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Implement single block splitting.

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Before spilling a live range, we split it into a separate range for each basic
block where it is used. That way we only get one reload per basic block if the
new smaller ranges can allocate to a register.

This type of splitting is already present in the standard spiller.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110934 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen
2010-08-12 17:07:14 +00:00
parent 727356fc7d
commit f1b05f2b0e
3 changed files with 158 additions and 5 deletions
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lib/CodeGen/SplitKit.h
+21 -5
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@@ -37,10 +37,6 @@ public:
const MachineLoopInfo &loops_;
const TargetInstrInfo &tii_;
private:
// Current live interval.
const LiveInterval *curli_;
// Instructions using the the current register.
typedef SmallPtrSet<const MachineInstr*, 16> InstrPtrSet;
InstrPtrSet usingInstrs_;
@@ -53,6 +49,10 @@ private:
typedef SmallPtrSet<const MachineLoop*, 16> LoopPtrSet;
LoopPtrSet usingLoops_;
private:
// Current live interval.
const LiveInterval *curli_;
// Sumarize statistics by counting instructions using curli_.
void analyzeUses();
@@ -118,6 +118,11 @@ public:
/// getBestSplitLoop - Return the loop where curli may best be split to a
/// separate register, or NULL.
const MachineLoop *getBestSplitLoop();
/// getMultiUseBlocks - Add basic blocks to Blocks that may benefit from
/// having curli split to a new live interval. Return true if Blocks can be
/// passed to SplitEditor::splitSingleBlocks.
bool getMultiUseBlocks(BlockPtrSet &Blocks);
};
/// SplitEditor - Edit machine code and LiveIntervals for live range
@@ -156,7 +161,7 @@ class SplitEditor {
/// getDupLI - Ensure dupli is created and return it.
LiveInterval *getDupLI();
/// valueMap_ - Map values in dupli to values in openIntv. These are direct 1-1
/// valueMap_ - Map values in cupli to values in openli. These are direct 1-1
/// mappings, and do not include values created by inserted copies.
DenseMap<const VNInfo*, VNInfo*> valueMap_;
@@ -192,6 +197,10 @@ public:
/// Create a new virtual register and live interval.
void openIntv();
/// enterIntvBefore - Enter openli before the instruction at Idx. If curli is
/// not live before Idx, a COPY is not inserted.
void enterIntvBefore(SlotIndex Idx);
/// enterIntvAtEnd - Enter openli at the end of MBB.
/// PhiMBB is a successor inside openli where a PHI value is created.
/// Currently, all entries must share the same PhiMBB.
@@ -203,6 +212,9 @@ public:
/// useIntv - indicate that all instructions in range should use openli.
void useIntv(SlotIndex Start, SlotIndex End);
/// leaveIntvAfter - Leave openli after the instruction at Idx.
void leaveIntvAfter(SlotIndex Idx);
/// leaveIntvAtTop - Leave the interval at the top of MBB.
/// Currently, only one value can leave the interval.
void leaveIntvAtTop(MachineBasicBlock &MBB);
@@ -222,6 +234,10 @@ public:
/// curli is still intact, and needs to be spilled or split further.
bool splitAroundLoop(const MachineLoop*);
/// splitSingleBlocks - Split curli into a separate live interval inside each
/// basic block in Blocks. Return true if curli has been completely replaced,
/// false if curli is still intact, and needs to be spilled or split further.
bool splitSingleBlocks(const SplitAnalysis::BlockPtrSet &Blocks);
};