Copy single reaching defs directly into the LiveInterval.

When findReachingDefs() finds that only one value can reach the basic
block, just copy the work list of visited blocks directly into the live
interval.

Sort the block list and use a LiveRangeUpdater to make the bulk add
fast.

When multiple reaching defs are found, transfer the work list to the
updateSSA() work list as before. Also use LiveRangeUpdater in
updateLiveIns() following updateSSA().

This makes live interval analysis more than 3x faster on one huge test
case.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175685 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 60 insertions, 34 deletions

diff --git a/lib/CodeGen/LiveRangeCalc.cpp b/lib/CodeGen/LiveRangeCalc.cpp
index c3ff4f1b6d..dede490d91 100644
--- a/lib/CodeGen/LiveRangeCalc.cpp
+++ b/lib/CodeGen/LiveRangeCalc.cpp
@@ -18,10 +18,11 @@
 
 using namespace llvm;
 
-void LiveRangeCalc::reset(const MachineFunction *MF,
+void LiveRangeCalc::reset(const MachineFunction *mf,
                           SlotIndexes *SI,
                           MachineDominatorTree *MDT,
                           VNInfo::Allocator *VNIA) {
+  MF = mf;
   MRI = &MF->getRegInfo();
   Indexes = SI;
   DomTree = MDT;
@@ -104,28 +105,28 @@ void LiveRangeCalc::extendToUses(LiveInterval *LI, unsigned Reg) {
 
 
 // Transfer information from the LiveIn vector to the live ranges.
-void LiveRangeCalc::updateLiveIns(VNInfo *OverrideVNI) {
+void LiveRangeCalc::updateLiveIns() {
+  LiveRangeUpdater Updater;
   for (SmallVectorImpl<LiveInBlock>::iterator I = LiveIn.begin(),
          E = LiveIn.end(); I != E; ++I) {
     if (!I->DomNode)
       continue;
     MachineBasicBlock *MBB = I->DomNode->getBlock();
-
-    VNInfo *VNI = OverrideVNI ? OverrideVNI : I->Value;
-    assert(VNI && "No live-in value found");
-
+    assert(I->Value && "No live-in value found");
     SlotIndex Start, End;
     tie(Start, End) = Indexes->getMBBRange(MBB);
 
     if (I->Kill.isValid())
-      I->LI->addRange(LiveRange(Start, I->Kill, VNI));
+      // Value is killed inside this block.
+      End = I->Kill;
     else {
-      I->LI->addRange(LiveRange(Start, End, VNI));
-      // The value is live-through, update LiveOut as well.  Defer the Domtree
-      // lookup until it is needed.
+      // The value is live-through, update LiveOut as well.
+      // Defer the Domtree lookup until it is needed.
       assert(Seen.test(MBB->getNumber()));
-      LiveOut[MBB] = LiveOutPair(VNI, (MachineDomTreeNode *)0);
+      LiveOut[MBB] = LiveOutPair(I->Value, (MachineDomTreeNode *)0);
     }
+    Updater.setDest(I->LI);
+    Updater.add(Start, End, I->Value);
   }
   LiveIn.clear();
 }
@@ -150,13 +151,11 @@ void LiveRangeCalc::extend(LiveInterval *LI,
   // multiple values, and we may need to create even more phi-defs to preserve
   // VNInfo SSA form.  Perform a search for all predecessor blocks where we
   // know the dominating VNInfo.
-  VNInfo *VNI = findReachingDefs(LI, KillMBB, Kill, PhysReg);
+  if (findReachingDefs(LI, KillMBB, Kill, PhysReg))
+    return;
 
   // When there were multiple different values, we may need new PHIs.
-  if (!VNI)
-    updateSSA();
-
-  updateLiveIns(VNI);
+  calculateValues();
 }
 
 
@@ -167,16 +166,18 @@ void LiveRangeCalc::calculateValues() {
   assert(Indexes && "Missing SlotIndexes");
   assert(DomTree && "Missing dominator tree");
   updateSSA();
-  updateLiveIns(0);
+  updateLiveIns();
 }
 
