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 "MCTargetDesc/WebAssemblyMCTargetDesc.h"
16 #include "WebAssembly.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"
23 using namespace llvm;
24 
25 #define DEBUG_TYPE "wasm-set-p2align-operands"
26 
27 namespace {
28 class WebAssemblySetP2AlignOperands final : public MachineFunctionPass {
29 public:
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 
48 char WebAssemblySetP2AlignOperands::ID = 0;
49 FunctionPass *llvm::createWebAssemblySetP2AlignOperands() {
50   return new WebAssemblySetP2AlignOperands();
51 }
52 
53 static 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 
74 bool 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       case WebAssembly::ATOMIC_LOAD_I32:
100       case WebAssembly::ATOMIC_LOAD8_U_I32:
101       case WebAssembly::ATOMIC_LOAD16_U_I32:
102       case WebAssembly::ATOMIC_LOAD_I64:
103       case WebAssembly::ATOMIC_LOAD8_U_I64:
104       case WebAssembly::ATOMIC_LOAD16_U_I64:
105       case WebAssembly::ATOMIC_LOAD32_U_I64:
106         RewriteP2Align(MI, WebAssembly::LoadP2AlignOperandNo);
107         break;
108       case WebAssembly::STORE_I32:
109       case WebAssembly::STORE_I64:
110       case WebAssembly::STORE_F32:
111       case WebAssembly::STORE_F64:
112       case WebAssembly::STORE8_I32:
113       case WebAssembly::STORE16_I32:
114       case WebAssembly::STORE8_I64:
115       case WebAssembly::STORE16_I64:
116       case WebAssembly::STORE32_I64:
117         RewriteP2Align(MI, WebAssembly::StoreP2AlignOperandNo);
118         break;
119       default:
120         break;
121       }
122     }
123   }
124 
125   return Changed;
126 }
127