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/*========================== begin_copyright_notice ============================
Copyright (C) 2022 Intel Corporation
SPDX-License-Identifier: MIT
============================= end_copyright_notice ===========================*/
#include "GenerateFrequencyData.hpp"
#include "Compiler/IGCPassSupport.h"
#include "common/igc_regkeys.hpp"
#include "Probe/Assertion.h"
#include <llvm/IR/Module.h>
#include <llvm/IR/Function.h>
#include <llvm/IR/Instructions.h>
#include <llvm/IR/InstVisitor.h>
#include "llvmWrapper/ADT/Optional.h"
#include <llvm/Analysis/BlockFrequencyInfo.h>
#include <llvm/Analysis/BranchProbabilityInfo.h>
#include <llvm/Analysis/LoopInfo.h>
#include <llvm/Analysis/SyntheticCountsUtils.h>
#include <llvm/ADT/Optional.h>
#include <llvm/Support/ScaledNumber.h>
#include <unordered_map>
#include <string>
using namespace llvm;
using Scaled64 = ScaledNumber<uint64_t>;
class GenerateFrequencyData : public ModulePass {
typedef enum {
PGSS_IGC_DUMP_BLK = 0x1,
PGSS_IGC_DUMP_FUNC = 0x2,
} PGSS_DUMP_t;
public:
static char ID;
GenerateFrequencyData() : ModulePass(ID), M(nullptr) {
IGC::initializeGenerateFrequencyDataPass(*PassRegistry::getPassRegistry());
}
bool runOnModule(Module &) override;
void runStaticAnalysis();
void updateStaticFuncFreq(DenseMap<Function *, ScaledNumber<uint64_t>> &Counts);
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
AU.addRequired<LoopInfoWrapperPass>();
AU.addRequired<BranchProbabilityInfoWrapperPass>();
AU.addRequired<BlockFrequencyInfoWrapperPass>();
}
Module *getModule() { return M; };
void setModule(Module *m) { M = m; };
private:
Module *M;
};
char GenerateFrequencyData::ID = 0;
#define PASS_FLAG "igc-generate-frequency-data"
#define PASS_DESC "Generate frequency data"
#define PASS_CFG_ONLY false
#define PASS_ANALYSIS false
namespace IGC {
IGC_INITIALIZE_PASS_BEGIN(GenerateFrequencyData, PASS_FLAG, PASS_DESC, PASS_CFG_ONLY, PASS_ANALYSIS)
IGC_INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
IGC_INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfoWrapperPass)
IGC_INITIALIZE_PASS_DEPENDENCY(BlockFrequencyInfoWrapperPass)
IGC_INITIALIZE_PASS_END(GenerateFrequencyData, PASS_FLAG, PASS_DESC, PASS_CFG_ONLY, PASS_ANALYSIS)
} // namespace IGC
llvm::ModulePass *IGC::createGenerateFrequencyDataPass() { return new GenerateFrequencyData(); }
bool GenerateFrequencyData::runOnModule(Module &M) {
setModule(&M);
runStaticAnalysis();
return false;
}
void GenerateFrequencyData::runStaticAnalysis() {
// Analyze function frequencies from SyntheticCountsPropagation
// PrintStaticProfilingForKernelSizeReduction(0x1, "------------------Static analysis start------------------")
DenseMap<Function *, ScaledNumber<uint64_t>> F_freqs;
DenseMap<BasicBlock *, ScaledNumber<uint64_t>> B_freqs;
LLVMContext &C = M->getContext();
updateStaticFuncFreq(F_freqs);
for (auto &F : M->getFunctionList()) {
if (F.empty() || F_freqs.find(&F) == F_freqs.end())
continue;
auto &BFI = getAnalysis<BlockFrequencyInfoWrapperPass>(F).getBFI();
Scaled64 EntryFreq(BFI.getEntryFreq(), 0);
if ((IGC_GET_FLAG_VALUE(PrintStaticProfileGuidedSpillCostAnalysis) & PGSS_IGC_DUMP_BLK) != 0)
dbgs() << "Function frequency of " << F.getName().str() << ": " << F_freqs[&F].toString() << "\n";
for (auto &B : F) {
Scaled64 BBCount(BFI.getBlockFreq(&B).getFrequency(), 0);
BBCount /= EntryFreq;
BBCount *= F_freqs[&F];
B_freqs[&B] = BBCount;
