parameter (nullptr=unknown).
+  Type *getParamByValType(unsigned ArgNo) const {
+    return AttributeSets.getParamByValType(ArgNo);
+  }
+
   /// Extract the number of dereferenceable bytes for a call or
   /// parameter (0=unknown).
   /// @param i AttributeList index, referring to a return value or argument.
   uint64_t getDereferenceableBytes(unsigned i) const {
     return AttributeSets.getDereferenceableBytes(i);
   }
 
   /// Extract the number of dereferenceable bytes for a parameter.

llvm/include/llvm/IR/InstrTypes.h

public:
   /// Extract the alignment of the return value.
   unsigned getRetAlignment() const { return Attrs.getRetAlignment(); }
 
   /// Extract the alignment for a call or parameter (0=unknown).
   unsigned getParamAlignment(unsigned ArgNo) const {
     return Attrs.getParamAlignment(ArgNo);
   }
 
+  /// Extract the byval type for a call or parameter (nullptr=unknown).
+  Type *getParamByValType(unsigned ArgNo) const {
+    return Attrs.getParamByValType(ArgNo);
+  }
+
   /// Extract the number of dereferenceable bytes for a call or
   /// parameter (0=unknown).
   uint64_t getDereferenceableBytes(unsigned i) const {
     return Attrs.getDereferenceableBytes(i);
   }
 
   /// Extract the number of dereferenceable_or_null bytes for a call or
   /// parameter (0=unknown).

llvm/lib/AsmParser/LLParser.h

private:
     bool ParseStandaloneMetadata();
     bool ParseNamedMetadata();
     bool ParseMDString(MDString *&Result);
     bool ParseMDNodeID(MDNode *&Result);
     bool ParseUnnamedAttrGrp();
     bool ParseFnAttributeValuePairs(AttrBuilder &B,
                                     std::vector<unsigned> &FwdRefAttrGrps,
                                     bool inAttrGrp, LocTy &BuiltinLoc);
+    bool ParseByValWithOptionalType(Type *&Result);
 
     // Module Summary Index Parsing.
     bool SkipModuleSummaryEntry();
     bool ParseSummaryEntry();
     bool ParseModuleEntry(unsigned ID);
     bool ParseModuleReference(StringRef &ModulePath);
     bool ParseGVReference(ValueInfo &VI, unsigned &GVId);
     bool ParseGVEntry(unsigned ID);

llvm/lib/AsmParser/LLParser.cpp

while (true) {
     }
     case lltok::kw_align: {
       unsigned Alignment;
       if (ParseOptionalAlignment(Alignment))
         return true;
       B.addAlignmentAttr(Alignment);
       continue;
     }
-    case lltok::kw_byval:           B.addAttribute(Attribute::ByVal); break;
+    case lltok::kw_byval: {
+      Type *Ty;
+      if (ParseByValWithOptionalType(Ty))
+        return true;
+      B.addByValAttr(Ty);
+      continue;
+    }
     case lltok::kw_dereferenceable: {
       uint64_t Bytes;
       if (ParseOptionalDerefAttrBytes(lltok::kw_dereferenceable, Bytes))
         return true;
       B.addDereferenceableAttr(Bytes);
       continue;
     }
     case lltok::kw_dereferenceable_or_null: {
bool LLParser::ParseParameterList(SmallVectorImpl<ParamInfo> &ArgList,
   if (IsMustTailCall && InVarArgsFunc)
     return TokError("expected '...' at end of argument list for musttail call "
                     "in varargs function");
 
   Lex.Lex();  // Lex the ')'.
   return false;
 }
 
+/// ParseByValWithOptionalType
+///   ::= byval
+///   ::= byval(<ty>)
+bool LLParser::ParseByValWithOptionalType(Type *&Result) {
+  Result = nullptr;
+  if (!EatIfPresent(lltok::kw_byval))
+    return true;
+  if (!EatIfPresent(lltok::lparen))
+    return false;
+  if (ParseType(Result))
+    return true;
+  if (!EatIfPresent(lltok::rparen))
+    return Error(Lex.getLoc(), "expected ')'");
+  return false;
+}
+
 /// ParseOptionalOperandBundles
 ///    ::= /*empty*/
 ///    ::= '[' OperandBundle [, OperandBundle ]* ']'
 ///
 /// OperandBundle
 ///    ::= bundle-tag '(' ')'
 ///    ::= bundle-tag '(' Type Value [, Type Value ]* ')'
 ///

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

Value *getValueSigned(SmallVectorImpl<uint64_t> &Record, unsigned Slot,
     if (Slot == Record.size()) return nullptr;
     unsigned ValNo = (unsigned)decodeSignRotatedValue(Record[Slot]);
     // Adjust the ValNo, if it was encoded relative to the InstNum.
     if (UseRelativeIDs)
       ValNo = InstNum - ValNo;
     return getFnValueByID(ValNo, Ty);
   }
 
+  /// Upgrades old-style typeless byval attributes by adding the corresponding
+  /// argument's pointee type.
+  void propagateByValTypes(CallBase *CB);
+
   /// Converts alignment exponent (i.e. power of two (or zero)) to the
   /// corresponding alignment to use. If alignment is too large, returns
   /// a corresponding error code.
   Error parseAlignmentValue(uint64_t Exponent, unsigned &Alignment);
   Error parseAttrKind(uint64_t Code, Attribute::AttrKind *Kind);
   Error parseModule(uint64_t ResumeBit, bool ShouldLazyLoadMetadata = false);
 
   Error parseComdatRecord(ArrayRef<uint64_t> Record);
case bitc::PARAMATTR_GRP_CODE_ENTRY: { // ENTRY: [grpid, idx, a0, a1, ...]
 
       AttrBuilder B;
       for (unsigned i = 2, e = Record.size(); i != e; ++i) {
         if (Record[i] == 0) {        // Enum attribute
           Attribute::AttrKind Kind;
           if (Error Err = parseAttrKind(Record[++i], &Kind))
             return Err;
 
+          // Upgrade old-style byval attribute to one with a type, even if it's
+          // nullptr. We will have to insert the real type when we associate
+          // this AttributeList with a function.
+          if (Kind == Attribute::ByVal)
+            B.addByValAttr(nullptr);
+
           B.addAttribute(Kind);
         } else if (Record[i] == 1) { // Integer attribute
           Attribute::AttrKind Kind;
           if (Error Err = parseAttrKind(Record[++i], &Kind))
             return Err;
           if (Kind == Attribute::Alignment)
             B.addAlignmentAttr(Record[++i]);
           else if (Kind == Attribute::StackAlignment)
             B.addStackAlignmentAttr(Record[++i]);
           else if (Kind == Attribute::Dereferenceable)
             B.addDereferenceableAttr(Record[++i]);
           else if (Kind == Attribute::DereferenceableOrNull)
             B.addDereferenceableOrNullAttr(Record[++i]);
           else if (Kind == Attribute::AllocSize)
             B.addAllocSizeAttrFromRawRepr(Record[++i]);
-        } else {                     // String attribute
-          assert((Record[i] == 3 || Record[i] == 4) &&
-                 "Invalid attribute group entry");
+        } else if (Record[i] == 3 || Record[i] == 4) { // String attribute
           bool HasValue = (Record[i++] == 4);
           SmallString<64> KindStr;
           SmallString<64> ValStr;
 
           while (Record[i] != 0 && i != e)
             KindStr += Record[i++];
           assert(Record[i] == 0 && "Kind string not null terminated");
 
           if (HasValue) {
             // Has a value associated with it.
             ++i; // Skip the '0' that terminates the "kind" string.
             while (Record[i] != 0 && i != e)
               ValStr += Record[i++];
             assert(Record[i] == 0 && "Value string not null terminated");
           }
 
           B.addAttribute(KindStr.str(), ValStr.str());
+        } else {
+          assert((Record[i] == 5 || Record[i] == 6) &&
+                 "Invalid attribute group entry");
+          bool HasType = Record[i] == 6;
+          Attribute::AttrKind Kind;
+          if (Error Err = parseAttrKind(Record[++i], &Kind))
+            return Err;
+          if (Kind == Attribute::ByVal)
+            B.addByValAttr(HasType ? getTypeByID(Record[++i]) : nullptr);
         }
       }
 
       MAttributeGroups[GrpID] = AttributeList::get(Context, Idx, B);
       break;
     }
     }
   }
Function *Func = Function::Create(FTy, GlobalValue::ExternalLinkage,
                                     AddrSpace, Name, TheModule);
 
   Func->setCallingConv(CC);
   bool isProto = Record[2];
   uint64_t RawLinkage = Record[3];
   Func->setLinkage(getDecodedLinkage(RawLinkage));
   Func->setAttributes(getAttributes(Record[4]));
 
+  // Upgrade any old-style byval without a type by propagating the argument's
+  // pointee type. There should be no opaque pointers where the byval type is
+  // implicit.
+  for (auto &Arg : Func->args()) {
+    if (Arg.hasByValAttr() && !Arg.getParamByValType()) {
+      Arg.removeAttr(Attribute::ByVal);
+      Arg.addAttr(Attribute::getWithByValType(
+          Context, Arg.getType()->getPointerElementType()));
+    }
+  }
+
   unsigned Alignment;
   if (Error Err = parseAlignmentValue(Record[5], Alignment))
     return Err;
   Func->setAlignment(Alignment);
   if (Record[6]) {
     if (Record[6] - 1 >= SectionTable.size())
       return error("Invalid ID");
     Func->setSection(SectionTable[Record[6] - 1]);
Error BitcodeReader::typeCheckLoadStoreInst(Type *ValType, Type *PtrType) {
   if (ValType && ValType != ElemType)
     return error("Explicit load/store type does not match pointee "
                  "type of pointer operand");
   if (!PointerType::isLoadableOrStorableType(ElemType))
     return error("Cannot load/store from pointer");
   return Error::success();
 }
 
