[X86][AsmParser] re-introduce 'offset' operator

[epastor]

Summary

Amend MS offset operator implementation, to more closely fit with its MS counterpart:

1. InlineAsm: evaluate non-local source entities to their (address) location
2. Provide a mean with which one may acquire the address of an assembly label via MS syntax, rather than yielding a memory reference (i.e. "offset asm_label" and "$asm_label" should be synonymous
3. address PR32530

Based on http://llvm.org/D37461

Fix broken test where the break appears unrelated.

• Set up appropriate memory-input rewrites for variable references.

• Intel-dialect assembly printing now correctly handles addresses by adding "offset".

• Pass offsets as immediate operands (using "r" constraint for offsets of locals).

[epastor]

Note: this currently breaks several test cases, at least some of which are valid.

Example: (minimized from ms-inline-asm-redundant-clobber.ll)
call void asm inteldialect "cmpxchg8b $0", "=*m"(i32* @Bar)
previously emitted
cmpxchg8b Bar(%rip)
and now (after the change to X86AsmPrinter.cpp) emits

<inline asm>:2:29: error: unknown token in expression
        cmpxchg8b [rip + offset Bar]
                                   ^

I'm not sure how to fix this... but among other problems, it seems we've ended up emitting offset even when emitting AT&T-syntax assembly. (The same error occurs if we pass -x86-asm-syntax=intel, too.) This appears to affect all indirect memory operands.

EDIT: This was a bad interpretation; the issue was that the operand was expanded into an inteldialect Intel expression, and the offset was immediately followed by ']'. Making offset legal before ']' and ')' fixes that problem.

[epastor]

• Allow offsets at the end of parenthesized expressions

[epastor]

Remaining test failures include:

call void asm sideeffect inteldialect "lea edi, dword ptr $0", "*m,~{edi},~{dirflag},~{fpsr},~{flags}"([2 x i32]* @results) nounwind
previously expanded as
lea edi, dword ptr [_results]
and now expands as
lea edi, dword ptr [offset _results]
This may be correct.

In C & C++,
__asm mov [eax], offset var
is now ambiguous, since "offset var" is not aliased directly to a pointer-sized register. I think this is technically correct, but I don't think I should make that decision without input.

[epastor]

• Fix tests expecting use of 'r' constraints for offset operands

[epastor]

• Fix Intel named operator parsing

[merge_guards_bot]

Unit tests: fail. 60824 tests passed, 4 failed and 726 were skipped.

failed: Clang.CodeGen/ms-inline-asm-64.c
failed: Clang.CodeGen/ms-inline-asm.c
failed: Clang.SemaTemplate/instantiation-depth-default.cpp
failed: LLVM.CodeGen/X86/ms-inline-asm.ll

clang-format: pass.

Build artifacts: console-log.txt, CMakeCache.txt, test-results.xml, diff.json

[epastor]

• Respect correct usage of offset.
• Don't assume implicit sizing on offset.
• Check that offset works in compound expressions.

[merge_guards_bot]

Unit tests: pass. 60854 tests passed, 0 failed and 726 were skipped.

clang-format: fail. Please format your changes with clang-format by running git-clang-format HEAD^ or apply this patch.

Build artifacts: console-log.txt, CMakeCache.txt, clang-format.patch, test-results.xml, diff.json

[epastor]

• Apply formatting fixes where reasonable

[merge_guards_bot]

Unit tests: pass. 60854 tests passed, 0 failed and 726 were skipped.

clang-format: fail. Please format your changes with clang-format by running git-clang-format HEAD^ or apply this patch.

Build artifacts: diff.json, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

[rnk]

Thanks! I made some comments. This code is convoluted. I don't think I can reason through all the edge cases, but this seems like an improvement. I'd suggest adding the recommended tests and any other corner case inputs you can think of, and after another round of review we can land it.

clang/test/CodeGen/ms-inline-asm-64.c

18

I guess this has the same semantics as it did before.

llvm/include/llvm/MC/MCParser/MCTargetAsmParser.h

74

These explicit empty StringRef initializations seem unnecessary, I'd suggest removing them.

99–100

nit, pack the bool after the unsigned for a smaller struct. Hey, we make a vector of these. :)

llvm/lib/MC/MCParser/AsmParser.cpp

5938–5943

Maybe this would be simpler with

auto rewrite_it = find_if(it, AsmStrRewrites.end(), [&](const AsmRewrite &OffsetAR) {
  // ... conditions below
});

llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp

1481

While this doesn't trigger warnings, it seems like it would be simpler to do the assignment as its own statement and then if (ParseErrror) return true;

I see that the local code style uses this pattern already, but I'm not sure that's a good reason to promote it and keep using it.

1484

ditto

1823

Please test this corner case, I imagine it looks like:

mov eax, offset 3

1827

Please add a test for this corner case, I'm curious to see if the error reporting really works.

[epastor]

• Address refactoring comments

[epastor]

Thanks for feedback!

clang/test/CodeGen/ms-inline-asm-64.c

18

It does; this previously resolved to a "qword ptr" mov automatically, since $0 unpacked as a (forced) 64-bit register name. Now we need to specify the size of the move, since the operand is an immediate rather than a register.

llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp

1823

Interesting. This corner case didn't trigger in that scenario; we get an "expected identifier" error message with good source location, followed by another error "use of undeclared label '3'" in debug builds... and in release builds, we instead get a crash. On tracing the crash, it's a AsmStrRewrite applying to a SMLoc not coming from the same string...

As near as I can tell, the issue is that we end up trying to parse "3" as a not-yet-declared label, as such expand it to __MSASMLABEL_.${:uid}__3, and then end up in a bad state because the operand rewrite is applying to the expanded symbol... which isn't in the same AsmString. If you use an actual undeclared label, you hit the same crash in release builds.

This is going to take some work; I'll get back to it in a day or two.

1827

This error reporting doesn't work, in fact. We instead get "cannot take the address of an rvalue of type 'int'", with bad source location. Will investigate why we end up there.

[merge_guards_bot]

Unit tests: pass. 60854 tests passed, 0 failed and 726 were skipped.

clang-tidy: fail. Please fix clang-tidy findings.

clang-format: fail. Please format your changes with clang-format by running git-clang-format HEAD^ or applying this patch.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

[epastor]

Fix issues around enum values and labels

• Only rewrite variables as offset operands; fixes crash due to conflicting rewrites for labels
• Recognize inline assembly references to enum values

llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp

1823

Fixed; we now get the same errors in this scenario as we do in the current LLVM trunk, reporting "expected identifier" and "use of undeclared label '3'".

On the other hand, I'm still working on finding a scenario that DOES trigger this corner case.

1827

Turns out Sema wasn't successfully recognizing inline-assembly references to enum values, so we were processing them through as labels, and only recognizing the problem late in processing. Fixed now, with accurate error reporting; test added.

[epastor]

• Removing accidental artifacts of local testing...

