| Issue |
130082
|
| Summary |
[SLPVectorizer] Occasional miscompile with a switch statement
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
usatiuk
|
Reduced reproducer:
```
; opt -S reduced.ll --passes=slp-vectorizer -slp-threshold=-99999
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-ni:1-p2:32:8:8:32-ni:2"
target triple = "x86_64-unknown-linux-gnu"
define i32 @test(i32 %0) {
entry:
switch i32 0, label %bci_130 [
i32 -4, label %bci_96
i32 3, label %bci_130
i32 1, label %bci_130
i32 9, label %bci_108
i32 0, label %bci_130
]
bci_130: ; preds = %bci_96, %bci_108, %entry, %entry, %entry, %entry
%1 = phi i32 [ 0, %bci_108 ], [ %0, %bci_96 ], [ %0, %entry ], [ %0, %entry ], [ %0, %entry ], [ %0, %entry ]
%local_2_10 = phi i32 [ 0, %bci_108 ], [ 0, %bci_96 ], [ 0, %entry ], [ 0, %entry ], [ 0, %entry ], [ 0, %entry ]
ret i32 0
bci_108: ; preds = %entry
br label %bci_130
bci_96: ; preds = %entry
br label %bci_130
}
```
Expected output:
```
; ModuleID = 'reduced.ll'
source_filename = "reduced.ll"
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-ni:1-p2:32:8:8:32-ni:2"
target triple = "x86_64-unknown-linux-gnu"
define i32 @test(i32 %0) {
entry:
%1 = insertelement <2 x i32> <i32 0, i32 poison>, i32 %0, i32 1
switch i32 0, label %bci_130 [
i32 -4, label %bci_96
i32 3, label %bci_130
i32 1, label %bci_130
i32 9, label %bci_108
i32 0, label %bci_130
]
bci_130: ; preds = %bci_96, %bci_108, %entry, %entry, %entry, %entry
%2 = phi <2 x i32> [ zeroinitializer, %bci_108 ], [ %1, %bci_96 ], [ %1, %entry ], [ %1, %entry ], [ %1, %entry ], [ %1, %entry ]
ret i32 0
bci_108: ; preds = %entry
br label %bci_130
bci_96: ; preds = %entry
br label %bci_130
}
```
But sometimes the result is:
```
; ModuleID = 'reduced.ll'
source_filename = "reduced.ll"
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-ni:1-p2:32:8:8:32-ni:2"
target triple = "x86_64-unknown-linux-gnu"
define i32 @test(i32 %0) {
entry:
%1 = insertelement <2 x i32> <i32 0, i32 poison>, i32 %0, i32 1
switch i32 0, label %bci_130 [
i32 -4, label %bci_96
i32 3, label %bci_130
i32 1, label %bci_130
i32 9, label %bci_108
i32 0, label %bci_130
]
bci_130: ; preds = %bci_96, %bci_108, %entry, %entry, %entry, %entry
%2 = phi <2 x i32> [ zeroinitializer, %bci_108 ], [ %3, %bci_96 ], [ %1, %entry ], [ %1, %entry ], [ %1, %entry ], [ %1, %entry ]
ret i32 0
bci_108: ; preds = %entry
br label %bci_130
bci_96: ; preds = %entry
%3 = load <2 x i32>, ptr poison, align 8
br label %bci_130
}
```
I have bisected the issue to commit https://github.com/llvm/llvm-project/commit/894935cb5146fd2ac6334cc8b11e6d6e0e264fe6
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