Auto-compute live intervals on demand.

When new virtual registers are created during splitting/spilling, defer
creation of the live interval until we need to use the live interval.

Along with the recent commits to notify LiveRangeEdit when new virtual
registers are created, this makes it possible for functions like
TargetInstrInfo::loadRegFromStackSlot() and
TargetInstrInfo::storeRegToStackSlot() to create multiple virtual
registers as part of the process of generating loads/stores for
different register classes, and then have the live intervals for those
new registers computed when they are needed.

llvm-svn: 188437

1 files changed, 11 insertions, 20 deletions

diff --git a/llvm/lib/CodeGen/Spiller.cpp b/llvm/lib/CodeGen/Spiller.cpp
index 209792fd407..d72c596a842 100644
--- a/llvm/lib/CodeGen/Spiller.cpp
+++ b/llvm/lib/CodeGen/Spiller.cpp
@@ -115,15 +115,14 @@ protected:
         indices.push_back(i);
       }
 
-      // Create a new vreg & interval for this instr.
-      LiveInterval *newLI = &LRE.create();
-      newLI->weight = HUGE_VALF;
+      // Create a new virtual register for the load and/or store.
+      unsigned NewVReg = LRE.create();
 
       // Update the reg operands & kill flags.
       for (unsigned i = 0; i < indices.size(); ++i) {
         unsigned mopIdx = indices[i];
         MachineOperand &mop = mi->getOperand(mopIdx);
-        mop.setReg(newLI->reg);
+        mop.setReg(NewVReg);
         if (mop.isUse() && !mi->isRegTiedToDefOperand(mopIdx)) {
           mop.setIsKill(true);
         }
@@ -133,28 +132,20 @@ protected:
       // Insert reload if necessary.
       MachineBasicBlock::iterator miItr(mi);
       if (hasUse) {
-        tii->loadRegFromStackSlot(*mi->getParent(), miItr, newLI->reg, ss, trc,
+        MachineInstrSpan MIS(miItr);
+
+        tii->loadRegFromStackSlot(*mi->getParent(), miItr, NewVReg, ss, trc,
                                   tri);
-        MachineInstr *loadInstr(prior(miItr));
-        SlotIndex loadIndex =
-          lis->InsertMachineInstrInMaps(loadInstr).getRegSlot();
-        SlotIndex endIndex = loadIndex.getNextIndex();
-        VNInfo *loadVNI =
-          newLI->getNextValue(loadIndex, lis->getVNInfoAllocator());
-        newLI->addRange(LiveRange(loadIndex, endIndex, loadVNI));
+        lis->InsertMachineInstrRangeInMaps(MIS.begin(), miItr);
       }
 
       // Insert store if necessary.
       if (hasDef) {
-        tii->storeRegToStackSlot(*mi->getParent(), llvm::next(miItr),newLI->reg,
+        MachineInstrSpan MIS(miItr);
+
+        tii->storeRegToStackSlot(*mi->getParent(), llvm::next(miItr), NewVReg,
                                  true, ss, trc, tri);
-        MachineInstr *storeInstr(llvm::next(miItr));
-        SlotIndex storeIndex =
-          lis->InsertMachineInstrInMaps(storeInstr).getRegSlot();
-        SlotIndex beginIndex = storeIndex.getPrevIndex();
-        VNInfo *storeVNI =
-          newLI->getNextValue(beginIndex, lis->getVNInfoAllocator());
-        newLI->addRange(LiveRange(beginIndex, storeIndex, storeVNI));
+        lis->InsertMachineInstrRangeInMaps(llvm::next(miItr), MIS.end());
       }
     }
   }