[llvm] ValueTracking: simplify udiv/urem recurrences (PR #108973)

[Ramkumar Ramachandra via llvm-commits]

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@@ -1543,6 +1543,21 @@ static void computeKnownBitsFromOperator(const Operator *I,
         }
         break;
       }
+
+      // Check for operations with the property that the magnitude of the
+      // result will never exceed that of the start value.
+      case Instruction::UDiv:
+      case Instruction::URem: {
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artagnon wrote:

Doesn't `matchSimpleRecurrence` set `R` to the start value? I've also checked for `RInst` to set the context correctly.

https://github.com/llvm/llvm-project/pull/108973