+void BitcodeReader::propagateByValTypes(CallBase *CB) {
+  for (unsigned i = 0; i < CB->getNumArgOperands(); ++i) {
+    if (CB->paramHasAttr(i, Attribute::ByVal) &&
+        !CB->getAttribute(i, Attribute::ByVal).getValueAsType()) {
+      CB->removeParamAttr(i, Attribute::ByVal);
+      CB->addParamAttr(
+          i, Attribute::getWithByValType(
+                 Context,
+                 CB->getArgOperand(i)->getType()->getPointerElementType()));
+    }
+  }
+}
+
 /// Lazily parse the specified function body block.
 Error BitcodeReader::parseFunctionBody(Function *F) {
   if (Stream.EnterSubBlock(bitc::FUNCTION_BLOCK_ID))
     return error("Invalid record");
 
   // Unexpected unresolved metadata when parsing function.
   if (MDLoader->hasFwdRefs())
     return error("Invalid function metadata: incoming forward references");
case bitc::FUNC_CODE_INST_INVOKE: {
 
       I = InvokeInst::Create(FTy, Callee, NormalBB, UnwindBB, Ops,
                              OperandBundles);
       OperandBundles.clear();
       InstructionList.push_back(I);
       cast<InvokeInst>(I)->setCallingConv(
           static_cast<CallingConv::ID>(CallingConv::MaxID & CCInfo));
       cast<InvokeInst>(I)->setAttributes(PAL);
+      propagateByValTypes(cast<CallBase>(I));
+
       break;
     }
     case bitc::FUNC_CODE_INST_RESUME: { // RESUME: [opval]
       unsigned Idx = 0;
       Value *Val = nullptr;
       if (getValueTypePair(Record, Idx, NextValueNo, Val))
         return error("Invalid record");
       I = ResumeInst::Create(Val);
case bitc::FUNC_CODE_INST_CALL: {
       if (CCInfo & 1 << bitc::CALL_TAIL)
         TCK = CallInst::TCK_Tail;
       if (CCInfo & (1 << bitc::CALL_MUSTTAIL))
         TCK = CallInst::TCK_MustTail;
       if (CCInfo & (1 << bitc::CALL_NOTAIL))
         TCK = CallInst::TCK_NoTail;
       cast<CallInst>(I)->setTailCallKind(TCK);
       cast<CallInst>(I)->setAttributes(PAL);
+      propagateByValTypes(cast<CallBase>(I));
       if (FMF.any()) {
         if (!isa<FPMathOperator>(I))
           return error("Fast-math-flags specified for call without "
                        "floating-point scalar or vector return type");
         I->setFastMathFlags(FMF);
       }
       break;
     }

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

for (ValueEnumerator::IndexAndAttrSet Pair : AttrGrps) {
     for (Attribute Attr : AS) {
       if (Attr.isEnumAttribute()) {
         Record.push_back(0);
         Record.push_back(getAttrKindEncoding(Attr.getKindAsEnum()));
       } else if (Attr.isIntAttribute()) {
         Record.push_back(1);
         Record.push_back(getAttrKindEncoding(Attr.getKindAsEnum()));
         Record.push_back(Attr.getValueAsInt());
-      } else {
+      } else if (Attr.isStringAttribute()) {
         StringRef Kind = Attr.getKindAsString();
         StringRef Val = Attr.getValueAsString();
 
         Record.push_back(Val.empty() ? 3 : 4);
         Record.append(Kind.begin(), Kind.end());
         Record.push_back(0);
         if (!Val.empty()) {
           Record.append(Val.begin(), Val.end());
           Record.push_back(0);
         }
+      } else {
+        assert(Attr.isTypeAttribute());
+        Type *Ty = Attr.getValueAsType();
+        Record.push_back(Ty ? 6 : 5);
+        Record.push_back(getAttrKindEncoding(Attr.getKindAsEnum()));
+        if (Ty)
+          Record.push_back(VE.getTypeID(Attr.getValueAsType()));
       }
     }
 
     Stream.EmitRecord(bitc::PARAMATTR_GRP_CODE_ENTRY, Record);
     Record.clear();
   }
 
   Stream.ExitBlock();
void ModuleBitcodeWriter::write() {
   Stream.EnterSubblock(bitc::MODULE_BLOCK_ID, 3);
   size_t BlockStartPos = Buffer.size();
 
   writeModuleVersion();
 
   // Emit blockinfo, which defines the standard abbreviations etc.
   writeBlockInfo();
 
+  // Emit information describing all of the types in the module.
+  writeTypeTable();
+
   // Emit information about attribute groups.
   writeAttributeGroupTable();
 
   // Emit information about parameter attributes.
   writeAttributeTable();
 
-  // Emit information describing all of the types in the module.
-  writeTypeTable();
-
   writeComdats();
 
   // Emit top-level description of module, including target triple, inline asm,
   // descriptors for global variables, and function prototype info.
   writeModuleInfo();
 
   // Emit constants.
   writeModuleConstants();

llvm/lib/Bitcode/Writer/ValueEnumerator.cpp

void ValueEnumerator::incorporateFunction(const Function &F) {
   InstructionCount = 0;
   NumModuleValues = Values.size();
 
   // Add global metadata to the function block.  This doesn't include
   // LocalAsMetadata.
   incorporateFunctionMetadata(F);
 
   // Adding function arguments to the value table.
-  for (const auto &I : F.args())
+  for (const auto &I : F.args()) {
     EnumerateValue(&I);
-
+    if (I.hasAttribute(Attribute::ByVal) && I.getParamByValType())
+      EnumerateType(I.getParamByValType());
+  }
   FirstFuncConstantID = Values.size();
 
   // Add all function-level constants to the value table.
   for (const BasicBlock &BB : F) {
     for (const Instruction &I : BB)
       for (const Use &OI : I.operands()) {
         if ((isa<Constant>(OI) && !isa<GlobalValue>(OI)) || isa<InlineAsm>(OI))
           EnumerateValue(OI);

