[llvm] [InstCombine] Fold `(icmp eq/ne (or (select cond, 0/NZ, 0/NZ), X), 0)` (PR #88183)

[Nikita Popov via llvm-commits]

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@@ -3487,6 +3487,67 @@ Instruction *InstCombinerImpl::foldICmpBinOpEqualityWithConstant(
       Value *And = Builder.CreateAnd(BOp0, NotBOC);
       return new ICmpInst(Pred, And, NotBOC);
     }
+    // (icmp eq (or (select cond, 0, NonZero), Other))
+    //  -> (and cond, (icmp eq Other, 0))
+    // (icmp ne (or (select cond, NonZero, 0), Other))
+    //  -> (or cond, (icmp ne Other, 0))
+    // (icmp ne (or (select cond, 0, NonZero), Other))
+    //  -> (or (not cond), (icmp ne Other, 0))
+    // (icmp eq (or (select cond, NonZero, 0), Other))
+    //  -> (and (not cond), (icmp eq Other, 0))
+    Value *Cond, *TV, *FV, *Other;
+    if (C.isZero() &&
+        match(BO, m_c_Or(m_Select(m_Value(Cond), m_Value(TV), m_Value(FV)),
+                         m_Value(Other)))) {
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nikic wrote:

Don't we need one-use on BO here? We're producing two instructions. I think multi-use is not tested for this fold?

https://github.com/llvm/llvm-project/pull/88183