[llvm] LoopIdiomRecognize: detect and convert powi idiom (PR #72650)

[Ramkumar Ramachandra via llvm-commits]

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@@ -549,33 +544,43 @@ bool LoopIdiomRecognize::runOnLoopBlock(
     BasicBlock *BB, const SCEV *BECount,
     SmallVectorImpl<BasicBlock *> &ExitBlocks) {
   // We can only promote stores in this block if they are unconditionally
-  // executed in the loop.  For a block to be unconditionally executed, it has
-  // to dominate all the exit blocks of the loop.  Verify this now.
+  // executed in the loop. The powi idiom also requires the block to be
+  // unconditionally executed. For a block to be unconditionally executed, it
+  // has to dominate all the exit blocks of the loop.
   for (BasicBlock *ExitBlock : ExitBlocks)
     if (!DT->dominates(BB, ExitBlock))
       return false;
 
   bool MadeChange = false;
-  // Look for store instructions, which may be optimized to memset/memcpy.
-  collectStores(BB);
 
-  // Look for a single store or sets of stores with a common base, which can be
-  // optimized into a memset (memset_pattern).  The latter most commonly happens
-  // with structs and handunrolled loops.
-  for (auto &SL : StoreRefsForMemset)
-    MadeChange |= processLoopStores(SL.second, BECount, ForMemset::Yes);
+  HasMemset = TLI->has(LibFunc_memset);
+  HasMemsetPattern = TLI->has(LibFunc_memset_pattern16);
+  HasMemcpy = TLI->has(LibFunc_memcpy);
+
+  if (HasMemset || HasMemsetPattern || HasMemcpy) {
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artagnon wrote:

Each function checks `HasMemset`, `HasMemsetPattern`, and `HasMemcpy`, when it needs them. This check is merely moved from the parent function to the child function.

https://github.com/llvm/llvm-project/pull/72650