[PATCH] D76360: [PPC][AIX] Emit correct Vaarg for 32BIT-AIX in clang

Thu Mar 26 10:18:18 PDT 2020

jasonliu added inline comments.

================
Comment at: clang/lib/CodeGen/TargetInfo.cpp:4205

-CharUnits PPC32_SVR4_ABIInfo::getParamTypeAlignment(QualType Ty) const {
+CharUnits PowerPC32ABIInfo::getParamTypeAlignment(QualType Ty) const {
   // Complex types are passed just like their elements
----------------
sfertile wrote:
> jasonliu wrote:
> > So for AIX we are taking PowerPC32ABIInfo right now. And we know EmitVAArg of this target does the right thing on AIX after the change. 
> > But for other functions, for example, getParamTypeAlignment, initDwarfEHRegSizeTable... Are we sure it's doing the right thing on AIX?
> > If we are not sure, is there anything we want to do (etc, put a comment on where it gets used or at the function definition)? Or are we fine to just leave it as it is and have a TODO in our head?
> Looking at the values in `initDwarfEHRegSizeTable` it has the right sizes for all the registers. Even though the OS is different the underlying hardware is the same. I'm not sure it's something that makes sense to support for AIX though, in which case I think its valid to return `true` to indicate its not supported. 
> 
> `getParamTypeAlignment` is used only in the context of the alignment for vaarg, we should make sure its correct for AIX since supporting vaarg is the scope of this patch.
In that case, is it better if we have lit test to actually exercise the path in getParamTypeAlignment to show that we actually confirmed the behavior is correct for AIX? And if it is some path we do not care for now(ComplexType? VectorType?), then we would want TODOs on them to show we need further investigation later. 

Repository:
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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D76360/new/

https://reviews.llvm.org/D76360