[merge_guards_bot]

Unit tests: unknown.

clang-tidy: fail. Please fix clang-tidy findings.

clang-format: fail. Please format your changes with clang-format by running git-clang-format HEAD^ or applying this patch.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt

[merge_guards_bot]

Unit tests: pass. 60854 tests passed, 0 failed and 726 were skipped.

clang-tidy: fail. Please fix clang-tidy findings.

clang-format: fail. Please format your changes with clang-format by running git-clang-format HEAD^ or applying this patch.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

[rnk]

lgtm, thanks!

llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp

1823

I see. Well, it sounds like it was a useful test. :)

[epastor]

Rebase on top of HEAD

• Add compatibility with dc5b614fa9a1 (which changed handling for call operands in x86 assembly)
• Remove another artifact of local testing

[epastor]

• Fix a few final issues.
  • Pack the AsmRewrite struct more optimally.
  • Only check if we can fuse rewrites with ones we haven't already reached!

llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp

1823

Very useful indeed!

[merge_guards_bot]

Unit tests: pass. 61144 tests passed, 0 failed and 728 were skipped.

clang-tidy: fail. Please fix clang-tidy findings.

clang-format: fail. Please format your changes with clang-format by running git-clang-format HEAD^ or applying this patch.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

[merge_guards_bot]

Unit tests: unknown.

clang-tidy: fail. Please fix clang-tidy findings.

clang-format: fail. Please format your changes with clang-format by running git-clang-format HEAD^ or applying this patch.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt

[epastor]

• The three-argument version of find_if is std::find_if, and the qualification is required.

[merge_guards_bot]

Unit tests: pass. 61144 tests passed, 0 failed and 728 were skipped.

clang-tidy: fail. Please fix clang-tidy findings.

clang-format: fail. Please format your changes with clang-format by running git-clang-format HEAD^ or applying this patch.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

clang/lib/Sema/SemaStmtAsm.cpp

 
 void Sema::FillInlineAsmIdentifierInfo(Expr *Res,
                                        llvm::InlineAsmIdentifierInfo &Info) {
   QualType T = Res->getType();
   Expr::EvalResult Eval;
   if (T->isFunctionType() || T->isDependentType())
     return Info.setLabel(Res);
   if (Res->isRValue()) {
-    if (isa<clang::EnumType>(T) && Res->EvaluateAsRValue(Eval, Context))
+    bool IsEnum = isa<clang::EnumType>(T);
+    if (DeclRefExpr *DRE = dyn_cast<clang::DeclRefExpr>(Res))
+      if (DRE->getDecl()->getKind() == Decl::EnumConstant)
+        IsEnum = true;
+    if (IsEnum && Res->EvaluateAsRValue(Eval, Context))
       return Info.setEnum(Eval.Val.getInt().getSExtValue());
+
     return Info.setLabel(Res);
   }
   unsigned Size = Context.getTypeSizeInChars(T).getQuantity();
   unsigned Type = Size;
   if (const auto *ATy = Context.getAsArrayType(T))
     Type = Context.getTypeSizeInChars(ATy->getElementType()).getQuantity();
   bool IsGlobalLV = false;
   if (Res->EvaluateAsLValue(Eval, Context))

clang/test/CodeGen/ms-inline-asm-64.c

 // REQUIRES: x86-registered-target
 // RUN: %clang_cc1 %s -triple x86_64-apple-darwin10 -fasm-blocks -emit-llvm -o - | FileCheck %s
 
 void t1() {
   int var = 10;
   __asm mov rax, offset var ; rax = address of myvar
 // CHECK: t1
 // CHECK: call void asm sideeffect inteldialect
 // CHECK-SAME: mov rax, $0
 // CHECK-SAME: "r,~{rax},~{dirflag},~{fpsr},~{flags}"(i32* %{{.*}})
 }
 
 void t2() {
   int var = 10;
-  __asm mov [eax], offset var
+  __asm mov qword ptr [eax], offset var
 // CHECK: t2
 // CHECK: call void asm sideeffect inteldialect
-// CHECK-SAME: mov [eax], $0
+// CHECK-SAME: mov qword ptr [eax], $0
 // CHECK-SAME: "r,~{dirflag},~{fpsr},~{flags}"(i32* %{{.*}})
 }
 
 struct t3_type { int a, b; };
 
 int t3() {
   struct t3_type foo;
   foo.a = 1;

clang/test/CodeGen/ms-inline-asm.c

 // CHECK: t15
   int lvar = 10;
   __asm mov eax, lvar        ; eax = 10
 // CHECK: mov eax, $0
   __asm mov eax, offset lvar ; eax = address of lvar
 // CHECK: mov eax, $1
   __asm mov eax, offset gvar ; eax = address of gvar
 // CHECK: mov eax, $2
-// CHECK: "*m,r,r,~{eax},~{dirflag},~{fpsr},~{flags}"(i32* %{{.*}}, i32* %{{.*}}, i32* @{{.*}})
+  __asm mov eax, offset gvar+1 ; eax = 1 + address of gvar
+// CHECK: mov eax, $3 + $$1
+  __asm mov eax, 1+offset gvar ; eax = 1 + address of gvar
+// CHECK: mov eax, $4 + $$1
+  __asm mov eax, 1+offset gvar+1 ; eax = 2 + address of gvar
+// CHECK: mov eax, $5 + $$2
+// CHECK: "*m,r,i,i,i,i,~{eax},~{dirflag},~{fpsr},~{flags}"(i32* %{{.*}}, i32* %{{.*}}, i32* @{{.*}}, i32* @{{.*}}, i32* @{{.*}}, i32* @{{.*}})
 }
 
 void t16() {
   int var = 10;
-  __asm mov [eax], offset var
+  __asm mov dword ptr [eax], offset var
 // CHECK: t16
-// CHECK: call void asm sideeffect inteldialect "mov [eax], $0", "r,~{dirflag},~{fpsr},~{flags}"(i32* %{{.*}})
+// CHECK: call void asm sideeffect inteldialect "mov dword ptr [eax], $0", "r,~{dirflag},~{fpsr},~{flags}"(i32* %{{.*}})
 }
 
 void t17() {
 // CHECK: t17
   __asm _emit 0x4A
 // CHECK: .byte 0x4A
   __asm _emit 0x43L
 // CHECK: .byte 0x43L

clang/test/CodeGen/ms-inline-asm.cpp

 void t2() {
   int lvar = 10;
   __asm mov eax, offset Foo::ptr
   __asm mov eax, offset Foo::Bar::ptr
 // CHECK-LABEL: define void @_Z2t2v()
 // CHECK: call void asm sideeffect inteldialect
 // CHECK-SAME: mov eax, $0
 // CHECK-SAME: mov eax, $1
-// CHECK-SAME: "r,r,~{eax},~{dirflag},~{fpsr},~{flags}"(i32** @_ZN3Foo3ptrE, i32** @_ZN3Foo3Bar3ptrE)
+// CHECK-SAME: "i,i,~{eax},~{dirflag},~{fpsr},~{flags}"(i32** @_ZN3Foo3ptrE, i32** @_ZN3Foo3Bar3ptrE)
 }
 
 // CHECK-LABEL: define void @_Z2t3v()
 void t3() {
   __asm mov eax, LENGTH Foo::ptr
   __asm mov eax, LENGTH Foo::Bar::ptr
   __asm mov eax, LENGTH Foo::arr
   __asm mov eax, LENGTH Foo::Bar::arr

clang/test/Parser/ms-inline-asm.c

 }
 void t12() {
   __asm jmp label // expected-error {{use of undeclared label 'label'}}
 }
 void t13() {
   __asm m{o}v eax, ebx // expected-error {{unknown token in expression}}
 }
 