if ((IGC_GET_FLAG_VALUE(PrintStaticProfileGuidedSpillCostAnalysis) & PGSS_IGC_DUMP_BLK) != 0)
dbgs() << "Block frequency of " << B.getName().str() << " " << &B << ": " << BBCount.toString() << "\n";
Instruction *last_inst = B.getTerminator();
if (last_inst) {
// llvm::dbgs() << "Digits: " << BBCount.getDigits() << "\n";
// llvm::dbgs() << "Scale: " << BBCount.getScale() << "\n";
MDNode *m_node = MDNode::get(C, MDString::get(C, std::to_string(BBCount.getDigits())));
last_inst->setMetadata("stats.blockFrequency.digits", m_node);
m_node = MDNode::get(C, MDString::get(C, std::to_string(BBCount.getScale())));
last_inst->setMetadata("stats.blockFrequency.scale", m_node);
}
}
}
return;
}
void GenerateFrequencyData::updateStaticFuncFreq(DenseMap<Function *, ScaledNumber<uint64_t>> &Counts) {
auto MayHaveIndirectCalls = [](Function &F) {
for (auto *U : F.users()) {
if (!isa<CallInst>(U) && !isa<InvokeInst>(U))
return true;
}
return false;
};
uint64_t InitialSyntheticCount = 10;
uint64_t InlineSyntheticCount = 15;
uint64_t ColdSyntheticCount = 5;
std::unordered_map<llvm::BasicBlock *, Scaled64> blockFreqs;
std::unordered_map<llvm::Function *, Scaled64> entryFreqs;
for (Function &F : getModule()->getFunctionList()) {
uint64_t InitialCount = InitialSyntheticCount;
if (!F.empty()) {
auto &BFI = getAnalysis<BlockFrequencyInfoWrapperPass>(F).getBFI();
entryFreqs[&F] = Scaled64(BFI.getEntryFreq(), 0);
for (auto &B : F)
blockFreqs[&B] = Scaled64(BFI.getBlockFreq(&B).getFrequency(), 0);
}
if (F.isDeclaration())
continue;
if (F.hasFnAttribute(llvm::Attribute::AlwaysInline) || F.hasFnAttribute(llvm::Attribute::InlineHint)) {
// Use a higher value for inline functions to account for the fact that
// these are usually beneficial to inline.
InitialCount = InlineSyntheticCount;
} else if (F.hasLocalLinkage() && !MayHaveIndirectCalls(F)) {
// Local functions without inline hints get counts only through
// propagation.
InitialCount = 0;
} else if (F.hasFnAttribute(llvm::Attribute::Cold) || F.hasFnAttribute(llvm::Attribute::NoInline)) {
// Use a lower value for noinline and cold functions.
InitialCount = ColdSyntheticCount;
}
Counts[&F] = Scaled64(InitialCount, 0);
}
// Edge includes information about the source. Hence ignore the first
// parameter.
auto GetCallSiteProfCount = [&](const CallGraphNode *, const CallGraphNode::CallRecord &Edge) {
std::optional<Scaled64> Res = std::nullopt;
if (!Edge.first)
return IGCLLVM::makeLLVMOptional(Res);
CallBase &CB = *cast<CallBase>(*Edge.first);
Function *Caller = CB.getCaller();
BasicBlock *CSBB = CB.getParent();
// Now compute the callsite count from relative frequency and
// entry count:
Scaled64 EntryFreq = entryFreqs[Caller];
Scaled64 BBCount = blockFreqs[CSBB];
IGC_ASSERT(EntryFreq != 0);
BBCount /= EntryFreq;
BBCount *= Counts[Caller];
return IGCLLVM::makeLLVMOptional(std::optional<Scaled64>(BBCount));
};
CallGraph CG(*M);
// Propgate the entry counts on the callgraph.
SyntheticCountsUtils<const CallGraph *>::propagate(&CG, GetCallSiteProfCount,
[&](const CallGraphNode *N, Scaled64 New) {
auto F = N->getFunction();
if (!F || F->isDeclaration())
return;
Counts[F] += New;
});
for (auto &F : M->getFunctionList()) {
if (F.empty())
continue;
if (Counts.find(&F) != Counts.end()) {
if ((IGC_GET_FLAG_VALUE(PrintStaticProfileGuidedSpillCostAnalysis) & PGSS_IGC_DUMP_FUNC) != 0)
dbgs() << F.getName().str() << " Freq: " << Counts[&F].toString() << "\n";
}
}
return;
}
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