llvm/lib/CodeGen/#SwiftErrorValueTracking.cpp#

+//===-- SwiftErrorValueTracking.cpp --------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This implements a limited mem2reg-like analysis to promote uses of function
+// arguments and allocas marked with swiftalloc from memory into virtual
+// registers tracked by this class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/SwiftErrorValueTracking.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/TargetInstrInfo.h"
+#include "llvm/CodeGen/TargetLowering.h"
+#include "llvm/IR/Value.h"
+
+using namespace llvm;
+
+/// Set up SwiftErrorVals by going through the function. If the function has
+/// swifterror argument, it will be the first entry.
+void SwiftErrorValueTracking::setFunction(MachineFunction &mf) {
+  MF = &mf;
+  Fn = &MF->getFunction();
+  TLI = MF->getSubtarget().getTargetLowering();
+  TII = MF->getSubtarget().getInstrInfo();
+
+  if (!TLI->supportSwiftError())
+    return;
+
+  SwiftErrorVals.clear();
+  VRegDefMap.clear();
+  VRegUpwardsUse.clear();
+  VRegDefUses.clear();
+  SwiftErrorArg = nullptr;
+
+  // Check if function has a swifterror argument.
+  bool HaveSeenSwiftErrorArg = false;
+  for (Function::const_arg_iterator AI = Fn->arg_begin(), AE = Fn->arg_end();
+       AI != AE; ++AI)
+    if (AI->hasSwiftErrorAttr()) {
+      assert(!HaveSeenSwiftErrorArg &&
+             "Must have only one swifterror parameter");
+      (void)HaveSeenSwiftErrorArg; // silence warning.
+      HaveSeenSwiftErrorArg = true;
+      SwiftErrorArg = &*AI;
+      SwiftErrorVals.push_back(&*AI);
+    }
+
+  for (const auto &LLVMBB : *Fn)
+    for (const auto &Inst : LLVMBB) {
+      if (const AllocaInst *Alloca = dyn_cast<AllocaInst>(&Inst))
+        if (Alloca->isSwiftError())
+          SwiftErrorVals.push_back(Alloca);
+    }
+}
+
+unsigned SwiftErrorValueTracking::getOrCreateVReg(const MachineBasicBlock *MBB,
+                                                  const Value *Val) {
+  auto Key = std::make_pair(MBB, Val);
+  auto It = VRegDefMap.find(Key);
+  // If this is the first use of this swifterror value in this basic block,
+  // create a new virtual register.
+  // After we processed all basic blocks we will satisfy this "upwards exposed
+  // use" by inserting a copy or phi at the beginning of this block.
+  if (It == VRegDefMap.end()) {
+    auto &DL = MF->getDataLayout();
+    const TargetRegisterClass *RC = TLI->getRegClassFor(TLI->getPointerTy(DL));
+    auto VReg = MF->getRegInfo().createVirtualRegister(RC);
+    VRegDefMap[Key] = VReg;
+    VRegUpwardsUse[Key] = VReg;
+    return VReg;
+  } else
+    return It->second;
+}
+
+void SwiftErrorValueTracking::setCurrentVReg(const MachineBasicBlock *MBB,
+                                             const Value *Val, unsigned VReg) {
+  VRegDefMap[std::make_pair(MBB, Val)] = VReg;
+}
+
+unsigned SwiftErrorValueTracking::getOrCreateVRegDefAt(
+    const Instruction *I, const MachineBasicBlock *MBB, const Value *Val) {
+  auto Key = PointerIntPair<const Instruction *, 1, bool>(I, true);
+  auto It = VRegDefUses.find(Key);
+  if (It != VRegDefUses.end())
+    return It->second;
+
+  auto &DL = MF->getDataLayout();
+  const TargetRegisterClass *RC = TLI->getRegClassFor(TLI->getPointerTy(DL));
+  unsigned VReg = MF->getRegInfo().createVirtualRegister(RC);
+  VRegDefUses[Key] = VReg;
+  setCurrentVReg(MBB, Val, VReg);
+  return VReg;
+}
+
+unsigned SwiftErrorValueTracking::getOrCreateVRegUseAt(
+    const Instruction *I, const MachineBasicBlock *MBB, const Value *Val) {
+  auto Key = PointerIntPair<const Instruction *, 1, bool>(I, false);
+  auto It = VRegDefUses.find(Key);
+  if (It != VRegDefUses.end())
+    return It->second;
+
+  unsigned VReg = getOrCreateVReg(MBB, Val);
+  VRegDefUses[Key] = VReg;
+  return VReg;
+}
+
+bool SwiftErrorValueTracking::createEntriesInEntryBlock(DebugLoc DbgLoc) {
+  if (!TLI->supportSwiftError())
+    return false;
+
+  // We only need to do this when we have swifterror parameter or swifterror
+  // alloc.
+  if (SwiftErrorVals.empty())
+    return false;
+
+  MachineBasicBlock *MBB = &*MF->begin();
+  auto &DL = MF->getDataLayout();
+  auto const *RC = TLI->getRegClassFor(TLI->getPointerTy(DL));
+  bool Inserted = false;
+  for (const auto *SwiftErrorVal : SwiftErrorVals) {
+    // We will always generate a copy from the argument. It is always used at
+    // least by the 'return' of the swifterror.
+    if (SwiftErrorArg && SwiftErrorArg == SwiftErrorVal)
+      continue;
+    unsigned VReg = MF->getRegInfo().createVirtualRegister(RC);
+    // Assign Undef to Vreg. We construct MI directly to make sure it works
+    // with FastISel.
+    BuildMI(*MBB, MBB->getFirstNonPHI(), DbgLoc,
+            TII->get(TargetOpcode::IMPLICIT_DEF), VReg);
+
+    setCurrentVReg(MBB, SwiftErrorVal, VReg);
+    Inserted = true;
+  }
+
+  return Inserted;
+}
+
+/// Propagate swifterror values through the machine function CFG.
+void SwiftErrorValueTracking::propagateVRegs() {
+  if (!TLI->supportSwiftError())
+    return;
+
+  // We only need to do this when we have swifterror parameter or swifterror
+  // alloc.
+  if (SwiftErrorVals.empty())
+    return;
+
+  // For each machine basic block in reverse post order.
+  ReversePostOrderTraversal<MachineFunction *> RPOT(MF);
+  for (MachineBasicBlock *MBB : RPOT) {
+    // For each swifterror value in the function.
+    for (const auto *SwiftErrorVal : SwiftErrorVals) {
+      auto Key = std::make_pair(MBB, SwiftErrorVal);
+      auto UUseIt = VRegUpwardsUse.find(Key);
+      auto VRegDefIt = VRegDefMap.find(Key);
+      bool UpwardsUse = UUseIt != VRegUpwardsUse.end();
+      unsigned UUseVReg = UpwardsUse ? UUseIt->second : 0;
+      bool DownwardDef = VRegDefIt != VRegDefMap.end();
+      assert(!(UpwardsUse && !DownwardDef) &&
+             "We can't have an upwards use but no downwards def");
+
+      // If there is no upwards exposed use and an entry for the swifterror in
+      // the def map for this value we don't need to do anything: We already
+      // have a downward def for this basic block.
+      if (!UpwardsUse && DownwardDef)
+        continue;
+
+      // Otherwise we either have an upwards exposed use vreg that we need to
+      // materialize or need to forward the downward def from predecessors.
+
+      // Check whether we have a single vreg def from all predecessors.
+      // Otherwise we need a phi.
+      SmallVector<std::pair<MachineBasicBlock *, unsigned>, 4> VRegs;
+      SmallSet<const MachineBasicBlock *, 8> Visited;
+      for (auto *Pred : MBB->predecessors()) {
+        if (!Visited.insert(Pred).second)
+          continue;
+        VRegs.push_back(std::make_pair(
+            Pred, getOrCreateVReg(Pred, SwiftErrorVal)));
+        if (Pred != MBB)
+          continue;
+        // We have a self-edge.
+        // If there was no upwards use in this basic block there is now one: the
+        // phi needs to use it self.
+        if (!UpwardsUse) {
+          UpwardsUse = true;
+          UUseIt = VRegUpwardsUse.find(Key);
+          assert(UUseIt != VRegUpwardsUse.end());
+          UUseVReg = UUseIt->second;
+        }
+      }
+
+      // We need a phi node if we have more than one predecessor with different
+      // downward defs.
+      bool needPHI =
+          VRegs.size() >= 1 &&
+          std::find_if(
+              VRegs.begin(), VRegs.end(),
+              [&](const std::pair<const MachineBasicBlock *, unsigned> &V)
+                  -> bool { return V.second != VRegs[0].second; }) !=
+              VRegs.end();
+
+      // If there is no upwards exposed used and we don't need a phi just
+      // forward the swifterror vreg from the predecessor(s).
+      if (!UpwardsUse && !needPHI) {
+        assert(!VRegs.empty() &&
+               "No predecessors? The entry block should bail out earlier");
+        // Just forward the swifterror vreg from the predecessor(s).
+        setCurrentVReg(MBB, SwiftErrorVal, VRegs[0].second);
+        continue;
+      }
+
+      auto DLoc = isa<Instruction>(SwiftErrorVal)
+                      ? cast<Instruction>(SwiftErrorVal)->getDebugLoc()
+                      : DebugLoc();
+      const auto *TII = MF->getSubtarget().getInstrInfo();
+
+      // If we don't need a phi create a copy to the upward exposed vreg.
+      if (!needPHI) {
+        assert(UpwardsUse);
+        assert(!VRegs.empty() &&
+               "No predecessors?  Is the Calling Convention correct?");
+        unsigned DestReg = UUseVReg;
+        BuildMI(*MBB, MBB->getFirstNonPHI(), DLoc, TII->get(TargetOpcode::COPY),
+                DestReg)
+            .addReg(VRegs[0].second);
+        continue;
+      }
+
+      // We need a phi: if there is an upwards exposed use we already have a
+      // destination virtual register number otherwise we generate a new one.
+      auto &DL = MF->getDataLayout();
+      auto const *RC = TLI->getRegClassFor(TLI->getPointerTy(DL));
+      unsigned PHIVReg =
+          UpwardsUse ? UUseVReg : MF->getRegInfo().createVirtualRegister(RC);
+      MachineInstrBuilder PHI =
+          BuildMI(*MBB, MBB->getFirstNonPHI(), DLoc,
+                  TII->get(TargetOpcode::PHI), PHIVReg);
+      for (auto BBRegPair : VRegs) {
+        PHI.addReg(BBRegPair.second).addMBB(BBRegPair.first);
+      }
+
+      // We did not have a definition in this block before: store the phi's vreg
+      // as this block downward exposed def.
+      if (!UpwardsUse)
+        setCurrentVReg(MBB, SwiftErrorVal, PHIVReg);
+    }
+  }
+}
+
+void SwiftErrorValueTracking::preassignVRegs(
+    MachineBasicBlock *MBB, BasicBlock::const_iterator Begin,
+    BasicBlock::const_iterator End) {
+  if (!TLI->supportSwiftError() || SwiftErrorVals.empty())
+    return;
+
+  // Iterator over instructions and assign vregs to swifterror defs and uses.
+  for (auto It = Begin; It != End; ++It) {
+    ImmutableCallSite CS(&*It);
+    if (CS) {
+      // A call-site with a swifterror argument is both use and def.
+      const Value *SwiftErrorAddr = nullptr;
+      for (auto &Arg : CS.args()) {
+        if (!Arg->isSwiftError())
+          continue;
+        // Use of swifterror.
+        assert(!SwiftErrorAddr && "Cannot have multiple swifterror arguments");
+        SwiftErrorAddr = &*Arg;
+        assert(SwiftErrorAddr->isSwiftError() &&
+               "Must have a swifterror value argument");
+        getOrCreateVRegUseAt(&*It, MBB, SwiftErrorAddr);
+      }
+      if (!SwiftErrorAddr)
+        continue;
+
+      // Def of swifterror.
+      getOrCreateVRegDefAt(&*It, MBB, SwiftErrorAddr);
+
+      // A load is a use.
+    } else if (const LoadInst *LI = dyn_cast<const LoadInst>(&*It)) {
+      const Value *V = LI->getOperand(0);
+      if (!V->isSwiftError())
+        continue;
+
+      getOrCreateVRegUseAt(LI, MBB, V);
+
+      // A store is a def.
+    } else if (const StoreInst *SI = dyn_cast<const StoreInst>(&*It)) {
+      const Value *SwiftErrorAddr = SI->getOperand(1);
+      if (!SwiftErrorAddr->isSwiftError())
+        continue;
+
+      // Def of swifterror.
+      getOrCreateVRegDefAt(&*It, MBB, SwiftErrorAddr);
+
+      // A return in a swiferror returning function is a use.
+    } else if (const ReturnInst *R = dyn_cast<const ReturnInst>(&*It)) {
+      const Function *F = R->getParent()->getParent();
+      if (!F->getAttributes().hasAttrSomewhere(Attribute::SwiftError))
+        continue;
+
+      getOrCreateVRegUseAt(R, MBB, SwiftErrorArg);
+    }
+  }
+}

llvm/lib/CodeGen/GlobalISel/CallLowering.cpp

if (Attrs.hasAttribute(OpIdx, Attribute::SwiftError))
     Arg.Flags.setSwiftError();
   if (Attrs.hasAttribute(OpIdx, Attribute::ByVal))
     Arg.Flags.setByVal();
   if (Attrs.hasAttribute(OpIdx, Attribute::InAlloca))
     Arg.Flags.setInAlloca();
 
   if (Arg.Flags.isByVal() || Arg.Flags.isInAlloca()) {
     Type *ElementTy = cast<PointerType>(Arg.Ty)->getElementType();
-    Arg.Flags.setByValSize(DL.getTypeAllocSize(ElementTy));
+
+    auto Ty = Attrs.getAttribute(OpIdx, Attribute::ByVal).getValueAsType();
+    Arg.Flags.setByValSize(DL.getTypeAllocSize(Ty ? Ty : ElementTy));
+
     // For ByVal, alignment should be passed from FE.  BE will guess if
     // this info is not there but there are cases it cannot get right.
     unsigned FrameAlign;
     if (FuncInfo.getParamAlignment(OpIdx - 2))
       FrameAlign = FuncInfo.getParamAlignment(OpIdx - 2);
     else
       FrameAlign = getTLI()->getByValTypeAlignment(ElementTy, DL);
     Arg.Flags.setByValAlign(FrameAlign);