+void t14() {
+  enum { A = 1, B };
+  __asm mov eax, offset A // expected-error {{offset operator cannot yet handle constants}}
+}
+
 int t_fail() { // expected-note {{to match this}}
   __asm 
   __asm { // expected-error 3 {{expected}} expected-note {{to match this}}

llvm/include/llvm/MC/MCParser/MCParsedAsmOperand.h

public:
   /// needAddressOf - Do we need to emit code to get the address of the
   /// variable/label?   Only valid when parsing MS-style inline assembly.
   virtual bool needAddressOf() const { return false; }
 
   /// isCallOperand - Is this an operand of an inline-assembly call instruction?
   /// Only valid when parsing MS-style inline assembly.
   virtual bool isCallOperand() const { return false; }
 
-  /// isOffsetOf - Do we need to emit code to get the offset of the variable,
-  /// rather then the value of the variable?   Only valid when parsing MS-style
-  /// inline assembly.
-  virtual bool isOffsetOf() const { return false; }
+  /// isOffsetOfLocal - Do we need to emit code to get the offset of the local
+  /// variable, rather than its value?   Only valid when parsing MS-style inline
+  /// assembly.
+  virtual bool isOffsetOfLocal() const { return false; }
 
   /// getOffsetOfLoc - Get the location of the offset operator.
   virtual SMLoc getOffsetOfLoc() const { return SMLoc(); }
 
   /// print - Print a debug representation of the operand to the given stream.
   virtual void print(raw_ostream &OS) const = 0;
 
   /// dump - Print to the debug stream.

llvm/include/llvm/MC/MCParser/MCTargetAsmParser.h

 
 // Represnt the various parts which makes up an intel expression,
 // used for emitting compound intel expressions
 struct IntelExpr {
   bool NeedBracs;
   int64_t Imm;
   StringRef BaseReg;
   StringRef IndexReg;
+  StringRef OffsetName;
   unsigned Scale;
 
-  IntelExpr(bool needBracs = false) : NeedBracs(needBracs), Imm(0),
-    BaseReg(StringRef()), IndexReg(StringRef()),
-    Scale(1) {}
-  // Compund immediate expression
-  IntelExpr(int64_t imm, bool needBracs) : IntelExpr(needBracs) {
-    Imm = imm;
-  }
-  // [Reg + ImmediateExpression]
-  // We don't bother to emit an immediate expression evaluated to zero
-  IntelExpr(StringRef reg, int64_t imm = 0, unsigned scale = 0,
-    bool needBracs = true) :
-    IntelExpr(imm, needBracs) {
-    IndexReg = reg;
+  IntelExpr()
+      : NeedBracs(false), Imm(0), BaseReg(StringRef()), IndexReg(StringRef()),
+        OffsetName(StringRef()), Scale(1) {}
+  // [BaseReg + IndexReg * ScaleExpression + OFFSET name + ImmediateExpression]
+  IntelExpr(StringRef baseReg, StringRef indexReg, unsigned scale,
+            StringRef offsetName, int64_t imm, bool needBracs)
+      : NeedBracs(needBracs), Imm(imm), BaseReg(baseReg), IndexReg(indexReg),
+        OffsetName(offsetName), Scale(1) {
     if (scale)
       Scale = scale;
   }
-  // [BaseReg + IndexReg * ScaleExpression + ImmediateExpression]
-  IntelExpr(StringRef baseReg, StringRef indexReg, unsigned scale = 0,
-    int64_t imm = 0, bool needBracs = true) :
-    IntelExpr(indexReg, imm, scale, needBracs) {
-    BaseReg = baseReg;
-  }
-  bool hasBaseReg() const {
-    return BaseReg.size();
-  }
-  bool hasIndexReg() const {
-    return IndexReg.size();
-  }
-  bool hasRegs() const {
-    return hasBaseReg() || hasIndexReg();
-  }
+  bool hasBaseReg() const { return !BaseReg.empty(); }
+  bool hasIndexReg() const { return !IndexReg.empty(); }
+  bool hasRegs() const { return hasBaseReg() || hasIndexReg(); }
+  bool hasOffset() const { return !OffsetName.empty(); }
+  // Normally we won't emit immediates unconditionally,
+  // unless we've got no other components
+  bool emitImm() const { return !(hasRegs() || hasOffset()); }
   bool isValid() const {
     return (Scale == 1) ||
            (hasIndexReg() && (Scale == 2 || Scale == 4 || Scale == 8));
   }
 };
 
 struct AsmRewrite {
   AsmRewriteKind Kind;
   SMLoc Loc;
   unsigned Len;
+  bool Done;
   int64_t Val;
   StringRef Label;
   IntelExpr IntelExp;
 
 public:
   AsmRewrite(AsmRewriteKind kind, SMLoc loc, unsigned len = 0, int64_t val = 0)
-    : Kind(kind), Loc(loc), Len(len), Val(val) {}
+    : Kind(kind), Loc(loc), Len(len), Done(false), Val(val) {}
   AsmRewrite(AsmRewriteKind kind, SMLoc loc, unsigned len, StringRef label)
     : AsmRewrite(kind, loc, len) { Label = label; }
   AsmRewrite(SMLoc loc, unsigned len, IntelExpr exp)
     : AsmRewrite(AOK_IntelExpr, loc, len) { IntelExp = exp; }
 };
 
 struct ParseInstructionInfo {
   SmallVectorImpl<AsmRewrite> *AsmRewrites = nullptr;

llvm/lib/MC/MCParser/AsmParser.cpp

if (Info.Opcode == ~0U)
       continue;
 
     const MCInstrDesc &Desc = MII->get(Info.Opcode);
 
     // Build the list of clobbers, outputs and inputs.
     for (unsigned i = 1, e = Info.ParsedOperands.size(); i != e; ++i) {
       MCParsedAsmOperand &Operand = *Info.ParsedOperands[i];
 
-      // Immediate.
-      if (Operand.isImm())
-        continue;
-
       // Register operand.
       if (Operand.isReg() && !Operand.needAddressOf() &&
           !getTargetParser().OmitRegisterFromClobberLists(Operand.getReg())) {
         unsigned NumDefs = Desc.getNumDefs();
         // Clobber.
         if (NumDefs && Operand.getMCOperandNum() < NumDefs)
           ClobberRegs.push_back(Operand.getReg());
         continue;
       }
 
       // Expr/Input or Output.
       StringRef SymName = Operand.getSymName();
       if (SymName.empty())
         continue;
 
       void *OpDecl = Operand.getOpDecl();
       if (!OpDecl)
         continue;
 
+      StringRef Constraint = Operand.getConstraint();
+      if (Operand.isImm()) {
+        // Offset as immediate
+        if (Operand.isOffsetOfLocal())
+          Constraint = "r";
+        else
+          Constraint = "i";
+      }
+
       bool isOutput = (i == 1) && Desc.mayStore();
       SMLoc Start = SMLoc::getFromPointer(SymName.data());
       if (isOutput) {
         ++InputIdx;
         OutputDecls.push_back(OpDecl);
         OutputDeclsAddressOf.push_back(Operand.needAddressOf());
-        OutputConstraints.push_back(("=" + Operand.getConstraint()).str());
+        OutputConstraints.push_back(("=" + Constraint).str());
         AsmStrRewrites.emplace_back(AOK_Output, Start, SymName.size());
       } else {
         InputDecls.push_back(OpDecl);
         InputDeclsAddressOf.push_back(Operand.needAddressOf());
-        InputConstraints.push_back(Operand.getConstraint().str());
+        InputConstraints.push_back(Constraint.str());
         if (Operand.isCallOperand())
           AsmStrRewrites.emplace_back(AOK_CallInput, Start, SymName.size());
         else
           AsmStrRewrites.emplace_back(AOK_Input, Start, SymName.size());
       }
     }
 
