#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
-#include "llvm/Target/TargetInstrInfo.h"
-
-#include <map>
+#include "llvm/CodeGen/MachineRegisterInfo.h"
namespace llvm {
-
+ class LiveVariables;
+
/// Lower PHI instructions to copies.
class PHIElimination : public MachineFunctionPass {
MachineRegisterInfo *MRI; // Machine register information
- private:
-
- typedef SmallSet<MachineBasicBlock*, 4> PHIKillList;
- typedef DenseMap<unsigned, PHIKillList> PHIKillMap;
- typedef DenseMap<unsigned, MachineBasicBlock*> PHIDefMap;
public:
-
- typedef PHIKillList::iterator phi_kill_iterator;
- typedef PHIKillList::const_iterator const_phi_kill_iterator;
-
static char ID; // Pass identification, replacement for typeid
PHIElimination() : MachineFunctionPass(&ID) {}
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
- /// Return true if the given vreg was defined by a PHI intsr prior to
- /// lowering.
- bool hasPHIDef(unsigned vreg) const {
- return PHIDefs.count(vreg);
- }
-
- /// Returns the block in which the PHI instruction which defined the
- /// given vreg used to reside.
- MachineBasicBlock* getPHIDefBlock(unsigned vreg) {
- PHIDefMap::iterator phiDefItr = PHIDefs.find(vreg);
- assert(phiDefItr != PHIDefs.end() && "vreg has no phi-def.");
- return phiDefItr->second;
- }
-
- /// Returns true if the given vreg was killed by a PHI instr.
- bool hasPHIKills(unsigned vreg) const {
- return PHIKills.count(vreg);
- }
-
- /// Returns an iterator over the BasicBlocks which contained PHI
- /// kills of this register prior to lowering.
- phi_kill_iterator phiKillsBegin(unsigned vreg) {
- PHIKillMap::iterator phiKillItr = PHIKills.find(vreg);
- assert(phiKillItr != PHIKills.end() && "vreg has no phi-kills.");
- return phiKillItr->second.begin();
- }
- phi_kill_iterator phiKillsEnd(unsigned vreg) {
- PHIKillMap::iterator phiKillItr = PHIKills.find(vreg);
- assert(phiKillItr != PHIKills.end() && "vreg has no phi-kills.");
- return phiKillItr->second.end();
- }
-
private:
/// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions
/// in predecessor basic blocks.
///
void analyzePHINodes(const MachineFunction& Fn);
- /// isLiveOut - Determine if Reg is live out from MBB, when not
- /// considering PHI nodes. This means that Reg is either killed by
- /// a successor block or passed through one.
- bool isLiveOut(unsigned Reg, const MachineBasicBlock &MBB,
- LiveVariables &LV);
+ /// Split critical edges where necessary for good coalescer performance.
+ bool SplitPHIEdges(MachineFunction &MF, MachineBasicBlock &MBB,
+ LiveVariables &LV);
- // FindCopyInsertPoint - Find a safe place in MBB to insert a copy from
- // SrcReg. This needs to be after any def or uses of SrcReg, but before
- // any subsequent point where control flow might jump out of the basic
- // block.
+ /// SplitCriticalEdge - Split a critical edge from A to B by
+ /// inserting a new MBB. Update branches in A and PHI instructions
+ /// in B. Return the new block.
+ MachineBasicBlock *SplitCriticalEdge(MachineBasicBlock *A,
+ MachineBasicBlock *B);
+
+ /// FindCopyInsertPoint - Find a safe place in MBB to insert a copy from
+ /// SrcReg when following the CFG edge to SuccMBB. This needs to be after
+ /// any def of SrcReg, but before any subsequent point where control flow
+ /// might jump out of the basic block.
MachineBasicBlock::iterator FindCopyInsertPoint(MachineBasicBlock &MBB,
+ MachineBasicBlock &SuccMBB,
unsigned SrcReg);
// SkipPHIsAndLabels - Copies need to be inserted after phi nodes and
// also after any exception handling labels: in landing pads execution
// starts at the label, so any copies placed before it won't be executed!
+ // We also deal with DBG_VALUEs, which are a bit tricky:
+ // PHI
+ // DBG_VALUE
+ // LABEL
+ // Here the DBG_VALUE needs to be skipped, and if it refers to a PHI it
+ // needs to be annulled or, better, moved to follow the label, as well.
+ // PHI
+ // DBG_VALUE
+ // no label
+ // Here it is not a good idea to skip the DBG_VALUE.
+ // FIXME: For now we skip and annul all DBG_VALUEs, maximally simple and
+ // maximally stupid.
MachineBasicBlock::iterator SkipPHIsAndLabels(MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) {
// Rather than assuming that EH labels come before other kinds of labels,
// just skip all labels.
- while (I != MBB.end() &&
- (I->getOpcode() == TargetInstrInfo::PHI || I->isLabel()))
+ while (I != MBB.end() &&
+ (I->isPHI() || I->isLabel() || I->isDebugValue())) {
+ if (I->isDebugValue() && I->getNumOperands()==3 &&
+ I->getOperand(0).isReg())
+ I->getOperand(0).setReg(0U);
++I;
+ }
return I;
}
- typedef std::pair<const MachineBasicBlock*, unsigned> BBVRegPair;
- typedef std::map<BBVRegPair, unsigned> VRegPHIUse;
+ typedef std::pair<unsigned, unsigned> BBVRegPair;
+ typedef DenseMap<BBVRegPair, unsigned> VRegPHIUse;
VRegPHIUse VRegPHIUseCount;
- PHIDefMap PHIDefs;
- PHIKillMap PHIKills;
// Defs of PHI sources which are implicit_def.
SmallPtrSet<MachineInstr*, 4> ImpDefs;
+
+ // Map reusable lowered PHI node -> incoming join register.
+ typedef DenseMap<MachineInstr*, unsigned,
+ MachineInstrExpressionTrait> LoweredPHIMap;
+ LoweredPHIMap LoweredPHIs;
};
}
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