1//=- WebAssemblySetP2AlignOperands.cpp - Set alignments on loads and stores -=//
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/// \file
10/// This file sets the p2align operands on load and store instructions.
11///
12//===----------------------------------------------------------------------===//
13
14#include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
15#include "WebAssembly.h"
16#include "WebAssemblyInstrInfo.h"
17#include "WebAssemblyMachineFunctionInfo.h"
18#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
19#include "llvm/CodeGen/MachineMemOperand.h"
20#include "llvm/CodeGen/Passes.h"
21#include "llvm/Support/Debug.h"
22#include "llvm/Support/raw_ostream.h"
23using namespace llvm;
24
25#define DEBUG_TYPE "wasm-set-p2align-operands"
26
27namespace {
28class WebAssemblySetP2AlignOperands final : public MachineFunctionPass {
29public:
30  static char ID; // Pass identification, replacement for typeid
31  WebAssemblySetP2AlignOperands() : MachineFunctionPass(ID) {}
32
33  StringRef getPassName() const override {
34    return "WebAssembly Set p2align Operands";
35  }
36
37  void getAnalysisUsage(AnalysisUsage &AU) const override {
38    AU.setPreservesCFG();
39    AU.addPreserved<MachineBlockFrequencyInfo>();
40    AU.addPreservedID(MachineDominatorsID);
41    MachineFunctionPass::getAnalysisUsage(AU);
42  }
43
44  bool runOnMachineFunction(MachineFunction &MF) override;
45};
46} // end anonymous namespace
47
48char WebAssemblySetP2AlignOperands::ID = 0;
49INITIALIZE_PASS(WebAssemblySetP2AlignOperands, DEBUG_TYPE,
50                "Set the p2align operands for WebAssembly loads and stores",
51                false, false)
52
53FunctionPass *llvm::createWebAssemblySetP2AlignOperands() {
54  return new WebAssemblySetP2AlignOperands();
55}
56
57static void rewriteP2Align(MachineInstr &MI, unsigned OperandNo) {
58  assert(MI.getOperand(OperandNo).getImm() == 0 &&
59         "ISel should set p2align operands to 0");
60  assert(MI.hasOneMemOperand() &&
61         "Load and store instructions have exactly one mem operand");
62  assert((*MI.memoperands_begin())->getSize() ==
63             (UINT64_C(1) << WebAssembly::GetDefaultP2Align(MI.getOpcode())) &&
64         "Default p2align value should be natural");
65  assert(MI.getDesc().OpInfo[OperandNo].OperandType ==
66             WebAssembly::OPERAND_P2ALIGN &&
67         "Load and store instructions should have a p2align operand");
68  uint64_t P2Align = Log2_64((*MI.memoperands_begin())->getAlignment());
69
70  // WebAssembly does not currently support supernatural alignment.
71  P2Align = std::min(P2Align,
72                     uint64_t(WebAssembly::GetDefaultP2Align(MI.getOpcode())));
73
74  MI.getOperand(OperandNo).setImm(P2Align);
75}
76
77bool WebAssemblySetP2AlignOperands::runOnMachineFunction(MachineFunction &MF) {
78  LLVM_DEBUG({
79    dbgs() << "********** Set p2align Operands **********\n"
80           << "********** Function: " << MF.getName() << '\n';
81  });
82
83  bool Changed = false;
84
85  for (auto &MBB : MF) {
86    for (auto &MI : MBB) {
87      int16_t P2AlignOpNum = WebAssembly::getNamedOperandIdx(
88          MI.getOpcode(), WebAssembly::OpName::p2align);
89      if (P2AlignOpNum != -1) {
90        rewriteP2Align(MI, P2AlignOpNum);
91        Changed = true;
92      }
93    }
94  }
95
96  return Changed;
97}
98