From 200ee7f52150cea29215379eb508dc199052372a Mon Sep 17 00:00:00 2001
From: Owen Anderson <resistor@mac.com>
Date: Tue, 6 Jan 2009 07:53:32 +0000
Subject: [PATCH] The phi construction algorithm used for interval
 reconstruction is complicated by two address instructions.  We need to keep
 track of things we've processed AS USES independetly of whether we've
 processed them as defs.

This fixes all known miscompilations when reconstruction is turned on.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61802 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/PreAllocSplitting.cpp | 40 +++++++++++++++++++++----------
 1 file changed, 27 insertions(+), 13 deletions(-)

diff --git a/lib/CodeGen/PreAllocSplitting.cpp b/lib/CodeGen/PreAllocSplitting.cpp
index d8e54e90f08..5a2948b852b 100644
--- a/lib/CodeGen/PreAllocSplitting.cpp
+++ b/lib/CodeGen/PreAllocSplitting.cpp
@@ -175,6 +175,7 @@ namespace {
     VNInfo* PerformPHIConstruction(MachineBasicBlock::iterator use,
                                    MachineBasicBlock* MBB,
                                    LiveInterval* LI,
+                                   SmallPtrSet<MachineInstr*, 4>& Visited,
             DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> >& Defs,
             DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> >& Uses,
                                       DenseMap<MachineInstr*, VNInfo*>& NewVNs,
@@ -593,6 +594,7 @@ VNInfo* PreAllocSplitting::PerformPHIConstruction(
                                                 MachineBasicBlock::iterator use,
                                                          MachineBasicBlock* MBB,
                                                                LiveInterval* LI,
+                                       SmallPtrSet<MachineInstr*, 4>& Visited,
              DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> >& Defs,
              DenseMap<MachineBasicBlock*, SmallPtrSet<MachineInstr*, 2> >& Uses,
                                        DenseMap<MachineInstr*, VNInfo*>& NewVNs,
@@ -600,7 +602,9 @@ VNInfo* PreAllocSplitting::PerformPHIConstruction(
                                  DenseMap<MachineBasicBlock*, VNInfo*>& Phis,
                                               bool toplevel, bool intrablock) {
   // Return memoized result if it's available.
-  if (intrablock && NewVNs.count(use))
+  if (toplevel && Visited.count(use) && NewVNs.count(use))
+    return NewVNs[use];
+  else if (!toplevel && intrablock && NewVNs.count(use))
     return NewVNs[use];
   else if (!intrablock && LiveOut.count(MBB))
     return LiveOut[MBB];
@@ -624,8 +628,8 @@ VNInfo* PreAllocSplitting::PerformPHIConstruction(
     
     if (MBB->pred_size() == 1) {
       Phis[MBB] = ret = PerformPHIConstruction((*MBB->pred_begin())->end(),
-                                          *(MBB->pred_begin()), LI, Defs,
-                                          Uses, NewVNs, LiveOut, Phis,
+                                          *(MBB->pred_begin()), LI, Visited,
+                                          Defs, Uses, NewVNs, LiveOut, Phis,
                                           false, false);
       unsigned EndIndex = 0;
       if (intrablock) {
@@ -646,9 +650,9 @@ VNInfo* PreAllocSplitting::PerformPHIConstruction(
       DenseMap<MachineBasicBlock*, VNInfo*> IncomingVNs;
       for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(),
            PE = MBB->pred_end(); PI != PE; ++PI) {
-        VNInfo* Incoming = PerformPHIConstruction((*PI)->end(), *PI, LI, Defs,
-                                            Uses, NewVNs, LiveOut, Phis,
-                                            false, false);
+        VNInfo* Incoming = PerformPHIConstruction((*PI)->end(), *PI, LI, 
+                                            Visited, Defs, Uses, NewVNs,
+                                            LiveOut, Phis, false, false);
         if (Incoming != 0)
           IncomingVNs[*PI] = Incoming;
       }
@@ -732,7 +736,7 @@ VNInfo* PreAllocSplitting::PerformPHIConstruction(
 
     // Now, recursively phi construct the VNInfo for the use we found,
     // and then extend it to include the instruction we care about
-    ret = PerformPHIConstruction(walker, MBB, LI, Defs, Uses,
+    ret = PerformPHIConstruction(walker, MBB, LI, Visited, Defs, Uses,
                                  NewVNs, LiveOut, Phis, false, true);
     
     // FIXME: Need to set kills properly for inter-block stuff.
@@ -789,7 +793,7 @@ VNInfo* PreAllocSplitting::PerformPHIConstruction(
     if (foundDef)
       ret = NewVNs[walker];
     else
-      ret = PerformPHIConstruction(walker, MBB, LI, Defs, Uses,
+      ret = PerformPHIConstruction(walker, MBB, LI, Visited, Defs, Uses,
                                    NewVNs, LiveOut, Phis, false, true);
 
     if (foundUse && LI->isKill(ret, StartIndex))
@@ -803,8 +807,11 @@ VNInfo* PreAllocSplitting::PerformPHIConstruction(
   
   // Memoize results so we don't have to recompute them.
   if (!intrablock) LiveOut[MBB] = ret;
-  else NewVNs[use] = ret;
-  
+  else {
+    NewVNs[use] = ret;
+    Visited.insert(use);
+  }
+
   return ret;
 }
 
@@ -831,7 +838,14 @@ void PreAllocSplitting::ReconstructLiveInterval(LiveInterval* LI) {
     unsigned DefIdx = LIs->getInstructionIndex(&*DI);
     DefIdx = LiveIntervals::getDefIndex(DefIdx);
     
-    VNInfo* NewVN = LI->getNextValue(DefIdx, /*FIXME*/ 0, Alloc);
+    VNInfo* NewVN = LI->getNextValue(DefIdx, 0, Alloc);
+    
+    // If the def is a move, set the copy field.
+    unsigned source, dest;
+    if (TII->isMoveInstr(*DI, source, dest))
+      if (dest == LI->reg)
+        NewVN->copy = &*DI;
+    
     NewVNs[&*DI] = NewVN;
   }
   
@@ -845,9 +859,10 @@ void PreAllocSplitting::ReconstructLiveInterval(LiveInterval* LI) {
   // the way.
   DenseMap<MachineBasicBlock*, VNInfo*> LiveOut;
   DenseMap<MachineBasicBlock*, VNInfo*> Phis;
+  SmallPtrSet<MachineInstr*, 4> Visited;
   for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(LI->reg),
        UE = MRI->use_end(); UI != UE; ++UI) {
-    PerformPHIConstruction(&*UI, UI->getParent(), LI, Defs,
+    PerformPHIConstruction(&*UI, UI->getParent(), LI, Visited, Defs,
                            Uses, NewVNs, LiveOut, Phis, true, true); 
   }
   
@@ -1116,7 +1131,6 @@ bool PreAllocSplitting::Rematerialize(unsigned vreg, VNInfo* ValNo,
   }
 
   RepairLiveInterval(CurrLI, ValNo, DefMI, RestoreIdx);
-
   ++NumSplits;
   ++NumRemats;
   return true;