llvm/lib/CodeGen/SelectionDAG/FastISel.cpp

if (Arg.IsInAlloca) {
       // inalloca. This way we can know how many bytes we should've allocated
       // and how many bytes a callee cleanup function will pop.  If we port
       // inalloca to more targets, we'll have to add custom inalloca handling in
       // the various CC lowering callbacks.
       Flags.setByVal();
     }
     if (Arg.IsByVal || Arg.IsInAlloca) {
       PointerType *Ty = cast<PointerType>(Arg.Ty);
       Type *ElementTy = Ty->getElementType();
-      unsigned FrameSize = DL.getTypeAllocSize(ElementTy);
-      // For ByVal, alignment should come from FE. BE will guess if this info is
-      // not there, but there are cases it cannot get right.
+      unsigned FrameSize =
+          DL.getTypeAllocSize(Arg.ByValType ? Arg.ByValType : ElementTy);
+
+      // For ByVal, alignment should come from FE. BE will guess if this info
+      // is not there, but there are cases it cannot get right.
       unsigned FrameAlign = Arg.Alignment;
       if (!FrameAlign)
         FrameAlign = TLI.getByValTypeAlignment(ElementTy, DL);
       Flags.setByValSize(FrameSize);
       Flags.setByValAlign(FrameAlign);
     }
     if (Arg.IsNest)
       Flags.setNest();

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

for (unsigned Value = 0, NumValues = ValueVTs.size(); Value != NumValues;
         // and how many bytes a callee cleanup function will pop.  If we port
         // inalloca to more targets, we'll have to add custom inalloca handling
         // in the various CC lowering callbacks.
         Flags.setByVal();
       }
       if (Args[i].IsByVal || Args[i].IsInAlloca) {
         PointerType *Ty = cast<PointerType>(Args[i].Ty);
         Type *ElementTy = Ty->getElementType();
-        Flags.setByValSize(DL.getTypeAllocSize(ElementTy));
-        // For ByVal, alignment should come from FE.  BE will guess if this
+
+        unsigned FrameSize = DL.getTypeAllocSize(
+            Args[i].ByValType ? Args[i].ByValType : ElementTy);
+        Flags.setByValSize(FrameSize);
+
         // info is not there but there are cases it cannot get right.
         unsigned FrameAlign;
         if (Args[i].Alignment)
           FrameAlign = Args[i].Alignment;
         else
           FrameAlign = getByValTypeAlignment(ElementTy, DL);
         Flags.setByValAlign(FrameAlign);
       }
       if (Args[i].IsNest)
for (unsigned Value = 0, NumValues = ValueVTs.size();
       if (F.getCallingConv() == CallingConv::X86_INTR) {
         // IA Interrupt passes frame (1st parameter) by value in the stack.
         if (ArgNo == 0)
           Flags.setByVal();
       }
       if (Flags.isByVal() || Flags.isInAlloca()) {
         PointerType *Ty = cast<PointerType>(Arg.getType());
         Type *ElementTy = Ty->getElementType();
-        Flags.setByValSize(DL.getTypeAllocSize(ElementTy));
-        // For ByVal, alignment should be passed from FE.  BE will guess if
-        // this info is not there but there are cases it cannot get right.
+
+        // For ByVal, size and alignment should be passed from FE.  BE will
+        // guess if this info is not there but there are cases it cannot get
+        // right.
+        unsigned FrameSize = DL.getTypeAllocSize(
+            Arg.getParamByValType() ? Arg.getParamByValType() : ElementTy);
+        Flags.setByValSize(FrameSize);
+
         unsigned FrameAlign;
         if (Arg.getParamAlignment())
           FrameAlign = Arg.getParamAlignment();
         else
           FrameAlign = TLI->getByValTypeAlignment(ElementTy, DL);
         Flags.setByValAlign(FrameAlign);
       }
       if (Arg.hasAttribute(Attribute::Nest))
         Flags.setNest();

llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

void TargetLoweringBase::ArgListEntry::setAttributes(const CallBase *Call,
   IsSRet = Call->paramHasAttr(ArgIdx, Attribute::StructRet);
   IsNest = Call->paramHasAttr(ArgIdx, Attribute::Nest);
   IsByVal = Call->paramHasAttr(ArgIdx, Attribute::ByVal);
   IsInAlloca = Call->paramHasAttr(ArgIdx, Attribute::InAlloca);
   IsReturned = Call->paramHasAttr(ArgIdx, Attribute::Returned);
   IsSwiftSelf = Call->paramHasAttr(ArgIdx, Attribute::SwiftSelf);
   IsSwiftError = Call->paramHasAttr(ArgIdx, Attribute::SwiftError);
   Alignment = Call->getParamAlignment(ArgIdx);
+  ByValType = Call->getParamByValType(ArgIdx);
 }
 
 /// Generate a libcall taking the given operands as arguments and returning a
 /// result of type RetVT.
 std::pair<SDValue, SDValue>
 TargetLowering::makeLibCall(SelectionDAG &DAG, RTLIB::Libcall LC, EVT RetVT,
                             ArrayRef<SDValue> Ops, bool isSigned,
                             const SDLoc &dl, bool doesNotReturn,

llvm/lib/IR/AttributeImpl.h

 #include <cstddef>
 #include <cstdint>
 #include <string>
 #include <utility>
 
 namespace llvm {
 
 class LLVMContext;
+class Type;
 
 //===----------------------------------------------------------------------===//
 /// \class
 /// This class represents a single, uniqued attribute. That attribute
 /// could be a single enum, a tuple, or a string.
 class AttributeImpl : public FoldingSetNode {
   unsigned char KindID; ///< Holds the AttrEntryKind of the attribute
 
 protected:
   enum AttrEntryKind {
     EnumAttrEntry,
     IntAttrEntry,
-    StringAttrEntry
+    StringAttrEntry,
+    TypeAttrEntry,
   };
 
   AttributeImpl(AttrEntryKind KindID) : KindID(KindID) {}
 
 public:
   // AttributesImpl is uniqued, these should not be available.
   AttributeImpl(const AttributeImpl &) = delete;
   AttributeImpl &operator=(const AttributeImpl &) = delete;
 
   virtual ~AttributeImpl();
 
   bool isEnumAttribute() const { return KindID == EnumAttrEntry; }
   bool isIntAttribute() const { return KindID == IntAttrEntry; }
   bool isStringAttribute() const { return KindID == StringAttrEntry; }
+  bool isTypeAttribute() const { return KindID == TypeAttrEntry; }
 
   bool hasAttribute(Attribute::AttrKind A) const;
   bool hasAttribute(StringRef Kind) const;
 
   Attribute::AttrKind getKindAsEnum() const;
   uint64_t getValueAsInt() const;
 
   StringRef getKindAsString() const;
   StringRef getValueAsString() const;
 
+  Type *getValueAsType() const;
+
   /// Used when sorting the attributes.
   bool operator<(const AttributeImpl &AI) const;
 
   void Profile(FoldingSetNodeID &ID) const {
     if (isEnumAttribute())
-      Profile(ID, getKindAsEnum(), 0);
+      Profile(ID, getKindAsEnum(), static_cast<uint64_t>(0));
     else if (isIntAttribute())
       Profile(ID, getKindAsEnum(), getValueAsInt());
-    else
+    else if (isStringAttribute())
       Profile(ID, getKindAsString(), getValueAsString());
+    else
+      Profile(ID, getKindAsEnum(), getValueAsType());
   }
 
   static void Profile(FoldingSetNodeID &ID, Attribute::AttrKind Kind,
                       uint64_t Val) {
     ID.AddInteger(Kind);
     if (Val) ID.AddInteger(Val);
   }
 
   static void Profile(FoldingSetNodeID &ID, StringRef Kind, StringRef Values) {
     ID.AddString(Kind);
     if (!Values.empty()) ID.AddString(Values);
   }
+
+  static void Profile(FoldingSetNodeID &ID, Attribute::AttrKind Kind,
+                      Type *Ty) {
+    ID.AddInteger(Kind);
+    ID.AddPointer(Ty);
+  }
 };
 
 //===----------------------------------------------------------------------===//
 /// \class
 /// A set of classes that contain the value of the
 /// attribute object. There are three main categories: enum attribute entries,
 /// represented by Attribute::AttrKind; alignment attribute entries; and string
 /// attribute enties, which are for target-dependent attributes.

 public:
   StringAttributeImpl(StringRef Kind, StringRef Val = StringRef())
       : AttributeImpl(StringAttrEntry), Kind(Kind), Val(Val) {}
 
   StringRef getStringKind() const { return Kind; }
   StringRef getStringValue() const { return Val; }
 };
 
+class TypeAttributeImpl : public EnumAttributeImpl {
+  virtual void anchor();
+
+  Type *Ty;
+
+public:
+  TypeAttributeImpl(Attribute::AttrKind Kind, Type *Ty)
+      : EnumAttributeImpl(TypeAttrEntry, Kind), Ty(Ty) {}
+
+  Type *getTypeValue() const { return Ty; }
+};
+
 //===----------------------------------------------------------------------===//
 /// \class
 /// This class represents a group of attributes that apply to one
 /// element: function, return type, or parameter.
 class AttributeSetNode final
     : public FoldingSetNode,
       private TrailingObjects<AttributeSetNode, Attribute> {
   friend TrailingObjects;
public:
   Attribute getAttribute(StringRef Kind) const;
 
   unsigned getAlignment() const;
   unsigned getStackAlignment() const;
   uint64_t getDereferenceableBytes() const;
   uint64_t getDereferenceableOrNullBytes() const;
   std::pair<unsigned, Optional<unsigned>> getAllocSizeArgs() const;
   std::string getAsString(bool InAttrGrp) const;
+  Type *getByValType() const;
 
   using iterator = const Attribute *;
 
   iterator begin() const { return getTrailingObjects<Attribute>(); }
   iterator end() const { return begin() + NumAttrs; }
 
   void Profile(FoldingSetNodeID &ID) const {
     Profile(ID, makeArrayRef(begin(), end()));

llvm/lib/IR/Attributes.cpp

if (!PA) {
     PA = new StringAttributeImpl(Kind, Val);
     pImpl->AttrsSet.InsertNode(PA, InsertPoint);
   }
 
