LiveInterval: Distribute subregister liveranges to new intervals in ConnectedVNInfoEqClasses::Distribute()

[MatzeB]

Summary

This improves ConnectedVNInfoEqClasses::Distribute() to distribute the
segments and value numbers in the subranges instead of conservatively
clearing all subregister info.

No separate test here, just clearing the subrange instead of properly
distributing them would however break my upcoming fix regarding dead super
register definitions.

[qcolombet]

Hi Matthias,

LGTM!

Thanks,
Q.

llvm/trunk/lib/CodeGen/LiveInterval.cpp

unsigned ConnectedVNInfoEqClasses::Classify(const LiveInterval *LI) {
   // Lump all the unused values in with the last used value.
   if (used && unused)
     EqClass.join(used->id, unused->id);
 
   EqClass.compress();
   return EqClass.getNumClasses();
 }
 
+template<typename LiveRangeT, typename EqClassesT>
+static void DistributeRange(LiveRangeT &LR, LiveRangeT *SplitLRs[],
+                            EqClassesT VNIClasses) {
+  // Move segments to new intervals.
+  LiveRange::iterator J = LR.begin(), E = LR.end();
+  while (J != E && VNIClasses[J->valno->id] == 0)
+    ++J;
+  for (LiveRange::iterator I = J; I != E; ++I) {
+    if (unsigned eq = VNIClasses[I->valno->id]) {
+      assert((SplitLRs[eq-1]->empty() || SplitLRs[eq-1]->expiredAt(I->start)) &&
+             "New intervals should be empty");
+      SplitLRs[eq-1]->segments.push_back(*I);
+    } else
+      *J++ = *I;
+  }
+  LR.segments.erase(J, E);
+
+  // Transfer VNInfos to their new owners and renumber them.
+  unsigned j = 0, e = LR.getNumValNums();
+  while (j != e && VNIClasses[j] == 0)
+    ++j;
+  for (unsigned i = j; i != e; ++i) {
+    VNInfo *VNI = LR.getValNumInfo(i);
+    if (unsigned eq = VNIClasses[i]) {
+      VNI->id = SplitLRs[eq-1]->getNumValNums();
+      SplitLRs[eq-1]->valnos.push_back(VNI);
+    } else {
+      VNI->id = j;
+      LR.valnos[j++] = VNI;
+    }
+  }
+  LR.valnos.resize(j);
+}
+
 void ConnectedVNInfoEqClasses::Distribute(LiveInterval &LI, LiveInterval *LIV[],
                                           MachineRegisterInfo &MRI) {
   // Rewrite instructions.
   for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(LI.reg),
        RE = MRI.reg_end(); RI != RE;) {
     MachineOperand &MO = *RI;
     MachineInstr *MI = RI->getParent();
     ++RI;
for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(LI.reg),
     // In the case of an <undef> use that isn't tied to any def, VNI will be
     // NULL. If the use is tied to a def, VNI will be the defined value.
     if (!VNI)
       continue;
     if (unsigned EqClass = getEqClass(VNI))
       MO.setReg(LIV[EqClass-1]->reg);
   }
 
-  // Move runs to new intervals.
-  LiveInterval::iterator J = LI.begin(), E = LI.end();
-  while (J != E && EqClass[J->valno->id] == 0)
-    ++J;
-  for (LiveInterval::iterator I = J; I != E; ++I) {
-    if (unsigned eq = EqClass[I->valno->id]) {
-      assert((LIV[eq-1]->empty() || LIV[eq-1]->expiredAt(I->start)) &&
-             "New intervals should be empty");
-      LIV[eq-1]->segments.push_back(*I);
-    } else
-      *J++ = *I;
+  // Distribute subregister liveranges.
+  if (LI.hasSubRanges()) {
+    unsigned NumComponents = EqClass.getNumClasses();
+    SmallVector<unsigned, 8> VNIMapping;
+    SmallVector<LiveInterval::SubRange*, 8> SubRanges;
+    BumpPtrAllocator &Allocator = LIS.getVNInfoAllocator();
+    for (LiveInterval::SubRange &SR : LI.subranges()) {
+      // Create new subranges in the split intervals and construct a mapping
+      // for the VNInfos in the subrange.
+      unsigned NumValNos = SR.valnos.size();
+      VNIMapping.clear();
+      VNIMapping.reserve(NumValNos);
+      SubRanges.clear();
+      SubRanges.resize(NumComponents-1, nullptr);
+      for (unsigned I = 0; I < NumValNos; ++I) {
+        const VNInfo &VNI = *SR.valnos[I];
+        const VNInfo *MainRangeVNI = LI.getVNInfoAt(VNI.def);
+        assert(MainRangeVNI != nullptr
+               && "SubRange def must have corresponding main range def");
+        unsigned ComponentNum = getEqClass(MainRangeVNI);
+        VNIMapping.push_back(ComponentNum);
+        if (ComponentNum > 0 && SubRanges[ComponentNum-1] == nullptr) {
+          SubRanges[ComponentNum-1]
+            = LIV[ComponentNum-1]->createSubRange(Allocator, SR.LaneMask);
         }
-  // TODO: do not cheat anymore by simply cleaning all subranges
-  LI.clearSubRanges();
-  LI.segments.erase(J, E);
-
-  // Transfer VNInfos to their new owners and renumber them.
-  unsigned j = 0, e = LI.getNumValNums();
-  while (j != e && EqClass[j] == 0)
-    ++j;
-  for (unsigned i = j; i != e; ++i) {
-    VNInfo *VNI = LI.getValNumInfo(i);
-    if (unsigned eq = EqClass[i]) {
-      VNI->id = LIV[eq-1]->getNumValNums();
-      LIV[eq-1]->valnos.push_back(VNI);
-    } else {
-      VNI->id = j;
-      LI.valnos[j++] = VNI;
       }
+      DistributeRange(SR, SubRanges.data(), VNIMapping);
+    }
+    LI.removeEmptySubRanges();
   }
-  LI.valnos.resize(j);
+
+  // Distribute main liverange.
+  DistributeRange(LI, LIV, EqClass);
 }