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

If there's an implicit-def of a super register, the propagation
must preserve this implicit-def. Knowing how and when to do this
may require target specific knowledge so just disable it for now.
    
Prior to 2def1c4, we checked that the copy had explicit 2 operands
when that was removed we started allowing implicit operands through.
This patch adds a check for implicit operands, but still allows
extra explicit operands which was the goal of 2def1c4.
    
Fixes #131478.

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/MachineCopyPropagation.cpp b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
index 224588b9d52e..6eab87c1292e 100644
--- a/llvm/lib/CodeGen/MachineCopyPropagation.cpp
+++ b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
@@ -1206,7 +1206,7 @@ void MachineCopyPropagation::BackwardCopyPropagateBlock(
     // Ignore non-trivial COPYs.
     std::optional<DestSourcePair> CopyOperands =
         isCopyInstr(MI, *TII, UseCopyInstr);
-    if (CopyOperands) {
+    if (CopyOperands && MI.getNumImplicitOperands() == 0) {
       Register DefReg = CopyOperands->Destination->getReg();
       Register SrcReg = CopyOperands->Source->getReg();