   // Return the Attribute that we found or created.
   return Attribute(PA);
 }
 
+Attribute Attribute::get(LLVMContext &Context, Attribute::AttrKind Kind,
+                         Type *Ty) {
+  LLVMContextImpl *pImpl = Context.pImpl;
+  FoldingSetNodeID ID;
+  ID.AddInteger(Kind);
+  ID.AddPointer(Ty);
+
+  void *InsertPoint;
+  AttributeImpl *PA = pImpl->AttrsSet.FindNodeOrInsertPos(ID, InsertPoint);
+
+  if (!PA) {
+    // If we didn't find any existing attributes of the same shape then create a
+    // new one and insert it.
+    PA = new TypeAttributeImpl(Kind, Ty);
+    pImpl->AttrsSet.InsertNode(PA, InsertPoint);
+  }
+
+  // Return the Attribute that we found or created.
+  return Attribute(PA);
+}
+
 Attribute Attribute::getWithAlignment(LLVMContext &Context, uint64_t Align) {
   assert(isPowerOf2_32(Align) && "Alignment must be a power of two.");
   assert(Align <= 0x40000000 && "Alignment too large.");
   return get(Context, Alignment, Align);
 }
 
 Attribute Attribute::getWithStackAlignment(LLVMContext &Context,
                                            uint64_t Align) {

 }
 
 Attribute Attribute::getWithDereferenceableOrNullBytes(LLVMContext &Context,
                                                        uint64_t Bytes) {
   assert(Bytes && "Bytes must be non-zero.");
   return get(Context, DereferenceableOrNull, Bytes);
 }
 
+Attribute Attribute::getWithByValType(LLVMContext &Context, Type *Ty) {
+  return get(Context, ByVal, Ty);
+}
+
 Attribute
 Attribute::getWithAllocSizeArgs(LLVMContext &Context, unsigned ElemSizeArg,
                                 const Optional<unsigned> &NumElemsArg) {
   assert(!(ElemSizeArg == 0 && NumElemsArg && *NumElemsArg == 0) &&
          "Invalid allocsize arguments -- given allocsize(0, 0)");
   return get(Context, AllocSize, packAllocSizeArgs(ElemSizeArg, NumElemsArg));
 }
 
 //===----------------------------------------------------------------------===//
 // Attribute Accessor Methods
 //===----------------------------------------------------------------------===//
 
 bool Attribute::isEnumAttribute() const {
   return pImpl && pImpl->isEnumAttribute();
 }
 
 bool Attribute::isIntAttribute() const {
   return pImpl && pImpl->isIntAttribute();
 }
 
 bool Attribute::isStringAttribute() const {
   return pImpl && pImpl->isStringAttribute();
 }
 
+bool Attribute::isTypeAttribute() const {
+  return pImpl && pImpl->isTypeAttribute();
+}
+
 Attribute::AttrKind Attribute::getKindAsEnum() const {
   if (!pImpl) return None;
-  assert((isEnumAttribute() || isIntAttribute()) &&
+  assert((isEnumAttribute() || isIntAttribute() || isTypeAttribute()) &&
          "Invalid attribute type to get the kind as an enum!");
   return pImpl->getKindAsEnum();
 }
 
 uint64_t Attribute::getValueAsInt() const {
   if (!pImpl) return 0;
   assert(isIntAttribute() &&
          "Expected the attribute to be an integer attribute!");

 
 StringRef Attribute::getValueAsString() const {
   if (!pImpl) return {};
   assert(isStringAttribute() &&
          "Invalid attribute type to get the value as a string!");
   return pImpl->getValueAsString();
 }
 
+Type *Attribute::getValueAsType() const {
+  if (!pImpl) return {};
+  assert(isTypeAttribute() &&
+         "Invalid attribute type to get the value as a type!");
+  return pImpl->getValueAsType();
+}
+
+
 bool Attribute::hasAttribute(AttrKind Kind) const {
   return (pImpl && pImpl->hasAttribute(Kind)) || (!pImpl && Kind == None);
 }
 
 bool Attribute::hasAttribute(StringRef Kind) const {
   if (!isStringAttribute()) return false;
   return pImpl && pImpl->hasAttribute(Kind);
 }
std::string Attribute::getAsString(bool InAttrGrp) const {
   if (hasAttribute(Attribute::SanitizeHWAddress))
     return "sanitize_hwaddress";
   if (hasAttribute(Attribute::AlwaysInline))
     return "alwaysinline";
   if (hasAttribute(Attribute::ArgMemOnly))
     return "argmemonly";
   if (hasAttribute(Attribute::Builtin))
     return "builtin";
-  if (hasAttribute(Attribute::ByVal))
-    return "byval";
   if (hasAttribute(Attribute::Convergent))
     return "convergent";
   if (hasAttribute(Attribute::SwiftError))
     return "swifterror";
   if (hasAttribute(Attribute::SwiftSelf))
     return "swiftself";
   if (hasAttribute(Attribute::InaccessibleMemOnly))
     return "inaccessiblememonly";
if (hasAttribute(Attribute::UWTable))
     return "uwtable";
   if (hasAttribute(Attribute::ZExt))
     return "zeroext";
   if (hasAttribute(Attribute::Cold))
     return "cold";
   if (hasAttribute(Attribute::ImmArg))
     return "immarg";
 
+  if (hasAttribute(Attribute::ByVal)) {
+    std::string Result;
+    Result += "byval";
+    Type *Ty = getValueAsType();
+    if (Ty) {
+      raw_string_ostream OS(Result);
+      Result += '(';
+      Ty->print(OS, false, true);
+      OS.flush();
+      Result += ')';
+    }
+    return Result;
+  }
+
   // FIXME: These should be output like this:
   //
   //   align=4
   //   alignstack=8
   //
   if (hasAttribute(Attribute::Alignment)) {
     std::string Result;
     Result += "align";

 AttributeImpl::~AttributeImpl() = default;
 
 void EnumAttributeImpl::anchor() {}
 
 void IntAttributeImpl::anchor() {}
 
 void StringAttributeImpl::anchor() {}
 
+void TypeAttributeImpl::anchor() {}
+
 bool AttributeImpl::hasAttribute(Attribute::AttrKind A) const {
   if (isStringAttribute()) return false;
   return getKindAsEnum() == A;
 }
 
 bool AttributeImpl::hasAttribute(StringRef Kind) const {
   if (!isStringAttribute()) return false;
   return getKindAsString() == Kind;
 }
 
 Attribute::AttrKind AttributeImpl::getKindAsEnum() const {
-  assert(isEnumAttribute() || isIntAttribute());
+  assert(isEnumAttribute() || isIntAttribute() || isTypeAttribute());
   return static_cast<const EnumAttributeImpl *>(this)->getEnumKind();
 }
 
 uint64_t AttributeImpl::getValueAsInt() const {
   assert(isIntAttribute());
   return static_cast<const IntAttributeImpl *>(this)->getValue();
 }
 
 StringRef AttributeImpl::getKindAsString() const {
   assert(isStringAttribute());
   return static_cast<const StringAttributeImpl *>(this)->getStringKind();
 }
 
 StringRef AttributeImpl::getValueAsString() const {
   assert(isStringAttribute());
   return static_cast<const StringAttributeImpl *>(this)->getStringValue();
 }
 
+Type *AttributeImpl::getValueAsType() const {
+  assert(isTypeAttribute());
+  return static_cast<const TypeAttributeImpl *>(this)->getTypeValue();
+}
+
 bool AttributeImpl::operator<(const AttributeImpl &AI) const {
   // This sorts the attributes with Attribute::AttrKinds coming first (sorted
   // relative to their enum value) and then strings.
   if (isEnumAttribute()) {
     if (AI.isEnumAttribute()) return getKindAsEnum() < AI.getKindAsEnum();
     if (AI.isIntAttribute()) return true;
     if (AI.isStringAttribute()) return true;
+    if (AI.isTypeAttribute()) return true;
+  }
+
+  if (isTypeAttribute()) {
+    if (AI.isEnumAttribute()) return false;
+    if (AI.isTypeAttribute()) {
+      if (getKindAsEnum() == AI.getKindAsEnum())
+        return getValueAsType() < AI.getValueAsType();
+      return getKindAsEnum() < AI.getKindAsEnum();
+    }
+    if (AI.isIntAttribute()) return true;
+    if (AI.isStringAttribute()) return true;
   }
 
   if (isIntAttribute()) {
     if (AI.isEnumAttribute()) return false;
+    if (AI.isTypeAttribute()) return false;
     if (AI.isIntAttribute()) {
       if (getKindAsEnum() == AI.getKindAsEnum())
         return getValueAsInt() < AI.getValueAsInt();
       return getKindAsEnum() < AI.getKindAsEnum();
     }
     if (AI.isStringAttribute()) return true;
   }
 
+  assert(isStringAttribute());
   if (AI.isEnumAttribute()) return false;
+  if (AI.isTypeAttribute()) return false;
   if (AI.isIntAttribute()) return false;
   if (getKindAsString() == AI.getKindAsString())
     return getValueAsString() < AI.getValueAsString();
   return getKindAsString() < AI.getKindAsString();
 }
 
 //===----------------------------------------------------------------------===//
 // AttributeSet Definition

 uint64_t AttributeSet::getDereferenceableBytes() const {
   return SetNode ? SetNode->getDereferenceableBytes() : 0;
 }
 
 uint64_t AttributeSet::getDereferenceableOrNullBytes() const {
   return SetNode ? SetNode->getDereferenceableOrNullBytes() : 0;
 }
 
