maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[WebAssembly] Add option to emit passive segments 

Summary:
Adds `--passive-segments` and `--active-segments` flags to control
what kind of segments are emitted. For now the default is always
to emit active segments so this is not a breaking change, but in
the future the default will be changed to passive segments when
shared memory is requested and active segments otherwise. When
passive segments are emitted, corresponding memory.init and
data.drop instructions are emitted in a `__wasm_init_memory`
function that is automatically called at the beginning of
`__wasm_call_ctors`.

Reviewers: sbc100, aheejin, dschuff

Subscribers: azakai, dschuff, jgravelle-google, sunfish, jfb, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59343

llvm-svn: 365088
This commit is contained in:
Thomas Lively 2019-07-03 22:04:54 +00:00
parent c96c174557
commit 6004d9a13d
13 changed files with 327 additions and 68 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

133
lld/test/wasm/data-segment-merging.ll
View File

@ -8,40 +8,117 @@ target triple = "wasm32-unknown-unknown"
@e = private constant [9 x i8] c"constant\00", align 1
@f = private constant i8 43, align 4
; RUN: llc -filetype=obj %s -o %t.data-segment-merging.o
; RUN: llc -mattr=+bulk-memory -filetype=obj %s -o %t.o
; RUN: wasm-ld -no-gc-sections --no-entry -o %t.merged.wasm %t.data-segment-merging.o
; RUN: wasm-ld -no-gc-sections --no-entry -o %t.merged.wasm %t.o
; RUN: obj2yaml %t.merged.wasm | FileCheck %s --check-prefix=MERGE
; MERGE-NOT: DATACOUNT
; MERGE: - Type: DATA
; MERGE: Segments:
; MERGE: Content: 68656C6C6F00676F6F6462796500776861746576657200002A000000
; MERGE: Content: 636F6E7374616E74000000002B
; MERGE-NOT: Content:
; MERGE-LABEL: - Type: DATA
; MERGE-NEXT: Segments:
; MERGE-NEXT: - SectionOffset: 7
; MERGE-NEXT: InitFlags: 0
; MERGE-NEXT: Offset:
; MERGE: Content: 68656C6C6F00676F6F6462796500776861746576657200002A000000
; MERGE-NEXT: - SectionOffset: 41
; MERGE-NEXT: InitFlags: 0
; MERGE-NEXT: Offset:
; MERGE: Content: 636F6E7374616E74000000002B
; MERGE-NEXT: - Type: CUSTOM
; MERGE-NEXT: Name: name
; MERGE-NEXT: FunctionNames:
; MERGE-NEXT: - Index: 0
; MERGE-NEXT: Name: __wasm_call_ctors
; MERGE-NOT: - Index:
; RUN: wasm-ld -no-gc-sections --no-entry --no-merge-data-segments -o %t.separate.wasm %t.data-segment-merging.o
; RUN: wasm-ld -no-gc-sections --no-entry --no-merge-data-segments -o %t.separate.wasm %t.o
; RUN: obj2yaml %t.separate.wasm | FileCheck %s --check-prefix=SEPARATE
; SEPARATE-NOT: DATACOUNT
; SEPARATE: - Type: DATA
; SEPARATE: Segments:
; SEPARATE: Content: 68656C6C6F00
; SEPARATE: Content: 676F6F6462796500
; SEPARATE: Content: '776861746576657200'
; SEPARATE: Content: 2A000000
; SEPARATE: Content: 636F6E7374616E7400
; SEPARATE: Content: 2B
; SEPARATE-NOT: Content:
; SEPARATE-LABEL: - Type: DATA
; SEPARATE-NEXT: Segments:
; SEPARATE-NEXT: - SectionOffset: 7
; SEPARATE-NEXT: InitFlags: 0
; SEPARATE-NEXT: Offset:
; SEPARATE: Content: 68656C6C6F00
; SEPARATE-NEXT: - SectionOffset: 19
; SEPARATE-NEXT: InitFlags: 0
; SEPARATE-NEXT: Offset:
; SEPARATE: Content: 676F6F6462796500
; SEPARATE-NEXT: - SectionOffset: 33
; SEPARATE-NEXT: InitFlags: 0
; SEPARATE-NEXT: Offset:
; SEPARATE: Content: '776861746576657200'
; SEPARATE-NEXT: - SectionOffset: 48
; SEPARATE-NEXT: InitFlags: 0
; SEPARATE-NEXT: Offset:
