Remove references to the 4.0 release as a major breaking (NFC)

[mehdi_amini]

Summary

This is cleaning up comments (mostly in the bitcode handling) about
removing some backward compatibility aspect in the 4.0 release.
Historically, "4.0" was used during the development of the 3.x
versions as "this future major breaking change version". At the time
the major number was used to indicate the compatibility. When we
reached 3.9 we decided to change the numbering, instead of going to
3.10 we went to 4.0 but after changing the meaning of the major
number to not mean anything anymore with respect to bitcode backward
compatibility.

The current policy
(https://llvm.org/docs/DeveloperPolicy.html#ir-backwards-compatibility)
indicates only now:

The current LLVM version supports loading any bitcode since version 3.0.

[echristo]

Do we want to actually do the breaking release?

Alternately we should probably use the deprecated part on DataLayout as well :)

-eric

[mehdi_amini]

In D82514#2113111, @echristo wrote:

Do we want to actually do the breaking release?

I don't think so?

Alternately we should probably use the deprecated part on DataLayout as well :)

I didn't quite get that?

[echristo]

In D82514#2113178, @mehdi_amini wrote:

In D82514#2113111, @echristo wrote:

Do we want to actually do the breaking release?

I don't think so?

I didn't either, but thought I'd ask :)

Alternately we should probably use the deprecated part on DataLayout as well :)

I didn't quite get that?

Oh, you removed a fixme in DataLayout.cpp.

[dexonsmith]

This LGTM, assuming @echristo is happy.

llvm/lib/IR/DataLayout.cpp

262–264

I think @echristo is suggesting updating this comment to match the new ones elsewhere ("Deprecated, but ...").

[echristo]

I'm happy with this as well - my only comment was the one Duncan pointed out :)

llvm/lib/IR/DataLayout.cpp

262–264

I was yes :)

[mehdi_amini]

llvm/lib/IR/DataLayout.cpp

262–264

Ah OK.

This isn't bitcode related though: we have a few occurrences of these in the LL parser as well that I didn't touch. I don't think there is a policy on these, what should I write? // Deprecated, but ignoring here to preserve loading older textual llvm ASM file ?

[echristo]

llvm/lib/IR/DataLayout.cpp

262–264

Works for me :)

llvm/docs/HowToUseAttributes.rst

 An ``AttributeList`` is also a uniqued and immutable object.  You create an
 ``AttributeList`` through the ``AttributeList::get`` methods.  You can add and
 remove attributes, which result in the creation of a new ``AttributeList``.
 
 An ``AttributeList`` object is designed to be passed around by value.
 
 Note: It is advised that you do *not* use the ``AttributeList`` "introspection"
 methods (e.g. ``Raw``, ``getRawPointer``, etc.).  These methods break
-encapsulation, and may be removed in a future release (i.e. LLVM 4.0).
+encapsulation, and may be removed in a future release.
 
 ``AttrBuilder``
 ===============
 
 Lastly, we have a "builder" class to help create the ``AttributeList`` object
 without having to create several different intermediate uniqued
 ``AttributeList`` objects.  The ``AttrBuilder`` class allows you to add and
 remove attributes at will.  The attributes won't be uniqued until you call the
 appropriate ``AttributeList::get`` method.
 
 An ``AttrBuilder`` object is *not* designed to be passed around by value.  It
 should be passed by reference.
 
 Note: It is advised that you do *not* use the ``AttrBuilder::addRawValue()``
 method or the ``AttrBuilder(uint64_t Val)`` constructor.  These are for
-backwards compatibility and may be removed in a future release (i.e. LLVM 4.0).
+backwards compatibility and may be removed in a future release.
 
 And that's basically it! A lot of functionality is hidden behind these classes,
 but the interfaces are pretty straight forward.
 

llvm/include/llvm/Bitcode/LLVMBitCodes.h

 /// MODULE blocks have a number of optional fields and subblocks.
 enum ModuleCodes {
   MODULE_CODE_VERSION = 1,     // VERSION:     [version#]
   MODULE_CODE_TRIPLE = 2,      // TRIPLE:      [strchr x N]
   MODULE_CODE_DATALAYOUT = 3,  // DATALAYOUT:  [strchr x N]
   MODULE_CODE_ASM = 4,         // ASM:         [strchr x N]
   MODULE_CODE_SECTIONNAME = 5, // SECTIONNAME: [strchr x N]
 
-  // FIXME: Remove DEPLIB in 4.0.
+  // Deprecated, but still needed to read old bitcode files.
   MODULE_CODE_DEPLIB = 6, // DEPLIB:      [strchr x N]
 
   // GLOBALVAR: [pointer type, isconst, initid,
   //             linkage, alignment, section, visibility, threadlocal]
   MODULE_CODE_GLOBALVAR = 7,
 
