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/MachineMemOperand.h"
19#include "llvm/CodeGen/Passes.h"
20#include "llvm/Support/Debug.h"
21#include "llvm/Support/raw_ostream.h"
22using namespace llvm;
23
24#define DEBUG_TYPE "wasm-set-p2align-operands"
25
26namespace {
27class WebAssemblySetP2AlignOperands final : public MachineFunctionPass {
28public:
29 static char ID; // Pass identification, replacement for typeid
30 WebAssemblySetP2AlignOperands() : MachineFunctionPass(ID) {}
31
32 StringRef getPassName() const override {
33 return "WebAssembly Set p2align Operands";
34 }
35
36 void getAnalysisUsage(AnalysisUsage &AU) const override {
37 AU.setPreservesCFG();
38 AU.addPreserved<MachineBlockFrequencyInfoWrapperPass>();
39 AU.addPreservedID(ID&: MachineDominatorsID);
40 MachineFunctionPass::getAnalysisUsage(AU);
41 }
42
43 bool runOnMachineFunction(MachineFunction &MF) override;
44};
45} // end anonymous namespace
46
47char WebAssemblySetP2AlignOperands::ID = 0;
48INITIALIZE_PASS(WebAssemblySetP2AlignOperands, DEBUG_TYPE,
49 "Set the p2align operands for WebAssembly loads and stores",
50 false, false)
51
52FunctionPass *llvm::createWebAssemblySetP2AlignOperands() {
53 return new WebAssemblySetP2AlignOperands();
54}
55
56static void rewriteP2Align(MachineInstr &MI, unsigned OperandNo) {
57 assert(MI.getOperand(OperandNo).getImm() == 0 &&
58 "ISel should set p2align operands to 0");
59 assert(MI.hasOneMemOperand() &&
60 "Load and store instructions have exactly one mem operand");
61 assert((*MI.memoperands_begin())->getSize() ==
62 (UINT64_C(1) << WebAssembly::GetDefaultP2Align(MI.getOpcode())) &&
63 "Default p2align value should be natural");
64 assert(MI.getDesc().operands()[OperandNo].OperandType ==
65 WebAssembly::OPERAND_P2ALIGN &&
66 "Load and store instructions should have a p2align operand");
67 uint64_t P2Align = Log2(A: (*MI.memoperands_begin())->getAlign());
68
69 // WebAssembly does not currently support supernatural alignment.
70 P2Align = std::min(a: P2Align,
71 b: uint64_t(WebAssembly::GetDefaultP2Align(Opc: MI.getOpcode())));
72
73 MI.getOperand(i: OperandNo).setImm(P2Align);
74}
75
76bool WebAssemblySetP2AlignOperands::runOnMachineFunction(MachineFunction &MF) {
77 LLVM_DEBUG({
78 dbgs() << "********** Set p2align Operands **********\n"
79 << "********** Function: " << MF.getName() << '\n';
80 });
81
82 bool Changed = false;
83
84 for (auto &MBB : MF) {
85 for (auto &MI : MBB) {
86 int16_t P2AlignOpNum = WebAssembly::getNamedOperandIdx(
87 Opcode: MI.getOpcode(), Name: WebAssembly::OpName::p2align);
88 if (P2AlignOpNum != -1) {
89 rewriteP2Align(MI, OperandNo: P2AlignOpNum);
90 Changed = true;
91 }
92 }
93 }
94
95 return Changed;
96}
97