     // Consider implicit defs to be clobbers.  Think of cpuid and push.
bool AsmParser::parseMSInlineAsm(
   // Build the IR assembly string.
   std::string AsmStringIR;
   raw_string_ostream OS(AsmStringIR);
   StringRef ASMString =
       SrcMgr.getMemoryBuffer(SrcMgr.getMainFileID())->getBuffer();
   const char *AsmStart = ASMString.begin();
   const char *AsmEnd = ASMString.end();
   array_pod_sort(AsmStrRewrites.begin(), AsmStrRewrites.end(), rewritesSort);
-  for (const AsmRewrite &AR : AsmStrRewrites) {
+  for (auto it = AsmStrRewrites.begin(); it != AsmStrRewrites.end(); ++it) {
+    const AsmRewrite &AR = *it;
+    // Check if this has already been covered by another rewrite...
+    if (AR.Done)
+      continue;
     AsmRewriteKind Kind = AR.Kind;
 
     const char *Loc = AR.Loc.getPointer();
     assert(Loc >= AsmStart && "Expected Loc to be at or after Start!");
 
     // Emit everything up to the immediate/expression.
     if (unsigned Len = Loc - AsmStart)
       OS << StringRef(AsmStart, Len);
case AOK_IntelExpr:
       if (AR.IntelExp.NeedBracs)
         OS << "[";
       if (AR.IntelExp.hasBaseReg())
         OS << AR.IntelExp.BaseReg;
       if (AR.IntelExp.hasIndexReg())
         OS << (AR.IntelExp.hasBaseReg() ? " + " : "")
            << AR.IntelExp.IndexReg;
       if (AR.IntelExp.Scale > 1)
-          OS << " * $$" << AR.IntelExp.Scale;
-      if (AR.IntelExp.Imm || !AR.IntelExp.hasRegs())
-        OS << (AR.IntelExp.hasRegs() ? " + $$" : "$$") << AR.IntelExp.Imm;
+      if (AR.IntelExp.hasOffset()) {
+        if (AR.IntelExp.hasRegs())
+          OS << " + ";
+        // Fuse this rewrite with a rewrite of the offset name, if present.
+        StringRef OffsetName = AR.IntelExp.OffsetName;
+        SMLoc OffsetLoc = SMLoc::getFromPointer(AR.IntelExp.OffsetName.data());
+        size_t OffsetLen = OffsetName.size();
+        auto rewrite_it = std::find_if(
+            it, AsmStrRewrites.end(), [&](const AsmRewrite &FusingAR) {
+              return FusingAR.Loc == OffsetLoc && FusingAR.Len == OffsetLen &&
+                     (FusingAR.Kind == AOK_Input ||
+                      FusingAR.Kind == AOK_CallInput);
+            });
+        if (rewrite_it == AsmStrRewrites.end()) {
+          OS << "offset " << OffsetName;
+        } else if (rewrite_it->Kind == AOK_CallInput) {
+          OS << "${" << InputIdx++ << ":P}";
+          rewrite_it->Done = true;
+        } else {
+          OS << '$' << InputIdx++;
+          rewrite_it->Done = true;
+        }
+      }
+      if (AR.IntelExp.Imm || AR.IntelExp.emitImm())
+        OS << (AR.IntelExp.emitImm() ? "$$" : " + $$") << AR.IntelExp.Imm;
       if (AR.IntelExp.NeedBracs)
         OS << "]";
       break;
     case AOK_Label:
       OS << Ctx.getAsmInfo()->getPrivateLabelPrefix() << AR.Label;
       break;
     case AOK_Input:
       OS << '$' << InputIdx++;

llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp

enum InfixCalculatorTok {
     IC_REGISTER
   };
 
   enum IntelOperatorKind {
     IOK_INVALID = 0,
     IOK_LENGTH,
     IOK_SIZE,
     IOK_TYPE,
-    IOK_OFFSET
   };
 
   class InfixCalculator {
     typedef std::pair< InfixCalculatorTok, int64_t > ICToken;
     SmallVector<InfixCalculatorTok, 4> InfixOperatorStack;
     SmallVector<ICToken, 4> PostfixStack;
 
     bool isUnaryOperator(const InfixCalculatorTok Op) {
enum IntelExprState {
     IES_INIT,
     IES_OR,
     IES_XOR,
     IES_AND,
     IES_LSHIFT,
     IES_RSHIFT,
     IES_PLUS,
     IES_MINUS,
+    IES_OFFSET,
     IES_NOT,
     IES_MULTIPLY,
     IES_DIVIDE,
     IES_MOD,
     IES_LBRAC,
     IES_RBRAC,
     IES_LPAREN,
     IES_RPAREN,
     IES_REGISTER,
     IES_INTEGER,
     IES_IDENTIFIER,
     IES_ERROR
   };
 
   class IntelExprStateMachine {
     IntelExprState State, PrevState;
     unsigned BaseReg, IndexReg, TmpReg, Scale;
     int64_t Imm;
     const MCExpr *Sym;
     StringRef SymName;
     InfixCalculator IC;
     InlineAsmIdentifierInfo Info;
     short BracCount;
     bool MemExpr;
+    bool OffsetOperator;
+    SMLoc OffsetOperatorLoc;
+
+    bool setSymRef(const MCExpr *Val, StringRef ID, StringRef &ErrMsg) {
+      if (Sym) {
+        ErrMsg = "cannot use more than one symbol in memory operand";
+        return true;
+      }
+      Sym = Val;
+      SymName = ID;
+      return false;
+    }
 
   public:
     IntelExprStateMachine()
         : State(IES_INIT), PrevState(IES_ERROR), BaseReg(0), IndexReg(0),
           TmpReg(0), Scale(0), Imm(0), Sym(nullptr), BracCount(0),
-          MemExpr(false) {}
+          MemExpr(false), OffsetOperator(false) {}
 
