[ArgPromotion] Miscompile at -O3

[dtcxzyw]

Reduced test case: https://godbolt.org/z/5z5sYv4nq

#include <stdint.h>
#include <stdio.h>
struct a {
  int16_t b;
  uint64_t c;
} f = {1};
uint8_t d, h;
static struct a *g[] = {&f, &f, &f, &f};
int32_t i;
static struct a j(struct a *q) {
  for (d = 5; d < 6; d = d + 1)
    f.b = h;
  return *q;
}
int main() {
  struct a *l = g[3];
  *l = j(l);
  i = f.b;
  printf("%d\n", i);
}

Bisected to ArgumentPromotionPass.

Before:

; ModuleID = 'test.c'
source_filename = "test.c"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

%struct.a = type { i16, i64 }

@f = dso_local global %struct.a { i16 1, i64 0 }, align 8
@i = dso_local local_unnamed_addr global i32 0, align 4
@.str = private unnamed_addr constant [4 x i8] c"%d\0A\00", align 1
@d = dso_local local_unnamed_addr global i8 0, align 1
@h = dso_local local_unnamed_addr global i8 0, align 1

; Function Attrs: nounwind uwtable
define dso_local i32 @main() local_unnamed_addr #0 {
entry:
  %tmp.sroa.4 = alloca [6 x i8], align 2
  call void @llvm.lifetime.start.p0(i64 6, ptr nonnull %tmp.sroa.4)
  %call = call fastcc { i16, i64 } @j(ptr noundef nonnull @f)
  %0 = extractvalue { i16, i64 } %call, 0
  %1 = extractvalue { i16, i64 } %call, 1
  store i16 %0, ptr @f, align 8, !tbaa !5
  call void @llvm.memcpy.p0.p0.i64(ptr noundef nonnull align 2 dereferenceable(6) getelementptr inbounds (i8, ptr @f, i64 2), ptr noundef nonnull align 2 dereferenceable(6) %tmp.sroa.4, i64 6, i1 false), !tbaa.struct !9
  store i64 %1, ptr getelementptr inbounds (%struct.a, ptr @f, i64 0, i32 1), align 8, !tbaa !10
  call void @llvm.lifetime.end.p0(i64 6, ptr nonnull %tmp.sroa.4)
  %conv = sext i16 %0 to i32
  store i32 %conv, ptr @i, align 4, !tbaa !12
  %call1 = call i32 (ptr, ...) @printf(ptr noundef nonnull dereferenceable(1) @.str, i32 noundef %conv)
  ret i32 0
}

; Function Attrs: mustprogress nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
declare void @llvm.lifetime.start.p0(i64 immarg, ptr nocapture) #1

; Function Attrs: nounwind uwtable
define internal fastcc { i16, i64 } @j(ptr nocapture noundef readonly %q) unnamed_addr #0 {
entry:
  br label %for.cond

for.cond:                                         ; preds = %for.body, %entry
  %storemerge = phi i8 [ 5, %entry ], [ %add, %for.body ]
  store i8 %storemerge, ptr @d, align 1, !tbaa !14
  %cmp = icmp ult i8 %storemerge, 6
  br i1 %cmp, label %for.body, label %for.end

for.body:                                         ; preds = %for.cond
  %0 = load i8, ptr @h, align 1, !tbaa !14
  %conv2 = zext i8 %0 to i16
  store i16 %conv2, ptr @f, align 8, !tbaa !15
  %1 = load i8, ptr @d, align 1, !tbaa !14
  %add = add i8 %1, 1
  br label %for.cond, !llvm.loop !17

for.end:                                          ; preds = %for.cond
  %retval.sroa.0.0.copyload = load i16, ptr %q, align 8, !tbaa !5
  %retval.sroa.25.0.q.addr.0..sroa_idx = getelementptr inbounds i8, ptr %q, i64 8
  %retval.sroa.25.0.copyload = load i64, ptr %retval.sroa.25.0.q.addr.0..sroa_idx, align 8, !tbaa !10
  %.fca.0.insert = insertvalue { i16, i64 } poison, i16 %retval.sroa.0.0.copyload, 0
  %.fca.1.insert = insertvalue { i16, i64 } %.fca.0.insert, i64 %retval.sroa.25.0.copyload, 1
  ret { i16, i64 } %.fca.1.insert
}

