MS inline ASM: mark the function noinline if the asm has labels (PR23715)

[hans]

Summary

This avoids defining the same label twice if the function gets inlined.

It's pretty hacky, but also very non-intrusive. (I also played with adding a flag on the MSAsmStmt and set that in ParseMicrosoftAsmStatement, but all that churn doesn't really buy us much.)

[rnk]

Looks terrible, please commit.

lib/CodeGen/CGStmt.cpp

2005

If this inline asm has labels, we should also add the noduplicate attribute to the callsite. That will prevent CFG transforms like tail duplication from duplicating it.

[majnemer]

lib/CodeGen/CGStmt.cpp

2005

Actually, isn't noduplicate sufficient? I'm having trouble seeing where noinline inhibits problematic transforms over noduplicate.

[rsmith]

test/CodeGen/ms-inline-asm.c

536

Why is this not a CHECK-LABEL any more?

[hans]

lib/CodeGen/CGStmt.cpp

2005

You're right. I'll just do that.

test/CodeGen/ms-inline-asm.c

536

FileCheck got upset:
error: found 'CHECK-LABEL:' with variable definition or use

lib/CodeGen/CGStmt.cpp

if (isa<MSAsmStmt>(&S)) {
     if (RetAI.isDirect() || RetAI.isExtend()) {
       // Make a fake lvalue for the return value slot.
       LValue ReturnSlot = MakeAddrLValue(ReturnValue, FnRetTy);
       CGM.getTargetCodeGenInfo().addReturnRegisterOutputs(
           *this, ReturnSlot, Constraints, ResultRegTypes, ResultTruncRegTypes,
           ResultRegDests, AsmString, S.getNumOutputs());
       SawAsmBlock = true;
     }
+
+    // If the assembly contains any labels, mark the function noinline. Inlining
+    // it could cause the callee to contain the same ASM label twice (PR23715).
+    // This is pretty hacky, but it works.
+    if (AsmString.find("__MSASMLABEL_") != std::string::npos)
+      CurFn->addFnAttr(llvm::Attribute::NoInline);
   }
 
   for (unsigned i = 0, e = S.getNumInputs(); i != e; i++) {
     const Expr *InputExpr = S.getInputExpr(i);
 
     TargetInfo::ConstraintInfo &Info = InputConstraintInfos[i];
 
     if (Info.allowsMemory())
llvm::FunctionType *FTy =
     llvm::FunctionType::get(ResultType, ArgTypes, false);
 
   bool HasSideEffect = S.isVolatile() || S.getNumOutputs() == 0;
   llvm::InlineAsm::AsmDialect AsmDialect = isa<MSAsmStmt>(&S) ?
     llvm::InlineAsm::AD_Intel : llvm::InlineAsm::AD_ATT;
   llvm::InlineAsm *IA =
     llvm::InlineAsm::get(FTy, AsmString, Constraints, HasSideEffect,
                          /* IsAlignStack */ false, AsmDialect);
   llvm::CallInst *Result = Builder.CreateCall(IA, Args);
   Result->addAttribute(llvm::AttributeSet::FunctionIndex,
                        llvm::Attribute::NoUnwind);
 
   // Attach readnone and readonly attributes.
   if (!HasSideEffect) {
     if (ReadNone)
       Result->addAttribute(llvm::AttributeSet::FunctionIndex,
                            llvm::Attribute::ReadNone);

test/CodeGen/ms-inline-asm.c

 // CHECK-LABEL: define void @xgetbv()
 // CHECK: call void asm sideeffect inteldialect "xgetbv", "~{eax},~{edx},~{dirflag},~{fpsr},~{flags}"()
 
 void label1() {
   __asm {
     label:
     jmp label
   }
-  // CHECK-LABEL: define void @label1
+  // CHECK: define void @label1() [[ATTR1:#[0-9]+]] {
   // CHECK: call void asm sideeffect inteldialect "{{.*}}__MSASMLABEL_.1__label:\0A\09jmp {{.*}}__MSASMLABEL_.1__label", "~{dirflag},~{fpsr},~{flags}"()
 }
 
 void label2() {
   __asm {
     jmp label
     label:
   }
typedef union _LARGE_INTEGER {
   unsigned long long QuadPart;
 } LARGE_INTEGER, *PLARGE_INTEGER;
 
 int test_indirect_field(LARGE_INTEGER LargeInteger) {
     __asm mov     eax, LargeInteger.LowPart
 }
 // CHECK-LABEL: define i32 @test_indirect_field(
 // CHECK: call i32 asm sideeffect inteldialect "mov eax, dword ptr $1",
+
+// Functions with inline asm containing labels should be noinline (PR23715)
+// CHECK: attributes [[ATTR1]] = { {{.*}}noinline{{.*}} }