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 "llvm/CodeGen/MachineBlockFrequencyInfo.h"
18#include "llvm/CodeGen/MachineFunctionAnalysisManager.h"
19#include "llvm/CodeGen/MachineMemOperand.h"
20#include "llvm/CodeGen/MachinePassManager.h"
21#include "llvm/CodeGen/Passes.h"
22#include "llvm/IR/Analysis.h"
23#include "llvm/Support/Debug.h"
24#include "llvm/Support/raw_ostream.h"
25using namespace llvm;
26
27#define DEBUG_TYPE "wasm-set-p2align-operands"
28
29namespace {
30class WebAssemblySetP2AlignOperandsLegacy final : public MachineFunctionPass {
31public:
32 static char ID; // Pass identification, replacement for typeid
33 WebAssemblySetP2AlignOperandsLegacy() : MachineFunctionPass(ID) {}
34
35 StringRef getPassName() const override {
36 return "WebAssembly Set p2align Operands";
37 }
38
39 void getAnalysisUsage(AnalysisUsage &AU) const override {
40 AU.setPreservesCFG();
41 AU.addPreserved<MachineBlockFrequencyInfoWrapperPass>();
42 AU.addPreservedID(ID&: MachineDominatorsID);
43 MachineFunctionPass::getAnalysisUsage(AU);
44 }
45
46 bool runOnMachineFunction(MachineFunction &MF) override;
47};
48} // end anonymous namespace
49
50char WebAssemblySetP2AlignOperandsLegacy::ID = 0;
51INITIALIZE_PASS(WebAssemblySetP2AlignOperandsLegacy, DEBUG_TYPE,
52 "Set the p2align operands for WebAssembly loads and stores",
53 false, false)
54
55FunctionPass *llvm::createWebAssemblySetP2AlignOperandsLegacyPass() {
56 return new WebAssemblySetP2AlignOperandsLegacy();
57}
58
59static void rewriteP2Align(MachineInstr &MI, unsigned OperandNo) {
60 assert(MI.getOperand(OperandNo).getImm() == 0 &&
61 "ISel should set p2align operands to 0");
62 assert(MI.hasOneMemOperand() &&
63 "Load and store instructions have exactly one mem operand");
64 assert((*MI.memoperands_begin())->getSize() ==
65 (UINT64_C(1) << WebAssembly::GetDefaultP2Align(MI.getOpcode())) &&
66 "Default p2align value should be natural");
67 assert(MI.getDesc().operands()[OperandNo].OperandType ==
68 WebAssembly::OPERAND_P2ALIGN &&
69 "Load and store instructions should have a p2align operand");
70 uint64_t P2Align = Log2(A: (*MI.memoperands_begin())->getAlign());
71
72 // WebAssembly does not currently support supernatural alignment.
73 P2Align = std::min(a: P2Align,
74 b: uint64_t(WebAssembly::GetDefaultP2Align(Opc: MI.getOpcode())));
75
76 MI.getOperand(i: OperandNo).setImm(P2Align);
77}
78
79static bool setP2AlignOperands(MachineFunction &MF) {
80 LLVM_DEBUG({
81 dbgs() << "********** Set p2align Operands **********\n"
82 << "********** Function: " << MF.getName() << '\n';
83 });
84
85 bool Changed = false;
86
87 for (auto &MBB : MF) {
88 for (auto &MI : MBB) {
89 int16_t P2AlignOpNum = WebAssembly::getNamedOperandIdx(
90 Opcode: MI.getOpcode(), Name: WebAssembly::OpName::p2align);
91 if (P2AlignOpNum != -1) {
92 rewriteP2Align(MI, OperandNo: P2AlignOpNum);
93 Changed = true;
94 }
95 }
96 }
97
98 return Changed;
99}
100
101bool WebAssemblySetP2AlignOperandsLegacy::runOnMachineFunction(
102 MachineFunction &MF) {
103 return setP2AlignOperands(MF);
104}
105
106PreservedAnalyses
107WebAssemblySetP2AlignOperandsPass::run(MachineFunction &MF,
108 MachineFunctionAnalysisManager &MFAM) {
109 return setP2AlignOperands(MF) ? getMachineFunctionPassPreservedAnalyses()
110 .preserveSet<CFGAnalyses>()
111 : PreservedAnalyses::all();
112}
113