cl::desc("Disable pre-register allocation tail duplication"));
static cl::opt<bool> EnableBlockPlacement("enable-block-placement",
cl::Hidden, cl::desc("Enable probability-driven block placement"));
+static cl::opt<bool> EnableBlockPlacementStats("enable-block-placement-stats",
+ cl::Hidden, cl::desc("Collect probability-driven block placement stats"));
static cl::opt<bool> DisableCodePlace("disable-code-place", cl::Hidden,
cl::desc("Disable code placement"));
static cl::opt<bool> DisableSSC("disable-ssc", cl::Hidden,
PM.add(createCodePlacementOptPass());
printNoVerify(PM, "After CodePlacementOpt");
}
+
+ // Run a separate pass to collect block placement statistics.
+ if (EnableBlockPlacementStats) {
+ PM.add(createMachineBlockPlacementStatsPass());
+ printNoVerify(PM, "After MachineBlockPlacementStats");
+ }
}
if (addPreEmitPass(PM, OptLevel))
#include <algorithm>
using namespace llvm;
+STATISTIC(NumCondBranches, "Number of conditional branches");
+STATISTIC(NumUncondBranches, "Number of uncondittional branches");
+STATISTIC(CondBranchTakenFreq,
+ "Potential frequency of taking conditional branches");
+STATISTIC(UncondBranchTakenFreq,
+ "Potential frequency of taking unconditional branches");
+
namespace {
/// \brief A structure for storing a weighted edge.
///
// differs from the original order.
return true;
}
+
+namespace {
+/// \brief A pass to compute block placement statistics.
+///
+/// A separate pass to compute interesting statistics for evaluating block
+/// placement. This is separate from the actual placement pass so that they can
+/// be computed in the absense of any placement transformations or when using
+/// alternative placement strategies.
+class MachineBlockPlacementStats : public MachineFunctionPass {
+ /// \brief A handle to the branch probability pass.
+ const MachineBranchProbabilityInfo *MBPI;
+
+ /// \brief A handle to the function-wide block frequency pass.
+ const MachineBlockFrequencyInfo *MBFI;
+
+public:
+ static char ID; // Pass identification, replacement for typeid
+ MachineBlockPlacementStats() : MachineFunctionPass(ID) {
+ initializeMachineBlockPlacementStatsPass(*PassRegistry::getPassRegistry());
+ }
+
+ bool runOnMachineFunction(MachineFunction &F);
+
+ void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<MachineBranchProbabilityInfo>();
+ AU.addRequired<MachineBlockFrequencyInfo>();
+ AU.setPreservesAll();
+ MachineFunctionPass::getAnalysisUsage(AU);
+ }
+
+ const char *getPassName() const { return "Block Placement Stats"; }
+};
+}
+
+char MachineBlockPlacementStats::ID = 0;
+INITIALIZE_PASS_BEGIN(MachineBlockPlacementStats, "block-placement-stats",
+ "Basic Block Placement Stats", false, false)
+INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
+INITIALIZE_PASS_DEPENDENCY(MachineBlockFrequencyInfo)
+INITIALIZE_PASS_END(MachineBlockPlacementStats, "block-placement-stats",
+ "Basic Block Placement Stats", false, false)
+
+FunctionPass *llvm::createMachineBlockPlacementStatsPass() {
+ return new MachineBlockPlacementStats();
+}
+
+bool MachineBlockPlacementStats::runOnMachineFunction(MachineFunction &F) {
+ // Check for single-block functions and skip them.
+ if (llvm::next(F.begin()) == F.end())
+ return false;
+
+ MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
+ MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
+
+ for (MachineFunction::iterator I = F.begin(), E = F.end(); I != E; ++I) {
+ BlockFrequency BlockFreq = MBFI->getBlockFreq(I);
+ Statistic &NumBranches = (I->succ_size() > 1) ? NumCondBranches
+ : NumUncondBranches;
+ Statistic &BranchTakenFreq = (I->succ_size() > 1) ? CondBranchTakenFreq
+ : UncondBranchTakenFreq;
+ for (MachineBasicBlock::succ_iterator SI = I->succ_begin(),
+ SE = I->succ_end();
+ SI != SE; ++SI) {
+ // Skip if this successor is a fallthrough.
+ if (I->isLayoutSuccessor(*SI))
+ continue;
+
+ BlockFrequency EdgeFreq = BlockFreq * MBPI->getEdgeProbability(I, *SI);
+ ++NumBranches;
+ BranchTakenFreq += EdgeFreq.getFrequency();
+ }
+ }
+
+ return false;
+}
+