#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include <algorithm>
-#include <map>
using namespace llvm;
+static cl::opt<bool>
+DisableEdgeSplitting("disable-phi-elim-edge-splitting", cl::init(false),
+ cl::Hidden, cl::desc("Disable critical edge splitting "
+ "during PHI elimination"));
+
namespace {
class PHIElimination : public MachineFunctionPass {
MachineRegisterInfo *MRI; // Machine register information
}
STATISTIC(NumAtomic, "Number of atomic phis lowered");
+STATISTIC(NumCriticalEdgesSplit, "Number of critical edges split");
STATISTIC(NumReused, "Number of reused lowered phis");
char PHIElimination::ID = 0;
bool Changed = false;
+ // This pass takes the function out of SSA form.
+ MRI->leaveSSA();
+
// Split critical edges to help the coalescer
- if (LiveVariables *LV = getAnalysisIfAvailable<LiveVariables>()) {
- MachineLoopInfo *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
- for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
- Changed |= SplitPHIEdges(MF, *I, *LV, MLI);
+ if (!DisableEdgeSplitting) {
+ if (LiveVariables *LV = getAnalysisIfAvailable<LiveVariables>()) {
+ MachineLoopInfo *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
+ for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
+ Changed |= SplitPHIEdges(MF, *I, *LV, MLI);
+ }
}
// Populate VRegPHIUseCount
}
bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
- MachineBasicBlock &MBB,
- LiveVariables &LV,
- MachineLoopInfo *MLI) {
+ MachineBasicBlock &MBB,
+ LiveVariables &LV,
+ MachineLoopInfo *MLI) {
if (MBB.empty() || !MBB.front().isPHI() || MBB.isLandingPad())
return false; // Quick exit for basic blocks without PHIs.
bool Changed = false;
- for (MachineBasicBlock::const_iterator BBI = MBB.begin(), BBE = MBB.end();
+ for (MachineBasicBlock::iterator BBI = MBB.begin(), BBE = MBB.end();
BBI != BBE && BBI->isPHI(); ++BBI) {
for (unsigned i = 1, e = BBI->getNumOperands(); i != e; i += 2) {
unsigned Reg = BBI->getOperand(i).getReg();
!LV.isLiveIn(Reg, MBB) && LV.isLiveOut(Reg, *PreMBB)) {
if (!MLI ||
!(MLI->getLoopFor(PreMBB) == MLI->getLoopFor(&MBB) &&
- MLI->isLoopHeader(&MBB)))
- Changed |= PreMBB->SplitCriticalEdge(&MBB, this) != 0;
+ MLI->isLoopHeader(&MBB))) {
+ if (PreMBB->SplitCriticalEdge(&MBB, this)) {
+ Changed = true;
+ ++NumCriticalEdgesSplit;
+ }
+ }
}
}
}
- return true;
+ return Changed;
}