     void addImm(int64_t imm) { Imm += imm; }
     short getBracCount() { return BracCount; }
     bool isMemExpr() { return MemExpr; }
+    bool isOffsetOperator() { return OffsetOperator; }
+    SMLoc getOffsetLoc() { return OffsetOperatorLoc; }
     unsigned getBaseReg() { return BaseReg; }
     unsigned getIndexReg() { return IndexReg; }
     unsigned getScale() { return Scale; }
     const MCExpr *getSym() { return Sym; }
     StringRef getSymName() { return SymName; }
     int64_t getImm() { return Imm + IC.execute(); }
     bool isValidEndState() {
       return State == IES_RBRAC || State == IES_INTEGER;
bool onPlus(StringRef &ErrMsg) {
       IntelExprState CurrState = State;
       switch (State) {
       default:
         State = IES_ERROR;
         break;
       case IES_INTEGER:
       case IES_RPAREN:
       case IES_REGISTER:
+      case IES_OFFSET:
         State = IES_PLUS;
         IC.pushOperator(IC_PLUS);
         if (CurrState == IES_REGISTER && PrevState != IES_MULTIPLY) {
           // If we already have a BaseReg, then assume this is the IndexReg with
           // no explicit scale.
           if (!BaseReg) {
             BaseReg = TmpReg;
           } else {
bool onMinus(StringRef &ErrMsg) {
       case IES_MOD:
       case IES_LPAREN:
       case IES_RPAREN:
       case IES_LBRAC:
       case IES_RBRAC:
       case IES_INTEGER:
       case IES_REGISTER:
       case IES_INIT:
+      case IES_OFFSET:
         State = IES_MINUS;
         // push minus operator if it is not a negate operator
         if (CurrState == IES_REGISTER || CurrState == IES_RPAREN ||
-            CurrState == IES_INTEGER  || CurrState == IES_RBRAC)
+            CurrState == IES_INTEGER  || CurrState == IES_RBRAC  ||
+            CurrState == IES_OFFSET)
           IC.pushOperator(IC_MINUS);
         else if (PrevState == IES_REGISTER && CurrState == IES_MULTIPLY) {
           // We have negate operator for Scale: it's illegal
           ErrMsg = "Scale can't be negative";
           return true;
         } else
           IC.pushOperator(IC_NEG);
         if (CurrState == IES_REGISTER && PrevState != IES_MULTIPLY) {
void onNot() {
       case IES_LBRAC:
       case IES_INIT:
         State = IES_NOT;
         IC.pushOperator(IC_NOT);
         break;
       }
       PrevState = CurrState;
     }
-
     bool onRegister(unsigned Reg, StringRef &ErrMsg) {
       IntelExprState CurrState = State;
       switch (State) {
       default:
         State = IES_ERROR;
         break;
       case IES_PLUS:
       case IES_LPAREN:
bool onIdentifierExpr(const MCExpr *SymRef, StringRef SymRefName,
       // InlineAsm: Treat an enum value as an integer
       if (ParsingInlineAsm)
         if (IDInfo.isKind(InlineAsmIdentifierInfo::IK_EnumVal))
           return onInteger(IDInfo.Enum.EnumVal, ErrMsg);
       // Treat a symbolic constant like an integer
       if (auto *CE = dyn_cast<MCConstantExpr>(SymRef))
         return onInteger(CE->getValue(), ErrMsg);
       PrevState = State;
-      bool HasSymbol = Sym != nullptr;
       switch (State) {
       default:
         State = IES_ERROR;
         break;
       case IES_PLUS:
       case IES_MINUS:
       case IES_NOT:
       case IES_INIT:
       case IES_LBRAC:
+        if (setSymRef(SymRef, SymRefName, ErrMsg))
+          return true;
         MemExpr = true;
         State = IES_INTEGER;
-        Sym = SymRef;
-        SymName = SymRefName;
         IC.pushOperand(IC_IMM);
         if (ParsingInlineAsm)
           Info = IDInfo;
         break;
       }
-      if (HasSymbol)
-        ErrMsg = "cannot use more than one symbol in memory operand";
-      return HasSymbol;
+      return false;
     }
     bool onInteger(int64_t TmpInt, StringRef &ErrMsg) {
       IntelExprState CurrState = State;
       switch (State) {
       default:
         State = IES_ERROR;
         break;
       case IES_PLUS:
public:
     }
     bool onRBrac() {
       IntelExprState CurrState = State;
       switch (State) {
       default:
         State = IES_ERROR;
         break;
       case IES_INTEGER:
+      case IES_OFFSET:
       case IES_REGISTER:
       case IES_RPAREN:
         if (BracCount-- != 1)
           return true;
         State = IES_RBRAC;
         if (CurrState == IES_REGISTER && PrevState != IES_MULTIPLY) {
           // If we already have a BaseReg, then assume this is the IndexReg with
           // no explicit scale.
public:
     }
     void onRParen() {
       PrevState = State;
       switch (State) {
       default:
         State = IES_ERROR;
         break;
       case IES_INTEGER:
+      case IES_OFFSET:
       case IES_REGISTER:
       case IES_RPAREN:
         State = IES_RPAREN;
         IC.pushOperator(IC_RPAREN);
         break;
       }
     }
+    bool onOffset(const MCExpr *Val, SMLoc OffsetLoc, StringRef ID,
+                  const InlineAsmIdentifierInfo &IDInfo, bool ParsingInlineAsm,
+                  StringRef &ErrMsg) {
+      PrevState = State;
+      switch (State) {
+      default:
+        ErrMsg = "unexpected offset operator expression";
+        return true;
+      case IES_PLUS:
+      case IES_INIT:
+      case IES_LBRAC:
+        if (setSymRef(Val, ID, ErrMsg))
+          return true;
+        OffsetOperator = true;
+        OffsetOperatorLoc = OffsetLoc;
+        State = IES_OFFSET;
+        // As we cannot yet resolve the actual value (offset), we retain
+        // the requested semantics by pushing a '0' to the operands stack
+        IC.pushOperand(IC_IMM);
+        if (ParsingInlineAsm) {
+          Info = IDInfo;
+        }
+        break;
+      }
+      return false;
+    }
   };
 
   bool Error(SMLoc L, const Twine &Msg, SMRange Range = None,
              bool MatchingInlineAsm = false) {
     MCAsmParser &Parser = getParser();
     if (MatchingInlineAsm) {
       if (!getLexer().isAtStartOfStatement())
         Parser.eatToEndOfStatement();
private:
   AddDefaultSrcDestOperands(OperandVector &Operands,
                             std::unique_ptr<llvm::MCParsedAsmOperand> &&Src,
                             std::unique_ptr<llvm::MCParsedAsmOperand> &&Dst);
   bool VerifyAndAdjustOperands(OperandVector &OrigOperands,
                                OperandVector &FinalOperands);
   std::unique_ptr<X86Operand> ParseOperand();
   std::unique_ptr<X86Operand> ParseATTOperand();
   std::unique_ptr<X86Operand> ParseIntelOperand();
-  std::unique_ptr<X86Operand> ParseIntelOffsetOfOperator();
+  bool ParseIntelOffsetOperator(const MCExpr *&Val, StringRef &ID,
+                                InlineAsmIdentifierInfo &Info, SMLoc &End);
   bool ParseIntelDotOperator(IntelExprStateMachine &SM, SMLoc &End);
   unsigned IdentifyIntelInlineAsmOperator(StringRef Name);
   unsigned ParseIntelInlineAsmOperator(unsigned OpKind);
   std::unique_ptr<X86Operand> ParseRoundingModeOp(SMLoc Start);
-  bool ParseIntelNamedOperator(StringRef Name, IntelExprStateMachine &SM);
+  bool ParseIntelNamedOperator(StringRef Name, IntelExprStateMachine &SM,
+                               bool &ParseError, SMLoc &End);
   void RewriteIntelExpression(IntelExprStateMachine &SM, SMLoc Start,
                               SMLoc End);
   bool ParseIntelExpression(IntelExprStateMachine &SM, SMLoc &End);
   bool ParseIntelInlineAsmIdentifier(const MCExpr *&Val, StringRef &Identifier,
                                      InlineAsmIdentifierInfo &Info,
-                                     bool IsUnevaluatedOperand, SMLoc &End);
+                                     bool IsUnevaluatedOperand, SMLoc &End,
+                                     bool IsParsingOffsetOperator = false);
 
   std::unique_ptr<X86Operand> ParseMemOperand(unsigned SegReg,
                                               const MCExpr *&Disp,
                                               const SMLoc &StartLoc,
                                               SMLoc &EndLoc);
 
