[llvm] [InstCombine] Improve handling of `not` and free inversion. (PR #66787)
via llvm-commits
llvm-commits at lists.llvm.org
Sun Nov 19 12:05:47 PST 2023
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@@ -2205,12 +2227,23 @@ Instruction *InstCombinerImpl::visitSub(BinaryOperator &I) {
// (~X) - (~Y) --> Y - X
// This is placed after the other reassociations and explicitly excludes a
// sub-of-sub pattern to avoid infinite looping.
- if (isFreeToInvert(Op0, Op0->hasOneUse()) &&
- isFreeToInvert(Op1, Op1->hasOneUse()) &&
- !match(Op0, m_Sub(m_ImmConstant(), m_Value()))) {
- Value *NotOp0 = Builder.CreateNot(Op0);
- Value *NotOp1 = Builder.CreateNot(Op1);
- return BinaryOperator::CreateSub(NotOp1, NotOp0);
+ {
+ auto m_AddSubInvertable = m_CombineOr(m_Add(m_Value(), m_ImmConstant()),
+ m_Sub(m_ImmConstant(), m_Value()));
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goldsteinn wrote:
The `sub` is unnecessary (will drop). But we rely on this fold for simplifying things like `(A + C0) - (B + C1)`
https://github.com/llvm/llvm-project/pull/66787
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