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Fix for PR2479: correctly optimize expressions like (a > 13) & (a ==

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15).

See also PR1800, which is about the signed case.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52608 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eli Friedman 2008-06-21 23:36:13 +00:00
parent 1adec83ae8
commit 5c1f172213
2 changed files with 12 additions and 2 deletions
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3
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -3691,8 +3691,7 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
case ICmpInst::ICMP_UGT:
switch (RHSCC) {
default: assert(0 && "Unknown integer condition code!");
case ICmpInst::ICMP_EQ: // (X u> 13 & X == 15) -> X > 13
return ReplaceInstUsesWith(I, LHS);
case ICmpInst::ICMP_EQ: // (X u> 13 & X == 15) -> X == 15
case ICmpInst::ICMP_UGT: // (X u> 13 & X u> 15) -> X u> 15
return ReplaceInstUsesWith(I, RHS);
case ICmpInst::ICMP_SGT: // (X u> 13 & X s> 15) -> no change

11
test/Transforms/InstCombine/2008-06-21-CompareMiscomp.ll Normal file
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@ -0,0 +1,11 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {icmp eq i32 %In, 15}
; PR2479
; (See also PR1800.)
define i1 @test(i32 %In) {
%c1 = icmp ugt i32 %In, 13
%c2 = icmp eq i32 %In, 15
%V = and i1 %c1, %c2
ret i1 %V
}