1 files changed, 35 insertions, 64 deletions

diff --git a/llvm/lib/CodeGen/MachineCopyPropagation.cpp b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
index 49d62e9..742de11 100644
--- a/llvm/lib/CodeGen/MachineCopyPropagation.cpp
+++ b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
@@ -872,12 +872,6 @@ void MachineCopyPropagation::forwardUses(MachineInstr &MI) {
     ++NumCopyForwards;
     Changed = true;
   }
-  // Attempt to canonicalize/optimize the instruction now its arguments have
-  // been mutated.
-  if (TII->simplifyInstruction(MI)) {
-    Changed = true;
-    LLVM_DEBUG(dbgs() << "MCP: After optimizeInstruction: " << MI);
-  }
 }
 
 void MachineCopyPropagation::ForwardCopyPropagateBlock(MachineBasicBlock &MBB) {
@@ -889,10 +883,8 @@ void MachineCopyPropagation::ForwardCopyPropagateBlock(MachineBasicBlock &MBB) {
     std::optional<DestSourcePair> CopyOperands =
         isCopyInstr(MI, *TII, UseCopyInstr);
     if (CopyOperands) {
-
       Register RegSrc = CopyOperands->Source->getReg();
       Register RegDef = CopyOperands->Destination->getReg();
-
       if (!TRI->regsOverlap(RegDef, RegSrc)) {
         assert(RegDef.isPhysical() && RegSrc.isPhysical() &&
               "MachineCopyPropagation should be run after register allocation!");
@@ -917,51 +909,6 @@ void MachineCopyPropagation::ForwardCopyPropagateBlock(MachineBasicBlock &MBB) {
         //  %ecx = COPY %eax
         if (eraseIfRedundant(MI, Def, Src) || eraseIfRedundant(MI, Src, Def))
           continue;
-
-        forwardUses(MI);
-
-        // Src may have been changed by forwardUses()
-        CopyOperands = isCopyInstr(MI, *TII, UseCopyInstr);
-        Src = CopyOperands->Source->getReg().asMCReg();
-
-        // If Src is defined by a previous copy, the previous copy cannot be
-        // eliminated.
-        ReadRegister(Src, MI, RegularUse);
-        for (const MachineOperand &MO : MI.implicit_operands()) {
-          if (!MO.isReg() || !MO.readsReg())
-            continue;
-          MCRegister Reg = MO.getReg().asMCReg();
-          if (!Reg)
-            continue;
-          ReadRegister(Reg, MI, RegularUse);
-        }
-
-        LLVM_DEBUG(dbgs() << "MCP: Copy is a deletion candidate: "; MI.dump());
-
-        // Copy is now a candidate for deletion.
-        if (!MRI->isReserved(Def))
-          MaybeDeadCopies.insert(&MI);
-
-        // If 'Def' is previously source of another copy, then this earlier copy's
-        // source is no longer available. e.g.
-        // %xmm9 = copy %xmm2
-        // ...
-        // %xmm2 = copy %xmm0
-        // ...
-        // %xmm2 = copy %xmm9
-        Tracker.clobberRegister(Def, *TRI, *TII, UseCopyInstr);
-        for (const MachineOperand &MO : MI.implicit_operands()) {
-          if (!MO.isReg() || !MO.isDef())
-            continue;
-          MCRegister Reg = MO.getReg().asMCReg();
-          if (!Reg)
-            continue;
-          Tracker.clobberRegister(Reg, *TRI, *TII, UseCopyInstr);
-        }
-
-        Tracker.trackCopy(&MI, *TRI, *TII, UseCopyInstr);
-
-        continue;
       }
     }
 
@@ -979,20 +926,36 @@ void MachineCopyPropagation::ForwardCopyPropagateBlock(MachineBasicBlock &MBB) {
 
     forwardUses(MI);
 
-    // It's possible that the previous transformation has resulted in a no-op
-    // register move (i.e. one where source and destination registers are the
-    // same and are not referring to a reserved register). If so, delete it.
-    CopyOperands = isCopyInstr(MI, *TII, UseCopyInstr);
-    if (CopyOperands &&
-        CopyOperands->Source->getReg() == CopyOperands->Destination->getReg() &&
-        !MRI->isReserved(CopyOperands->Source->getReg())) {
-      MI.eraseFromParent();
-      NumDeletes++;
+    // Attempt to canonicalize/optimize the instruction now its arguments have
+    // been mutated.  This may convert MI from a non-copy to a copy instruction.
+    if (TII->simplifyInstruction(MI)) {
       Changed = true;
-      continue;
+      LLVM_DEBUG(dbgs() << "MCP: After simplifyInstruction: " << MI);
+    }
+
+    CopyOperands = isCopyInstr(MI, *TII, UseCopyInstr);
+    if (CopyOperands) {
+      Register RegSrc = CopyOperands->Source->getReg();
+      Register RegDef = CopyOperands->Destination->getReg();
+      // It's possible that the previous transformations have resulted in a
+      // no-op register move (i.e. one where source and destination registers
+      // are the same and are not referring to a reserved register). If so,
+      // delete it.
+      if (RegSrc == RegDef && !MRI->isReserved(RegSrc)) {
+        MI.eraseFromParent();
+        NumDeletes++;
+        Changed = true;
+        continue;
+      }
+
+      if (!TRI->regsOverlap(RegDef, RegSrc)) {
+        // Copy is now a candidate for deletion.
+        MCRegister Def = RegDef.asMCReg();
+        if (!MRI->isReserved(Def))
+          MaybeDeadCopies.insert(&MI);
+      }
     }
 
-    // Not a copy.
     SmallVector<Register, 4> Defs;
     const MachineOperand *RegMask = nullptr;
     for (const MachineOperand &MO : MI.operands()) {
@@ -1072,6 +1035,14 @@ void MachineCopyPropagation::ForwardCopyPropagateBlock(MachineBasicBlock &MBB) {
     // Any previous copy definition or reading the Defs is no longer available.
     for (MCRegister Reg : Defs)
       Tracker.clobberRegister(Reg, *TRI, *TII, UseCopyInstr);
+
+    if (CopyOperands) {
+      Register RegSrc = CopyOperands->Source->getReg();
+      Register RegDef = CopyOperands->Destination->getReg();
+      if (!TRI->regsOverlap(RegDef, RegSrc)) {
+        Tracker.trackCopy(&MI, *TRI, *TII, UseCopyInstr);
+      }
+    }
   }
 
   bool TracksLiveness = MRI->tracksLiveness();