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Invert and-of-or into or-of-and when doing so would allow us to clear bits of the and's mask.

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This can result in increased opportunities for store narrowing in code generation.  Update a number of
tests for this change.  This fixes <rdar://problem/8285027>.

Additionally, because this inverts the order of ors and ands, some patterns for optimizing or-of-and-of-or
no longer fire in instances where they did originally.  Add a simple transform which recaptures most of these
opportunities: if we have an or-of-constant-or and have failed to fold away the inner or, commute the order 
of the two ors, to give the non-constant or a chance for simplification instead.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@113679 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson
2010-09-11 05:48:06 +00:00
parent 1c4e934666
commit 26c5663283
5 changed files with 69 additions and 22 deletions
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35
lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
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@@ -207,12 +207,26 @@ Instruction *InstCombiner::OptAndOp(Instruction *Op,
}
break;
case Instruction::Or:
if (Op->hasOneUse() && Together != OpRHS) {
// (X | C1) & C2 --> (X | (C1&C2)) & C2
Value *Or = Builder->CreateOr(X, Together);
Or->takeName(Op);
return BinaryOperator::CreateAnd(Or, AndRHS);
if (Op->hasOneUse()){
if (Together != OpRHS) {
// (X | C1) & C2 --> (X | (C1&C2)) & C2
Value *Or = Builder->CreateOr(X, Together);
Or->takeName(Op);
return BinaryOperator::CreateAnd(Or, AndRHS);
}
ConstantInt *TogetherCI = dyn_cast<ConstantInt>(Together);
if (TogetherCI && !TogetherCI->isZero()){
// (X | C1) & C2 --> (X & (C2^(C1&C2))) | C1
// NOTE: This reduces the number of bits set in the & mask, which
// can expose opportunities for store narrowing.
Together = ConstantExpr::getXor(AndRHS, Together);
Value *And = Builder->CreateAnd(X, Together);
And->takeName(Op);
return BinaryOperator::CreateOr(And, OpRHS);
}
}
break;
case Instruction::Add:
if (Op->hasOneUse()) {
@@ -1943,6 +1957,17 @@ Instruction *InstCombiner::visitOr(BinaryOperator &I) {
}
}
// Note: If we've gotten to the point of visiting the outer OR, then the
// inner one couldn't be simplified. If it was a constant, then it won't
// be simplified by a later pass either, so we try swapping the inner/outer
// ORs in the hopes that we'll be able to simplify it this way.
// (X|C) | V --> (X|V) | C
if (Op0->hasOneUse() && match(Op0, m_Or(m_Value(A), m_ConstantInt(C1)))) {
Value *Inner = Builder->CreateOr(Op0, Op1);
Inner->takeName(Op0);
return BinaryOperator::CreateOr(Inner, C1);
}
return Changed ? &I : 0;
}