   // FUNCTION:  [type, callingconv, isproto, linkage, paramattrs, alignment,
   //             section, visibility, gc, unnamed_addr]
enum ModuleCodes {
   MODULE_CODE_HASH = 17,
 
   // IFUNC: [ifunc value type, addrspace, resolver val#, linkage, visibility]
   MODULE_CODE_IFUNC = 18,
 };
 
 /// PARAMATTR blocks have code for defining a parameter attribute set.
 enum AttributeCodes {
-  // FIXME: Remove `PARAMATTR_CODE_ENTRY_OLD' in 4.0
+  // Deprecated, but still needed to read old bitcode files.
   PARAMATTR_CODE_ENTRY_OLD = 1, // ENTRY: [paramidx0, attr0,
                                 //         paramidx1, attr1...]
   PARAMATTR_CODE_ENTRY = 2,     // ENTRY: [attrgrp0, attrgrp1, ...]
   PARAMATTR_GRP_CODE_ENTRY = 3  // ENTRY: [grpid, idx, attr0, attr1, ...]
 };
 
 /// TYPE blocks have codes for each type primitive they use.
 enum TypeCodes {

llvm/lib/Bitcode/Reader/BitcodeAnalyzer.cpp

case bitc::MODULE_BLOCK_ID:
     switch (CodeID) {
     default:
       return None;
       STRINGIFY_CODE(MODULE_CODE, VERSION)
       STRINGIFY_CODE(MODULE_CODE, TRIPLE)
       STRINGIFY_CODE(MODULE_CODE, DATALAYOUT)
       STRINGIFY_CODE(MODULE_CODE, ASM)
       STRINGIFY_CODE(MODULE_CODE, SECTIONNAME)
-      STRINGIFY_CODE(MODULE_CODE, DEPLIB) // FIXME: Remove in 4.0
+      STRINGIFY_CODE(MODULE_CODE, DEPLIB) // Deprecated, present in old bitcode
       STRINGIFY_CODE(MODULE_CODE, GLOBALVAR)
       STRINGIFY_CODE(MODULE_CODE, FUNCTION)
       STRINGIFY_CODE(MODULE_CODE, ALIAS)
       STRINGIFY_CODE(MODULE_CODE, GCNAME)
       STRINGIFY_CODE(MODULE_CODE, VSTOFFSET)
       STRINGIFY_CODE(MODULE_CODE, METADATA_VALUES_UNUSED)
       STRINGIFY_CODE(MODULE_CODE, SOURCE_FILENAME)
       STRINGIFY_CODE(MODULE_CODE, HASH)

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

static void addRawAttributeValue(AttrBuilder &B, uint64_t Val) {
   }
 }
 
 /// This fills an AttrBuilder object with the LLVM attributes that have
 /// been decoded from the given integer. This function must stay in sync with
 /// 'encodeLLVMAttributesForBitcode'.
 static void decodeLLVMAttributesForBitcode(AttrBuilder &B,
                                            uint64_t EncodedAttrs) {
-  // FIXME: Remove in 4.0.
-
   // The alignment is stored as a 16-bit raw value from bits 31--16.  We shift
   // the bits above 31 down by 11 bits.
   unsigned Alignment = (EncodedAttrs & (0xffffULL << 16)) >> 16;
   assert((!Alignment || isPowerOf2_32(Alignment)) &&
          "Alignment must be a power of two.");
 
   if (Alignment)
     B.addAlignmentAttr(Alignment);
while (true) {
     Record.clear();
     Expected<unsigned> MaybeRecord = Stream.readRecord(Entry.ID, Record);
     if (!MaybeRecord)
       return MaybeRecord.takeError();
     switch (MaybeRecord.get()) {
     default:  // Default behavior: ignore.
       break;
     case bitc::PARAMATTR_CODE_ENTRY_OLD: // ENTRY: [paramidx0, attr0, ...]
-      // FIXME: Remove in 4.0.
+      // Deprecated, but still needed to read old bitcode files.
       if (Record.size() & 1)
         return error("Invalid record");
 
