WebAssemblySetP2AlignOperands.cpp revision 303231 
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  const char *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
53bool WebAssemblySetP2AlignOperands::runOnMachineFunction(MachineFunction &MF) {
54  DEBUG({
55    dbgs() << "********** Set p2align Operands **********\n"
56           << "********** Function: " << MF.getName() << '\n';
57  });
58
59  bool Changed = false;
60
61  for (auto &MBB : MF) {
62    for (auto &MI : MBB) {
63      switch (MI.getOpcode()) {
64      case WebAssembly::LOAD_I32:
65      case WebAssembly::LOAD_I64:
66      case WebAssembly::LOAD_F32:
67      case WebAssembly::LOAD_F64:
68      case WebAssembly::LOAD8_S_I32:
69      case WebAssembly::LOAD8_U_I32:
70      case WebAssembly::LOAD16_S_I32:
71      case WebAssembly::LOAD16_U_I32:
72      case WebAssembly::LOAD8_S_I64:
73      case WebAssembly::LOAD8_U_I64:
74      case WebAssembly::LOAD16_S_I64:
75      case WebAssembly::LOAD16_U_I64:
76      case WebAssembly::LOAD32_S_I64:
77      case WebAssembly::LOAD32_U_I64:
78      case WebAssembly::STORE_I32:
79      case WebAssembly::STORE_I64:
80      case WebAssembly::STORE_F32:
81      case WebAssembly::STORE_F64:
82      case WebAssembly::STORE8_I32:
83      case WebAssembly::STORE16_I32:
84      case WebAssembly::STORE8_I64:
85      case WebAssembly::STORE16_I64:
86      case WebAssembly::STORE32_I64: {
87        assert(MI.getOperand(3).getImm() == 0 &&
88               "ISel should set p2align operands to 0");
89        assert(MI.hasOneMemOperand() &&
90               "Load and store instructions have exactly one mem operand");
91        assert((*MI.memoperands_begin())->getSize() ==
92                   (UINT64_C(1)
93                    << WebAssembly::GetDefaultP2Align(MI.getOpcode())) &&
94               "Default p2align value should be natural");
95        assert(MI.getDesc().OpInfo[3].OperandType ==
96                   WebAssembly::OPERAND_P2ALIGN &&
97               "Load and store instructions should have a p2align operand");
98        uint64_t P2Align = Log2_64((*MI.memoperands_begin())->getAlignment());
99
100        // WebAssembly does not currently support supernatural alignment.
101        P2Align = std::min(
102            P2Align, uint64_t(WebAssembly::GetDefaultP2Align(MI.getOpcode())));
103
104        MI.getOperand(3).setImm(P2Align);
105        break;
106      }
107      default:
108        break;
109      }
110    }
111  }
112
113  return Changed;
114}
115