From 4594db516a269fce2bde53aeae62882a371b804b Mon Sep 17 00:00:00 2001
From: Hans Wennborg <hans@hanshq.net>
Date: Wed, 8 Feb 2017 16:42:21 +0000
Subject: [PATCH] MachineCopyPropagation: Respect implicit operands of COPY

Cherry pick llvm r294088 to 4.0 branch with slight changes to the way
undef operands are handled.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_40@294473 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/MachineCopyPropagation.cpp | 48 +++++++++++++++++---------
 1 file changed, 31 insertions(+), 17 deletions(-)

diff --git a/lib/CodeGen/MachineCopyPropagation.cpp b/lib/CodeGen/MachineCopyPropagation.cpp
index 92d043df26b..5de6dec29fb 100644
--- a/lib/CodeGen/MachineCopyPropagation.cpp
+++ b/lib/CodeGen/MachineCopyPropagation.cpp
@@ -61,6 +61,7 @@ namespace {
 
   private:
     void ClobberRegister(unsigned Reg);
+    void ReadRegister(unsigned Reg);
     void CopyPropagateBlock(MachineBasicBlock &MBB);
     bool eraseIfRedundant(MachineInstr &Copy, unsigned Src, unsigned Def);
 
@@ -120,6 +121,18 @@ void MachineCopyPropagation::ClobberRegister(unsigned Reg) {
   }
 }
 
+void MachineCopyPropagation::ReadRegister(unsigned Reg) {
+  // If 'Reg' is defined by a copy, the copy is no longer a candidate
+  // for elimination.
+  for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) {
+    Reg2MIMap::iterator CI = CopyMap.find(*AI);
+    if (CI != CopyMap.end()) {
+      DEBUG(dbgs() << "MCP: Copy is used - not dead: "; CI->second->dump());
+      MaybeDeadCopies.remove(CI->second);
+    }
+  }
+}
+
 /// Return true if \p PreviousCopy did copy register \p Src to register \p Def.
 /// This fact may have been obscured by sub register usage or may not be true at
 /// all even though Src and Def are subregisters of the registers used in
@@ -212,12 +225,14 @@ void MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
 
       // If Src is defined by a previous copy, the previous copy cannot be
       // eliminated.
-      for (MCRegAliasIterator AI(Src, TRI, true); AI.isValid(); ++AI) {
-        Reg2MIMap::iterator CI = CopyMap.find(*AI);
-        if (CI != CopyMap.end()) {
-          DEBUG(dbgs() << "MCP: Copy is no longer dead: "; CI->second->dump());
-          MaybeDeadCopies.remove(CI->second);
-        }
+      ReadRegister(Src);
+      for (const MachineOperand &MO : MI->implicit_operands()) {
+        if (!MO.isReg() || !MO.readsReg())
+          continue;
+        unsigned Reg = MO.getReg();
+        if (!Reg)
+          continue;
+        ReadRegister(Reg);
       }
 
       DEBUG(dbgs() << "MCP: Copy is a deletion candidate: "; MI->dump());
@@ -234,6 +249,14 @@ void MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
       // ...
       // %xmm2<def> = copy %xmm9
       ClobberRegister(Def);
+      for (const MachineOperand &MO : MI->implicit_operands()) {
+        if (!MO.isReg() || !MO.isDef())
+          continue;
+        unsigned Reg = MO.getReg();
+        if (!Reg)
+          continue;
+        ClobberRegister(Reg);
+      }
 
       // Remember Def is defined by the copy.
       for (MCSubRegIterator SR(Def, TRI, /*IncludeSelf=*/true); SR.isValid();
@@ -268,17 +291,8 @@ void MachineCopyPropagation::CopyPropagateBlock(MachineBasicBlock &MBB) {
 
       if (MO.isDef()) {
         Defs.push_back(Reg);
-        continue;
-      }
-
-      // If 'Reg' is defined by a copy, the copy is no longer a candidate
-      // for elimination.
-      for (MCRegAliasIterator AI(Reg, TRI, true); AI.isValid(); ++AI) {
-        Reg2MIMap::iterator CI = CopyMap.find(*AI);
-        if (CI != CopyMap.end()) {
-          DEBUG(dbgs() << "MCP: Copy is used - not dead: "; CI->second->dump());
-          MaybeDeadCopies.remove(CI->second);
-        }
+      } else {
+        ReadRegister(Reg);
       }
       // Treat undef use like defs for copy propagation but not for
       // dead copy. We would need to do a liveness check to be sure the copy
-- 
2.40.0