   X86::CondCode ParseConditionCode(StringRef CCode);
 
return X86Operand::CreateMem(getPointerWidth(), SegReg, Disp, BaseReg,
                                  IndexReg, Scale, Start, End, Size, Identifier,
                                  Decl, FrontendSize);
   }
 }
 
 // Some binary bitwise operators have a named synonymous
 // Query a candidate string for being such a named operator
 // and if so - invoke the appropriate handler
-bool X86AsmParser::ParseIntelNamedOperator(StringRef Name, IntelExprStateMachine &SM) {
+bool X86AsmParser::ParseIntelNamedOperator(StringRef Name,
+                                           IntelExprStateMachine &SM,
+                                           bool &ParseError, SMLoc &End) {
   // A named operator should be either lower or upper case, but not a mix
   if (Name.compare(Name.lower()) && Name.compare(Name.upper()))
     return false;
-  if (Name.equals_lower("not"))
+  if (Name.equals_lower("not")) {
     SM.onNot();
-  else if (Name.equals_lower("or"))
+  } else if (Name.equals_lower("or")) {
     SM.onOr();
-  else if (Name.equals_lower("shl"))
+  } else if (Name.equals_lower("shl")) {
     SM.onLShift();
-  else if (Name.equals_lower("shr"))
+  } else if (Name.equals_lower("shr")) {
     SM.onRShift();
-  else if (Name.equals_lower("xor"))
+  } else if (Name.equals_lower("xor")) {
     SM.onXor();
-  else if (Name.equals_lower("and"))
+  } else if (Name.equals_lower("and")) {
     SM.onAnd();
-  else if (Name.equals_lower("mod"))
+  } else if (Name.equals_lower("mod")) {
     SM.onMod();
-  else
+  } else if (Name.equals_lower("offset")) {
+    SMLoc OffsetLoc = getTok().getLoc();
+    const MCExpr *Val = nullptr;
+    StringRef ID;
+    InlineAsmIdentifierInfo Info;
+    ParseError = ParseIntelOffsetOperator(Val, ID, Info, End);
+    if (ParseError)
+      return true;
+    StringRef ErrMsg;
+    ParseError =
+        SM.onOffset(Val, OffsetLoc, ID, Info, isParsingInlineAsm(), ErrMsg);
+    if (ParseError)
+      return Error(SMLoc::getFromPointer(Name.data()), ErrMsg);
+  } else {
     return false;
+  }
+  if (!Name.equals_lower("offset"))
+    End = consumeToken();
   return true;
 }
 
 bool X86AsmParser::ParseIntelExpression(IntelExprStateMachine &SM, SMLoc &End) {
   MCAsmParser &Parser = getParser();
   const AsmToken &Tok = Parser.getTok();
   StringRef ErrMsg;
 
case AsmToken::Identifier: {
       // Register
       unsigned Reg;
       if (Tok.is(AsmToken::Identifier) && !ParseRegister(Reg, IdentLoc, End)) {
         if (SM.onRegister(Reg, ErrMsg))
           return Error(Tok.getLoc(), ErrMsg);
         break;
       }
       // Operator synonymous ("not", "or" etc.)
-      if ((UpdateLocLex = ParseIntelNamedOperator(Identifier, SM)))
+      bool ParseError = false;
+      if (ParseIntelNamedOperator(Identifier, SM, ParseError, End)) {
+        if (ParseError)
+          return true;
         break;
+      }
       // Symbol reference, when parsing assembly content
       InlineAsmIdentifierInfo Info;
       const MCExpr *Val;
       if (!isParsingInlineAsm()) {
         if (getParser().parsePrimaryExpr(Val, End)) {
           return Error(Tok.getLoc(), "Unexpected identifier!");
         } else if (SM.onIdentifierExpr(Val, Identifier, Info, false, ErrMsg)) {
           return Error(IdentLoc, ErrMsg);
         } else
           break;
       }
       // MS InlineAsm operators (TYPE/LENGTH/SIZE)
       if (unsigned OpKind = IdentifyIntelInlineAsmOperator(Identifier)) {
-        if (OpKind == IOK_OFFSET)
-          return Error(IdentLoc, "Dealing OFFSET operator as part of"
-            "a compound immediate expression is yet to be supported");
         if (int64_t Val = ParseIntelInlineAsmOperator(OpKind)) {
           if (SM.onInteger(Val, ErrMsg))
             return Error(IdentLoc, ErrMsg);
         } else
           return true;
         break;
       }
       // MS Dot Operator expression
bool X86AsmParser::ParseIntelExpression(IntelExprStateMachine &SM, SMLoc &End) {
   return false;
 }
 
 void X86AsmParser::RewriteIntelExpression(IntelExprStateMachine &SM,
                                           SMLoc Start, SMLoc End) {
   SMLoc Loc = Start;
   unsigned ExprLen = End.getPointer() - Start.getPointer();
   // Skip everything before a symbol displacement (if we have one)
-  if (SM.getSym()) {
+  if (SM.getSym() && !SM.isOffsetOperator()) {
     StringRef SymName = SM.getSymName();
-    if (unsigned Len =  SymName.data() - Start.getPointer())
+    if (unsigned Len = SymName.data() - Start.getPointer())
       InstInfo->AsmRewrites->emplace_back(AOK_Skip, Start, Len);
     Loc = SMLoc::getFromPointer(SymName.data() + SymName.size());
     ExprLen = End.getPointer() - (SymName.data() + SymName.size());
     // If we have only a symbol than there's no need for complex rewrite,
     // simply skip everything after it
     if (!(SM.getBaseReg() || SM.getIndexReg() || SM.getImm())) {
       if (ExprLen)
         InstInfo->AsmRewrites->emplace_back(AOK_Skip, Loc, ExprLen);
       return;
     }
   }
   // Build an Intel Expression rewrite
   StringRef BaseRegStr;
   StringRef IndexRegStr;
+  StringRef OffsetNameStr;
   if (SM.getBaseReg())
     BaseRegStr = X86IntelInstPrinter::getRegisterName(SM.getBaseReg());
   if (SM.getIndexReg())
     IndexRegStr = X86IntelInstPrinter::getRegisterName(SM.getIndexReg());
+  if (SM.isOffsetOperator())
+    OffsetNameStr = SM.getSymName();
   // Emit it
-  IntelExpr Expr(BaseRegStr, IndexRegStr, SM.getScale(), SM.getImm(), SM.isMemExpr());
+  IntelExpr Expr(BaseRegStr, IndexRegStr, SM.getScale(), OffsetNameStr,
+                 SM.getImm(), SM.isMemExpr());
   InstInfo->AsmRewrites->emplace_back(Loc, ExprLen, Expr);
 }
 
 // Inline assembly may use variable names with namespace alias qualifiers.
-bool X86AsmParser::ParseIntelInlineAsmIdentifier(const MCExpr *&Val,
-                                                 StringRef &Identifier,
-                                                 InlineAsmIdentifierInfo &Info,
-                                                 bool IsUnevaluatedOperand,
-                                                 SMLoc &End) {
+bool X86AsmParser::ParseIntelInlineAsmIdentifier(
+    const MCExpr *&Val, StringRef &Identifier, InlineAsmIdentifierInfo &Info,
+    bool IsUnevaluatedOperand, SMLoc &End, bool IsParsingOffsetOperator) {
   MCAsmParser &Parser = getParser();
   assert(isParsingInlineAsm() && "Expected to be parsing inline assembly.");
   Val = nullptr;
 
