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

[Akshay Deodhar via llvm-commits]

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@@ -177,22 +203,154 @@ class StraightLineStrengthReduce {
     // Points to the immediate basis of this candidate, or nullptr if we cannot
     // find any basis for this candidate.
     Candidate *Basis = nullptr;
+
+    DKind DeltaKind = InvalidDelta;
+
+    // Store SCEV of Stride to compute delta from different strides
+    const SCEV *StrideSCEV = nullptr;
+
+    // Points to (Y - X) that will be used to rewrite this candidate.
+    Value *Delta = nullptr;
+
+    /// Cost model: Evaluate the computational efficiency of the candidate.
+    ///
+    /// Efficiency levels (higher is better):
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akshayrdeodhar wrote:

Maybe have an enum here instead of raw values?

https://github.com/llvm/llvm-project/pull/162930