[llvm] [SCEV] Directly use NUW on mul in getUDivExpr (PR #217235)

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llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-analysis

Author: Ramkumar Ramachandra (artagnon)

<details>
<summary>Changes</summary>

Eliminate the roundabout and expensive zero extend expressions, and use the wrap flags on the expression directly.

Proof: https://alive2.llvm.org/ce/z/e7YFi_

---
Full diff: https://github.com/llvm/llvm-project/pull/217235.diff


1 Files Affected:

- (modified) llvm/lib/Analysis/ScalarEvolution.cpp (+2-5) 


``````````diff
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 1707c6c17fe23..826e1afbe084e 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -3581,16 +3581,13 @@ const SCEV *ScalarEvolution::getUDivExpr(SCEVUse LHS, SCEVUse RHS) {
         }
       // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
       if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
-        SmallVector<SCEVUse, 4> Operands;
-        for (const SCEV *Op : M->operands())
-          Operands.push_back(getZeroExtendExpr(Op, ExtTy));
-        if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands)) {
+        if (M->hasNoUnsignedWrap()) {
           // Find an operand that's safely divisible.
           for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
             const SCEV *Op = M->getOperand(i);
             const SCEV *Div = getUDivExpr(Op, RHSC);
             if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) {
-              Operands = SmallVector<SCEVUse, 4>(M->operands());
+              SmallVector<SCEVUse, 4> Operands(M->operands());
               Operands[i] = Div;
               return getMulExpr(Operands);
             }

``````````

</details>


https://github.com/llvm/llvm-project/pull/217235