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InstCombine: FoldOrOfICmps harder

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We may be in a situation where the icmps might not be near each other in
a tree of or instructions.  Try to dig out related compare instructions
and see if they combine.

N.B.  This won't fire on deep trees of compares because rewritting the
tree might end up creating a net increase of IR.  We may have to resort
to something more sophisticated if this is a real problem.

llvm-svn: 222928
This commit is contained in:
David Majnemer 2014-11-28 19:58:29 +00:00
parent a072cee758
commit 87a17a0975
2 changed files with 35 additions and 2 deletions
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27
lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -2305,11 +2305,34 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
if (SwappedForXor)
std::swap(Op0, Op1);
if (ICmpInst *RHS = dyn_cast<ICmpInst>(I.getOperand(1)))
if (ICmpInst *LHS = dyn_cast<ICmpInst>(I.getOperand(0)))
{
ICmpInst *LHS = dyn_cast<ICmpInst>(Op0);
ICmpInst *RHS = dyn_cast<ICmpInst>(Op1);
if (LHS && RHS)
if (Value *Res = FoldOrOfICmps(LHS, RHS, &I))
return ReplaceInstUsesWith(I, Res);
// TODO: Make this recursive; it's a little tricky because an arbitrary
// number of 'or' instructions might have to be created.
Value *X, *Y;
if (LHS && match(Op1, m_OneUse(m_Or(m_Value(X), m_Value(Y))))) {
if (auto *Cmp = dyn_cast<ICmpInst>(X))
if (Value *Res = FoldOrOfICmps(LHS, Cmp, &I))
return ReplaceInstUsesWith(I, Builder->CreateOr(Res, Y));
if (auto *Cmp = dyn_cast<ICmpInst>(Y))
if (Value *Res = FoldOrOfICmps(LHS, Cmp, &I))
return ReplaceInstUsesWith(I, Builder->CreateOr(Res, X));
}
if (RHS && match(Op0, m_OneUse(m_Or(m_Value(X), m_Value(Y))))) {
if (auto *Cmp = dyn_cast<ICmpInst>(X))
if (Value *Res = FoldOrOfICmps(Cmp, RHS, &I))
return ReplaceInstUsesWith(I, Builder->CreateOr(Res, Y));
if (auto *Cmp = dyn_cast<ICmpInst>(Y))
if (Value *Res = FoldOrOfICmps(Cmp, RHS, &I))
return ReplaceInstUsesWith(I, Builder->CreateOr(Res, X));
}
}
// (fcmp uno x, c) | (fcmp uno y, c) -> (fcmp uno x, y)
if (FCmpInst *LHS = dyn_cast<FCmpInst>(I.getOperand(0)))
if (FCmpInst *RHS = dyn_cast<FCmpInst>(I.getOperand(1)))

10
test/Transforms/InstCombine/or.ll
View File

@ -506,3 +506,13 @@ define i1 @test47(i8 signext %c) {
; CHECK-NEXT: add i8 %1, -65
; CHECK-NEXT: icmp ult i8 %2, 27
}
define i1 @test48(i64 %x, i1 %b) {
%1 = icmp ult i64 %x, 2305843009213693952
%2 = icmp ugt i64 %x, 2305843009213693951
%.b = or i1 %2, %b
%3 = or i1 %1, %.b
ret i1 %3
; CHECK-LABEL: @test48(
; CHECK-NEXT: ret i1 true
}