+Type *AttributeSet::getByValType() const {
+  return SetNode ? SetNode->getByValType() : nullptr;
+}
+
 std::pair<unsigned, Optional<unsigned>> AttributeSet::getAllocSizeArgs() const {
   return SetNode ? SetNode->getAllocSizeArgs()
                  : std::pair<unsigned, Optional<unsigned>>(0, 0);
 }
 
 std::string AttributeSet::getAsString(bool InAttrGrp) const {
   return SetNode ? SetNode->getAsString(InAttrGrp) : "";
 }
AttributeSetNode *AttributeSetNode::get(LLVMContext &C, const AttrBuilder &B) {
   SmallVector<Attribute, 8> Attrs;
   for (Attribute::AttrKind Kind = Attribute::None;
        Kind != Attribute::EndAttrKinds; Kind = Attribute::AttrKind(Kind + 1)) {
     if (!B.contains(Kind))
       continue;
 
     Attribute Attr;
     switch (Kind) {
+    case Attribute::ByVal:
+      Attr = Attribute::getWithByValType(C, B.getByValType());
+      break;
     case Attribute::Alignment:
       Attr = Attribute::getWithAlignment(C, B.getAlignment());
       break;
     case Attribute::StackAlignment:
       Attr = Attribute::getWithStackAlignment(C, B.getStackAlignment());
       break;
     case Attribute::Dereferenceable:
       Attr = Attribute::getWithDereferenceableBytes(

 
 unsigned AttributeSetNode::getStackAlignment() const {
   for (const auto I : *this)
     if (I.hasAttribute(Attribute::StackAlignment))
       return I.getStackAlignment();
   return 0;
 }
 
+Type *AttributeSetNode::getByValType() const {
+  for (const auto I : *this)
+    if (I.hasAttribute(Attribute::ByVal))
+      return I.getValueAsType();
+  return 0;
+}
+
 uint64_t AttributeSetNode::getDereferenceableBytes() const {
   for (const auto I : *this)
     if (I.hasAttribute(Attribute::Dereferenceable))
       return I.getDereferenceableBytes();
   return 0;
 }
 
 uint64_t AttributeSetNode::getDereferenceableOrNullBytes() const {

 unsigned AttributeList::getRetAlignment() const {
   return getAttributes(ReturnIndex).getAlignment();
 }
 
 unsigned AttributeList::getParamAlignment(unsigned ArgNo) const {
   return getAttributes(ArgNo + FirstArgIndex).getAlignment();
 }
 
+Type *AttributeList::getParamByValType(unsigned Index) const {
+  return getAttributes(Index+FirstArgIndex).getByValType();
+}
+
+
 unsigned AttributeList::getStackAlignment(unsigned Index) const {
   return getAttributes(Index).getStackAlignment();
 }
 
 uint64_t AttributeList::getDereferenceableBytes(unsigned Index) const {
   return getAttributes(Index).getDereferenceableBytes();
 }
 
for (const auto &A : AS)
     addAttribute(A);
 }
 
 void AttrBuilder::clear() {
   Attrs.reset();
   TargetDepAttrs.clear();
   Alignment = StackAlignment = DerefBytes = DerefOrNullBytes = 0;
   AllocSizeArgs = 0;
+  ByValType = nullptr;
 }
 
 AttrBuilder &AttrBuilder::addAttribute(Attribute::AttrKind Val) {
   assert((unsigned)Val < Attribute::EndAttrKinds && "Attribute out of range!");
   assert(Val != Attribute::Alignment && Val != Attribute::StackAlignment &&
          Val != Attribute::Dereferenceable && Val != Attribute::AllocSize &&
          "Adding integer attribute without adding a value!");
   Attrs[Val] = true;
   return *this;
 }
 
 AttrBuilder &AttrBuilder::addAttribute(Attribute Attr) {
   if (Attr.isStringAttribute()) {
     addAttribute(Attr.getKindAsString(), Attr.getValueAsString());
     return *this;
   }
 
   Attribute::AttrKind Kind = Attr.getKindAsEnum();
   Attrs[Kind] = true;
 
   if (Kind == Attribute::Alignment)
     Alignment = Attr.getAlignment();
   else if (Kind == Attribute::StackAlignment)
     StackAlignment = Attr.getStackAlignment();
+  else if (Kind == Attribute::ByVal)
+    ByValType = Attr.getValueAsType();
   else if (Kind == Attribute::Dereferenceable)
     DerefBytes = Attr.getDereferenceableBytes();
   else if (Kind == Attribute::DereferenceableOrNull)
     DerefOrNullBytes = Attr.getDereferenceableOrNullBytes();
   else if (Kind == Attribute::AllocSize)
     AllocSizeArgs = Attr.getValueAsInt();
   return *this;
 }
 
 AttrBuilder &AttrBuilder::addAttribute(StringRef A, StringRef V) {
   TargetDepAttrs[A] = V;
   return *this;
 }
 
 AttrBuilder &AttrBuilder::removeAttribute(Attribute::AttrKind Val) {
   assert((unsigned)Val < Attribute::EndAttrKinds && "Attribute out of range!");
   Attrs[Val] = false;
 
   if (Val == Attribute::Alignment)
     Alignment = 0;
   else if (Val == Attribute::StackAlignment)
     StackAlignment = 0;
+  else if (Val == Attribute::ByVal)
+    ByValType = nullptr;
   else if (Val == Attribute::Dereferenceable)
     DerefBytes = 0;
   else if (Val == Attribute::DereferenceableOrNull)
     DerefOrNullBytes = 0;
   else if (Val == Attribute::AllocSize)
     AllocSizeArgs = 0;
 
   return *this;
AttrBuilder &AttrBuilder::addAllocSizeAttrFromRawRepr(uint64_t RawArgs) {
 
   Attrs[Attribute::AllocSize] = true;
   // Reuse existing machinery to store this as a single 64-bit integer so we can
   // save a few bytes over using a pair<unsigned, Optional<unsigned>>.
   AllocSizeArgs = RawArgs;
   return *this;
 }
 
+AttrBuilder &AttrBuilder::addByValAttr(Type *Ty) {
+  Attrs[Attribute::ByVal] = true;
+  ByValType = Ty;
+  return *this;
+}
+
 AttrBuilder &AttrBuilder::merge(const AttrBuilder &B) {
   // FIXME: What if both have alignments, but they don't match?!
   if (!Alignment)
     Alignment = B.Alignment;
 
   if (!StackAlignment)
     StackAlignment = B.StackAlignment;
 

llvm/lib/IR/Function.cpp

return Attrs.hasParamAttribute(getArgNo(), Attribute::ByVal) ||
          Attrs.hasParamAttribute(getArgNo(), Attribute::InAlloca);
 }
 
 unsigned Argument::getParamAlignment() const {
   assert(getType()->isPointerTy() && "Only pointers have alignments");
   return getParent()->getParamAlignment(getArgNo());
 }
 
+Type *Argument::getParamByValType() const {
+  assert(getType()->isPointerTy() && "Only pointers have byval types");
+  return getParent()->getParamByValType(getArgNo());
+}
+
 uint64_t Argument::getDereferenceableBytes() const {
   assert(getType()->isPointerTy() &&
          "Only pointers have dereferenceable bytes");
   return getParent()->getParamDereferenceableBytes(getArgNo());
 }
 
 uint64_t Argument::getDereferenceableOrNullBytes() const {
   assert(getType()->isPointerTy() &&

llvm/lib/IR/Verifier.cpp

Assert(!(Attrs.hasAttribute(Attribute::ReadOnly) &&
          V);
 
   Assert(!(Attrs.hasAttribute(Attribute::NoInline) &&
            Attrs.hasAttribute(Attribute::AlwaysInline)),
          "Attributes "
          "'noinline and alwaysinline' are incompatible!",
          V);
 
+  if (Attrs.hasAttribute(Attribute::ByVal) && Attrs.getByValType()) {
+    Assert(Attrs.getByValType() == cast<PointerType>(Ty)->getElementType(),
+           "Attribute 'byval' type does not match parameter!");
+  }
+
   AttrBuilder IncompatibleAttrs = AttributeFuncs::typeIncompatible(Ty);
   Assert(!AttrBuilder(Attrs).overlaps(IncompatibleAttrs),
          "Wrong types for attribute: " +
              AttributeSet::get(Context, IncompatibleAttrs).getAsString(),
          V);
 
   if (PointerType *PTy = dyn_cast<PointerType>(Ty)) {
     SmallPtrSet<Type*, 4> Visited;

llvm/test/Assembler/#invalid-size2.ll#

+; RUN: not llvm-as %s -o /dev/null 2>&1 | FileCheck %s
+
+; CHECK: error: invalid use of parameter-only attribute on a function
+declare i8* @ret_size() byvsize 4

llvm/test/Assembler/byval-type-attr.ll

+; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis | FileCheck %s
+
+; CHECK: define void @foo(i32* byval(i32) align 4)
+define void @foo(i32* byval(i32) align 4) {
+  ret void
+}
+
+; CHECK: define void @bar({ i32*, i8 }* byval({ i32*, i8 }) align 4)
+define void @bar({i32*, i8}* byval({i32*, i8}) align 4) {
+  ret void
+}
+
+define void @caller({ i32*, i8 }* %ptr) personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
+; CHECK: call void @bar({ i32*, i8 }* byval({ i32*, i8 }) %ptr)
+; CHECK: invoke void @bar({ i32*, i8 }* byval({ i32*, i8 }) %ptr)
+  call void @bar({i32*, i8}* byval %ptr)
+  invoke void @bar({i32*, i8}* byval %ptr) to label %success unwind label %fail
+
+success:
+  ret void
+
+fail:
+  landingpad { i8*, i32 } cleanup
+  ret void
+}
+
+; CHECK: declare void @baz([8 x i8]* byval([8 x i8]))
+%named_type = type [8 x i8]
+declare void @baz(%named_type* byval(%named_type))
+
+declare i32 @__gxx_personality_v0(...)

