[llvm] Simplify `(a % b) lt/ge (b-1)` into `(a % b) eq/ne (b-1)` (PR #72504)
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llvm-commits at lists.llvm.org
Sun Nov 19 10:05:06 PST 2023
================
@@ -6837,6 +6837,25 @@ Instruction *InstCombinerImpl::visitICmpInst(ICmpInst &I) {
Changed = true;
}
+ {
+ Value *X, *Y;
+ const APInt *C;
+ ICmpInst::Predicate Pred = I.getPredicate();
+ if ((Pred == ICmpInst::ICMP_SGE || Pred == ICmpInst::ICMP_SLT) &&
+ match(Op0, m_OneUse(m_SRem(m_Value(X), m_Value(Y)))) &&
+ ((match(Op1, m_OneUse(m_c_Add(m_Deferred(Y), m_AllOnes()))) &&
----------------
goldsteinn wrote:
You could also handle `sle` w/ `Y + -2` (instead of `slt` + `Y + -1`). Likewise in context of @dtcxzyw proofs, you could do `sge` w/ `Y + 2`.
You can also handle `urem` with `sge`/`slt`/`uge`/`ult`:
https://alive2.llvm.org/ce/z/9nBnWe
https://github.com/llvm/llvm-project/pull/72504
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