       for (unsigned i = 0, e = Record.size(); i != e; i += 2) {
         AttrBuilder B;
         decodeLLVMAttributesForBitcode(B, Record[i+1]);
         Attrs.push_back(AttributeList::get(Context, Record[i], B));
       }
case bitc::TYPE_CODE_POINTER: { // POINTER: [pointee type] or
       ResultTy = getTypeByID(Record[0]);
       if (!ResultTy ||
           !PointerType::isValidElementType(ResultTy))
         return error("Invalid type");
       ResultTy = PointerType::get(ResultTy, AddressSpace);
       break;
     }
     case bitc::TYPE_CODE_FUNCTION_OLD: {
-      // FIXME: attrid is dead, remove it in LLVM 4.0
+      // Deprecated, but still needed to read old bitcode files.
       // FUNCTION: [vararg, attrid, retty, paramty x N]
       if (Record.size() < 3)
         return error("Invalid record");
       SmallVector<Type*, 8> ArgTys;
       for (unsigned i = 3, e = Record.size(); i != e; ++i) {
         if (Type *T = getTypeByID(Record[i]))
           ArgTys.push_back(T);
         else
case bitc::CST_CODE_CE_EXTRACTELT
         return error("Invalid record");
       Constant *Op0 = ValueList.getConstantFwdRef(Record[1], OpTy);
       Constant *Op1 = nullptr;
       if (Record.size() == 4) {
         Type *IdxTy = getTypeByID(Record[2]);
         if (!IdxTy)
           return error("Invalid record");
         Op1 = ValueList.getConstantFwdRef(Record[3], IdxTy);
-      } else // TODO: Remove with llvm 4.0
+      } else {
+        // Deprecated, but still needed to read old bitcode files.
         Op1 = ValueList.getConstantFwdRef(Record[2], Type::getInt32Ty(Context));
+      }
       if (!Op1)
         return error("Invalid record");
       V = ConstantExpr::getExtractElement(Op0, Op1);
       break;
     }
     case bitc::CST_CODE_CE_INSERTELT
         : { // CE_INSERTELT: [opval, opval, opty, opval]
       VectorType *OpTy = dyn_cast<VectorType>(CurTy);
       if (Record.size() < 3 || !OpTy)
         return error("Invalid record");
       Constant *Op0 = ValueList.getConstantFwdRef(Record[0], OpTy);
       Constant *Op1 = ValueList.getConstantFwdRef(Record[1],
                                                   OpTy->getElementType());
       Constant *Op2 = nullptr;
       if (Record.size() == 4) {
         Type *IdxTy = getTypeByID(Record[2]);
         if (!IdxTy)
           return error("Invalid record");
         Op2 = ValueList.getConstantFwdRef(Record[3], IdxTy);
-      } else // TODO: Remove with llvm 4.0
+      } else {
+        // Deprecated, but still needed to read old bitcode files.
         Op2 = ValueList.getConstantFwdRef(Record[2], Type::getInt32Ty(Context));
+      }
       if (!Op2)
         return error("Invalid record");
       V = ConstantExpr::getInsertElement(Op0, Op1, Op2);
       break;
     }
     case bitc::CST_CODE_CE_SHUFFLEVEC: { // CE_SHUFFLEVEC: [opval, opval, opval]
       VectorType *OpTy = dyn_cast<VectorType>(CurTy);
       if (Record.size() < 3 || !OpTy)
case bitc::CST_CODE_CE_CMP: {     // CE_CMP: [opty, opval, opval, pred]
 
       if (OpTy->isFPOrFPVectorTy())
         V = ConstantExpr::getFCmp(Record[3], Op0, Op1);
       else
         V = ConstantExpr::getICmp(Record[3], Op0, Op1);
       break;
     }
     // This maintains backward compatibility, pre-asm dialect keywords.
-    // FIXME: Remove with the 4.0 release.
+    // Deprecated, but still needed to read old bitcode files.
     case bitc::CST_CODE_INLINEASM_OLD: {
       if (Record.size() < 2)
         return error("Invalid record");
       std::string AsmStr, ConstrStr;
       bool HasSideEffects = Record[0] & 1;
       bool IsAlignStack = Record[0] >> 1;
       unsigned AsmStrSize = Record[1];
       if (2+AsmStrSize >= Record.size())
Error BitcodeReader::parseGlobalVarRecord(ArrayRef<uint64_t> Record) {
   std::string Section;
   if (Record[5]) {
     if (Record[5] - 1 >= SectionTable.size())
       return error("Invalid ID");
     Section = SectionTable[Record[5] - 1];
   }
   GlobalValue::VisibilityTypes Visibility = GlobalValue::DefaultVisibility;
   // Local linkage must have default visibility.
+  // auto-upgrade `hidden` and `protected` for old bitcode.
   if (Record.size() > 6 && !GlobalValue::isLocalLinkage(Linkage))
-    // FIXME: Change to an error if non-default in 4.0.
     Visibility = getDecodedVisibility(Record[6]);
 
   GlobalVariable::ThreadLocalMode TLM = GlobalVariable::NotThreadLocal;
   if (Record.size() > 7)
     TLM = getDecodedThreadLocalMode(Record[7]);
 
