[llvm] [MemCpyOpt] Drop dead `memmove` calls on `memset`'d source data (PR #101930)

[Nikita Popov via llvm-commits]

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@@ -1843,12 +1844,77 @@ bool MemCpyOptPass::processMemCpy(MemCpyInst *M, BasicBlock::iterator &BBI) {
   return false;
 }
 
+/// Memmove calls with overlapping src/dest buffers that come after a memset may
+/// be removed.
+bool MemCpyOptPass::isMemMoveMemSetDependency(MemMoveInst *M) {
+  const auto &DL = M->getDataLayout();
+  MemSetInst *MS = nullptr;
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nikic wrote:

Move MS declaration down.

https://github.com/llvm/llvm-project/pull/101930