Simplifications to liveinterval analysis, no functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29896 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 36 insertions, 37 deletions

diff --git a/lib/CodeGen/LiveInterval.cpp b/lib/CodeGen/LiveInterval.cpp
index 80c050f..7f16b31 100644
--- a/lib/CodeGen/LiveInterval.cpp
+++ b/lib/CodeGen/LiveInterval.cpp
@@ -374,21 +374,25 @@ LiveInterval::FindLiveRangeContaining(unsigned Idx) {
 /// is the result of a copy instruction in the source program, that occurs at
 /// index 'CopyIdx' that copies from 'Other' to 'this'.
 void LiveInterval::join(LiveInterval &Other, unsigned CopyIdx) {
-  const LiveRange *SourceLR = Other.getLiveRangeContaining(CopyIdx-1);
-  const LiveRange *DestLR = getLiveRangeContaining(CopyIdx);
-  assert(SourceLR && DestLR && "Not joining due to a copy?");
-  unsigned MergedSrcValIdx = SourceLR->ValId;
-  unsigned MergedDstValIdx = DestLR->ValId;
-
   // Try to do the least amount of work possible.  In particular, if there are
   // more liverange chunks in the other set than there are in the 'this' set,
   // swap sets to merge the fewest chunks in possible.
-  if (Other.ranges.size() > ranges.size()) {
-    std::swap(MergedSrcValIdx, MergedDstValIdx);
-    std::swap(ranges, Other.ranges);
-    std::swap(NumValues, Other.NumValues);
-    std::swap(InstDefiningValue, Other.InstDefiningValue);
+  //
+  // Also, if one range is a physreg and one is a vreg, we always merge from the
+  // vreg into the physreg, which leaves the vreg intervals pristine.
+  unsigned OtherOffs = 1, ThisOffs = 0;
+  if ((Other.ranges.size() > ranges.size() &&
+      MRegisterInfo::isVirtualRegister(reg)) ||
+      MRegisterInfo::isPhysicalRegister(Other.reg)) {
+    swap(Other);
+    std::swap(ThisOffs, OtherOffs);
   }
+  
+  const LiveRange *SourceLR = Other.getLiveRangeContaining(CopyIdx-OtherOffs);
+  const LiveRange *DestLR = getLiveRangeContaining(CopyIdx-ThisOffs);
+  assert(SourceLR && DestLR && "Not joining due to a copy?");
+  unsigned MergedSrcValIdx = SourceLR->ValId;
+  unsigned MergedDstValIdx = DestLR->ValId;
 
   // Join the ranges of other into the ranges of this interval.
   std::map<unsigned, unsigned> Dst2SrcIdxMap;
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index d094da9..0672fc6 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -790,39 +790,34 @@ bool LiveIntervals::JoinCopy(MachineInstr *CopyMI,
     return false;
   }
 
+  // Okay, we can join these two intervals.  If one of the intervals being
+  // joined is a physreg, this method always canonicalizes DestInt to be it.
+  // The output "SrcInt" will not have been modified.
+  DestInt.join(SrcInt, MIDefIdx);
+
+  bool Swapped = SrcReg == DestInt.reg;
+  if (Swapped)
+    std::swap(SrcReg, DstReg);
+  assert(MRegisterInfo::isVirtualRegister(SrcReg) &&
+         "LiveInterval::join didn't work right!");
+                               
   // 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);
+  if (MRegisterInfo::isPhysicalRegister(DstReg)) {
+    for (const unsigned *AS = mri_->getAliasSet(DstReg); *AS; ++AS)
+      getInterval(*AS).MergeInClobberRanges(SrcInt);
   }
 
-  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");
-    
-  if (!MRegisterInfo::isPhysicalRegister(SrcReg)) {
-    r2iMap_.erase(SrcReg);
-    r2rMap_[SrcReg] = DstReg;
-  } else {
-    // Otherwise merge the data structures the other way so we don't lose
-    // the physreg information.
-    r2rMap_[DstReg] = SrcReg;
-    DestInt.reg = SrcReg;
-    SrcInt.swap(DestInt);
-    r2iMap_.erase(DstReg);
-  }
+  
+  // If the intervals were swapped by Join, swap them back so that the register
+  // mapping (in the r2i map) is correct.
+  if (Swapped) SrcInt.swap(DestInt);
+  r2iMap_.erase(SrcReg);
+  r2rMap_[SrcReg] = DstReg;
+
   ++numJoins;
   return true;
 }