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//===-- InsertCodePrefetch.cpp ---=========--------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
/// \file
/// Code Prefetch Insertion Pass.
//===----------------------------------------------------------------------===//
/// This pass inserts code prefetch instructions according to the prefetch
/// directives in the basic block section profile. The target of a prefetch can
/// be the beginning of any dynamic basic block, that is the beginning of a
/// machine basic block, or immediately after a callsite. A global symbol is
/// emitted at the position of the target so it can be addressed from the
/// prefetch instruction from any module.
//===----------------------------------------------------------------------===//
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/CodeGen/BasicBlockSectionUtils.h"
#include "llvm/CodeGen/BasicBlockSectionsProfileReader.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/InitializePasses.h"
using namespace llvm;
#define DEBUG_TYPE "insert-code-prefetch"
namespace {
class InsertCodePrefetch : public MachineFunctionPass {
public:
static char ID;
InsertCodePrefetch() : MachineFunctionPass(ID) {
initializeInsertCodePrefetchPass(*PassRegistry::getPassRegistry());
}
StringRef getPassName() const override {
return "Code Prefetch Inserter Pass";
}
void getAnalysisUsage(AnalysisUsage &AU) const override;
// Sets prefetch targets based on the bb section profile.
bool runOnMachineFunction(MachineFunction &MF) override;
};
} // end anonymous namespace
//===----------------------------------------------------------------------===//
// Implementation
//===----------------------------------------------------------------------===//
char InsertCodePrefetch::ID = 0;
INITIALIZE_PASS_BEGIN(InsertCodePrefetch, DEBUG_TYPE, "Code prefetch insertion",
true, false)
INITIALIZE_PASS_DEPENDENCY(BasicBlockSectionsProfileReaderWrapperPass)
INITIALIZE_PASS_END(InsertCodePrefetch, DEBUG_TYPE, "Code prefetch insertion",
true, false)
bool InsertCodePrefetch::runOnMachineFunction(MachineFunction &MF) {
assert(MF.getTarget().getBBSectionsType() == BasicBlockSection::List &&
"BB Sections list not enabled!");
if (hasInstrProfHashMismatch(MF))
return false;
// Set each block's prefetch targets so AsmPrinter can emit a special symbol
// there.
SmallVector<CallsiteID> PrefetchTargets =
getAnalysis<BasicBlockSectionsProfileReaderWrapperPass>()
.getPrefetchTargetsForFunction(MF.getName());
DenseMap<UniqueBBID, SmallVector<unsigned>> PrefetchTargetsByBBID;
for (const auto &Target : PrefetchTargets)
PrefetchTargetsByBBID[Target.BBID].push_back(Target.CallsiteIndex);
// Sort and uniquify the callsite indices for every block.
for (auto &[K, V] : PrefetchTargetsByBBID) {
llvm::sort(V);
V.erase(llvm::unique(V), V.end());
}
for (auto &MBB : MF) {
auto R = PrefetchTargetsByBBID.find(*MBB.getBBID());
if (R == PrefetchTargetsByBBID.end())
continue;
MBB.setPrefetchTargetCallsiteIndexes(R->second);
}
return false;
}
void InsertCodePrefetch::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequired<BasicBlockSectionsProfileReaderWrapperPass>();
MachineFunctionPass::getAnalysisUsage(AU);
}
MachineFunctionPass *llvm::createInsertCodePrefetchPass() {
return new InsertCodePrefetch();
}
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