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InstCombine: Reduce "X shift (A srem B)" to "X shift (A urem B)" iff B is positive.

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This allows to transform the rem in "1 << ((int)x % 8);" to an and.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120028 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer
2010-11-23 18:52:42 +00:00
parent e104f1bccb
commit b70ebd2aa3
3 changed files with 28 additions and 10 deletions
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11
test/Transforms/InstCombine/shift.ll
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@@ -441,3 +441,14 @@ entry:
; CHECK: %ins = or i128 %tmp23, %A
; CHECK: %tmp46 = trunc i128 %ins to i64
}
define i32 @test38(i32 %x) nounwind readnone {
entry:
%rem = srem i32 %x, 32
%shl = shl i32 1, %rem
ret i32 %shl
; CHECK: @test38
; CHECK-NOT: srem
; CHECK: ret i32
}