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 ↗

(On Diff #42353)

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 ↗

(On Diff #42353)

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 ↗

(On Diff #42353)

Why is this not a CHECK-LABEL any more?

[hans]

lib/CodeGen/CGStmt.cpp

2005 ↗

(On Diff #42353)

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

test/CodeGen/ms-inline-asm.c

536 ↗

(On Diff #42353)

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

cfe/trunk/lib/CodeGen/CGStmt.cpp

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);
 
+  if (isa<MSAsmStmt>(&S)) {
+    // If the assembly contains any labels, mark the call noduplicate to prevent
+    // defining the same ASM label twice (PR23715). This is pretty hacky, but it
+    // works.
+    if (AsmString.find("__MSASMLABEL_") != std::string::npos)
+      Result->addAttribute(llvm::AttributeSet::FunctionIndex,
+                           llvm::Attribute::NoDuplicate);
+  }
+
   // Attach readnone and readonly attributes.
   if (!HasSideEffect) {
     if (ReadNone)
       Result->addAttribute(llvm::AttributeSet::FunctionIndex,
                            llvm::Attribute::ReadNone);
     else if (ReadOnly)
       Result->addAttribute(llvm::AttributeSet::FunctionIndex,
                            llvm::Attribute::ReadOnly);

cfe/trunk/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: call void asm sideeffect inteldialect "{{.*}}__MSASMLABEL_.1__label:\0A\09jmp {{.*}}__MSASMLABEL_.1__label", "~{dirflag},~{fpsr},~{flags}"()
+  // CHECK-LABEL: define void @label1()
+  // CHECK: call void asm sideeffect inteldialect "{{.*}}__MSASMLABEL_.1__label:\0A\09jmp {{.*}}__MSASMLABEL_.1__label", "~{dirflag},~{fpsr},~{flags}"() [[ATTR1:#[0-9]+]]
 }
 
 void label2() {
   __asm {
     jmp label
     label:
   }
   // CHECK-LABEL: define void @label2
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",
+
+// MS ASM containing labels must not be duplicated (PR23715).
+// CHECK: attributes [[ATTR1]] = { {{.*}}noduplicate{{.*}} }