; Function Attrs: mustprogress 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) #2

; Function Attrs: mustprogress nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
declare void @llvm.lifetime.end.p0(i64 immarg, ptr nocapture) #1

; Function Attrs: nofree nounwind
declare noundef i32 @printf(ptr nocapture noundef readonly, ...) local_unnamed_addr #3

attributes #0 = { nounwind uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
attributes #1 = { mustprogress nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
attributes #2 = { mustprogress nocallback nofree nounwind willreturn memory(argmem: readwrite) }
attributes #3 = { nofree nounwind "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }

!llvm.module.flags = !{!0, !1, !2, !3}
!llvm.ident = !{!4}

!0 = !{i32 1, !"wchar_size", i32 4}
!1 = !{i32 8, !"PIC Level", i32 2}
!2 = !{i32 7, !"PIE Level", i32 2}
!3 = !{i32 7, !"uwtable", i32 2}
!4 = !{!"clang version 19.0.0git"}
!5 = !{!6, !6, i64 0}
!6 = !{!"short", !7, i64 0}
!7 = !{!"omnipotent char", !8, i64 0}
!8 = !{!"Simple C/C++ TBAA"}
!9 = !{i64 6, i64 8, !10}
!10 = !{!11, !11, i64 0}
!11 = !{!"long", !7, i64 0}
!12 = !{!13, !13, i64 0}
!13 = !{!"int", !7, i64 0}
!14 = !{!7, !7, i64 0}
!15 = !{!16, !6, i64 0}
!16 = !{!"a", !6, i64 0, !11, i64 8}
!17 = distinct !{!17, !18}
!18 = !{!"llvm.loop.mustprogress"}

After:

; ModuleID = 'test.c'
source_filename = "test.c"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

%struct.a = type { i16, i64 }

@f = dso_local global %struct.a { i16 1, i64 0 }, align 8
@i = dso_local local_unnamed_addr global i32 0, align 4
@.str = private unnamed_addr constant [4 x i8] c"%d\0A\00", align 1
@d = dso_local local_unnamed_addr global i8 0, align 1
@h = dso_local local_unnamed_addr global i8 0, align 1

; Function Attrs: nounwind uwtable
define dso_local i32 @main() local_unnamed_addr #0 {
entry:
  %tmp.sroa.4 = alloca [6 x i8], align 2
  call void @llvm.lifetime.start.p0(i64 6, ptr nonnull %tmp.sroa.4)
  %f.val = load i16, ptr @f, align 8
  %0 = getelementptr i8, ptr @f, i64 8
  %f.val4 = load i64, ptr %0, align 8
  %call = call fastcc { i16, i64 } @j(i16 %f.val, i64 %f.val4)
  %1 = extractvalue { i16, i64 } %call, 0
  %2 = extractvalue { i16, i64 } %call, 1
  store i16 %1, ptr @f, align 8, !tbaa !5
  call void @llvm.memcpy.p0.p0.i64(ptr noundef nonnull align 2 dereferenceable(6) getelementptr inbounds (i8, ptr @f, i64 2), ptr noundef nonnull align 2 dereferenceable(6) %tmp.sroa.4, i64 6, i1 false), !tbaa.struct !9
  store i64 %2, ptr getelementptr inbounds (%struct.a, ptr @f, i64 0, i32 1), align 8, !tbaa !10
  call void @llvm.lifetime.end.p0(i64 6, ptr nonnull %tmp.sroa.4)
  %conv = sext i16 %1 to i32
  store i32 %conv, ptr @i, align 4, !tbaa !12
  %call1 = call i32 (ptr, ...) @printf(ptr noundef nonnull dereferenceable(1) @.str, i32 noundef %conv)
  ret i32 0
}

; Function Attrs: mustprogress nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
declare void @llvm.lifetime.start.p0(i64 immarg, ptr nocapture) #1

