GVN incorrectly changes a load into a bitcast #48826
Description
| Bugzilla Link | 49482 |
| Resolution | FIXED |
| Resolved on | Jun 03, 2021 23:16 |
| Version | trunk |
| OS | All |
| Blocks | #48661 #48289 |
| CC | @jdoerfert,@tstellar,@wsmoses |
| Fixed by commit(s) | 875891a 77b63ce |
Extended Description
GVN has emits incorrect results when given an invariant.group
; ModuleID = 'tc.ll'
source_filename = "Main.cpp"
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"
%struct.c = type { double, double }
@.str = private unnamed_addr constant [4 x i8] c"%f\0A\00", align 1
; Function Attrs: norecurse uwtable mustprogress
define dso_local i32 @​main() local_unnamed_addr #​0 {
entry:
%call = tail call noalias dereferenceable_or_null(12297664) i8* @​malloc(i64 12297664) #​3
%0 = bitcast i8* %call to %struct.c*
%call1 = tail call noalias dereferenceable_or_null(12297664) i8* @​malloc(i64 12297664) #​3
br label %for.body
for.body: ; preds = %for.body, %entry
%indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
%tr = trunc i64 %indvars.iv to i32
%conv = sitofp i32 %tr to double
%a = getelementptr inbounds %struct.c, %struct.c* %0, i64 %indvars.iv, i32 0
store double %conv, double* %a, align 8
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%exitcond.not = icmp eq i64 %indvars.iv.next, 768604
br i1 %exitcond.not, label %for.cond.cleanup, label %for.body, !llvm.loop !​2
for.cond.cleanup: ; preds = %for.body
%arrayidx7.i.i = getelementptr inbounds i8, i8* %call, i64 10489184
%malloccall19.i = call noalias nonnull dereferenceable(16) dereferenceable_or_null(16) i8* @​malloc(i64 16) #​3, !noalias !​4
%_malloccache.i = bitcast i8* %malloccall19.i to %struct.c**
%malloccall23.i = call noalias nonnull dereferenceable(16) dereferenceable_or_null(16) i8* @​malloc(i64 16) #​3, !noalias !​4
br label %for.body.i
for.body.i: ; preds = %for.body.i, %for.cond.cleanup
%iv.i = phi i64 [ 0, %for.cond.cleanup ], [ %iv.next.i, %for.body.i ]
%1 = phi double [ 0.000000e+00, %for.cond.cleanup ], [ %add.i, %for.body.i ]
%iv.next.i = add nuw nsw i64 %iv.i, 1
%2 = bitcast i8* %arrayidx7.i.i to %struct.c*
%3 = getelementptr inbounds %struct.c*, %struct.c** %_malloccache.i, i64 %iv.i
store %struct.c* %2, %struct.c** %3, align 8, !invariant.group !​7
%a10.i.i = getelementptr inbounds %struct.c, %struct.c* %2, i64 0, i32 0
%4 = load double, double* %a10.i.i, align 8, !invariant.group !​8
%sub.i.i = fsub double 1.000000e+00, %4
%div11.i.i = fdiv double 1.000000e+00, %sub.i.i
%add.i = fadd double %1, %div11.i.i
%exitcond.i.not = icmp eq i64 %iv.next.i, 2
br i1 %exitcond.i.not, label %diffe_Z1pP1cPd.exit, label %for.body.i, !llvm.loop !​9
diffe_Z1pP1cPd.exit: ; preds = %for.body.i
%call4 = call i32 (i8*, ...) @​printf(i8* nonnull dereferenceable(1) getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i64 0, i64 0), double %add.i)
ret i32 0
}
; Function Attrs: inaccessiblememonly nofree nounwind willreturn
declare dso_local noalias noundef i8* @​malloc(i64 noundef) local_unnamed_addr #​1
; Function Attrs: nofree nounwind
declare dso_local noundef i32 @​printf(i8* nocapture noundef readonly, ...) local_unnamed_addr #​2
attributes #​0 = { norecurse 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 = { inaccessiblememonly nofree nounwind willreturn "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 = { nofree nounwind "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 (git%github.com:llvm/llvm-project d163e75c81c1609855b98cbdffa0141c70d8578d)"}
!​2 = distinct !{#2, !​3}
!​3 = !{!"llvm.loop.mustprogress"}
!​4 = !{#5}
!​5 = distinct !{#5, !​6, !"diffe_Z1pP1cPd: %q"}
!​6 = distinct !{#6, !"diffe_Z1pP1cPd"}
!​7 = distinct !{}
!​8 = distinct !{}
!​9 = distinct !{#9, !​3}
$ /mnt/sabrent/wmoses/llvm13/build/bin/opt tc.ll | /mnt/sabrent/wmoses/llvm13/build/bin/lli -
-0.000003
$ /mnt/sabrent/wmoses/llvm13/build/bin/opt -gvn tc.ll | /mnt/sabrent/wmoses/llvm13/build/bin/lli -
2.000000
Removing one of the two invariant.groups appears to fix the incorrect behavior of gvn.