   GlobalValue::UnnamedAddr UnnamedAddr = GlobalValue::UnnamedAddr::None;
   if (Record.size() > 8)
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]);
   }
   // Local linkage must have default visibility.
+  // auto-upgrade `hidden` and `protected` for old bitcode.
   if (!Func->hasLocalLinkage())
-    // FIXME: Change to an error if non-default in 4.0.
     Func->setVisibility(getDecodedVisibility(Record[7]));
   if (Record.size() > 8 && Record[8]) {
     if (Record[8] - 1 >= GCTable.size())
       return error("Invalid ID");
     Func->setGC(GCTable[Record[8] - 1]);
   }
   GlobalValue::UnnamedAddr UnnamedAddr = GlobalValue::UnnamedAddr::None;
   if (Record.size() > 9)
if (BitCode == bitc::MODULE_CODE_ALIAS ||
     NewGA = GlobalAlias::create(Ty, AddrSpace, getDecodedLinkage(Linkage), Name,
                                 TheModule);
   else
     NewGA = GlobalIFunc::create(Ty, AddrSpace, getDecodedLinkage(Linkage), Name,
                                 nullptr, TheModule);
 
   assert(NewGA->getValueType() == flattenPointerTypes(FullTy) &&
          "Incorrect fully structured type provided for GlobalIndirectSymbol");
-  // Old bitcode files didn't have visibility field.
   // Local linkage must have default visibility.
+  // auto-upgrade `hidden` and `protected` for old bitcode.
   if (OpNum != Record.size()) {
     auto VisInd = OpNum++;
     if (!NewGA->hasLocalLinkage())
-      // FIXME: Change to an error if non-default in 4.0.
       NewGA->setVisibility(getDecodedVisibility(Record[VisInd]));
   }
   if (BitCode == bitc::MODULE_CODE_ALIAS ||
       BitCode == bitc::MODULE_CODE_ALIAS_OLD) {
     if (OpNum != Record.size())
       NewGA->setDLLStorageClass(getDecodedDLLStorageClass(Record[OpNum++]));
     else
       upgradeDLLImportExportLinkage(NewGA, Linkage);
while (true) {
     case bitc::MODULE_CODE_ASM: {  // ASM: [strchr x N]
       std::string S;
       if (convertToString(Record, 0, S))
         return error("Invalid record");
       TheModule->setModuleInlineAsm(S);
       break;
     }
     case bitc::MODULE_CODE_DEPLIB: {  // DEPLIB: [strchr x N]
-      // FIXME: Remove in 4.0.
+      // Deprecated, but still needed to read old bitcode files.
       std::string S;
       if (convertToString(Record, 0, S))
         return error("Invalid record");
       // Ignore value.
       break;
     }
     case bitc::MODULE_CODE_SECTIONNAME: {  // SECTIONNAME: [strchr x N]
       std::string S;

llvm/lib/Bitcode/Reader/MetadataLoader.cpp

for (unsigned i = 0; i != Size; ++i) {
       MDNode *MD = MetadataList.getMDNodeFwdRefOrNull(Record[i]);
       if (!MD)
         return error("Invalid named metadata: expect fwd ref to MDNode");
       NMD->addOperand(MD);
     }
     break;
   }
   case bitc::METADATA_OLD_FN_NODE: {
-    // FIXME: Remove in 4.0.
+    // Deprecated, but still needed to read old bitcode files.
     // This is a LocalAsMetadata record, the only type of function-local
     // metadata.
     if (Record.size() % 2 == 1)
       return error("Invalid record");
 
     // If this isn't a LocalAsMetadata record, we're dropping it.  This used
     // to be legal, but there's no upgrade path.
     auto dropRecord = [&] {
case bitc::METADATA_OLD_FN_NODE: {
 
     MetadataList.assignValue(
         LocalAsMetadata::get(ValueList.getValueFwdRef(Record[1], Ty)),
         NextMetadataNo);
     NextMetadataNo++;
     break;
   }
   case bitc::METADATA_OLD_NODE: {
-    // FIXME: Remove in 4.0.
+    // Deprecated, but still needed to read old bitcode files.
     if (Record.size() % 2 == 1)
       return error("Invalid record");
 
     unsigned Size = Record.size();
     SmallVector<Metadata *, 8> Elts;
     for (unsigned i = 0; i != Size; i += 2) {
       Type *Ty = getTypeByID(Record[i]);
       if (!Ty)

llvm/lib/IR/DataLayout.cpp

if (Tok == "ni") {
 
       continue;
     }
 
     char Specifier = Tok.front();
     Tok = Tok.substr(1);
 
     switch (Specifier) {
     case 's':
-      // Ignored for backward compatibility.
-      // FIXME: remove this on LLVM 4.0.
+      // Deprecated, but ignoring here to preserve loading older textual llvm
+      // ASM file
       break;
     case 'E':
       BigEndian = true;
       break;
     case 'e':
       BigEndian = false;
       break;
     case 'p': {