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-rw-r--r--include/llvm/CodeGen/Passes.h5
-rw-r--r--include/llvm/InitializePasses.h1
-rw-r--r--lib/CodeGen/CodeGen.cpp1
-rw-r--r--lib/CodeGen/LLVMTargetMachine.cpp8
-rw-r--r--lib/CodeGen/MachineBlockPlacement.cpp83
5 files changed, 98 insertions, 0 deletions
diff --git a/include/llvm/CodeGen/Passes.h b/include/llvm/CodeGen/Passes.h
index 7d0c412..bf440f4 100644
--- a/include/llvm/CodeGen/Passes.h
+++ b/include/llvm/CodeGen/Passes.h
@@ -159,6 +159,11 @@ namespace llvm {
/// probabilities.
FunctionPass *createMachineBlockPlacementPass();
+ /// MachineBlockPlacementStats Pass - This pass collects statistics about the
+ /// basic block placement using branch probabilities and block frequency
+ /// information.
+ FunctionPass *createMachineBlockPlacementStatsPass();
+
/// Code Placement Pass - This pass optimize code placement and aligns loop
/// headers to target specific alignment boundary.
FunctionPass *createCodePlacementOptPass();
diff --git a/include/llvm/InitializePasses.h b/include/llvm/InitializePasses.h
index b5344fc..47a7779 100644
--- a/include/llvm/InitializePasses.h
+++ b/include/llvm/InitializePasses.h
@@ -147,6 +147,7 @@ void initializeLowerInvokePass(PassRegistry&);
void initializeLowerSwitchPass(PassRegistry&);
void initializeMachineBlockFrequencyInfoPass(PassRegistry&);
void initializeMachineBlockPlacementPass(PassRegistry&);
+void initializeMachineBlockPlacementStatsPass(PassRegistry&);
void initializeMachineBranchProbabilityInfoPass(PassRegistry&);
void initializeMachineCSEPass(PassRegistry&);
void initializeMachineDominatorTreePass(PassRegistry&);
diff --git a/lib/CodeGen/CodeGen.cpp b/lib/CodeGen/CodeGen.cpp
index a911534..899baad 100644
--- a/lib/CodeGen/CodeGen.cpp
+++ b/lib/CodeGen/CodeGen.cpp
@@ -29,6 +29,7 @@ void llvm::initializeCodeGen(PassRegistry &Registry) {
initializeLiveVariablesPass(Registry);
initializeMachineBlockFrequencyInfoPass(Registry);
initializeMachineBlockPlacementPass(Registry);
+ initializeMachineBlockPlacementStatsPass(Registry);
initializeMachineCSEPass(Registry);
initializeMachineDominatorTreePass(Registry);
initializeMachineLICMPass(Registry);
diff --git a/lib/CodeGen/LLVMTargetMachine.cpp b/lib/CodeGen/LLVMTargetMachine.cpp
index 268584c..3e69069 100644
--- a/lib/CodeGen/LLVMTargetMachine.cpp
+++ b/lib/CodeGen/LLVMTargetMachine.cpp
@@ -55,6 +55,8 @@ static cl::opt<bool> DisableEarlyTailDup("disable-early-taildup", cl::Hidden,
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,
@@ -499,6 +501,12 @@ bool LLVMTargetMachine::addCommonCodeGenPasses(PassManagerBase &PM,
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))
diff --git a/lib/CodeGen/MachineBlockPlacement.cpp b/lib/CodeGen/MachineBlockPlacement.cpp
index 21582b9..53a8779 100644
--- a/lib/CodeGen/MachineBlockPlacement.cpp
+++ b/lib/CodeGen/MachineBlockPlacement.cpp
@@ -48,6 +48,13 @@
#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.
///
@@ -481,3 +488,79 @@ bool MachineBlockPlacement::runOnMachineFunction(MachineFunction &F) {
// 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;
+}
+
generated by cgit v1.1 at 2024-09-12 09:34:10 +0000