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 MachineFunctionPass::getAnalysisUsage(AU);
42 }
43
44 bool runOnMachineFunction(MachineFunction &MF) override;
45};
46} // end anonymous namespace
47
48char WebAssemblySetP2AlignOperandsLegacy::ID = 0;
49INITIALIZE_PASS(WebAssemblySetP2AlignOperandsLegacy, DEBUG_TYPE,
50 "Set the p2align operands for WebAssembly loads and stores",
51 false, false)
52
53FunctionPass *llvm::createWebAssemblySetP2AlignOperandsLegacyPass() {
54 return new WebAssemblySetP2AlignOperandsLegacy();
55}
56
57static 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().operands()[OperandNo].OperandType ==
66 WebAssembly::OPERAND_P2ALIGN &&
67 "Load and store instructions should have a p2align operand");
68 uint64_t P2Align = Log2(A: (*MI.memoperands_begin())->getAlign());
69
70 // WebAssembly does not currently support supernatural alignment.
71 P2Align = std::min(a: P2Align,
72 b: uint64_t(WebAssembly::GetDefaultP2Align(Opc: MI.getOpcode())));
73
74 MI.getOperand(i: OperandNo).setImm(P2Align);
75}
76
77static bool setP2AlignOperands(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 Opcode: MI.getOpcode(), Name: WebAssembly::OpName::p2align);
89 if (P2AlignOpNum != -1) {
90 rewriteP2Align(MI, OperandNo: P2AlignOpNum);
91 Changed = true;
92 }
93 }
94 }
95
96 return Changed;
97}
98
99bool WebAssemblySetP2AlignOperandsLegacy::runOnMachineFunction(
100 MachineFunction &MF) {
101 return setP2AlignOperands(MF);
102}
103
104PreservedAnalyses
105WebAssemblySetP2AlignOperandsPass::run(MachineFunction &MF,
106 MachineFunctionAnalysisManager &MFAM) {
107 return setP2AlignOperands(MF) ? getMachineFunctionPassPreservedAnalyses()
108 .preserveSet<CFGAnalyses>()
109 : PreservedAnalyses::all();
110}
111