[PATCH] D79035: [clang][AIX] Implement ABIInfo and TargetCodeGenInfo for AIX

Tue May 5 08:03:31 PDT 2020

Xiangling_L added inline comments.

================
Comment at: clang/lib/CodeGen/TargetInfo.cpp:4317
+  if (isAggregateTypeForABI(RetTy))
+    return getNaturalAlignIndirect(RetTy);
+
----------------
Xiangling_L wrote:
> jasonliu wrote:
> > Xiangling_L wrote:
> > > This method uses the ABI alignment of the given aggregate type which I think is not ideal due to our AIX special alignment rule. We need to use preferred alignment in this case.
> > > Btw also I think it's not necessary for you to rebase your patch on the power alignment patch, I can refresh the testcase when I am dealing with that one.
> > As it is right now in master, there is no difference between natural alignment and preferred alignment for AIX. The tentative direction is to use preferred alignment to record the actual alignment on AIX, but it is not finalized yet. I would rather leave this part of the work for the patch that's going to implement the power alignment rule for AIX.
> `getNaturalAlignIndirect` uses ABI align which is for sure not correct on AIX target for Aggregate types. What we want is the actual alignment here.
> 
> So I am not sure if we want to take `getNaturalAlignIndirect` for granted even if we know it's not correct semantically.
Comment update:
For the power alignment patch, after some investigation, to test IR alignment value for struct as argument and return type, it should base on this ABI patch. 

So I agree that we can rely on power alignment patch later to update this part.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D79035/new/

https://reviews.llvm.org/D79035