   StringRef LineBuf(Identifier.data());
   SemaCallback->LookupInlineAsmIdentifier(LineBuf, Info, IsUnevaluatedOperand);
 
   const AsmToken &Tok = Parser.getTok();
bool X86AsmParser::ParseIntelInlineAsmIdentifier(
 
   // If the identifier lookup was unsuccessful, assume that we are dealing with
   // a label.
   if (Info.isKind(InlineAsmIdentifierInfo::IK_Invalid)) {
     StringRef InternalName =
       SemaCallback->LookupInlineAsmLabel(Identifier, getSourceManager(),
                                          Loc, false);
     assert(InternalName.size() && "We should have an internal name here.");
-    // Push a rewrite for replacing the identifier name with the internal name.
+    // Push a rewrite for replacing the identifier name with the internal name,
+    // unless we are parsing the operand of an offset operator
+    if (!IsParsingOffsetOperator)
       InstInfo->AsmRewrites->emplace_back(AOK_Label, Loc, Identifier.size(),
                                           InternalName);
+    else
+      Identifier = InternalName;
   } else if (Info.isKind(InlineAsmIdentifierInfo::IK_EnumVal))
     return false;
   // Create the symbol reference.
   MCSymbol *Sym = getContext().getOrCreateSymbol(Identifier);
   MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
   Val = MCSymbolRefExpr::create(Sym, Variant, getParser().getContext());
   return false;
 }
bool X86AsmParser::ParseIntelDotOperator(IntelExprStateMachine &SM, SMLoc &End) {
   End = SMLoc::getFromPointer(DotDispStr.data());
   const char *DotExprEndLoc = DotDispStr.data() + DotDispStr.size();
   while (Tok.getLoc().getPointer() < DotExprEndLoc)
     Lex();
   SM.addImm(Offset);
   return false;
 }
 
-/// Parse the 'offset' operator.  This operator is used to specify the
-/// location rather then the content of a variable.
-std::unique_ptr<X86Operand> X86AsmParser::ParseIntelOffsetOfOperator() {
-  MCAsmParser &Parser = getParser();
-  const AsmToken &Tok = Parser.getTok();
-  SMLoc OffsetOfLoc = Tok.getLoc();
-  Parser.Lex(); // Eat offset.
-
-  const MCExpr *Val;
-  InlineAsmIdentifierInfo Info;
-  SMLoc Start = Tok.getLoc(), End;
-  StringRef Identifier = Tok.getString();
-  if (ParseIntelInlineAsmIdentifier(Val, Identifier, Info,
-                                    /*Unevaluated=*/false, End))
-    return nullptr;
-
-  void *Decl = nullptr;
-  // FIXME: MS evaluates "offset <Constant>" to the underlying integral
-  if (Info.isKind(InlineAsmIdentifierInfo::IK_EnumVal))
-    return ErrorOperand(Start, "offset operator cannot yet handle constants");
-  else if (Info.isKind(InlineAsmIdentifierInfo::IK_Var))
-    Decl = Info.Var.Decl;
-  // Don't emit the offset operator.
-  InstInfo->AsmRewrites->emplace_back(AOK_Skip, OffsetOfLoc, 7);
-
-  // The offset operator will have an 'r' constraint, thus we need to create
-  // register operand to ensure proper matching.  Just pick a GPR based on
-  // the size of a pointer.
-  bool Parse32 = is32BitMode() || Code16GCC;
-  unsigned RegNo = is64BitMode() ? X86::RBX : (Parse32 ? X86::EBX : X86::BX);
-
-  return X86Operand::CreateReg(RegNo, Start, End, /*GetAddress=*/true,
-                               OffsetOfLoc, Identifier, Decl);
+/// Parse the 'offset' operator.
+/// This operator is used to specify the location of a given operand
+bool X86AsmParser::ParseIntelOffsetOperator(const MCExpr *&Val, StringRef &ID,
+                                            InlineAsmIdentifierInfo &Info,
+                                            SMLoc &End) {
+  // Eat offset, mark start of identifier.
+  SMLoc Start = Lex().getLoc();
+  ID = getTok().getString();
+  if (!isParsingInlineAsm()) {
+    if ((getTok().isNot(AsmToken::Identifier) &&
+         getTok().isNot(AsmToken::String)) ||
+        getParser().parsePrimaryExpr(Val, End))
+      return Error(Start, "unexpected token!");
+  } else if (ParseIntelInlineAsmIdentifier(Val, ID, Info, false, End, true)) {
+    return Error(Start, "unable to lookup expression");
+  } else if (Info.isKind(InlineAsmIdentifierInfo::IK_EnumVal)) {
+    return Error(Start, "offset operator cannot yet handle constants");
+  }
+  return false;
 }
 
 // Query a candidate string for being an Intel assembly operator
 // Report back its kind, or IOK_INVALID if does not evaluated as a known one
 unsigned X86AsmParser::IdentifyIntelInlineAsmOperator(StringRef Name) {
   return StringSwitch<unsigned>(Name)
     .Cases("TYPE","type",IOK_TYPE)
     .Cases("SIZE","size",IOK_SIZE)
     .Cases("LENGTH","length",IOK_LENGTH)
-    .Cases("OFFSET","offset",IOK_OFFSET)
     .Default(IOK_INVALID);
 }
 
 /// Parse the 'LENGTH', 'TYPE' and 'SIZE' operators.  The LENGTH operator
 /// returns the number of elements in an array.  It returns the value 1 for
 /// non-array variables.  The SIZE operator returns the size of a C or C++
 /// variable.  A variable's size is the product of its LENGTH and TYPE.  The
 /// TYPE operator returns the size of a C or C++ type or variable. If the
bool X86AsmParser::ParseIntelMemoryOperandSize(unsigned &Size) {
   return false;
 }
 
 std::unique_ptr<X86Operand> X86AsmParser::ParseIntelOperand() {
   MCAsmParser &Parser = getParser();
   const AsmToken &Tok = Parser.getTok();
   SMLoc Start, End;
 
-  // FIXME: Offset operator
-  // Should be handled as part of immediate expression, as other operators
-  // Currently, only supported as a stand-alone operand
-  if (isParsingInlineAsm())
-    if (IdentifyIntelInlineAsmOperator(Tok.getString()) == IOK_OFFSET)
-      return ParseIntelOffsetOfOperator();
-
   // Parse optional Size directive.
   unsigned Size;
   if (ParseIntelMemoryOperandSize(Size))
     return nullptr;
   bool PtrInOperand = bool(Size);
 
   Start = Tok.getLoc();
 
std::unique_ptr<X86Operand> X86AsmParser::ParseIntelOperand() {
   const MCExpr *ImmDisp = MCConstantExpr::create(Imm, getContext());
   if (Disp && Imm)
     Disp = MCBinaryExpr::createAdd(Disp, ImmDisp, getContext());
   if (!Disp)
     Disp = ImmDisp;
 
