Completely change the way that joining with physregs is implemented. This

paves the way for future changes, increases coallescing opportunities (in
theory, not witnessed in practice), and eliminates the really expensive
LiveIntervals::overlapsAliases method.

llvm-svn: 29890

1 files changed, 32 insertions, 28 deletions

diff --git a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
index 5a7587f0e5e..d094da9ed11 100644
--- a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -673,7 +673,8 @@ bool LiveIntervals::AdjustCopiesBackFrom(LiveInterval &IntA, LiveInterval &IntB,
   // Make sure that the end of the live range is inside the same block as
   // CopyMI.
   MachineInstr *ValLREndInst = getInstructionFromIndex(ValLR->end-1);
-  if (ValLREndInst->getParent() != CopyMI->getParent()) return false;
+  if (!ValLREndInst || 
+      ValLREndInst->getParent() != CopyMI->getParent()) return false;
 
   // Okay, we now know that ValLR ends in the same block that the CopyMI
   // live-range starts.  If there are no intervening live ranges between them in
@@ -685,7 +686,18 @@ bool LiveIntervals::AdjustCopiesBackFrom(LiveInterval &IntA, LiveInterval &IntB,
   // Okay, we can merge them.  We need to insert a new liverange:
   // [ValLR.end, BLR.begin) of either value number, then we merge the
   // two value numbers.
-  IntB.addRange(LiveRange(ValLR->end, BLR->start, BValNo));
+  unsigned FillerStart = ValLR->end, FillerEnd = BLR->start;
+  IntB.addRange(LiveRange(FillerStart, FillerEnd, BValNo));
+
+  // If the IntB live range is assigned to a physical register, and if that
+  // physreg has aliases, 
+  if (MRegisterInfo::isPhysicalRegister(IntB.reg)) {
+    for (const unsigned *AS = mri_->getAliasSet(IntB.reg); *AS; ++AS) {
+      LiveInterval &AliasLI = getInterval(*AS);
+      AliasLI.addRange(LiveRange(FillerStart, FillerEnd,
+                                 AliasLI.getNextValue(~0U)));
+    }
+  }
 
   // Okay, merge "B1" into the same value number as "B0".
   if (BValNo != ValLR->ValId)
@@ -773,19 +785,30 @@ bool LiveIntervals::JoinCopy(MachineInstr *CopyMI,
   if (!Joinable && AdjustCopiesBackFrom(SrcInt, DestInt, CopyMI, MIDefIdx))
     return true;
   
-  // If this looks joinable, do the final, expensive last check, checking to see
-  // if aliases overlap.  If they do, we can never join these.
-  if (Joinable && overlapsAliases(&SrcInt, &DestInt)) {
-    DEBUG(std::cerr << "Alias Overlap Interference!\n");
-    return true;   // Can never join these.
-  }
-  
   if (!Joinable) {
     DEBUG(std::cerr << "Interference!\n");
     return false;
   }
 
+  // If we're about to merge live ranges into a physical register live range,
+  // we have to update any aliased register's live ranges to indicate that they
+  // have clobbered values for this range.
+  if (MRegisterInfo::isPhysicalRegister(SrcReg) ||
+      MRegisterInfo::isPhysicalRegister(DstReg)) {
+    // Figure out which register is the physical reg and which one is the
+    // virtreg.
+    LiveInterval *PhysRegLI = &SrcInt, *VirtRegLI = &DestInt;
+    if (MRegisterInfo::isPhysicalRegister(DstReg))
+      std::swap(PhysRegLI, VirtRegLI);
+    
+    for (const unsigned *AS = mri_->getAliasSet(PhysRegLI->reg); *AS; ++AS)
+      getInterval(*AS).MergeInClobberRanges(*VirtRegLI);
+  }
+
   DestInt.join(SrcInt, MIDefIdx);
+  // FIXME: If SrcInt/DestInt are physregs, we must insert the new liveranges
+  // into all aliasing registers as clobbers.
+                               
   DEBUG(std::cerr << "\n\t\tJoined.  Result = "; DestInt.print(std::cerr, mri_);
         std::cerr << "\n");
     
@@ -911,25 +934,6 @@ bool LiveIntervals::differingRegisterClasses(unsigned RegA,
     return !RegClass->contains(RegB);
 }
 
-bool LiveIntervals::overlapsAliases(const LiveInterval *LHS,
-                                    const LiveInterval *RHS) const {
-  if (!MRegisterInfo::isPhysicalRegister(LHS->reg)) {
-    if (!MRegisterInfo::isPhysicalRegister(RHS->reg))
-      return false;   // vreg-vreg merge has no aliases!
-    std::swap(LHS, RHS);
-  }
-
-  assert(MRegisterInfo::isPhysicalRegister(LHS->reg) &&
-         MRegisterInfo::isVirtualRegister(RHS->reg) &&
-         "first interval must describe a physical register");
-
-  for (const unsigned *AS = mri_->getAliasSet(LHS->reg); *AS; ++AS)
-    if (RHS->overlaps(getInterval(*AS)))
-      return true;
-
-  return false;
-}
-
 LiveInterval LiveIntervals::createInterval(unsigned reg) {
   float Weight = MRegisterInfo::isPhysicalRegister(reg) ?
                        (float)HUGE_VAL :0.0F;