LTO: Use the correct mangler function in LTOCodeGenerator::applyScopeRestrictions().

[pcc]

Summary

We need to use the overload of Mangler::getNameWithPrefix that takes a
GlobalValue in order to mangle in the stdcall stack byte count for Windows
targets.

[mehdi_amini]

LGTM. Thanks!

llvm/lib/LTO/LTOCodeGenerator.cpp

425 ↗

(On Diff #74418)

Can you add the comment for the bool: Mang.getNameWithPrefix(MangledName, &GV, /* CannotUsePrivateLabel */ false) ?

[mehdi_amini]

Out of curiosity: how did you find this?

[pcc]

The COFF port of LLD uses the legacy LTOCodeGenerator, at least for now. @hans found this while building Chromium with LLD and LTO (crbug.com/655125).

llvm/trunk/lib/LTO/LTOCodeGenerator.cpp

 }
 
 void LTOCodeGenerator::applyScopeRestrictions() {
   if (ScopeRestrictionsDone)
     return;
 
   // Declare a callback for the internalize pass that will ask for every
   // candidate GlobalValue if it can be internalized or not.
+  Mangler Mang;
   SmallString<64> MangledName;
   auto mustPreserveGV = [&](const GlobalValue &GV) -> bool {
     // Unnamed globals can't be mangled, but they can't be preserved either.
     if (!GV.hasName())
       return false;
 
     // Need to mangle the GV as the "MustPreserveSymbols" StringSet is filled
     // with the linker supplied name, which on Darwin includes a leading
     // underscore.
     MangledName.clear();
     MangledName.reserve(GV.getName().size() + 1);
-    Mangler::getNameWithPrefix(MangledName, GV.getName(),
-                               MergedModule->getDataLayout());
+    Mang.getNameWithPrefix(MangledName, &GV, /*CannotUsePrivateLabel=*/false);
     return MustPreserveSymbols.count(MangledName);
   };
 
   // Preserve linkonce value on linker request
   preserveDiscardableGVs(*MergedModule, mustPreserveGV);
 
   if (!ShouldInternalize)
     return;

llvm/trunk/test/LTO/X86/stdcall.ll

+; RUN: llvm-as < %s > %t
+; RUN: llvm-lto -exported-symbol=_DllMain@12 -filetype=asm -o - %t | FileCheck %s
+
+target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
+target triple = "i386-pc-windows-msvc19.0.23918"
+
+; CHECK: .globl _DllMain@12
+define x86_stdcallcc i32 @DllMain(i8* %module, i32 %reason, i8* %reserved) {
+  ret i32 1
+}