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

[Artem Belevich via llvm-commits]

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@@ -741,20 +728,30 @@ void StraightLineStrengthReduce::setBasisAndDeltaFor(Candidate &C) {
 
   if (const auto *BaseDeltaCandidates =
           CandidateDict.getCandidatesWithDeltaKind(C, Candidate::BaseDelta)) {
-    if (SearchFrom(*BaseDeltaCandidates, For(Candidate::BaseDelta))) {
+    if ((C.CandidateKind != Candidate::Mul) &&
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Artem-B wrote:

Why is Mul a special case? A comment would be useful.

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