[llvm] Reland "Redesign Straight-Line Strength Reduction (SLSR) (#162930)" (PR #169614)

[Artem Belevich via llvm-commits]

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@@ -625,14 +626,24 @@ static void unifyBitWidth(APInt &A, APInt &B) {
     B = B.sext(A.getBitWidth());
 }
 
-Constant *StraightLineStrengthReduce::getIndexDelta(Candidate &C,
-                                                    Candidate &Basis) {
-  APInt Idx = C.Index->getValue(), BasisIdx = Basis.Index->getValue();
-  unifyBitWidth(Idx, BasisIdx);
-  APInt IndexDelta = Idx - BasisIdx;
-  IntegerType *DeltaType =
-      IntegerType::get(C.Ins->getContext(), IndexDelta.getBitWidth());
-  return ConstantInt::get(DeltaType, IndexDelta);
+Value *StraightLineStrengthReduce::getDelta(const Candidate &C,
+                                            const Candidate &Basis,
+                                            Candidate::DKind K) const {
+  if (K == Candidate::IndexDelta) {
+    APInt Idx = C.Index->getValue(), BasisIdx = Basis.Index->getValue();
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Artem-B wrote:

Nit: multiple initialized variables on the same line are hard to read. Instantiating them separately makes it easier to tell where `BasisIdx` comes from.

https://github.com/llvm/llvm-project/pull/169614