llvm/test/Assembler/invalid-byval-type1.ll

+; RUN: not llvm-as %s -o /dev/null 2>&1 | FileCheck %s
+
+; CHECK: Attribute 'byval' type does not match parameter!
+declare void @foo(i32* byval(i8))

llvm/test/Assembler/invalid-byval-type2.ll

+; RUN: not llvm-as %s -o /dev/null 2>&1 | FileCheck %s
+
+; CHECK: error: void type only allowed for function results
+declare void @foo(i32* byval(void))

llvm/test/Assembler/invalid-byval-type3.ll

+; RUN: not llvm-as %s -o /dev/null 2>&1 | FileCheck %s
+
+; CHECK: Attributes 'byval' and 'inalloca' do not support unsized types!
+declare void @foo(void()* byval(void()))

llvm/test/Assembler/invalid-size1.ll

+; RUN: not llvm-as %s -o /dev/null 2>&1 | FileCheck %s
+
+; CHECK: error: expected function name
+declare i8* size 4 @ret_size()

llvm/test/Bitcode/attributes-3.3.ll

 
 define void @f7(i8* noalias)
 ; CHECK: define void @f7(i8* noalias)
 {
         ret void;
 }
 
 define void @f8(i8* byval)
-; CHECK: define void @f8(i8* byval)
+; CHECK: define void @f8(i8* byval(i8))
 {
         ret void;
 }
 
 define void @f9(i8* nest)
 ; CHECK: define void @f9(i8* nest)
 {
         ret void;

llvm/test/Bitcode/attributes.ll

 
 define void @f7(i8* noalias)
 ; CHECK: define void @f7(i8* noalias)
 {
         ret void;
 }
 
 define void @f8(i8* byval)
-; CHECK: define void @f8(i8* byval)
+; CHECK: define void @f8(i8* byval(i8))
 {
         ret void;
 }
 
 define void @f9(i8* nest)
 ; CHECK: define void @f9(i8* nest)
 {
         ret void;

llvm/test/Bitcode/byval-upgrade.test

+RUN: llvm-dis %p/Inputs/byval-upgrade.bc -o - | FileCheck %s
+
+Make sure we upgrade old-stile IntAttribute byval records to a fully typed
+version correctly.
+
+CHECK: call void @bar({ i32*, i8 }* byval({ i32*, i8 }) %ptr)
+CHECK: invoke void @bar({ i32*, i8 }* byval({ i32*, i8 }) %ptr)

llvm/test/Bitcode/compatibility-3.6.ll

 ; Functions -- Parameter attributes
 declare void @f.param.zeroext(i8 zeroext)
 ; CHECK: declare void @f.param.zeroext(i8 zeroext)
 declare void @f.param.signext(i8 signext)
 ; CHECK: declare void @f.param.signext(i8 signext)
 declare void @f.param.inreg(i8 inreg)
 ; CHECK: declare void @f.param.inreg(i8 inreg)
 declare void @f.param.byval({ i8, i8 }* byval)
-; CHECK: declare void @f.param.byval({ i8, i8 }* byval)
+; CHECK: declare void @f.param.byval({ i8, i8 }* byval({ i8, i8 }))
 declare void @f.param.inalloca(i8* inalloca)
 ; CHECK: declare void @f.param.inalloca(i8* inalloca)
 declare void @f.param.sret(i8* sret)
 ; CHECK: declare void @f.param.sret(i8* sret)
 declare void @f.param.noalias(i8* noalias)
 ; CHECK: declare void @f.param.noalias(i8* noalias)
 declare void @f.param.nocapture(i8* nocapture)
 ; CHECK: declare void @f.param.nocapture(i8* nocapture)

llvm/test/Bitcode/compatibility-3.7.ll

 ; Functions -- Parameter attributes
 declare void @f.param.zeroext(i8 zeroext)
 ; CHECK: declare void @f.param.zeroext(i8 zeroext)
 declare void @f.param.signext(i8 signext)
 ; CHECK: declare void @f.param.signext(i8 signext)
 declare void @f.param.inreg(i8 inreg)
 ; CHECK: declare void @f.param.inreg(i8 inreg)
 declare void @f.param.byval({ i8, i8 }* byval)
-; CHECK: declare void @f.param.byval({ i8, i8 }* byval)
+; CHECK: declare void @f.param.byval({ i8, i8 }* byval({ i8, i8 }))
 declare void @f.param.inalloca(i8* inalloca)
 ; CHECK: declare void @f.param.inalloca(i8* inalloca)
 declare void @f.param.sret(i8* sret)
 ; CHECK: declare void @f.param.sret(i8* sret)
 declare void @f.param.noalias(i8* noalias)
 ; CHECK: declare void @f.param.noalias(i8* noalias)
 declare void @f.param.nocapture(i8* nocapture)
 ; CHECK: declare void @f.param.nocapture(i8* nocapture)

llvm/test/Bitcode/compatibility-3.8.ll

 ; Functions -- Parameter attributes
 declare void @f.param.zeroext(i8 zeroext)
 ; CHECK: declare void @f.param.zeroext(i8 zeroext)
 declare void @f.param.signext(i8 signext)
 ; CHECK: declare void @f.param.signext(i8 signext)
 declare void @f.param.inreg(i8 inreg)
 ; CHECK: declare void @f.param.inreg(i8 inreg)
 declare void @f.param.byval({ i8, i8 }* byval)
-; CHECK: declare void @f.param.byval({ i8, i8 }* byval)
+; CHECK: declare void @f.param.byval({ i8, i8 }* byval({ i8, i8 }))
 declare void @f.param.inalloca(i8* inalloca)
 ; CHECK: declare void @f.param.inalloca(i8* inalloca)
 declare void @f.param.sret(i8* sret)
 ; CHECK: declare void @f.param.sret(i8* sret)
 declare void @f.param.noalias(i8* noalias)
 ; CHECK: declare void @f.param.noalias(i8* noalias)
 declare void @f.param.nocapture(i8* nocapture)
 ; CHECK: declare void @f.param.nocapture(i8* nocapture)

llvm/test/Bitcode/compatibility-3.9.ll

 ; Functions -- Parameter attributes
 declare void @f.param.zeroext(i8 zeroext)
 ; CHECK: declare void @f.param.zeroext(i8 zeroext)
 declare void @f.param.signext(i8 signext)
 ; CHECK: declare void @f.param.signext(i8 signext)
 declare void @f.param.inreg(i8 inreg)
 ; CHECK: declare void @f.param.inreg(i8 inreg)
 declare void @f.param.byval({ i8, i8 }* byval)
-; CHECK: declare void @f.param.byval({ i8, i8 }* byval)
+; CHECK: declare void @f.param.byval({ i8, i8 }* byval({ i8, i8 }))
 declare void @f.param.inalloca(i8* inalloca)
 ; CHECK: declare void @f.param.inalloca(i8* inalloca)
 declare void @f.param.sret(i8* sret)
 ; CHECK: declare void @f.param.sret(i8* sret)
 declare void @f.param.noalias(i8* noalias)
 ; CHECK: declare void @f.param.noalias(i8* noalias)
 declare void @f.param.nocapture(i8* nocapture)
 ; CHECK: declare void @f.param.nocapture(i8* nocapture)

llvm/test/Bitcode/compatibility-4.0.ll

 ; Functions -- Parameter attributes
 declare void @f.param.zeroext(i8 zeroext)
 ; CHECK: declare void @f.param.zeroext(i8 zeroext)
 declare void @f.param.signext(i8 signext)
 ; CHECK: declare void @f.param.signext(i8 signext)
 declare void @f.param.inreg(i8 inreg)
 ; CHECK: declare void @f.param.inreg(i8 inreg)
 declare void @f.param.byval({ i8, i8 }* byval)
-; CHECK: declare void @f.param.byval({ i8, i8 }* byval)
+; CHECK: declare void @f.param.byval({ i8, i8 }* byval({ i8, i8 }))
 declare void @f.param.inalloca(i8* inalloca)
 ; CHECK: declare void @f.param.inalloca(i8* inalloca)
 declare void @f.param.sret(i8* sret)
 ; CHECK: declare void @f.param.sret(i8* sret)
 declare void @f.param.noalias(i8* noalias)
 ; CHECK: declare void @f.param.noalias(i8* noalias)
 declare void @f.param.nocapture(i8* nocapture)
 ; CHECK: declare void @f.param.nocapture(i8* nocapture)

llvm/test/Bitcode/compatibility-5.0.ll

 ; Functions -- Parameter attributes
 declare void @f.param.zeroext(i8 zeroext)
 ; CHECK: declare void @f.param.zeroext(i8 zeroext)
 declare void @f.param.signext(i8 signext)
 ; CHECK: declare void @f.param.signext(i8 signext)
 declare void @f.param.inreg(i8 inreg)
 ; CHECK: declare void @f.param.inreg(i8 inreg)
 declare void @f.param.byval({ i8, i8 }* byval)
-; CHECK: declare void @f.param.byval({ i8, i8 }* byval)
+; CHECK: declare void @f.param.byval({ i8, i8 }* byval({ i8, i8 }))
 declare void @f.param.inalloca(i8* inalloca)
 ; CHECK: declare void @f.param.inalloca(i8* inalloca)
 declare void @f.param.sret(i8* sret)
 ; CHECK: declare void @f.param.sret(i8* sret)
 declare void @f.param.noalias(i8* noalias)
 ; CHECK: declare void @f.param.noalias(i8* noalias)
 declare void @f.param.nocapture(i8* nocapture)
 ; CHECK: declare void @f.param.nocapture(i8* nocapture)

