[llvm] [ValueTracking] Infer `exact` for `udiv` and `sdiv` (PR #126438)

[via llvm-commits]

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@@ -2555,6 +2555,71 @@ bool llvm::isKnownToBeAPowerOfTwo(const Value *V, bool OrZero, unsigned Depth,
   }
 }
 
+bool llvm::isKnownToBeZeroFromAssumes(const Value *V, const SimplifyQuery &Q) {
+
+  if (Q.AC && Q.CxtI) {
+    for (auto &AssumeVH : Q.AC->assumptionsFor(V)) {
+      if (!AssumeVH)
+        continue;
+      CallInst *I = cast<CallInst>(AssumeVH);
+      const Value *Cond = I->getArgOperand(0);
+      if (match(Cond,
+                m_SpecificICmp(ICmpInst::ICMP_EQ, m_Specific(V), m_Zero())) &&
+          isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
+        return true;
+      }
+    }
+  }
+
+  return false;
+}
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goldsteinn wrote:

I can't imagine this is useful, if we have `assume((icmp eq X, 0))` we will replace `X` with `0`.

https://github.com/llvm/llvm-project/pull/126438