From ac94863a1c090f2221ff2e21b7ee5480bd1db594 Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Fri, 11 Dec 2009 06:01:00 +0000
Subject: [PATCH] Coalesce insert_subreg undef, x first to avoid phase ordering
 issue.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91103 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/LiveIntervalAnalysis.cpp     | 10 +++++++++-
 lib/CodeGen/SimpleRegisterCoalescing.cpp | 15 +++++++++++----
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 4d73b509246..8806439f543 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -745,8 +745,16 @@ unsigned LiveIntervals::getVNInfoSourceReg(const VNInfo *VNI) const {
   if (VNI->getCopy()->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG) {
     // If it's extracting out of a physical register, return the sub-register.
     unsigned Reg = VNI->getCopy()->getOperand(1).getReg();
-    if (TargetRegisterInfo::isPhysicalRegister(Reg))
+    if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
+      unsigned SrcSubReg = VNI->getCopy()->getOperand(2).getImm();
+      unsigned DstSubReg = VNI->getCopy()->getOperand(0).getSubReg();
+      if (SrcSubReg == DstSubReg)
+        // %reg1034:3<def> = EXTRACT_SUBREG %EDX, 3
+        // reg1034 can still be coalesced to EDX.
+        return Reg;
+      assert(DstSubReg == 0);
       Reg = tri_->getSubReg(Reg, VNI->getCopy()->getOperand(2).getImm());
+    }
     return Reg;
   } else if (VNI->getCopy()->getOpcode() == TargetInstrInfo::INSERT_SUBREG ||
              VNI->getCopy()->getOpcode() == TargetInstrInfo::SUBREG_TO_REG)
diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 5ebe557d1a3..810fabeef7b 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -2422,9 +2422,15 @@ void SimpleRegisterCoalescing::CopyCoalesceInMBB(MachineBasicBlock *MBB,
 
     // If this isn't a copy nor a extract_subreg, we can't join intervals.
     unsigned SrcReg, DstReg, SrcSubIdx, DstSubIdx;
+    bool isInsUndef = false;
     if (Inst->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG) {
       DstReg = Inst->getOperand(0).getReg();
       SrcReg = Inst->getOperand(1).getReg();
+    } else if (Inst->getOpcode() == TargetInstrInfo::INSERT_SUBREG) {
+      DstReg = Inst->getOperand(0).getReg();
+      SrcReg = Inst->getOperand(2).getReg();
+      if (Inst->getOperand(1).isUndef())
+        isInsUndef = true;
     } else if (Inst->getOpcode() == TargetInstrInfo::INSERT_SUBREG ||
                Inst->getOpcode() == TargetInstrInfo::SUBREG_TO_REG) {
       DstReg = Inst->getOperand(0).getReg();
@@ -2434,7 +2440,8 @@ void SimpleRegisterCoalescing::CopyCoalesceInMBB(MachineBasicBlock *MBB,
 
     bool SrcIsPhys = TargetRegisterInfo::isPhysicalRegister(SrcReg);
     bool DstIsPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
-    if (li_->hasInterval(SrcReg) && li_->getInterval(SrcReg).empty())
+    if (isInsUndef ||
+        (li_->hasInterval(SrcReg) && li_->getInterval(SrcReg).empty()))
       ImpDefCopies.push_back(CopyRec(Inst, 0));
     else if (SrcIsPhys || DstIsPhys)
       PhysCopies.push_back(CopyRec(Inst, 0));
@@ -2442,9 +2449,9 @@ void SimpleRegisterCoalescing::CopyCoalesceInMBB(MachineBasicBlock *MBB,
       VirtCopies.push_back(CopyRec(Inst, 0));
   }
 
-  // Try coalescing implicit copies first, followed by copies to / from
-  // physical registers, then finally copies from virtual registers to
-  // virtual registers.
+  // Try coalescing implicit copies and insert_subreg <undef> first,
+  // followed by copies to / from physical registers, then finally copies
+  // from virtual registers to virtual registers.
   for (unsigned i = 0, e = ImpDefCopies.size(); i != e; ++i) {
     CopyRec &TheCopy = ImpDefCopies[i];
     bool Again = false;