   // RegNo != 0 specifies a valid segment register,
   // and we are parsing a segment override
-  if (!SM.isMemExpr() && !RegNo)
+  if (!SM.isMemExpr() && !RegNo) {
+    if (isParsingInlineAsm() && SM.isOffsetOperator()) {
+      const InlineAsmIdentifierInfo Info = SM.getIdentifierInfo();
+      if (Info.isKind(InlineAsmIdentifierInfo::IK_Var)) {
+        // Disp includes the address of a variable; make sure this is recorded
+        // for later handling.
+        return X86Operand::CreateImm(Disp, Start, End, SM.getSymName(),
+                                     Info.Var.Decl, Info.Var.IsGlobalLV);
+      }
+    }
+
     return X86Operand::CreateImm(Disp, Start, End);
+  }
 
   StringRef ErrMsg;
   unsigned BaseReg = SM.getBaseReg();
   unsigned IndexReg = SM.getIndexReg();
   unsigned Scale = SM.getScale();
 
   if (Scale == 0 && BaseReg != X86::ESP && BaseReg != X86::RSP &&
       (IndexReg == X86::ESP || IndexReg == X86::RSP))

llvm/lib/Target/X86/AsmParser/X86Operand.h

struct X86Operand final : public MCParsedAsmOperand {
   };
 
   struct PrefOp {
     unsigned Prefixes;
   };
 
   struct ImmOp {
     const MCExpr *Val;
+    bool LocalRef;
   };
 
   struct MemOp {
     unsigned SegReg;
     const MCExpr *Disp;
     unsigned BaseReg;
     unsigned IndexReg;
     unsigned Scale;
bool isImmUnsignedi8() const {
     if (!isImm()) return false;
     // If this isn't a constant expr, just assume it fits and let relaxation
     // handle it.
     const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(getImm());
     if (!CE) return true;
     return isImmUnsignedi8Value(CE->getValue());
   }
 
-  bool isOffsetOf() const override {
-    return OffsetOfLoc.getPointer();
-  }
+  bool isOffsetOfLocal() const override { return isImm() && Imm.LocalRef; }
 
-  bool needAddressOf() const override {
-    return AddressOf;
-  }
+  bool needAddressOf() const override { return AddressOf; }
 
   bool isCallOperand() const override { return CallOperand; }
   void setCallOperand(bool IsCallOperand) { CallOperand = IsCallOperand; }
 
   bool isMem() const override { return Kind == Memory; }
   bool isMemUnsized() const {
     return Kind == Memory && Mem.Size == 0;
   }
struct X86Operand final : public MCParsedAsmOperand {
   static std::unique_ptr<X86Operand>
   CreatePrefix(unsigned Prefixes, SMLoc StartLoc, SMLoc EndLoc) {
     auto Res = std::make_unique<X86Operand>(Prefix, StartLoc, EndLoc);
     Res->Pref.Prefixes = Prefixes;
     return Res;
   }
 
   static std::unique_ptr<X86Operand> CreateImm(const MCExpr *Val,
-                                               SMLoc StartLoc, SMLoc EndLoc) {
+                                               SMLoc StartLoc, SMLoc EndLoc,
+                                               StringRef SymName = StringRef(),
+                                               void *OpDecl = nullptr,
+                                               bool GlobalRef = true) {
     auto Res = std::make_unique<X86Operand>(Immediate, StartLoc, EndLoc);
-    Res->Imm.Val = Val;
+    Res->Imm.Val      = Val;
+    Res->Imm.LocalRef = !GlobalRef;
+    Res->SymName      = SymName;
+    Res->OpDecl       = OpDecl;
+    Res->AddressOf    = true;
     return Res;
   }
 
   /// Create an absolute memory operand.
   static std::unique_ptr<X86Operand>
   CreateMem(unsigned ModeSize, const MCExpr *Disp, SMLoc StartLoc, SMLoc EndLoc,
             unsigned Size = 0, StringRef SymName = StringRef(),
             void *OpDecl = nullptr, unsigned FrontendSize = 0) {

llvm/lib/Target/X86/X86AsmPrinter.cpp

void X86AsmPrinter::PrintOperand(const MachineInstr *MI, unsigned OpNo,
   case MachineOperand::MO_Immediate:
     if (IsATT)
       O << '$';
     O << MO.getImm();
     return;
 
   case MachineOperand::MO_ConstantPoolIndex:
   case MachineOperand::MO_GlobalAddress: {
-    if (IsATT)
+    switch (MI->getInlineAsmDialect()) {
+    default:
+      llvm_unreachable("unknown assembly dialect!");
+    case InlineAsm::AD_ATT:
       O << '$';
+      break;
+    case InlineAsm::AD_Intel:
+      O << "offset ";
+      break;
+    }
     PrintSymbolOperand(MO, O);
     break;
   }
   case MachineOperand::MO_BlockAddress: {
     MCSymbol *Sym = GetBlockAddressSymbol(MO.getBlockAddress());
     Sym->print(O, MAI);
     break;
   }

llvm/test/CodeGen/X86/ms-inline-asm.ll

entry:
   %res = alloca i32*, align 4
   call void asm sideeffect inteldialect "lea edi, dword ptr $0", "*m,~{edi},~{dirflag},~{fpsr},~{flags}"([2 x i32]* @results) nounwind
   call void asm sideeffect inteldialect "mov dword ptr $0, edi", "=*m,~{dirflag},~{fpsr},~{flags}"(i32** %res) nounwind
   %0 = load i32*, i32** %res, align 4
   ret i32* %0
 ; CHECK-LABEL: t30:
 ; CHECK: {{## InlineAsm Start|#APP}}
 ; CHECK: .intel_syntax
-; CHECK: lea edi, dword ptr [{{_?}}results]
+; CHECK: lea edi, dword ptr [offset {{_?}}results]
 ; CHECK: .att_syntax
 ; CHECK: {{## InlineAsm End|#NO_APP}}
 ; CHECK: {{## InlineAsm Start|#APP}}
 ; CHECK: .intel_syntax
 ; CHECK: mov dword ptr [esp], edi
 ; CHECK: .att_syntax
 ; CHECK: {{## InlineAsm End|#NO_APP}}
 ; CHECK: movl (%esp), %eax

llvm/test/CodeGen/X86/offset-operator.ll

+; RUN: llc -mtriple=x86_64-unknown-linux-gnu -x86-asm-syntax=intel -relocation-model=static < %s | FileCheck %s
+
+; Test we are emitting the 'offset' operator upon an immediate reference of a label:
+; The emitted 'att-equivalent' of this one is "movl $.L.str, %eax"
+
+@.str = private unnamed_addr constant [1 x i8] zeroinitializer, align 1
+
+define i8* @test_offset_operator() {
+; CHECK-LABEL: test_offset_operator:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    mov eax, offset .L.str
+; CHECK-NEXT:    ret
+entry:
+  ret i8* getelementptr inbounds ([1 x i8], [1 x i8]* @.str, i64 0, i64 0)
+}

llvm/test/MC/X86/pr32530.s

+// RUN: llvm-mc -triple x86_64-unknown-unknown -x86-asm-syntax=intel %s | FileCheck %s
+
+.text
+// CHECK: movq    $msg, %rsi
+// CHECK: movq    $msg+314159, %rax
+// CHECK: movq    $msg-89793, msg-6535(%rax,%rbx,2)
+  mov rsi,  offset msg
+  mov rax,  offset "msg" + 314159
+  mov qword ptr [rax + 2*rbx + offset msg - 6535],  offset msg - 89793
+.data
+msg:
+  .ascii "Hello, world!\n"
+