; SEPARATE: Content: 2A000000
; SEPARATE-NEXT: - SectionOffset: 58
; SEPARATE-NEXT: InitFlags: 0
; SEPARATE-NEXT: Offset:
; SEPARATE: Content: 636F6E7374616E7400
; SEPARATE-NEXT: - SectionOffset: 73
; SEPARATE-NEXT: InitFlags: 0
; SEPARATE-NEXT: Offset:
; SEPARATE: Content: 2B
; SEPARATE-NEXT: - Type: CUSTOM
; SEPARATE-NEXT: Name: name
; SEPARATE-NEXT: FunctionNames:
; SEPARATE-NEXT: - Index: 0
; SEPARATE-NEXT: Name: __wasm_call_ctors
; SEPARATE-NOT: - Index:
; RUN: llc -filetype=obj %s -mattr=+bulk-memory -o %t.data-segment-merging.bulk-memory.o
; RUN: wasm-ld -no-gc-sections --no-entry -o %t.merged.bulk-memory.wasm %t.data-segment-merging.bulk-memory.o
; RUN: obj2yaml %t.merged.bulk-memory.wasm | FileCheck %s --check-prefix=BULK-MEMORY
; RUN: wasm-ld -no-gc-sections --no-entry --passive-segments -o %t.merged.passive.wasm %t.o
; RUN: obj2yaml %t.merged.passive.wasm | FileCheck %s --check-prefix=PASSIVE-MERGE
; BULK-MEMORY: - Type: DATACOUNT
; BULK-MEMORY: Count: 2
; BULK-MEMORY: - Type: DATA
; BULK-MEMORY: Segments:
; BULK-MEMORY: Content: 68656C6C6F00676F6F6462796500776861746576657200002A000000
; BULK-MEMORY: Content: 636F6E7374616E74000000002B
; BULK-MEMORY-NOT: Content:
; PASSIVE-MERGE-LABEL: - Type: DATACOUNT
; PASSIVE-MERGE-NEXT: Count: 2
; PASSIVE-MERGE-LABEL: - Type: DATA
; PASSIVE-MERGE-NEXT: Segments:
; PASSIVE-MERGE-NEXT: - SectionOffset: 3
; PASSIVE-MERGE-NEXT: InitFlags: 1
; PASSIVE-MERGE-NEXT: Content: 68656C6C6F00676F6F6462796500776861746576657200002A000000
; PASSIVE-MERGE-NEXT: - SectionOffset: 33
; PASSIVE-MERGE-NEXT: InitFlags: 1
; PASSIVE-MERGE-NEXT: Content: 636F6E7374616E74000000002B
; PASSIVE-MERGE-NEXT: - Type: CUSTOM
; PASSIVE-MERGE-NEXT: Name: name
; PASSIVE-MERGE-NEXT: FunctionNames:
; PASSIVE-MERGE-NEXT: - Index: 0
; PASSIVE-MERGE-NEXT: Name: __wasm_call_ctors
; PASSIVE-MERGE-NEXT: - Index: 1
; PASSIVE-MERGE-NEXT: Name: __wasm_init_memory
; PASSIVE-MERGE-NOT: - Index:
; RUN: wasm-ld -no-gc-sections --no-entry --passive-segments -no-merge-data-segments -o %t.separate.passive.wasm %t.o
; RUN: obj2yaml %t.separate.passive.wasm | FileCheck %s --check-prefix=PASSIVE-SEPARATE
; PASSIVE-SEPARATE-LABEL: - Type: DATACOUNT
; PASSIVE-SEPARATE-NEXT: Count: 6
; PASSIVE-SEPARATE-LABEL: - Type: DATA
; PASSIVE-SEPARATE-NEXT: Segments:
; PASSIVE-SEPARATE-NEXT: - SectionOffset: 3
; PASSIVE-SEPARATE-NEXT: InitFlags: 1
; PASSIVE-SEPARATE-NEXT: Content: 68656C6C6F00
; PASSIVE-SEPARATE-NEXT: - SectionOffset: 11
; PASSIVE-SEPARATE-NEXT: InitFlags: 1
; PASSIVE-SEPARATE-NEXT: Content: 676F6F6462796500
; PASSIVE-SEPARATE-NEXT: - SectionOffset: 21
; PASSIVE-SEPARATE-NEXT: InitFlags: 1
; PASSIVE-SEPARATE-NEXT: Content: '776861746576657200'
; PASSIVE-SEPARATE-NEXT: - SectionOffset: 32
; PASSIVE-SEPARATE-NEXT: InitFlags: 1
; PASSIVE-SEPARATE-NEXT: Content: 2A000000
; PASSIVE-SEPARATE-NEXT: - SectionOffset: 38
; PASSIVE-SEPARATE-NEXT: InitFlags: 1
; PASSIVE-SEPARATE-NEXT: Content: 636F6E7374616E7400
; PASSIVE-SEPARATE-NEXT: - SectionOffset: 49
; PASSIVE-SEPARATE-NEXT: InitFlags: 1
; PASSIVE-SEPARATE-NEXT: Content: 2B
; PASSIVE-SEPARATE-NEXT: - Type: CUSTOM
; PASSIVE-SEPARATE-NEXT: Name: name
; PASSIVE-SEPARATE-NEXT: FunctionNames:
; PASSIVE-SEPARATE-NEXT: - Index: 0
; PASSIVE-SEPARATE-NEXT: Name: __wasm_call_ctors
; PASSIVE-SEPARATE-NEXT: - Index: 1
; PASSIVE-SEPARATE-NEXT: Name: __wasm_init_memory
; PASSIVE-SEPARATE-NOT: - Index

