LLVM 19.0.0git
WebAssemblyWasmObjectWriter.cpp
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1//===-- WebAssemblyWasmObjectWriter.cpp - WebAssembly Wasm Writer ---------===//
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 handles Wasm-specific object emission, converting LLVM's
11/// internal fixups into the appropriate relocations.
12///
13//===----------------------------------------------------------------------===//
14
19#include "llvm/MC/MCFixup.h"
24#include "llvm/MC/MCValue.h"
28
29using namespace llvm;
30
31namespace {
32class WebAssemblyWasmObjectWriter final : public MCWasmObjectTargetWriter {
33public:
34 explicit WebAssemblyWasmObjectWriter(bool Is64Bit, bool IsEmscripten);
35
36private:
37 unsigned getRelocType(const MCValue &Target, const MCFixup &Fixup,
38 const MCSectionWasm &FixupSection,
39 bool IsLocRel) const override;
40};
41} // end anonymous namespace
42
43WebAssemblyWasmObjectWriter::WebAssemblyWasmObjectWriter(bool Is64Bit,
44 bool IsEmscripten)
45 : MCWasmObjectTargetWriter(Is64Bit, IsEmscripten) {}
46
47static const MCSection *getTargetSection(const MCExpr *Expr) {
48 if (auto SyExp = dyn_cast<MCSymbolRefExpr>(Expr)) {
49 if (SyExp->getSymbol().isInSection())
50 return &SyExp->getSymbol().getSection();
51 return nullptr;
52 }
53
54 if (auto BinOp = dyn_cast<MCBinaryExpr>(Expr)) {
55 auto SectionLHS = getTargetSection(BinOp->getLHS());
56 auto SectionRHS = getTargetSection(BinOp->getRHS());
57 return SectionLHS == SectionRHS ? nullptr : SectionLHS;
58 }
59
60 if (auto UnOp = dyn_cast<MCUnaryExpr>(Expr))
61 return getTargetSection(UnOp->getSubExpr());
62
63 return nullptr;
64}
65
66unsigned WebAssemblyWasmObjectWriter::getRelocType(
67 const MCValue &Target, const MCFixup &Fixup,
68 const MCSectionWasm &FixupSection, bool IsLocRel) const {
69 const MCSymbolRefExpr *RefA = Target.getSymA();
70 assert(RefA);
71 auto& SymA = cast<MCSymbolWasm>(RefA->getSymbol());
72
73 MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
74
75 switch (Modifier) {
78 return wasm::R_WASM_GLOBAL_INDEX_LEB;
80 assert(SymA.isFunction());
81 return is64Bit() ? wasm::R_WASM_TABLE_INDEX_REL_SLEB64
82 : wasm::R_WASM_TABLE_INDEX_REL_SLEB;
84 return is64Bit() ? wasm::R_WASM_MEMORY_ADDR_TLS_SLEB64
85 : wasm::R_WASM_MEMORY_ADDR_TLS_SLEB;
87 assert(SymA.isData());
88 return is64Bit() ? wasm::R_WASM_MEMORY_ADDR_REL_SLEB64
89 : wasm::R_WASM_MEMORY_ADDR_REL_SLEB;
91 return wasm::R_WASM_TYPE_INDEX_LEB;
93 break;
95 return wasm::R_WASM_FUNCTION_INDEX_I32;
96 default:
97 report_fatal_error("unknown VariantKind");
98 break;
99 }
100
101 switch (unsigned(Fixup.getKind())) {
103 if (SymA.isFunction())
104 return wasm::R_WASM_TABLE_INDEX_SLEB;
105 return wasm::R_WASM_MEMORY_ADDR_SLEB;
107 if (SymA.isFunction())
108 return wasm::R_WASM_TABLE_INDEX_SLEB64;
109 return wasm::R_WASM_MEMORY_ADDR_SLEB64;
111 if (SymA.isGlobal())
112 return wasm::R_WASM_GLOBAL_INDEX_LEB;
113 if (SymA.isFunction())
114 return wasm::R_WASM_FUNCTION_INDEX_LEB;
115 if (SymA.isTag())
116 return wasm::R_WASM_TAG_INDEX_LEB;
117 if (SymA.isTable())
118 return wasm::R_WASM_TABLE_NUMBER_LEB;
119 return wasm::R_WASM_MEMORY_ADDR_LEB;
121 assert(SymA.isData());
