[PATCH] D98144: [CodeGenPrepare] Fix isIVIncrement (PR49466)

[Jordan Rupprecht via Phabricator via llvm-commits]

rupprecht added a comment.

Here's an IR reproducer, derived from the C++ one I provided in the reverting commit (as before, it reproduces with "clang -O2", although it doesn't with "opt -O2"):

  ; ModuleID = '/tmp/repro.cc'
  source_filename = "/tmp/repro.cc"
  target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
  target triple = "x86_64-unknown-linux-gnu"
  
  %class.D = type { i64 }
  %class.a = type { %class.g }
  %class.g = type { i32*, i32* }
  
  $_ZNK1aIliEixEl = comdat any
  
  $_ZNK1aIliE1jEv = comdat any
  
  @o = dso_local local_unnamed_addr global i32 0, align 4
  @p = dso_local local_unnamed_addr global i32 0, align 4
  @.str = private unnamed_addr constant [1 x i8] zeroinitializer, align 1
  
  ; Function Attrs: uwtable mustprogress
  define dso_local void @_ZN1D1qERK1aIliE(%class.D* nocapture nonnull dereferenceable(8) %0, %class.a* nonnull align 8 dereferenceable(16) %1) local_unnamed_addr #0 align 2 {
    %3 = call i64 @_ZNK1aIliEixEl(%class.a* nonnull dereferenceable(16) %1, i64 0) #3
    %4 = icmp eq i64 %3, 0
    br i1 %4, label %26, label %5
  
  5:                                                ; preds = %2
    %6 = call i64 @_ZNK1aIliE1jEv(%class.a* nonnull dereferenceable(16) %1)
    %7 = icmp eq i64 %6, 0
    br i1 %7, label %26, label %8
  
  8:                                                ; preds = %5
    %9 = getelementptr inbounds %class.D, %class.D* %0, i64 0, i32 0
    br label %10
  
  10:                                               ; preds = %8, %18
    %11 = phi i64 [ 0, %8 ], [ %23, %18 ]
    %12 = call i64 @_ZNK1aIliEixEl(%class.a* nonnull dereferenceable(16) %1, i64 %11) #3
    %13 = icmp eq i64 %12, 0
    br i1 %13, label %18, label %14
  
  14:                                               ; preds = %10, %14
    %15 = load i32, i32* @o, align 4, !tbaa !2
    %16 = call i32 @_Z3fn1IiiEiT_T0_PKc(i32 %15, i32 0, i8* getelementptr inbounds ([1 x i8], [1 x i8]* @.str, i64 0, i64 0))
    %17 = icmp eq i32 %16, 0
    br i1 %17, label %18, label %14, !llvm.loop !6
  
  18:                                               ; preds = %14, %10
    %19 = call i64 @_ZNK1aIliEixEl(%class.a* nonnull dereferenceable(16) %1, i64 %11) #3
    %20 = load i32, i32* @p, align 4, !tbaa !2
    %21 = sext i32 %20 to i64
    %22 = sdiv i64 %19, %21
    store i64 %22, i64* %9, align 8, !tbaa !9
    %23 = add i64 %11, 1
    %24 = call i64 @_ZNK1aIliE1jEv(%class.a* nonnull dereferenceable(16) %1)
    %25 = icmp eq i64 %24, 0
    br i1 %25, label %26, label %10, !llvm.loop !12
  
  26:                                               ; preds = %18, %5, %2
    ret void
  }
  
  ; Function Attrs: nounwind uwtable willreturn mustprogress
  define linkonce_odr dso_local i64 @_ZNK1aIliEixEl(%class.a* nonnull dereferenceable(16) %0, i64 %1) local_unnamed_addr #1 comdat align 2 {
    %3 = getelementptr inbounds %class.a, %class.a* %0, i64 0, i32 0, i32 0
    %4 = load i32*, i32** %3, align 8, !tbaa !13
    %5 = getelementptr inbounds i32, i32* %4, i64 %1
    %6 = load i32, i32* %5, align 4, !tbaa !2
    %7 = sext i32 %6 to i64
    ret i64 %7
  }
  
  ; Function Attrs: nounwind uwtable willreturn mustprogress
  define linkonce_odr dso_local i64 @_ZNK1aIliE1jEv(%class.a* nonnull dereferenceable(16) %0) local_unnamed_addr #1 comdat align 2 {
    %2 = getelementptr inbounds %class.a, %class.a* %0, i64 0, i32 0, i32 1
    %3 = load i32*, i32** %2, align 8, !tbaa !16
    %4 = getelementptr inbounds %class.a, %class.a* %0, i64 0, i32 0, i32 0
    %5 = load i32*, i32** %4, align 8, !tbaa !13
    %6 = ptrtoint i32* %3 to i64
    %7 = ptrtoint i32* %5 to i64
    %8 = sub i64 %6, %7
    %9 = ashr exact i64 %8, 2
    ret i64 %9
  }
  
  declare dso_local i32 @_Z3fn1IiiEiT_T0_PKc(i32, i32, i8*) local_unnamed_addr #2
  
  attributes #0 = { uwtable mustprogress "frame-pointer"="none" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
  attributes #1 = { nounwind uwtable willreturn mustprogress "frame-pointer"="none" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
  attributes #2 = { "frame-pointer"="none" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
  attributes #3 = { nounwind }
  
  !llvm.module.flags = !{!0}
  !llvm.ident = !{!1}
  
  !0 = !{i32 1, !"wchar_size", i32 4}
  !1 = !{!"clang version 13.0.0 (https://github.com/llvm/llvm-project.git dfd27ebbd0eb137c9a439b7c537bb87ba903efd3)"}
  !2 = !{!3, !3, i64 0}
  !3 = !{!"int", !4, i64 0}
  !4 = !{!"omnipotent char", !5, i64 0}
  !5 = !{!"Simple C++ TBAA"}
  !6 = distinct !{!6, !7, !8}
  !7 = !{!"llvm.loop.mustprogress"}
  !8 = !{!"llvm.loop.unroll.disable"}
  !9 = !{!10, !11, i64 0}
  !10 = !{!"_ZTS1D", !11, i64 0}
  !11 = !{!"long", !4, i64 0}
  !12 = distinct !{!12, !7, !8}
  !13 = !{!14, !15, i64 0}
  !14 = !{!"_ZTS1g", !15, i64 0, !15, i64 8}
  !15 = !{!"any pointer", !4, i64 0}
  !16 = !{!14, !15, i64 8}


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D98144/new/

https://reviews.llvm.org/D98144