Resurrect some ancient code to add spill ranges without attempting folding, remat, or splitting. This code has been updated to current APIs

in so far as it compiles and, in theory, works, but does not take advantage of recent advancements.  For instance, it could be improved by using
MachineRegisterInfo::use_iterator.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54924 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/LiveIntervalAnalysis.h

@@ -323,6 +323,13 @@ namespace llvm {
     addIntervalsForSpills(const LiveInterval& i,
                           const MachineLoopInfo *loopInfo, VirtRegMap& vrm,
                           float &SSWeight);
+    
+    /// addIntervalsForSpillsFast - Quickly create new intervals for spilled
+    /// defs / uses without remat or splitting.
+    std::vector<LiveInterval*>
+    addIntervalsForSpillsFast(const LiveInterval &li,
+                              const MachineLoopInfo *loopInfo,
+                              VirtRegMap &vrm, float& SSWeight);
 
     /// spillPhysRegAroundRegDefsUses - Spill the specified physical register
     /// around all defs and uses of the specified interval.

lib/CodeGen/LiveIntervalAnalysis.cpp

@@ -1597,6 +1597,111 @@ LiveIntervals::handleSpilledImpDefs(const LiveInterval &li, VirtRegMap &vrm,
 }
 
 
+std::vector<LiveInterval*> LiveIntervals::
+addIntervalsForSpillsFast(const LiveInterval &li,
+                          const MachineLoopInfo *loopInfo,
+                          VirtRegMap &vrm, float& SSWeight) {
+  unsigned slot = vrm.assignVirt2StackSlot(li.reg);
+  
+  // since this is called after the analysis is done we don't know if
+  // LiveVariables is available
+  lv_ = getAnalysisToUpdate<LiveVariables>();
+
+  std::vector<LiveInterval*> added;
+
+  assert(li.weight != HUGE_VALF &&
+         "attempt to spill already spilled interval!");
+
+  DOUT << "\t\t\t\tadding intervals for spills for interval: ";
+  DEBUG(li.dump());
+  DOUT << '\n';
+
+  const TargetRegisterClass* rc = mri_->getRegClass(li.reg);
+
+  for (LiveInterval::Ranges::const_iterator
+         i = li.ranges.begin(), e = li.ranges.end(); i != e; ++i) {
+    unsigned index = getBaseIndex(i->start);
+    unsigned end = getBaseIndex(i->end-1) + InstrSlots::NUM;
+    for (; index != end; index += InstrSlots::NUM) {
+      // skip deleted instructions
+      while (index != end && !getInstructionFromIndex(index))
+        index += InstrSlots::NUM;
+      if (index == end) break;
+
+      MachineInstr *MI = getInstructionFromIndex(index);
+
+      for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
+        MachineOperand& mop = MI->getOperand(i);
+        if (mop.isRegister() && mop.getReg() == li.reg) {
+          // Create a new virtual register for the spill interval.
+          unsigned NewVReg = mri_->createVirtualRegister(rc);
+            
+          // Scan all of the operands of this instruction rewriting operands
+          // to use NewVReg instead of li.reg as appropriate.  We do this for
+          // two reasons:
+          //
+          //   1. If the instr reads the same spilled vreg multiple times, we
+          //      want to reuse the NewVReg.
+          //   2. If the instr is a two-addr instruction, we are required to
+          //      keep the src/dst regs pinned.
+          //
+          // Keep track of whether we replace a use and/or def so that we can
+          // create the spill interval with the appropriate range. 
+          mop.setReg(NewVReg);
+          
+          bool HasUse = mop.isUse();
+          bool HasDef = mop.isDef();
+          for (unsigned j = i+1, e = MI->getNumOperands(); j != e; ++j) {
+            if (MI->getOperand(j).isReg() &&
+                MI->getOperand(j).getReg() == li.reg) {
+              MI->getOperand(j).setReg(NewVReg);
+              HasUse |= MI->getOperand(j).isUse();
+              HasDef |= MI->getOperand(j).isDef();
+            }
+          }
+
+          // create a new register for this spill
+          vrm.grow();
+          vrm.assignVirt2StackSlot(NewVReg, slot);
+          LiveInterval &nI = getOrCreateInterval(NewVReg);
+          assert(nI.empty());
+
+          // the spill weight is now infinity as it
+          // cannot be spilled again
+          nI.weight = HUGE_VALF;
+
+          if (HasUse) {
+            LiveRange LR(getLoadIndex(index), getUseIndex(index),
+                         nI.getNextValue(~0U, 0, getVNInfoAllocator()));
+            DOUT << " +" << LR;
+            nI.addRange(LR);
+          }
+          if (HasDef) {
+            LiveRange LR(getDefIndex(index), getStoreIndex(index),
+                         nI.getNextValue(~0U, 0, getVNInfoAllocator()));
+            DOUT << " +" << LR;
+            nI.addRange(LR);
+          }
+          
+          added.push_back(&nI);
+
+          // update live variables if it is available
+          if (lv_)
+            lv_->addVirtualRegisterKilled(NewVReg, MI);
+          
+          DOUT << "\t\t\t\tadded new interval: ";
+          DEBUG(nI.dump());
+          DOUT << '\n';
+        }
+      }
+    }
+  }
+  
+  SSWeight = HUGE_VALF;
+
+  return added;
+}
+
 std::vector<LiveInterval*> LiveIntervals::
 addIntervalsForSpills(const LiveInterval &li,
                       const MachineLoopInfo *loopInfo, VirtRegMap &vrm,