[llvm] [SCEV] Simplify SCEVExpr for PHI to SCEV for operand if operands are identical (PR #115945)
Yingwei Zheng via llvm-commits
llvm-commits at lists.llvm.org
Thu Nov 14 18:39:18 PST 2024
================
@@ -6019,6 +6019,37 @@ const SCEV *ScalarEvolution::createNodeFromSelectLikePHI(PHINode *PN) {
return nullptr;
}
+// Returns SCEV for the first operand of a phi if all phi operands have
+// identical opcodes and operands
+// eg.
+// a: %add = %a + %b
+// br %c
+// b: %add1 = %a + %b
+// br %c
+// c: %phi = phi [%add, a], [%add1, b]
+// scev(%phi) => scev(%add)
+const SCEV *
+ScalarEvolution::createNodeForPHIWithIdenticalOperands(PHINode *PN) {
+ BinaryOperator *CommonInst = nullptr;
+ for (Value *Incoming : PN->incoming_values()) {
+ BinaryOperator *IncomingInst = dyn_cast<BinaryOperator>(Incoming);
+ if (CommonInst) {
+ if (!(IncomingInst && CommonInst->isIdenticalTo(IncomingInst))) {
+ // Not identical, give up
+ CommonInst = nullptr;
+ break;
----------------
dtcxzyw wrote:
```suggestion
return nullptr;
```
https://github.com/llvm/llvm-project/pull/115945
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