[LLVMdev] [cfe-dev] x86_64-pc-win32 ABI var arg code gen bug? Is the bitcode correct? Or is it the code gen?

[Andrew Fish]

On May 17, 2011, at 6:28 AM, NAKAMURA Takumi wrote:

> Andrew,
> 
> That is not a clang issue.
> 
> I think, in practice, {rcx, rdx, r8, r9} might not need to be spilled
> to "home area" in that case,
> because va_arg would not touch former 4 args.
> Lemme know if you had issues.
> 

I'm seeing a code gen issue with x86_64-pc-win32-darwin for this test case. So I was looking at the assembly for code gen and ABI issues. I agree that for this test case the spill is code that could optimized out. 

It looks like my bug was related to the sizeof (va_list) being incorrect for my triple, probably was set to struct __va_list_tag and not char*.  I tried a local fix, but I think this fix was broken. I noticed that the top of tree has fixed the issue. 

Thank you for the quick response, it was helpful for me to fully understand what is going on.

Thanks,

Andrew