[llvm-bugs] [Bug 49482] New: GVN incorrectly handles invariant.group

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49482

            Bug ID: 49482
           Summary: GVN incorrectly handles invariant.group
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: wmoses at mit.edu
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org

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.

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20210309/aaf2a720/attachment-0001.html>