 
-VNInfo *LiveRangeCalc::findReachingDefs(LiveInterval *LI,
-                                        MachineBasicBlock *KillMBB,
-                                        SlotIndex Kill,
-                                        unsigned PhysReg) {
-  // Blocks where LI should be live-in.
-  SmallVector<MachineBasicBlock*, 16> WorkList(1, KillMBB);
+bool LiveRangeCalc::findReachingDefs(LiveInterval *LI,
+                                     MachineBasicBlock *KillMBB,
+                                     SlotIndex Kill,
+                                     unsigned PhysReg) {
+  unsigned KillMBBNum = KillMBB->getNumber();
+
+  // Block numbers where LI should be live-in.
+  SmallVector<unsigned, 16> WorkList(1, KillMBBNum);
 
   // Remember if we have seen more than one value.
   bool UniqueVNI = true;
@@ -184,7 +185,7 @@ VNInfo *LiveRangeCalc::findReachingDefs(LiveInterval *LI,
 
   // Using Seen as a visited set, perform a BFS for all reaching defs.
   for (unsigned i = 0; i != WorkList.size(); ++i) {
-    MachineBasicBlock *MBB = WorkList[i];
+    MachineBasicBlock *MBB = MF->getBlockNumbered(WorkList[i]);
 
 #ifndef NDEBUG
     if (MBB->pred_empty()) {
@@ -231,25 +232,50 @@ VNInfo *LiveRangeCalc::findReachingDefs(LiveInterval *LI,
 
        // No, we need a live-in value for Pred as well
        if (Pred != KillMBB)
-          WorkList.push_back(Pred);
+          WorkList.push_back(Pred->getNumber());
        else
           // Loopback to KillMBB, so value is really live through.
          Kill = SlotIndex();
     }
   }
 
-  // Transfer WorkList to LiveInBlocks in reverse order.
-  // This ordering works best with updateSSA().
   LiveIn.clear();
-  LiveIn.reserve(WorkList.size());
-  while(!WorkList.empty())
-    addLiveInBlock(LI, DomTree->getNode(WorkList.pop_back_val()));
 
-  // The kill block may not be live-through.
-  assert(LiveIn.back().DomNode->getBlock() == KillMBB);
-  LiveIn.back().Kill = Kill;
+  // Both updateSSA() and LiveRangeUpdater benefit from ordered blocks, but
+  // neither require it. Skip the sorting overhead for small updates.
+  if (WorkList.size() > 4)
+    array_pod_sort(WorkList.begin(), WorkList.end());
+
+  // If a unique reaching def was found, blit in the live ranges immediately.
+  if (UniqueVNI) {
+    LiveRangeUpdater Updater(LI);
+    for (SmallVectorImpl<unsigned>::const_iterator
+         I = WorkList.begin(), E = WorkList.end(); I != E; ++I) {
+       SlotIndex Start, End;
+       tie(Start, End) = Indexes->getMBBRange(*I);
+       // Trim the live range in KillMBB.
+       if (*I == KillMBBNum && Kill.isValid())
+         End = Kill;
+       else
+         LiveOut[MF->getBlockNumbered(*I)] =
+           LiveOutPair(TheVNI, (MachineDomTreeNode *)0);
+       Updater.add(Start, End, TheVNI);
+    }
+    return true;
+  }
+
+  // Multiple values were found, so transfer the work list to the LiveIn array
+  // where UpdateSSA will use it as a work list.
+  LiveIn.reserve(WorkList.size());
+  for (SmallVectorImpl<unsigned>::const_iterator
+       I = WorkList.begin(), E = WorkList.end(); I != E; ++I) {
+    MachineBasicBlock *MBB = MF->getBlockNumbered(*I);
+    addLiveInBlock(LI, DomTree->getNode(MBB));
+    if (MBB == KillMBB)
+      LiveIn.back().Kill = Kill;
+  }
 
-  return UniqueVNI ? TheVNI : 0;
+  return false;
 }