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ad214c8e9e
If the NUW bit is set for 0 - Y, we know that all values for Y other than 0 would produce a poison value. This allows us to replace (0 - Y) with 0 in the expression (X - (0 - Y)) which will ultimately leave us with X. This partially fixes PR20189. llvm-svn: 214384
31 lines
610 B
LLVM
31 lines
610 B
LLVM
; RUN: opt < %s -instsimplify -S | FileCheck %s
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define i64 @pow2(i32 %x) {
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; CHECK-LABEL: @pow2(
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%negx = sub i32 0, %x
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%x2 = and i32 %x, %negx
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%e = zext i32 %x2 to i64
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%nege = sub i64 0, %e
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%e2 = and i64 %e, %nege
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ret i64 %e2
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; CHECK: ret i64 %e
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}
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define i64 @pow2b(i32 %x) {
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; CHECK-LABEL: @pow2b(
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%sh = shl i32 2, %x
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%e = zext i32 %sh to i64
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%nege = sub i64 0, %e
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%e2 = and i64 %e, %nege
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ret i64 %e2
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; CHECK: ret i64 %e
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}
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define i32 @sub_neg_nuw(i32 %x, i32 %y) {
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; CHECK-LABEL: @sub_neg_nuw(
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%neg = sub nuw i32 0, %y
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%sub = sub i32 %x, %neg
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ret i32 %sub
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; CHECK: ret i32 %x
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}
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