1//===- bolt/Passes/AllocCombiner.cpp --------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements the AllocCombinerPass class.
10//
11//===----------------------------------------------------------------------===//
12
13#include "bolt/Passes/AllocCombiner.h"
14
15#define DEBUG_TYPE "alloccombiner"
16
17using namespace llvm;
18
19namespace opts {
20
21extern cl::opt<bolt::FrameOptimizationType> FrameOptimization;
22
23} // end namespace opts
24
25namespace llvm {
26namespace bolt {
27
28static bool getStackAdjustmentSize(const BinaryContext &BC, const MCInst &Inst,
29 int64_t &Adjustment) {
30 return BC.MIB->evaluateStackOffsetExpr(
31 Inst, Output&: Adjustment, Input1: std::make_pair(x: BC.MIB->getStackPointer(), y: 0LL),
32 Input2: std::make_pair(x: 0, y: 0LL));
33}
34
35static bool isIndifferentToSP(const MCInst &Inst, const BinaryContext &BC) {
36 if (BC.MIB->isCFI(Inst))
37 return true;
38
39 const MCInstrDesc &II = BC.MII->get(Opcode: Inst.getOpcode());
40 if (BC.MIB->isTerminator(Inst) ||
41 II.hasImplicitDefOfPhysReg(Reg: BC.MIB->getStackPointer(), MRI: BC.MRI.get()) ||
42 II.hasImplicitUseOfPhysReg(Reg: BC.MIB->getStackPointer()))
43 return false;
44
45 for (const MCOperand &Operand : MCPlus::primeOperands(Inst))
46 if (Operand.isReg() && Operand.getReg() == BC.MIB->getStackPointer())
47 return false;
48 return true;
49}
50
51static bool shouldProcess(const BinaryFunction &Function) {
52 return Function.isSimple() && Function.hasCFG() && !Function.isIgnored();
53}
54
55static void runForAllWeCare(std::map<uint64_t, BinaryFunction> &BFs,
56 std::function<void(BinaryFunction &)> Task) {
57 for (auto &It : BFs) {
58 BinaryFunction &Function = It.second;
59 if (shouldProcess(Function))
60 Task(Function);
61 }
62}
63
64void AllocCombinerPass::combineAdjustments(BinaryFunction &BF) {
65 BinaryContext &BC = BF.getBinaryContext();
66 for (BinaryBasicBlock &BB : BF) {
67 MCInst *Prev = nullptr;
68 for (MCInst &Inst : llvm::reverse(C&: BB)) {
69 if (isIndifferentToSP(Inst, BC))
70 continue; // Skip updating Prev
71
72 int64_t Adjustment = 0LL;
73 if (!Prev || !BC.MIB->isStackAdjustment(Inst) ||
74 !BC.MIB->isStackAdjustment(Inst: *Prev) ||
75 !getStackAdjustmentSize(BC, Inst: *Prev, Adjustment)) {
76 Prev = &Inst;
77 continue;
78 }
79
80 LLVM_DEBUG({
81 dbgs() << "At \"" << BF.getPrintName() << "\", combining: \n";
82 Inst.dump();
83 Prev->dump();
84 dbgs() << "Adjustment: " << Adjustment << "\n";
85 });
86
87 if (BC.MIB->isSUB(Inst))
88 Adjustment = -Adjustment;
89
90 BC.MIB->addToImm(Inst, Amt&: Adjustment, Ctx: BC.Ctx.get());
91
92 LLVM_DEBUG({
93 dbgs() << "After adjustment:\n";
94 Inst.dump();
95 });
96
97 BB.eraseInstruction(II: BB.findInstruction(Inst: Prev));
98 ++NumCombined;
99 DynamicCountCombined += BB.getKnownExecutionCount();
100 FuncsChanged.insert(V: &BF);
101 Prev = &Inst;
102 }
103 }
104}
105
106Error AllocCombinerPass::runOnFunctions(BinaryContext &BC) {
107 if (opts::FrameOptimization == FOP_NONE)
108 return Error::success();
109
110 runForAllWeCare(BFs&: BC.getBinaryFunctions(), Task: [&](BinaryFunction &Function) {
111 combineAdjustments(BF&: Function);
112 });
113
114 BC.outs() << "BOLT-INFO: Allocation combiner: " << NumCombined
115 << " empty spaces coalesced (dyn count: " << DynamicCountCombined
116 << ").\n";
117 return Error::success();
118}
119
120} // end namespace bolt
121} // end namespace llvm
122

source code of bolt/lib/Passes/AllocCombiner.cpp