99
lld/test/wasm/data-segments.ll Normal file
View File

@ -0,0 +1,99 @@
; RUN: llc -filetype=obj %s -o %t.atomics.o -mattr=+atomics
; RUN: llc -filetype=obj %s -o %t.bulk-mem.o -mattr=+bulk-memory
; RUN: llc -filetype=obj %s -o %t.atomics.bulk-mem.o -mattr=+atomics,+bulk-memory
; atomics => active segments (TODO: error)
; RUN: wasm-ld -no-gc-sections --no-entry --shared-memory --max-memory=131072 %t.atomics.o -o %t.atomics.wasm
; RUN: obj2yaml %t.atomics.wasm | FileCheck %s --check-prefix ACTIVE
; atomics, active segments => active segments
; RUN: wasm-ld -no-gc-sections --no-entry --shared-memory --max-memory=131072 --active-segments %t.atomics.o -o %t.atomics.active.wasm
; RUN: obj2yaml %t.atomics.active.wasm | FileCheck %s --check-prefix ACTIVE
; atomics, passive segments => error
; RUN: not wasm-ld -no-gc-sections --no-entry --shared-memory --max-memory=131072 --passive-segments %t.atomics.o -o %t.atomics.passive.wasm 2>&1 | FileCheck %s --check-prefix ERROR
; bulk memory => active segments
; RUN: wasm-ld -no-gc-sections --no-entry %t.bulk-mem.o -o %t.bulk-mem.wasm
; RUN: obj2yaml %t.bulk-mem.wasm | FileCheck %s --check-prefix ACTIVE
; bulk-memory, active segments => active segments
; RUN: wasm-ld -no-gc-sections --no-entry --active-segments %t.bulk-mem.o -o %t.bulk-mem.active.wasm
; RUN: obj2yaml %t.bulk-mem.active.wasm | FileCheck %s --check-prefix ACTIVE
; bulk memory, passive segments => passive segments
; RUN: wasm-ld -no-gc-sections --no-entry --passive-segments %t.bulk-mem.o -o %t.bulk-mem.passive.wasm
; RUN: obj2yaml %t.bulk-mem.passive.wasm | FileCheck %s --check-prefix PASSIVE
; atomics, bulk memory => active segments (TODO: passive)
; RUN: wasm-ld -no-gc-sections --no-entry --shared-memory --max-memory=131072 %t.atomics.bulk-mem.o -o %t.atomics.bulk-mem.wasm
; RUN: obj2yaml %t.atomics.bulk-mem.wasm | FileCheck %s --check-prefix ACTIVE
; atomics, bulk memory, active segments => active segments
; RUN: wasm-ld -no-gc-sections --no-entry --shared-memory --max-memory=131072 --active-segments %t.atomics.bulk-mem.o -o %t.atomics.bulk-mem.active.wasm
; RUN: obj2yaml %t.atomics.bulk-mem.active.wasm | FileCheck %s --check-prefix ACTIVE
; atomics, bulk memory, passive segments => passive segments
; RUN: wasm-ld -no-gc-sections --no-entry --shared-memory --max-memory=131072 --passive-segments %t.atomics.bulk-mem.o -o %t.atomics.bulk-mem.passive.wasm
; RUN: obj2yaml %t.atomics.bulk-mem.passive.wasm | FileCheck %s --check-prefix PASSIVE
target triple = "wasm32-unknown-unknown"
@a = hidden global [6 x i8] c"hello\00", align 1
@b = hidden global [8 x i8] c"goodbye\00", align 1
@c = hidden global [9 x i8] c"whatever\00", align 1
