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Recognize and simplify

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(A+B) == A  ->  B == 0
A == (A+B)  ->  B == 0



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124567 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Anders Carlsson 2011-01-30 22:01:13 +00:00
parent 8352062e52
commit 77bc49e5e2
2 changed files with 27 additions and 1 deletions
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12
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -2341,7 +2341,17 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
if (match(Op1, m_Sub(m_Specific(Op0), m_Value(B))))
return new ICmpInst(I.getPredicate(), B,
Constant::getNullValue(B->getType()));
// (A+B) == A -> B == 0
if (match(Op0, m_Add(m_Specific(Op1), m_Value(B))))
return new ICmpInst(I.getPredicate(), B,
Constant::getNullValue(B->getType()));
// A == (A+B) -> B == 0
if (match(Op1, m_Add(m_Specific(Op0), m_Value(B))))
return new ICmpInst(I.getPredicate(), B,
Constant::getNullValue(B->getType()));
// (X&Z) == (Y&Z) -> (X^Y) & Z == 0
if (Op0->hasOneUse() && Op1->hasOneUse() &&
match(Op0, m_And(m_Value(A), m_Value(B))) &&

16
test/Transforms/InstCombine/add.ll
View File

@ -275,3 +275,19 @@ define i32 @test36(i32 %a) {
%q = and i32 %z, 1 ; always zero
ret i32 %q
}
define i32 @test37(i32 %a, i32 %b) nounwind readnone {
entry:
%add = add nsw i32 %a, %b
%cmp = icmp eq i32 %add, %a
%conv = zext i1 %cmp to i32
ret i32 %conv
}
define i32 @test38(i32 %a, i32 %b) nounwind readnone {
entry:
%add = add nsw i32 %a, %b
%cmp = icmp eq i32 %add, %a
%conv = zext i1 %cmp to i32
ret i32 %conv
}