Add LiveIntervals::shrinkToUses().

After uses of a live range are removed, recompute the live range to only cover
the remaining uses. This is necessary after rematerializing the value before
some (but not all) uses.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125058 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 9 insertions, 21 deletions

diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index a859f6e074..b56dd81a3c 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -587,6 +587,7 @@ SimpleRegisterCoalescing::TrimLiveIntervalToLastUse(SlotIndex CopyIdx,
 /// ReMaterializeTrivialDef - If the source of a copy is defined by a trivial
 /// computation, replace the copy by rematerialize the definition.
 bool SimpleRegisterCoalescing::ReMaterializeTrivialDef(LiveInterval &SrcInt,
+                                                       bool preserveSrcInt,
                                                        unsigned DstReg,
                                                        unsigned DstSubIdx,
                                                        MachineInstr *CopyMI) {
@@ -642,30 +643,12 @@ bool SimpleRegisterCoalescing::ReMaterializeTrivialDef(LiveInterval &SrcInt,
 
   RemoveCopyFlag(DstReg, CopyMI);
 
-  // If copy kills the source register, find the last use and propagate
-  // kill.
-  bool checkForDeadDef = false;
   MachineBasicBlock *MBB = CopyMI->getParent();
-  if (SrcLR->end == CopyIdx.getDefIndex())
-    if (!TrimLiveIntervalToLastUse(CopyIdx, MBB, SrcInt, SrcLR)) {
-      checkForDeadDef = true;
-    }
-
   MachineBasicBlock::iterator MII =
     llvm::next(MachineBasicBlock::iterator(CopyMI));
   tii_->reMaterialize(*MBB, MII, DstReg, DstSubIdx, DefMI, *tri_);
   MachineInstr *NewMI = prior(MII);
 
-  if (checkForDeadDef) {
-    // PR4090 fix: Trim interval failed because there was no use of the
-    // source interval in this MBB. If the def is in this MBB too then we
-    // should mark it dead:
-    if (DefMI->getParent() == MBB) {
-      DefMI->addRegisterDead(SrcInt.reg, tri_);
-      SrcLR->end = SrcLR->start.getNextSlot();
-    }
-  }
-
   // CopyMI may have implicit operands, transfer them over to the newly
   // rematerialized instruction. And update implicit def interval valnos.
   for (unsigned i = CopyMI->getDesc().getNumOperands(),
@@ -684,6 +667,11 @@ bool SimpleRegisterCoalescing::ReMaterializeTrivialDef(LiveInterval &SrcInt,
   ReMatDefs.insert(DefMI);
   DEBUG(dbgs() << "Remat: " << *NewMI);
   ++NumReMats;
+
+  // The source interval can become smaller because we removed a use.
+  if (preserveSrcInt)
+    li_->shrinkToUses(&SrcInt);
+
   return true;
 }
 
@@ -714,7 +702,7 @@ SimpleRegisterCoalescing::UpdateRegDefsUses(const CoalescerPair &CP) {
           UseMI->getOperand(0).getReg() != SrcReg &&
           UseMI->getOperand(0).getReg() != DstReg &&
           !JoinedCopies.count(UseMI) &&
-          ReMaterializeTrivialDef(li_->getInterval(SrcReg),
+          ReMaterializeTrivialDef(li_->getInterval(SrcReg), false,
                                   UseMI->getOperand(0).getReg(), 0, UseMI))
         continue;
     }
@@ -1056,7 +1044,7 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
       // Before giving up coalescing, if definition of source is defined by
       // trivial computation, try rematerializing it.
       if (!CP.isFlipped() &&
-          ReMaterializeTrivialDef(JoinVInt, CP.getDstReg(), 0, CopyMI))
+          ReMaterializeTrivialDef(JoinVInt, true, CP.getDstReg(), 0, CopyMI))
         return true;
 
       ++numAborts;
@@ -1076,7 +1064,7 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
     // If definition of source is defined by trivial computation, try
     // rematerializing it.
     if (!CP.isFlipped() &&
-        ReMaterializeTrivialDef(li_->getInterval(CP.getSrcReg()),
+        ReMaterializeTrivialDef(li_->getInterval(CP.getSrcReg()), true,
                                 CP.getDstReg(), 0, CopyMI))
       return true;