[llvm] [Codegen] Remove redundant instruction using machinelateCleanup (PR #139716)

[Matt Arsenault via llvm-commits]

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@@ -186,13 +186,24 @@ static bool isCandidate(const MachineInstr *MI, Register &DefedReg,
   for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
     const MachineOperand &MO = MI->getOperand(i);
     if (MO.isReg()) {
-      if (MO.isDef() && DefedReg == MCRegister::NoRegister) {
+      if (MO.isDef()) {
         if (i == 0 && !MO.isImplicit() && !MO.isDead())
           DefedReg = MO.getReg();
-        else
+        else if (i != 0 && DefedReg != MCRegister::NoRegister) {
+          if (MO.isDead() && MO.isImplicit()) {
+            continue;
+          } else if (MO.isImplicit() &&
+                     MI->getParent()
+                         ->getParent()
+                         ->getSubtarget()
+                         .getRegisterInfo()
+                         ->isSubRegister(MO.getReg(), DefedReg)) {
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arsenm wrote:

This shouldn't have to do so much to find TRI, just pass it into isCandidate as an argument.

Also probably should use regsOverlap instead of isSubRegister?

https://github.com/llvm/llvm-project/pull/139716