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Added instcombine pattern to spot comparing -val or val against 0.

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(val != 0) == (-val != 0) so "abs(val) != 0" becomes "val != 0"

Fixes <rdar://problem/10482509>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145563 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Pete Cooper
2011-12-01 03:58:40 +00:00
parent 618c1dbd29
commit 65a6b57c33
2 changed files with 24 additions and 0 deletions
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14
lib/Transforms/InstCombine/InstCombineCompares.cpp
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@@ -1795,6 +1795,20 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
if (Value *V = SimplifyICmpInst(I.getPredicate(), Op0, Op1, TD))
return ReplaceInstUsesWith(I, V);
// comparing -val or val with non-zero is the same as just comparing val
// ie, (val != 0) == (-val != 0)
if (I.getPredicate() == ICmpInst::ICMP_NE && match(Op1, m_Zero()))
{
Value *Cond, *SubSrc, *SelectFalse;
if (match(Op0, m_Select(m_Value(Cond), m_Sub(m_Zero(), m_Value(SubSrc)),
m_Value(SelectFalse)))) {
if (SubSrc == SelectFalse) {
return CmpInst::Create(Instruction::ICmp, I.getPredicate(),
SubSrc, Op1);
}
}
}
Type *Ty = Op0->getType();
// icmp's with boolean values can always be turned into bitwise operations