[llvm-commits] [llvm] r143537 - in /llvm/trunk: include/llvm/CodeGen/Passes.h include/llvm/InitializePasses.h lib/CodeGen/CodeGen.cpp lib/CodeGen/LLVMTargetMachine.cpp lib/CodeGen/MachineBlockPlacement.cpp
Chandler Carruth
chandlerc at gmail.com
Wed Nov 2 00:17:12 PDT 2011
Author: chandlerc
Date: Wed Nov 2 02:17:12 2011
New Revision: 143537
URL: http://llvm.org/viewvc/llvm-project?rev=143537&view=rev
Log:
Begin collecting some of the statistics for block placement discussed on
the mailing list. Suggestions for other statistics to collect would be
awesome. =]
Currently these are implemented as a separate pass guarded by a separate
flag. I'm not thrilled by that, but I wanted to be able to collect the
statistics for the old code placement as well as the new in order to
have a point of comparison. I'm planning on folding them into the single
pass if / when there is only one pass of interest.
Modified:
llvm/trunk/include/llvm/CodeGen/Passes.h
llvm/trunk/include/llvm/InitializePasses.h
llvm/trunk/lib/CodeGen/CodeGen.cpp
llvm/trunk/lib/CodeGen/LLVMTargetMachine.cpp
llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp
Modified: llvm/trunk/include/llvm/CodeGen/Passes.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/Passes.h?rev=143537&r1=143536&r2=143537&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/Passes.h (original)
+++ llvm/trunk/include/llvm/CodeGen/Passes.h Wed Nov 2 02:17:12 2011
@@ -159,6 +159,11 @@
/// 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();
Modified: llvm/trunk/include/llvm/InitializePasses.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/InitializePasses.h?rev=143537&r1=143536&r2=143537&view=diff
==============================================================================
--- llvm/trunk/include/llvm/InitializePasses.h (original)
+++ llvm/trunk/include/llvm/InitializePasses.h Wed Nov 2 02:17:12 2011
@@ -147,6 +147,7 @@
void initializeLowerSwitchPass(PassRegistry&);
void initializeMachineBlockFrequencyInfoPass(PassRegistry&);
void initializeMachineBlockPlacementPass(PassRegistry&);
+void initializeMachineBlockPlacementStatsPass(PassRegistry&);
void initializeMachineBranchProbabilityInfoPass(PassRegistry&);
void initializeMachineCSEPass(PassRegistry&);
void initializeMachineDominatorTreePass(PassRegistry&);
Modified: llvm/trunk/lib/CodeGen/CodeGen.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/CodeGen.cpp?rev=143537&r1=143536&r2=143537&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/CodeGen.cpp (original)
+++ llvm/trunk/lib/CodeGen/CodeGen.cpp Wed Nov 2 02:17:12 2011
@@ -29,6 +29,7 @@
initializeLiveVariablesPass(Registry);
initializeMachineBlockFrequencyInfoPass(Registry);
initializeMachineBlockPlacementPass(Registry);
+ initializeMachineBlockPlacementStatsPass(Registry);
initializeMachineCSEPass(Registry);
initializeMachineDominatorTreePass(Registry);
initializeMachineLICMPass(Registry);
Modified: llvm/trunk/lib/CodeGen/LLVMTargetMachine.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LLVMTargetMachine.cpp?rev=143537&r1=143536&r2=143537&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/LLVMTargetMachine.cpp (original)
+++ llvm/trunk/lib/CodeGen/LLVMTargetMachine.cpp Wed Nov 2 02:17:12 2011
@@ -55,6 +55,8 @@
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 @@
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))
Modified: llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp?rev=143537&r1=143536&r2=143537&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp Wed Nov 2 02:17:12 2011
@@ -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 @@
// 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;
+}
+
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