122 return wasm::R_WASM_MEMORY_ADDR_LEB64;
123 case FK_Data_4:
124 if (SymA.isFunction()) {
125 if (FixupSection.isMetadata())
126 return wasm::R_WASM_FUNCTION_OFFSET_I32;
127 assert(FixupSection.isWasmData());
128 return wasm::R_WASM_TABLE_INDEX_I32;
129 }
130 if (SymA.isGlobal())
131 return wasm::R_WASM_GLOBAL_INDEX_I32;
132 if (auto Section = static_cast<const MCSectionWasm *>(
133 getTargetSection(Fixup.getValue()))) {
134 if (Section->isText())
135 return wasm::R_WASM_FUNCTION_OFFSET_I32;
136 else if (!Section->isWasmData())
137 return wasm::R_WASM_SECTION_OFFSET_I32;
138 }
139 return IsLocRel ? wasm::R_WASM_MEMORY_ADDR_LOCREL_I32
140 : wasm::R_WASM_MEMORY_ADDR_I32;
141 case FK_Data_8:
142 if (SymA.isFunction()) {
143 if (FixupSection.isMetadata())
144 return wasm::R_WASM_FUNCTION_OFFSET_I64;
145 return wasm::R_WASM_TABLE_INDEX_I64;
146 }
147 if (SymA.isGlobal())
148 llvm_unreachable("unimplemented R_WASM_GLOBAL_INDEX_I64");
149 if (auto Section = static_cast<const MCSectionWasm *>(
150 getTargetSection(Fixup.getValue()))) {
151 if (Section->isText())
152 return wasm::R_WASM_FUNCTION_OFFSET_I64;
153 else if (!Section->isWasmData())
154 llvm_unreachable("unimplemented R_WASM_SECTION_OFFSET_I64");
155 }
156 assert(SymA.isData());
157 return wasm::R_WASM_MEMORY_ADDR_I64;
158 default:
159 llvm_unreachable("unimplemented fixup kind");
160 }
161}
162
163std::unique_ptr<MCObjectTargetWriter>
164llvm::createWebAssemblyWasmObjectWriter(bool Is64Bit, bool IsEmscripten) {
165 return std::make_unique<WebAssemblyWasmObjectWriter>(Is64Bit, IsEmscripten);
166}
PowerPC TLS Dynamic Call Fixup
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
This file provides WebAssembly-specific target descriptions.
static const MCSection * getTargetSection(const MCExpr *Expr)
static bool is64Bit(const char *name)
Base class for the full range of assembler expressions which are needed for parsing.
Definition: MCExpr.h:35
Encode information on a single operation to perform on a byte sequence (e.g., an encoded instruction)...
Definition: MCFixup.h:71
This represents a section on wasm.
Definition: MCSectionWasm.h:26
bool isWasmData() const
Definition: MCSectionWasm.h:72
bool isMetadata() const
Definition: MCSectionWasm.h:73
Instances of this class represent a uniqued identifier for a section in the current translation unit.
Definition: MCSection.h:35
Represent a reference to a symbol from inside an expression.
Definition: MCExpr.h:192
const MCSymbol & getSymbol() const
Definition: MCExpr.h:410
This represents an "assembler immediate".
Definition: MCValue.h:36
virtual unsigned getRelocType(const MCValue &Target, const MCFixup &Fixup, const MCSectionWasm &FixupSection, bool IsLocRel) const =0
Target - Wrapper for Target specific information.
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
std::unique_ptr< MCObjectTargetWriter > createWebAssemblyWasmObjectWriter(bool Is64Bit, bool IsEmscripten)
void report_fatal_error(Error Err, bool gen_crash_diag=true)
Report a serious error, calling any installed error handler.
Definition: Error.cpp:167
@ FK_Data_8
A eight-byte fixup.
Definition: MCFixup.h:26
@ FK_Data_4
A four-byte fixup.
Definition: MCFixup.h:25