[llvm-commits] [llvm] r139792 - /llvm/trunk/lib/CodeGen/LiveIntervalAnalysis.cpp

[Jakob Stoklund Olesen]

Author: stoklund
Date: Thu Sep 15 10:24:16 2011
New Revision: 139792

URL: http://llvm.org/viewvc/llvm-project?rev=139792&view=rev
Log:
Speed up LiveIntervals::shrinkToUse with some caching.

Blocks with multiple PHI successors only need to go on the worklist
once.  Use a SmallPtrSet to track the live-out blocks that have already
been handled.  This is a lot faster than the two live range check we
would otherwise do.

Also stop recomputing hasPHIKill flags.  Like RenumberValues(), it is
conservatively correct to leave them in, and they are not used for
anything important.

Modified:
    llvm/trunk/lib/CodeGen/LiveIntervalAnalysis.cpp

Modified: llvm/trunk/lib/CodeGen/LiveIntervalAnalysis.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveIntervalAnalysis.cpp?rev=139792&r1=139791&r2=139792&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/LiveIntervalAnalysis.cpp (original)
+++ llvm/trunk/lib/CodeGen/LiveIntervalAnalysis.cpp Thu Sep 15 10:24:16 2011
@@ -747,6 +747,9 @@
   // Find all the values used, including PHI kills.
   SmallVector<std::pair<SlotIndex, VNInfo*>, 16> WorkList;
 
+  // Blocks that have already been added to WorkList as live-out.
+  SmallPtrSet<MachineBasicBlock*, 16> LiveOut;
+
   // Visit all instructions reading li->reg.
   for (MachineRegisterInfo::reg_iterator I = mri_->reg_begin(li->reg);
        MachineInstr *UseMI = I.skipInstruction();) {
@@ -780,8 +783,6 @@
     VNInfo *VNI = *I;
     if (VNI->isUnused())
       continue;
-    // We may eliminate PHI values, so recompute PHIKill flags.
-    VNI->setHasPHIKill(false);
     NewLI.addRange(LiveRange(VNI->def, VNI->def.getNextSlot(), VNI));
 
     // A use tied to an early-clobber def ends at the load slot and isn't caught
@@ -813,13 +814,12 @@
       // The PHI is live, make sure the predecessors are live-out.
       for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
            PE = MBB->pred_end(); PI != PE; ++PI) {
+        if (!LiveOut.insert(*PI))
+          continue;
         SlotIndex Stop = getMBBEndIdx(*PI).getPrevSlot();
-        VNInfo *PVNI = li->getVNInfoAt(Stop);
         // A predecessor is not required to have a live-out value for a PHI.
-        if (PVNI) {
-          PVNI->setHasPHIKill(true);
+        if (VNInfo *PVNI = li->getVNInfoAt(Stop))
           WorkList.push_back(std::make_pair(Stop, PVNI));
-        }
       }
       continue;
     }
@@ -831,6 +831,8 @@
     // Make sure VNI is live-out from the predecessors.
     for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
          PE = MBB->pred_end(); PI != PE; ++PI) {
+      if (!LiveOut.insert(*PI))
+        continue;
       SlotIndex Stop = getMBBEndIdx(*PI).getPrevSlot();
       assert(li->getVNInfoAt(Stop) == VNI && "Wrong value out of predecessor");
       WorkList.push_back(std::make_pair(Stop, VNI));