[PATCH] D133036: [InstCombine] Treat passing undef to noundef params as UB

[Tim Neumann via Phabricator via cfe-commits]

TimNN added a comment.

I've included excerpts from the IR below. It will take me a bit to provide something compilable. Though you are right, the `noundef` did indeed get removed from the `call`.

  *** IR Dump Before DeadArgumentEliminationPass on [module] ***
  ; Function Attrs: nonlazybind uwtable
  define void @_RNvXs2_NtNtCs840rfDNPFol_10proc_macro6bridge3rpcbINtB5_6EncodeuE6encodeB9_(i1 noundef zeroext %0, ptr noalias noundef align 8 dereferenceable(40) %1, ptr noalias nocapture noundef nonnull readnone align 1 %2) unnamed_addr #0 !dbg !18135 {
    %4 = zext i1 %0 to i8, !dbg !18137
    call void @_RNvXs0_NtNtCs840rfDNPFol_10proc_macro6bridge3rpchINtB5_6EncodeuE6encodeB9_(i8 %4, ptr noalias noundef nonnull align 8 dereferenceable(40) %1, ptr noalias noundef nonnull align 1 %2), !dbg !18137
    ret void, !dbg !18138
  }
  *** IR Dump After DeadArgumentEliminationPass on [module] ***
  ; Function Attrs: nonlazybind uwtable
  define void @_RNvXs2_NtNtCs840rfDNPFol_10proc_macro6bridge3rpcbINtB5_6EncodeuE6encodeB9_(i1 noundef zeroext %0, ptr noalias noundef align 8 dereferenceable(40) %1, ptr noalias nocapture noundef nonnull readnone align 1 %2) unnamed_addr #0 !dbg !18136 {
    %4 = zext i1 %0 to i8, !dbg !18138
    call void @_RNvXs0_NtNtCs840rfDNPFol_10proc_macro6bridge3rpchINtB5_6EncodeuE6encodeB9_(i8 %4, ptr noalias noundef nonnull align 8 dereferenceable(40) %1, ptr noalias nonnull align 1 poison), !dbg !18138
    ret void, !dbg !18139
  }
  *** IR Dump Before InstCombinePass on _RNvXs2_NtNtCs840rfDNPFol_10proc_macro6bridge3rpcbINtB5_6EncodeuE6encodeB9_ ***
  ; Function Attrs: nonlazybind uwtable
  define available_externally void @_RNvXs2_NtNtCs840rfDNPFol_10proc_macro6bridge3rpcbINtB5_6EncodeuE6encodeB9_(i1 noundef zeroext %0, ptr noalias noundef align 8 dereferenceable(40) %1, ptr noalias nocapture noundef nonnull readnone align 1 %2) unnamed_addr #2 !dbg !20759 {
    %4 = zext i1 %0 to i8, !dbg !20762
    call void @_RNvXs0_NtNtCs840rfDNPFol_10proc_macro6bridge3rpchINtB5_6EncodeuE6encodeB9_(i8 %4, ptr noalias noundef nonnull align 8 dereferenceable(40) %1, ptr noalias nonnull align 1 poison), !dbg !20762
    ret void, !dbg !20763
  }
  *** IR Dump After InstCombinePass on _RNvXs2_NtNtCs840rfDNPFol_10proc_macro6bridge3rpcbINtB5_6EncodeuE6encodeB9_ ***
  ; Function Attrs: nonlazybind uwtable
  define available_externally void @_RNvXs2_NtNtCs840rfDNPFol_10proc_macro6bridge3rpcbINtB5_6EncodeuE6encodeB9_(i1 noundef zeroext %0, ptr noalias noundef align 8 dereferenceable(40) %1, ptr noalias nocapture noundef nonnull readnone align 1 %2) unnamed_addr #2 !dbg !20759 {
    store i1 true, ptr poison, align 1
    ret void, !dbg !20762
  }


Repository:
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  https://reviews.llvm.org/D133036/new/

https://reviews.llvm.org/D133036