PDB shows wrong calling convention when compiling static functions on Windows x86

[momo5502]

Compiling the following sample for Windows x86 with -O3 shows that static_func will have fastcc applied to it:

static __declspec(noinline) int static_func(int arg1){
	
	return arg1 * 2;
}

int main(int argc, char* argv[]) {
	return static_func(argc);
}

https://godbolt.org/z/Pcroj66c4

The PDB however shows NearC, so cdecl, instead of FastCall.

The reason this happens is because GlobalOpt updates the CC, but not the debug info:

llvm-project/llvm/lib/Transforms/IPO/GlobalOpt.cpp

Line 2022 in aa8a1fa

F.setCallingConv(CallingConv::Fast);

I feel like the DISubroutineType should be updated to DW_CC_BORLAND_msfastcall for Windows x86. So that the PDB depicts the correct CC.

[llvmbot]

@llvm/issue-subscribers-debuginfo

Author: Maurice Heumann (momo5502)

Compiling the following sample for Windows x86 with -O3 shows that `static_func` will have `fastcc` applied to it:

static __declspec(noinline) int static_func(int arg1){
	
	return arg1 * 2;
}

int main(int argc, char* argv[]) {
	return static_func(argc);
}

https://godbolt.org/z/Pcroj66c4

The PDB however shows NearC, so cdecl, instead of FastCall.

The reason this happens is because GlobalOpt updates the CC, but not the debug info:

llvm-project/llvm/lib/Transforms/IPO/GlobalOpt.cpp

Line 2022 in aa8a1fa

F.setCallingConv(CallingConv::Fast);

I feel like the DISubroutineType should be updated to DW_CC_BORLAND_msfastcall for Windows x86. So that the PDB depicts the correct CC.