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dcc9291851
Summary: As a starting step, we only use one simple heuristic: if the sign bits of both a and b are zero, we can prove "add a, b" do not unsigned overflow, and thus convert it to "add nuw a, b". Updated all affected tests and added two new tests (@zero_sign_bit and @zero_sign_bit2) in AddOverflow.ll Test Plan: make check-all Reviewers: eliben, rafael, meheff, chandlerc Reviewed By: chandlerc Subscribers: chandlerc, llvm-commits Differential Revision: http://reviews.llvm.org/D4144 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211084 91177308-0d34-0410-b5e6-96231b3b80d8
10 lines
223 B
LLVM
10 lines
223 B
LLVM
; RUN: opt < %s -instcombine -S | grep "add nuw nsw i32"
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define double @x(i32 %a, i32 %b) nounwind {
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%m = lshr i32 %a, 24
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%n = and i32 %m, %b
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%o = sitofp i32 %n to double
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%p = fadd double %o, 1.0
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ret double %p
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}
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