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Also fold (A+B) == A -> B == 0 when the add is commuted.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125411 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer 2011-02-11 21:46:48 +00:00
parent 1021236c74
commit b6c8cb4422
2 changed files with 23 additions and 13 deletions
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6
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -2351,12 +2351,14 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
Constant::getNullValue(B->getType()));
// (A+B) == A -> B == 0
if (match(Op0, m_Add(m_Specific(Op1), m_Value(B))))
if (match(Op0, m_Add(m_Specific(Op1), m_Value(B))) ||
match(Op0, m_Add(m_Value(B), m_Specific(Op1))))
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))))
if (match(Op1, m_Add(m_Specific(Op0), m_Value(B))) ||
match(Op1, m_Add(m_Value(B), m_Specific(Op0))))
return new ICmpInst(I.getPredicate(), B,
Constant::getNullValue(B->getType()));

30
test/Transforms/InstCombine/add.ll
View File

@ -276,18 +276,26 @@ define i32 @test36(i32 %a) {
ret i32 %q
}
define i32 @test37(i32 %a, i32 %b) nounwind readnone {
entry:
%add = add nsw i32 %a, %b
define i1 @test37(i32 %a, i32 %b) nounwind readnone {
%add = add i32 %a, %b
%cmp = icmp eq i32 %add, %a
%conv = zext i1 %cmp to i32
ret i32 %conv
ret i1 %cmp
}
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
define i1 @test38(i32 %a, i32 %b) nounwind readnone {
%add = add i32 %a, %b
%cmp = icmp eq i32 %add, %b
ret i1 %cmp
}
define i1 @test39(i32 %a, i32 %b) nounwind readnone {
%add = add i32 %b, %a
%cmp = icmp eq i32 %add, %a
ret i1 %cmp
}
define i1 @test40(i32 %a, i32 %b) nounwind readnone {
%add = add i32 %b, %a
%cmp = icmp eq i32 %add, %b
ret i1 %cmp
}