Beginning SplitKit - utility classes for live range splitting.

This is a work in progress. So far we have some basic loop analysis to help
determine where it is useful to split a live range around a loop.

The actual loop splitting code from Splitter.cpp is also going to move in here.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108842 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 26 insertions, 1 deletions

diff --git a/lib/CodeGen/InlineSpiller.cpp b/lib/CodeGen/InlineSpiller.cpp
index 3c6c761b38..fc0357eda7 100644
--- a/lib/CodeGen/InlineSpiller.cpp
+++ b/lib/CodeGen/InlineSpiller.cpp
@@ -14,6 +14,7 @@
 
 #define DEBUG_TYPE "spiller"
 #include "Spiller.h"
+#include "SplitKit.h"
 #include "VirtRegMap.h"
 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
@@ -39,6 +40,8 @@ class InlineSpiller : public Spiller {
   const TargetRegisterInfo &tri_;
   const BitVector reserved_;
 
+  SplitAnalysis splitAnalysis_;
+
   // Variables that are valid during spill(), but used by multiple methods.
   LiveInterval *li_;
   std::vector<LiveInterval*> *newIntervals_;
@@ -62,7 +65,8 @@ public:
       mri_(mf->getRegInfo()),
       tii_(*mf->getTarget().getInstrInfo()),
       tri_(*mf->getTarget().getRegisterInfo()),
-      reserved_(tri_.getReservedRegs(mf_)) {}
+      reserved_(tri_.getReservedRegs(mf_)),
+      splitAnalysis_(mf, lis, mli) {}
 
   void spill(LiveInterval *li,
              std::vector<LiveInterval*> &newIntervals,
@@ -70,6 +74,8 @@ public:
              SlotIndex *earliestIndex);
 
 private:
+  bool split();
+
   bool allUsesAvailableAt(const MachineInstr *OrigMI, SlotIndex OrigIdx,
                           SlotIndex UseIdx);
   bool reMaterializeFor(MachineBasicBlock::iterator MI);
@@ -91,6 +97,22 @@ Spiller *createInlineSpiller(MachineFunction *mf,
 }
 }
 
+/// split - try splitting the current interval into pieces that may allocate
+/// separately. Return true if successful.
+bool InlineSpiller::split() {
+  // FIXME: Add intra-MBB splitting.
+  if (lis_.intervalIsInOneMBB(*li_))
+    return false;
+
+  splitAnalysis_.analyze(li_);
+
+  if (const MachineLoop *loop = splitAnalysis_.getBestSplitLoop()) {
+    if (splitAroundLoop(splitAnalysis_, loop))
+      return true;
+  }
+  return false;
+}
+
 /// allUsesAvailableAt - Return true if all registers used by OrigMI at
 /// OrigIdx are also available with the same value at UseIdx.
 bool InlineSpiller::allUsesAvailableAt(const MachineInstr *OrigMI,
@@ -338,6 +360,9 @@ void InlineSpiller::spill(LiveInterval *li,
   rc_ = mri_.getRegClass(li->reg);
   spillIs_ = &spillIs;
 
+  if (split())
+    return;
+
   reMaterializeAll();
 
   // Remat may handle everything.