[llvm] [DA] Cache delinearization results. NFCI. (PR #164379)

[Ryotaro Kasuga via llvm-commits]

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@@ -3463,11 +3463,37 @@ bool DependenceInfo::tryDelinearize(Instruction *Src, Instruction *Dst,
 
   SmallVector<const SCEV *, 4> SrcSubscripts, DstSubscripts;
 
-  if (!tryDelinearizeFixedSize(Src, Dst, SrcAccessFn, DstAccessFn,
-                               SrcSubscripts, DstSubscripts) &&
-      !tryDelinearizeParametricSize(Src, Dst, SrcAccessFn, DstAccessFn,
-                                    SrcSubscripts, DstSubscripts))
-    return false;
+  // Check cache for both Src and Dst subscripts
+  auto SrcCacheKey = std::make_tuple(Src, SrcLoop, SrcAccessFn);
+  auto DstCacheKey = std::make_tuple(Dst, DstLoop, DstAccessFn);
+  auto SrcCacheIt = DelinearizationCache.find(SrcCacheKey);
+  auto DstCacheIt = DelinearizationCache.find(DstCacheKey);
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kasuga-fj wrote:

Consider using `try_emplace` to avoid repeated hash lookup.

https://github.com/llvm/llvm-project/pull/164379