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//===- bolt/Passes/AllocCombiner.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
//
//===----------------------------------------------------------------------===//
//
// This file implements the AllocCombinerPass class.
//
//===----------------------------------------------------------------------===//
#include "bolt/Passes/AllocCombiner.h"
#define DEBUG_TYPE "alloccombiner"
using namespace llvm;
namespace opts {
extern cl::opt<bolt::FrameOptimizationType> FrameOptimization;
} // end namespace opts
namespace llvm {
namespace bolt {
static bool getStackAdjustmentSize(const BinaryContext &BC, const MCInst &Inst,
int64_t &Adjustment) {
return BC.MIB->evaluateStackOffsetExpr(
Inst, Adjustment, std::make_pair(BC.MIB->getStackPointer(), 0LL),
std::make_pair(0, 0LL));
}
static bool isIndifferentToSP(const MCInst &Inst, const BinaryContext &BC) {
if (BC.MIB->isCFI(Inst))
return true;
const MCInstrDesc &II = BC.MII->get(Inst.getOpcode());
if (BC.MIB->isTerminator(Inst) ||
II.hasImplicitDefOfPhysReg(BC.MIB->getStackPointer(), BC.MRI.get()) ||
II.hasImplicitUseOfPhysReg(BC.MIB->getStackPointer()))
return false;
for (const MCOperand &Operand : MCPlus::primeOperands(Inst))
if (Operand.isReg() && Operand.getReg() == BC.MIB->getStackPointer())
return false;
return true;
}
static bool shouldProcess(const BinaryFunction &Function) {
return Function.isSimple() && Function.hasCFG() && !Function.isIgnored();
}
static void runForAllWeCare(std::map<uint64_t, BinaryFunction> &BFs,
std::function<void(BinaryFunction &)> Task) {
for (auto &It : BFs) {
BinaryFunction &Function = It.second;
if (shouldProcess(Function))
Task(Function);
}
}
void AllocCombinerPass::combineAdjustments(BinaryFunction &BF) {
BinaryContext &BC = BF.getBinaryContext();
for (BinaryBasicBlock &BB : BF) {
MCInst *Prev = nullptr;
for (MCInst &Inst : llvm::reverse(BB)) {
if (isIndifferentToSP(Inst, BC))
continue; // Skip updating Prev
int64_t Adjustment = 0LL;
if (!Prev || !BC.MIB->isStackAdjustment(Inst) ||
!BC.MIB->isStackAdjustment(*Prev) ||
!getStackAdjustmentSize(BC, *Prev, Adjustment)) {
Prev = &Inst;
continue;
}
LLVM_DEBUG({
dbgs() << "At \"" << BF.getPrintName() << "\", combining: \n";
Inst.dump();
Prev->dump();
dbgs() << "Adjustment: " << Adjustment << "\n";
});
if (BC.MIB->isSUB(Inst))
Adjustment = -Adjustment;
BC.MIB->addToImm(Inst, Adjustment, BC.Ctx.get());
LLVM_DEBUG({
dbgs() << "After adjustment:\n";
Inst.dump();
});
BB.eraseInstruction(BB.findInstruction(Prev));
++NumCombined;
DynamicCountCombined += BB.getKnownExecutionCount();
FuncsChanged.insert(&BF);
Prev = &Inst;
}
}
}
void AllocCombinerPass::runOnFunctions(BinaryContext &BC) {
if (opts::FrameOptimization == FOP_NONE)
return;
runForAllWeCare(BC.getBinaryFunctions(), [&](BinaryFunction &Function) {
combineAdjustments(Function);
});
outs() << "BOLT-INFO: Allocation combiner: " << NumCombined
<< " empty spaces coalesced (dyn count: " << DynamicCountCombined
<< ").\n";
}
} // end namespace bolt
} // end namespace llvm
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