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"
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
WebAssemblySetP2AlignOperands()31 WebAssemblySetP2AlignOperands() : MachineFunctionPass(ID) {}
32
getPassName() const33 StringRef getPassName() const override {
34 return "WebAssembly Set p2align Operands";
35 }
36
getAnalysisUsage(AnalysisUsage & AU) const37 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 INITIALIZE_PASS(WebAssemblySetP2AlignOperands, DEBUG_TYPE,
50 "Set the p2align operands for WebAssembly loads and stores",
51 false, false)
52
createWebAssemblySetP2AlignOperands()53 FunctionPass *llvm::createWebAssemblySetP2AlignOperands() {
54 return new WebAssemblySetP2AlignOperands();
55 }
56
rewriteP2Align(MachineInstr & MI,unsigned OperandNo)57 static 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((*MI.memoperands_begin())->getAlign());
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
runOnMachineFunction(MachineFunction & MF)77 bool 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