llvm/test/Bitcode/compatibility-6.0.ll

 ; Functions -- Parameter attributes
 declare void @f.param.zeroext(i8 zeroext)
 ; CHECK: declare void @f.param.zeroext(i8 zeroext)
 declare void @f.param.signext(i8 signext)
 ; CHECK: declare void @f.param.signext(i8 signext)
 declare void @f.param.inreg(i8 inreg)
 ; CHECK: declare void @f.param.inreg(i8 inreg)
 declare void @f.param.byval({ i8, i8 }* byval)
-; CHECK: declare void @f.param.byval({ i8, i8 }* byval)
+; CHECK: declare void @f.param.byval({ i8, i8 }* byval({ i8, i8 }))
 declare void @f.param.inalloca(i8* inalloca)
 ; CHECK: declare void @f.param.inalloca(i8* inalloca)
 declare void @f.param.sret(i8* sret)
 ; CHECK: declare void @f.param.sret(i8* sret)
 declare void @f.param.noalias(i8* noalias)
 ; CHECK: declare void @f.param.noalias(i8* noalias)
 declare void @f.param.nocapture(i8* nocapture)
 ; CHECK: declare void @f.param.nocapture(i8* nocapture)

llvm/test/Bitcode/compatibility.ll

 ; Functions -- Parameter attributes
 declare void @f.param.zeroext(i8 zeroext)
 ; CHECK: declare void @f.param.zeroext(i8 zeroext)
 declare void @f.param.signext(i8 signext)
 ; CHECK: declare void @f.param.signext(i8 signext)
 declare void @f.param.inreg(i8 inreg)
 ; CHECK: declare void @f.param.inreg(i8 inreg)
 declare void @f.param.byval({ i8, i8 }* byval)
-; CHECK: declare void @f.param.byval({ i8, i8 }* byval)
+; CHECK: declare void @f.param.byval({ i8, i8 }* byval({ i8, i8 }))
 declare void @f.param.inalloca(i8* inalloca)
 ; CHECK: declare void @f.param.inalloca(i8* inalloca)
 declare void @f.param.sret(i8* sret)
 ; CHECK: declare void @f.param.sret(i8* sret)
 declare void @f.param.noalias(i8* noalias)
 ; CHECK: declare void @f.param.noalias(i8* noalias)
 declare void @f.param.nocapture(i8* nocapture)
 ; CHECK: declare void @f.param.nocapture(i8* nocapture)
define i8** @constexpr() {
   ; CHECK: ret i8** getelementptr inbounds ({ [4 x i8*], [4 x i8*] }, { [4 x i8*], [4 x i8*] }* null, i32 0, inrange i32 1, i32 2)
   ret i8** getelementptr inbounds ({ [4 x i8*], [4 x i8*] }, { [4 x i8*], [4 x i8*] }* null, i32 0, inrange i32 1, i32 2)
 }
 
 ; immarg attribute
 declare void @llvm.test.immarg.intrinsic(i32 immarg)
 ; CHECK: declare void @llvm.test.immarg.intrinsic(i32 immarg)
 
+; byval attribute with type
+%named_type = type [8 x i8]
+declare void @byval_type(i32* byval(i32) align 2)
+declare void @byval_type2({ i8, i8* }* byval({ i8, i8* }))
+declare void @byval_named_type(%named_type* byval(%named_type))
+; CHECK: declare void @byval_type(i32* byval(i32) align 2)
+; CHECK: declare void @byval_type2({ i8, i8* }* byval({ i8, i8* }))
+; CHECK: declare void @byval_named_type([8 x i8]* byval([8 x i8]))
+
 ; CHECK: attributes #0 = { alignstack=4 }
 ; CHECK: attributes #1 = { alignstack=8 }
 ; CHECK: attributes #2 = { alwaysinline }
 ; CHECK: attributes #3 = { cold }
 ; CHECK: attributes #4 = { convergent }
 ; CHECK: attributes #5 = { inlinehint }
 ; CHECK: attributes #6 = { jumptable }
 ; CHECK: attributes #7 = { minsize }

llvm/test/Bitcode/highLevelStructure.3.2.ll

 ; CHECK: declare void @ParamAttr2(i8* nest)
 declare void @ParamAttr2(i8* nest)
 ; CHECK: declare void @ParamAttr3(i8* sret)
 declare void @ParamAttr3(i8* sret)
 ; CHECK: declare void @ParamAttr4(i8 signext)
 declare void @ParamAttr4(i8 signext)
 ; CHECK: declare void @ParamAttr5(i8* inreg)
 declare void @ParamAttr5(i8* inreg)
-; CHECK: declare void @ParamAttr6(i8* byval)
+; CHECK: declare void @ParamAttr6(i8* byval(i8))
 declare void @ParamAttr6(i8* byval)
 ; CHECK: declare void @ParamAttr7(i8* noalias)
 declare void @ParamAttr7(i8* noalias)
 ; CHECK: declare void @ParamAttr8(i8* nocapture)
 declare void @ParamAttr8(i8* nocapture)
 ; CHECK: declare void @ParamAttr9{{[(i8* nest noalias nocapture) | (i8* noalias nocapture nest)]}}
 declare void @ParamAttr9(i8* nest noalias nocapture)
 ; CHECK: declare void @ParamAttr10{{[(i8* sret noalias nocapture) | (i8* noalias nocapture sret)]}}
 declare void @ParamAttr10(i8* sret noalias nocapture)
-;CHECK: declare void @ParamAttr11{{[(i8* byval noalias nocapture) | (i8* noalias nocapture byval)]}}
+;CHECK: declare void @ParamAttr11{{[(i8* byval(i8) noalias nocapture) | (i8* noalias nocapture byval(i8))]}}
 declare void @ParamAttr11(i8* byval noalias nocapture)
 ;CHECK: declare void @ParamAttr12{{[(i8* inreg noalias nocapture) | (i8* noalias nocapture inreg)]}}
 declare void @ParamAttr12(i8* inreg noalias nocapture)
 
 
 ; NamedTypesTest
 define void @NamedTypes() {
 entry:

llvm/test/CodeGen/AArch64/byval-type.ll

+; RUN: llc -mtriple=aarch64-linux-gnu %s -o - | FileCheck %s
+
+define i8 @byval_match(i8* byval(i8) align 1, i8* byval %ptr) {
+; CHECK-LABEL: byval_match:
+; CHECK: ldrb w0, [sp, #8]
+  %res = load i8, i8* %ptr
+  ret i8 %res
+}
+
+define void @caller_match(i8* %p0, i8* %p1) {
+; CHECK-LABEL: caller_match:
+; CHECK: ldrb [[P1:w[0-9]+]], [x1]
+; CHECK: strb [[P1]], [sp, #8]
+; CHECK: ldrb [[P0:w[0-9]+]], [x0]
+; CHECK: strb [[P0]], [sp]
+; CHECK: bl byval_match
+  call i8 @byval_match(i8* byval(i8) align 1 %p0, i8* byval %p1)
+  ret void
+}
+
+define i8 @byval_large([3 x i64]* byval([3 x i64]) align 8, i8* byval %ptr) {
+; CHECK-LABEL: byval_large:
+; CHECK: ldrb w0, [sp, #24]
+  %res = load i8, i8* %ptr
+  ret i8 %res
+}
+
+define void @caller_large([3 x i64]* %p0, i8* %p1) {
+; CHECK-LABEL: caller_large:
+; CHECK: ldr [[P0HI:x[0-9]+]], [x0, #16]
+; CHECK: ldr [[P0LO:q[0-9]+]], [x0]
+; CHECK: str [[P0HI]], [sp, #16]
+; CHECK: str [[P0LO]], [sp]
+; CHECK: bl byval_large
+  call i8 @byval_large([3 x i64]* byval([3 x i64]) align 8 %p0, i8* byval %p1)
+  ret void
+}

llvm/test/Transforms/Inline/byval-tail-call.ll

define void @bar2(i32* byval %x) {
   ret void
 }
 
 define void @foobar(i32* %x) {
 ; CHECK-LABEL: define void @foobar(
 ; CHECK: %[[POS:.*]] = alloca i32
 ; CHECK: %[[VAL:.*]] = load i32, i32* %x
 ; CHECK: store i32 %[[VAL]], i32* %[[POS]]
-; CHECK: tail call void @ext2(i32* byval nonnull %[[POS]]
+; CHECK: tail call void @ext2(i32* nonnull byval %[[POS]]
 ; CHECK: ret void
   tail call void @bar2(i32* byval %x)
   ret void
 }
 
 define void @barfoo() {
 ; CHECK-LABEL: define void @barfoo(
 ; CHECK: %[[POS:.*]] = alloca i32
 ; CHECK: %[[VAL:.*]] = load i32, i32* %x
 ; CHECK: store i32 %[[VAL]], i32* %[[POS]]
-; CHECK: tail call void @ext2(i32* byval nonnull %[[POS]]
+; CHECK: tail call void @ext2(i32* nonnull byval %[[POS]]
 ; CHECK: ret void
   %x = alloca i32
   tail call void @bar2(i32* byval %x)
   ret void
 }

llvm/unittests/IR/AttributesTest.cpp

 //===- llvm/unittest/IR/AttributesTest.cpp - Attributes unit tests --------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/DerivedTypes.h"
 #include "gtest/gtest.h"
 using namespace llvm;
 
 namespace {
 
 TEST(Attributes, Uniquing) {
   LLVMContext C;
 

 TEST(Attributes, OverflowGet) {
   LLVMContext C;
   std::pair<unsigned, Attribute> Attrs[] = { { AttributeList::ReturnIndex, Attribute::get(C, Attribute::SExt) },
                                              { AttributeList::FunctionIndex, Attribute::get(C, Attribute::ReadOnly) } };
   AttributeList AL = AttributeList::get(C, Attrs);
   EXPECT_EQ(2U, AL.getNumAttrSets());
 }
 
+TEST(Attributes, StringRepresentation) {
+  LLVMContext C;
+  StructType *Ty = StructType::create(Type::getInt32Ty(C), "mystruct");
+
+  // Insufficiently careful printing can result in byval(%mystruct = { i32 })
+  Attribute A = Attribute::getWithByValType(C, Ty);
+  EXPECT_EQ(A.getAsString(), "byval(%mystruct)");
+
+  A = Attribute::getWithByValType(C, nullptr);
+  EXPECT_EQ(A.getAsString(), "byval");
+
+  A = Attribute::getWithByValType(C, Type::getInt32Ty(C));
+  EXPECT_EQ(A.getAsString(), "byval(i32)");
+}
+
 } // end anonymous namespace