| Issue |
64676
|
| Summary |
Dead Code Elimination Regression at -O3 (trunk vs. llvmorg-16.0.6)
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
SvenjaScherrer
|
```c
static struct {
int b;
int c;
} e, f;
static int g;
static short h, i, af;
static char j = 83;
void foo(void);
void bar247_(void);
void bar6_(void);
void bar24_(void);
static char(a)(char k, char l) { return k + l; }
static int(d)(int k) { return k; }
static void m(int k, char l) {
if (!(k >= 52 && k <= 402))
bar247_();
int ak = j = 82;
for (; i < 4; i = ak)
if (d(l))
;
else {
af = h + 9;
h = af;
j = 0;
}
}
int main() {
f = e;
d(0);
m(af, 5);
int ac;
short ad;
if (f.c)
bar6_();
ac = j;
m(ac, 4);
if (ac <= 82)
bar24_();
ad = 0;
for (; ad <= 4; ad = a(ad, 2)) {
if (!(ac >= 2 && ac <= 92))
foo();
for (; g < 30; ++g)
ac = 6;
}
}
```
`clang-5d814b384826 (trunk) -O3` cannot eliminate the call to foo but `clang-llvmorg-16.0.6 -O3` can.
-----------------------------------------------------------------------
`clang-5d814b3848265da8c10ca29d5e55f0637c5b50ef -O3 case.c -S -emit-llvm -o case.ll`
<details ><summary>Emitted IR</summary><p>
```ll
; ModuleID = 'case.c'
source_filename = "case.c"
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.anon = type { i32, i32 }
@f = internal unnamed_addr global %struct.anon zeroinitializer, align 8
@j = internal unnamed_addr global i1 false, align 1
@g = internal unnamed_addr global i1 false, align 4
@i = internal unnamed_addr global i1 false, align 2
; Function Attrs: nounwind uwtable
define dso_local i32 @main() local_unnamed_addr #0 {
store i64 0, ptr @f, align 8
tail call void @bar247_() #2
store i1 true, ptr @j, align 1
%1 = load i1, ptr @i, align 2
br i1 %1, label %3, label %2
2: ; preds = %0
store i1 true, ptr @i, align 2
br label %3
3: ; preds = %0, %2
%4 = load i32, ptr getelementptr inbounds (%struct.anon, ptr @f, i64 0, i32 1), align 4, !tbaa !5
%5 = icmp eq i32 %4, 0
br i1 %5, label %11, label %6
6: ; preds = %3
tail call void @bar6_() #2
%7 = load i1, ptr @j, align 1
%8 = select i1 %7, i8 82, i8 83
%9 = zext i8 %8 to i32
%10 = add nsw i32 %9, -2
br label %11
11: ; preds = %6, %3
%12 = phi i32 [ %10, %6 ], [ 80, %3 ]
%13 = phi i8 [ %8, %6 ], [ 82, %3 ]
store i1 true, ptr @j, align 1
%14 = load i1, ptr @i, align 2
br i1 %14, label %16, label %15
15: ; preds = %11
store i1 true, ptr @i, align 2
br label %16
16: ; preds = %11, %15
%17 = icmp eq i8 %13, 83
br i1 %17, label %19, label %18
18: ; preds = %16
tail call void @bar24_() #2
br label %19
19: ; preds = %18, %16
%20 = icmp ult i32 %12, 91
br i1 %20, label %22, label %21
21: ; preds = %19
tail call void @foo() #2
br label %22
22: ; preds = %19, %21
%23 = load i1, ptr @g, align 4
br i1 %23, label %24, label %32
24: ; preds = %22
%25 = icmp ult i32 %12, 91
br i1 %25, label %28, label %26
26: ; preds = %24
tail call void @foo() #2
%27 = load i1, ptr @g, align 4
br i1 %27, label %28, label %32
28: ; preds = %24, %26
%29 = icmp ult i32 %12, 91
br i1 %29, label %33, label %30
30: ; preds = %28
tail call void @foo() #2
%31 = load i1, ptr @g, align 4
br i1 %31, label %33, label %32
32: ; preds = %30, %26, %22
store i1 true, ptr @g, align 4
br label %33
