[PATCH] D134282: [CGP] Add generic TargetLowering::shouldAlignPointerArgs() implementation

[David Tenty via Phabricator via llvm-commits]

daltenty added a comment.

Here's an IR only example which will exhibit the invalid AIX assembly after this change:

  target datalayout = "E-m:a-i64:64-n32:64-S128-v256:256:256-v512:512:512"
  target triple = "powerpc64-ibm-aix"
  
  @.str = private unnamed_addr constant [14 x i8] c"error message\00"
  
  define internal fastcc void @_ZN12_GLOBAL__N_12anIPKclPcEET1_T_T0_S4_() {
  entry:
    store i64 0, ptr @.str, align 8
    unreachable
  }
  
  define internal fastcc void @_ZN12_GLOBAL__N_12alIPKcPcEEvT_S4_T0_(i64 %0) {
  entry:
    tail call void @llvm.memcpy.p0.p0.i64(ptr null, ptr @.str, i64 %0, i1 false)
    ret void
  }
  
  ; Function Attrs: nocallback nofree nounwind willreturn memory(argmem: readwrite)
  declare void @llvm.memcpy.p0.p0.i64(ptr noalias nocapture writeonly, ptr noalias nocapture readonly, i64, i1 immarg) #0
  
  attributes #0 = { nocallback nofree nounwind willreturn memory(argmem: readwrite) }

We see the same TOC reference without a def:

  .csect .rodata.str1.8L...str[RO],2
  .tc .rodata.str1.1L...str[TC],.rodata.str1.1L...str[RO]
  .tc .rodata.str1.8L...str[TC],.rodata.str1.8L...str[RO]

The problem seems to lie in the fact that we codegen the first function with no explicit alignment for `@.str` resulting in TOC references to the `.rodata.str1.1L` section  , but after this change when doing CodeGenPrepare we modify the alignment on `@.str` to 8, which changes the MCSection (i.e. csect) name for the final object we emit.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D134282/new/

https://reviews.llvm.org/D134282