; Function Attrs: nounwind uwtable
define internal fastcc { i16, i64 } @j(i16 %q.0.val, i64 %q.8.val) unnamed_addr #0 {
entry:
  br label %for.cond

for.cond:                                         ; preds = %for.body, %entry
  %storemerge = phi i8 [ 5, %entry ], [ %add, %for.body ]
  store i8 %storemerge, ptr @d, align 1, !tbaa !14
  %cmp = icmp ult i8 %storemerge, 6
  br i1 %cmp, label %for.body, label %for.end

for.body:                                         ; preds = %for.cond
  %0 = load i8, ptr @h, align 1, !tbaa !14
  %conv2 = zext i8 %0 to i16
  store i16 %conv2, ptr @f, align 8, !tbaa !15
  %1 = load i8, ptr @d, align 1, !tbaa !14
  %add = add i8 %1, 1
  br label %for.cond, !llvm.loop !17

for.end:                                          ; preds = %for.cond
  %.fca.0.insert = insertvalue { i16, i64 } poison, i16 %q.0.val, 0
  %.fca.1.insert = insertvalue { i16, i64 } %.fca.0.insert, i64 %q.8.val, 1
  ret { i16, i64 } %.fca.1.insert
}

; Function Attrs: mustprogress 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) #2

; Function Attrs: mustprogress nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
declare void @llvm.lifetime.end.p0(i64 immarg, ptr nocapture) #1

; Function Attrs: nofree nounwind
declare noundef i32 @printf(ptr nocapture noundef readonly, ...) local_unnamed_addr #3

attributes #0 = { nounwind uwtable "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
attributes #1 = { mustprogress nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
attributes #2 = { mustprogress nocallback nofree nounwind willreturn memory(argmem: readwrite) }
attributes #3 = { nofree nounwind "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cmov,+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }

!llvm.module.flags = !{!0, !1, !2, !3}
!llvm.ident = !{!4}

!0 = !{i32 1, !"wchar_size", i32 4}
!1 = !{i32 8, !"PIC Level", i32 2}
!2 = !{i32 7, !"PIE Level", i32 2}
!3 = !{i32 7, !"uwtable", i32 2}
!4 = !{!"clang version 19.0.0git"}
!5 = !{!6, !6, i64 0}
!6 = !{!"short", !7, i64 0}
!7 = !{!"omnipotent char", !8, i64 0}
!8 = !{!"Simple C/C++ TBAA"}
!9 = !{i64 6, i64 8, !10}
!10 = !{!11, !11, i64 0}
!11 = !{!"long", !7, i64 0}
!12 = !{!13, !13, i64 0}
!13 = !{!"int", !7, i64 0}
!14 = !{!7, !7, i64 0}
!15 = !{!16, !6, i64 0}
!16 = !{!"a", !6, i64 0, !11, i64 8}
!17 = distinct !{!17, !18}
!18 = !{!"llvm.loop.mustprogress"}

We cannot promote the loads because %q aliases with @f.

LLVM version: 0f501c3

[dtcxzyw]

cc @nikic @fhahn

[fhahn]

Hmm, cannot reproduce with plain opt.

[fhahn]

Ok reproduced with custom use list order. Will prepare a fix soon

[antoniofrighetto]

Just out of curiosity, when querying AA, we are expecting canInstructionRangeModRef to return true on the first load popped out (%retval.sroa.25.0.copyload) here, correct?

[fhahn]

Just out of curiosity, when querying AA, we are expecting canInstructionRangeModRef to return true on the first load popped out (%retval.sroa.25.0.copyload) here, correct?

No, AFAICT AA is working correctly, but the results are used for incorrect caching, see #84835

[antoniofrighetto]

Just out of curiosity, when querying AA, we are expecting canInstructionRangeModRef to return true on the first load popped out (%retval.sroa.25.0.copyload) here, correct?

No, AFAICT AA is working correctly, but the results are used for incorrect caching, see #84835

Makes sense, thanks (didn't see the PR opened by the time had commented).

[fhahn]

Makes sense, thanks (didn't see the PR opened by the time had commented).

Unfortunately Github does not seem to notify when a PR mentions an issue :(