[InstSimplify] Generalize simplification of icmps with monotonic operands #69471
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goldsteinn
reviewed
Oct 18, 2023
goldsteinn
reviewed
Oct 18, 2023
| @@ -3103,6 +3103,54 @@ static Value *simplifyICmpWithConstant(CmpInst::Predicate Pred, Value *LHS, | |||
| return nullptr; | |||
| } | |||
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| /// Get values V_i such that V uge V_i (Greater) or V ule V_i (!Greater). | |||
| static void getUnsignedMonotonicValues(SmallPtrSetImpl<Value *> &Res, Value *V, | |||
| bool Greater, unsigned Depth = 0) { | |||
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Would replace greater with an enum that also support GreaterOrEq and LessOrEq. Also think a bool for Signed makes sense.
goldsteinn
reviewed
Oct 18, 2023
| Value *X, *Y; | ||
| if (Greater) { | ||
| if (match(V, m_Or(m_Value(X), m_Value(Y))) || | ||
| match(V, m_Intrinsic<Intrinsic::uadd_sat>(m_Value(X), m_Value(Y)))) { |
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You can imagine a lot more cases for this. Imo should just be a switch from the start.
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Also these matches aren't Greater, they are GreaterOrEq.
goldsteinn
reviewed
Oct 18, 2023
| match(V, m_UDiv(m_Value(X), m_Value())) || | ||
| match(V, m_LShr(m_Value(X), m_Value())) || | ||
| match(V, m_Intrinsic<Intrinsic::usub_sat>(m_Value(X)))) { | ||
| getUnsignedMonotonicValues(Res, X, Greater, Depth); |
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Don't need complete coverage here, but can you add TODO for some additional freebies (min/max/add+nuw/sub+nuw/mul+nuw/shl+nuw/ashr+signbit/etc...)
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InstSimplify currently folds patterns like
(x | y) uge xand(x & y) ule xto true. However, it cannot handle combinations of such situations, such as(x | y) uge (x & z)etc.To support this, recursively collect operands of monotonic instructions (that preserve either a greater-or-equal or less-or-equal relationship) and then check whether any of them match.