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Transform any logical shift of a power of two into an exact/NUW shift when

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in a known-non-zero context.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131887 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2011-05-23 00:21:50 +00:00
parent f415d8b646
commit 05cd886561
2 changed files with 38 additions and 0 deletions
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21
test/Transforms/InstCombine/shift.ll
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@ -506,3 +506,24 @@ define i32 @test41(i32 %a, i32 %b) nounwind {
; CHECK-NEXT: shl i32 8, %b
; CHECK-NEXT: ret i32
}
define i32 @test42(i32 %a, i32 %b) nounwind {
%div = lshr i32 4096, %b ; must be exact otherwise we'd divide by zero
%div2 = udiv i32 %a, %div
ret i32 %div2
; CHECK: @test42
; CHECK-NEXT: lshr exact i32 4096, %b
}
define i32 @test43(i32 %a, i32 %b) nounwind {
%div = shl i32 4096, %b ; must be exact otherwise we'd divide by zero
%div2 = udiv i32 %a, %div
ret i32 %div2
; CHECK: @test43
; CHECK-NEXT: add i32 %b, 12
; CHECK-NEXT: lshr
; CHECK-NEXT: ret
}