f7ef0721d6
See the following case:
```
; bin/opt -passes="print<scalar-evolution>" test.ll --disable-output
define i32 @widget() {
b:
br label %b1
b1: ; preds = %b5, %b
%phi = phi i32 [ 0, %b ], [ %udiv6, %b5 ]
%phi2 = phi i32 [ 1, %b ], [ %add, %b5 ]
%icmp = icmp eq i32 %phi, 0
br i1 %icmp, label %b3, label %b8
b3: ; preds = %b1
%udiv = udiv i32 10, %phi2
%urem = urem i32 %udiv, 10
%icmp4 = icmp eq i32 %urem, 0
br i1 %icmp4, label %b7, label %b5
b5: ; preds = %b3
%udiv6 = udiv i32 %phi2, 0
%add = add i32 %phi2, 1
br label %b1
b7: ; preds = %b3
ret i32 5
b8: ; preds = %b1
ret i32 7
}
```
```
%phi2 = phi i32 [ 1, %b ], [ %add, %b5 ] --> {1,+,1}<nuw><nsw><%b1>
%udiv6 = udiv i32 %phi2, 0 --> ({1,+,1}<nuw><nsw><%b1> /u 0)
%phi = phi i32 [ 0, %b ], [ %udiv6, %b5 ] --> ({0,+,1}<nuw><nsw><%b1> /u 0)
```
`ScalarEvolution::createAddRecFromPHI` gives a wrong SCEV result for
`%phi`:
d7d6fb1804/llvm/lib/Analysis/ScalarEvolution.cpp (L5926-L5950)
It converts `phi(0, ({1,+,1}<nuw><nsw><%b1> /u 0))` into `phi(0 / 0,
({1,+,1}<nuw><nsw><%b1> /u 0))`. Then it simplifies the expr into
`{0,+,1}<nuw><nsw><%b1> /u 0`.
As we did in
acd700a24b,
this patch disallows udiv simplification if we cannot prove that the
denominator is a well-defined non-zero value.
Fixes https://github.com/llvm/llvm-project/issues/117133.
45 lines
1022 B
LLVM
45 lines
1022 B
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
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; RUN: opt -S -passes=indvars < %s | FileCheck %s
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define i32 @widget() {
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; CHECK-LABEL: define i32 @widget() {
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; CHECK-NEXT: [[B:.*:]]
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; CHECK-NEXT: br label %[[B1:.*]]
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; CHECK: [[B1]]:
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; CHECK-NEXT: br i1 true, label %[[B3:.*]], label %[[B8:.*]]
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; CHECK: [[B3]]:
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; CHECK-NEXT: br i1 true, label %[[B7:.*]], label %[[B5:.*]]
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; CHECK: [[B5]]:
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; CHECK-NEXT: br label %[[B1]]
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; CHECK: [[B7]]:
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; CHECK-NEXT: ret i32 5
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; CHECK: [[B8]]:
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; CHECK-NEXT: ret i32 7
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;
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b:
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br label %b1
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b1:
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%phi = phi i32 [ 0, %b ], [ %udiv6, %b5 ]
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%phi2 = phi i32 [ 1, %b ], [ %add, %b5 ]
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%icmp = icmp eq i32 %phi, 0
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br i1 %icmp, label %b3, label %b8
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b3:
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%udiv = udiv i32 10, %phi2
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%urem = urem i32 %udiv, 10
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%icmp4 = icmp eq i32 %urem, 0
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br i1 %icmp4, label %b7, label %b5
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b5:
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%udiv6 = udiv i32 %phi2, 0
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%add = add i32 %phi2, 1
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br label %b1
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b7:
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ret i32 5
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b8:
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ret i32 7
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}
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