[llvm] [MCP] Disable BackwardCopyPropagateBlock for copies with implicit registers. (PR #137687)

[Matt Arsenault via llvm-commits]

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@@ -1200,7 +1200,7 @@ void MachineCopyPropagation::BackwardCopyPropagateBlock(
     // Ignore non-trivial COPYs.
     std::optional<DestSourcePair> CopyOperands =
         isCopyInstr(MI, *TII, UseCopyInstr);
-    if (CopyOperands) {
+    if (CopyOperands && MI.getNumImplicitOperands() == 0) {
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arsenm wrote:

I guess it does in the target instruction implementations, not the base copy handling 

https://github.com/llvm/llvm-project/pull/137687