WebAssemblySetP2AlignOperands.cpp revision 314564 
1//=- WebAssemblySetP2AlignOperands.cpp - Set alignments on loads and stores -=//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9///
10/// \file
11/// \brief This file sets the p2align operands on load and store instructions.
12///
13//===----------------------------------------------------------------------===//
14
15#include "WebAssembly.h"
16#include "MCTargetDesc/WebAssemblyMCTargetDesc.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;
49FunctionPass *llvm::createWebAssemblySetP2AlignOperands() {
50  return new WebAssemblySetP2AlignOperands();
51}
52
53static void RewriteP2Align(MachineInstr &MI, unsigned OperandNo) {
54  assert(MI.getOperand(OperandNo).getImm() == 0 &&
55         "ISel should set p2align operands to 0");
56  assert(MI.hasOneMemOperand() &&
57         "Load and store instructions have exactly one mem operand");
58  assert((*MI.memoperands_begin())->getSize() ==
59             (UINT64_C(1)
60              << WebAssembly::GetDefaultP2Align(MI.getOpcode())) &&
61         "Default p2align value should be natural");
62  assert(MI.getDesc().OpInfo[OperandNo].OperandType ==
63             WebAssembly::OPERAND_P2ALIGN &&
64         "Load and store instructions should have a p2align operand");
65  uint64_t P2Align = Log2_64((*MI.memoperands_begin())->getAlignment());
66
67  // WebAssembly does not currently support supernatural alignment.
68  P2Align = std::min(
69      P2Align, uint64_t(WebAssembly::GetDefaultP2Align(MI.getOpcode())));
70
71  MI.getOperand(OperandNo).setImm(P2Align);
72}
73
74bool WebAssemblySetP2AlignOperands::runOnMachineFunction(MachineFunction &MF) {
75  DEBUG({
76    dbgs() << "********** Set p2align Operands **********\n"
77           << "********** Function: " << MF.getName() << '\n';
78  });
79
80  bool Changed = false;
81
82  for (auto &MBB : MF) {
83    for (auto &MI : MBB) {
84      switch (MI.getOpcode()) {
85      case WebAssembly::LOAD_I32:
86      case WebAssembly::LOAD_I64:
87      case WebAssembly::LOAD_F32:
88      case WebAssembly::LOAD_F64:
89      case WebAssembly::LOAD8_S_I32:
90      case WebAssembly::LOAD8_U_I32:
91      case WebAssembly::LOAD16_S_I32:
92      case WebAssembly::LOAD16_U_I32:
93      case WebAssembly::LOAD8_S_I64:
94      case WebAssembly::LOAD8_U_I64:
95      case WebAssembly::LOAD16_S_I64:
96      case WebAssembly::LOAD16_U_I64:
97      case WebAssembly::LOAD32_S_I64:
98      case WebAssembly::LOAD32_U_I64:
99        RewriteP2Align(MI, WebAssembly::LoadP2AlignOperandNo);
100        break;
101      case WebAssembly::STORE_I32:
102      case WebAssembly::STORE_I64:
103      case WebAssembly::STORE_F32:
104      case WebAssembly::STORE_F64:
105      case WebAssembly::STORE8_I32:
106      case WebAssembly::STORE16_I32:
107      case WebAssembly::STORE8_I64:
108      case WebAssembly::STORE16_I64:
109      case WebAssembly::STORE32_I64:
110        RewriteP2Align(MI, WebAssembly::StoreP2AlignOperandNo);
111        break;
112      default:
113        break;
114      }
115    }
116  }
117
118  return Changed;
119}
120