From fc2fcb4165f10fb1708c528014379cb9e1738bab Mon Sep 17 00:00:00 2001
From: Jakob Stoklund Olesen <stoklund@2pi.dk>
Date: Wed, 18 May 2011 04:18:19 +0000
Subject: [PATCH] Properly shrink live ranges after deleting dead copies. Clean
 up after all joined copies.

LiveInterval::shrinkToUses recomputes the live range from scratch instead of
removing snippets. This should avoid the problem with dangling live ranges.

Leave physreg identity copies alone. They can be created when joining a virtreg
with a physreg. They don't affect register allocation, and they will be removed
by the rewriter.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131521 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/SimpleRegisterCoalescing.cpp | 29 ++++--------------------
 1 file changed, 5 insertions(+), 24 deletions(-)

diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 1a2151fecf2..f55dc7dab57 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -1038,6 +1038,7 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
 
   // If they are already joined we continue.
   if (CP.getSrcReg() == CP.getDstReg()) {
+    markAsJoined(CopyMI);
     DEBUG(dbgs() << "\tCopy already coalesced.\n");
     return false;  // Not coalescable.
   }
@@ -1696,13 +1697,11 @@ bool SimpleRegisterCoalescing::runOnMachineFunction(MachineFunction &fn) {
           // or else the scavenger may complain. LowerSubregs will
           // delete them later.
           DoDelete = false;
-        
+
         if (MI->allDefsAreDead()) {
-          if (li_->hasInterval(SrcReg)) {
-            LiveInterval &li = li_->getInterval(SrcReg);
-            if (!ShortenDeadCopySrcLiveRange(li, MI))
-              ShortenDeadCopyLiveRange(li, MI);
-          }
+          if (TargetRegisterInfo::isVirtualRegister(SrcReg) &&
+              li_->hasInterval(SrcReg))
+            li_->shrinkToUses(&li_->getInterval(SrcReg));
           DoDelete = true;
         }
         if (!DoDelete) {
@@ -1754,24 +1753,6 @@ bool SimpleRegisterCoalescing::runOnMachineFunction(MachineFunction &fn) {
           DeadDefs.clear();
       }
 
-      // If the move will be an identity move delete it
-      if (MI->isIdentityCopy()) {
-        unsigned SrcReg = MI->getOperand(1).getReg();
-        if (li_->hasInterval(SrcReg)) {
-          LiveInterval &RegInt = li_->getInterval(SrcReg);
-          // If def of this move instruction is dead, remove its live range
-          // from the destination register's live interval.
-          if (MI->allDefsAreDead()) {
-            if (!ShortenDeadCopySrcLiveRange(RegInt, MI))
-              ShortenDeadCopyLiveRange(RegInt, MI);
-          }
-        }
-        li_->RemoveMachineInstrFromMaps(MI);
-        mii = mbbi->erase(mii);
-        ++numPeep;
-        continue;
-      }
-
       ++mii;
 
       // Check for now unnecessary kill flags.