33: ; preds = %32, %28, %30
ret i32 0
}
declare void @bar6_() local_unnamed_addr #1
declare void @bar24_() local_unnamed_addr #1
declare void @foo() local_unnamed_addr #1
declare void @bar247_() local_unnamed_addr #1
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 = { "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 #2 = { nounwind }
!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 18.0.0 ([email protected]:llvm/llvm-project.git 5d814b3848265da8c10ca29d5e55f0637c5b50ef)"}
!5 = !{!6, !7, i64 4}
!6 = !{!"", !7, i64 0, !7, i64 4}
!7 = !{!"int", !8, i64 0}
!8 = !{!"omnipotent char", !9, i64 0}
!9 = !{!"Simple C/C++ TBAA"}
```
</p></details>
-----------------------------------------------------------------------
`clang-af2ed9f794c422923414d162dd1f48d986e2d6e3 -O3 case.c -S -emit-llvm -o case.ll`
<details ><summary>Emitted IR</summary><p>
```ll
; ModuleID = 'case.c'
source_filename = "case.c"
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.anon = type { i32, i32 }
@f = internal unnamed_addr global %struct.anon zeroinitializer, align 8
@j = internal unnamed_addr global i1 false, align 1
@g = internal unnamed_addr global i1 false, align 4
@i = internal unnamed_addr global i1 false, align 2
; Function Attrs: nounwind uwtable
define dso_local i32 @main() local_unnamed_addr #0 {
store i64 0, ptr @f, align 8
tail call void @bar247_() #2
store i1 true, ptr @j, align 1
%1 = load i1, ptr @i, align 2
br i1 %1, label %3, label %2
2: ; preds = %0
store i1 true, ptr @i, align 2
br label %3
3: ; preds = %0, %2
%4 = load i32, ptr getelementptr inbounds (%struct.anon, ptr @f, i64 0, i32 1), align 4, !tbaa !5
%5 = icmp eq i32 %4, 0
br i1 %5, label %9, label %6
6: ; preds = %3
tail call void @bar6_() #2
%7 = load i1, ptr @j, align 1
%8 = select i1 %7, i8 82, i8 83
br label %9
9: ; preds = %6, %3
%10 = phi i8 [ %8, %6 ], [ 82, %3 ]
store i1 true, ptr @j, align 1
%11 = load i1, ptr @i, align 2
br i1 %11, label %13, label %12
12: ; preds = %9
store i1 true, ptr @i, align 2
br label %13
13: ; preds = %9, %12
%14 = icmp eq i8 %10, 83
br i1 %14, label %16, label %15
15: ; preds = %13
tail call void @bar24_() #2
br label %16
16: ; preds = %13, %15
%17 = load i1, ptr @g, align 4
br i1 %17, label %19, label %18
18: ; preds = %16
store i1 true, ptr @g, align 4
br label %19
19: ; preds = %16, %18
ret i32 0
}
declare void @bar6_() local_unnamed_addr #1
declare void @bar24_() local_unnamed_addr #1
declare void @bar247_() local_unnamed_addr #1
attributes #0 = { nounwind uwtable "min-legal-vector-width"="0" "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 = { "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 = { nounwind }
!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 16.0.6 ([email protected]:llvm/llvm-project.git 7cbf1a2591520c2491aa35339f227775f4d3adf6)"}
!5 = !{!6, !7, i64 4}
!6 = !{!"", !7, i64 0, !7, i64 4}
!7 = !{!"int", !8, i64 0}
!8 = !{!"omnipotent char", !9, i64 0}
!9 = !{!"Simple C/C++ TBAA"}
```
</p></details>
-----------------------------------------------------------------------
Bisects to cde681c865302f689f0937e5ec2e127a089a4db3
Committed by: @nikic
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