@d = hidden global i32 42, align 4
@e = private constant [9 x i8] c"constant\00", align 1
@f = private constant i8 43, align 4
; ERROR: 'bulk-memory' feature must be used in order to emit passive segments
; ACTIVE-LABEL: - Type: CODE
; ACTIVE-NEXT: Functions:
; ACTIVE-NEXT: - Index: 0
; ACTIVE-NEXT: Locals: []
; ACTIVE-NEXT: Body: 0B
; ACTIVE-NEXT: - Type: DATA
; ACTIVE-NEXT: Segments:
; ACTIVE-NEXT: - SectionOffset: 7
; ACTIVE-NEXT: InitFlags: 0
; ACTIVE-NEXT: Offset:
; ACTIVE-NEXT: Opcode: I32_CONST
; ACTIVE-NEXT: Value: 1024
; ACTIVE-NEXT: Content: 68656C6C6F00676F6F6462796500776861746576657200002A000000
; ACTIVE-NEXT: - SectionOffset: 41
; ACTIVE-NEXT: InitFlags: 0
; ACTIVE-NEXT: Offset:
; ACTIVE-NEXT: Opcode: I32_CONST
; ACTIVE-NEXT: Value: 1052
; ACTIVE-NEXT: Content: 636F6E7374616E74000000002B
; ACTIVE-NEXT: - Type: CUSTOM
; ACTIVE-NEXT: Name: name
; ACTIVE-NEXT: FunctionNames:
; ACTIVE-NEXT: - Index: 0
; ACTIVE-NEXT: Name: __wasm_call_ctors
; PASSIVE-LABEL: - Type: CODE
; PASSIVE-NEXT: Functions:
; PASSIVE-NEXT: - Index: 0
; PASSIVE-NEXT: Locals: []
; PASSIVE-NEXT: Body: 10010B
; PASSIVE-NEXT: - Index: 1
; PASSIVE-NEXT: Locals: []
; PASSIVE-NEXT: Body: 4180084100411CFC080000FC0900419C084100410DFC080100FC09010B
; PASSIVE-NEXT: - Type: DATA
; PASSIVE-NEXT: Segments:
; PASSIVE-NEXT: - SectionOffset: 3
; PASSIVE-NEXT: InitFlags: 1
; PASSIVE-NEXT: Content: 68656C6C6F00676F6F6462796500776861746576657200002A000000
; PASSIVE-NEXT: - SectionOffset: 33
; PASSIVE-NEXT: InitFlags: 1
; PASSIVE-NEXT: Content: 636F6E7374616E74000000002B
; PASSIVE-NEXT: - Type: CUSTOM
; PASSIVE-NEXT: Name: name
; PASSIVE-NEXT: FunctionNames:
; PASSIVE-NEXT: - Index: 0
; PASSIVE-NEXT: Name: __wasm_call_ctors
; PASSIVE-NEXT: - Index: 1
; PASSIVE-NEXT: Name: __wasm_init_memory

1
lld/wasm/Config.h
View File

@ -34,6 +34,7 @@ struct Configuration {
bool GcSections;
bool ImportMemory;
bool SharedMemory;
bool PassiveSegments;
bool ImportTable;
bool MergeDataSegments;
bool Pie;

18
lld/wasm/Driver.cpp
View File

@ -320,6 +320,9 @@ static void readConfigs(opt::InputArgList &Args) {
Args.hasFlag(OPT_fatal_warnings, OPT_no_fatal_warnings, false);
Config->ImportMemory = Args.hasArg(OPT_import_memory);
Config->SharedMemory = Args.hasArg(OPT_shared_memory);
// TODO: Make passive segments the default with shared memory
Config->PassiveSegments =
Args.hasFlag(OPT_passive_segments, OPT_active_segments, false);
Config->ImportTable = Args.hasArg(OPT_import_table);
Config->LTOO = args::getInteger(Args, OPT_lto_O, 2);
Config->LTOPartitions = args::getInteger(Args, OPT_lto_partitions, 1);
@ -460,10 +463,19 @@ static void createSyntheticSymbols() {
"__wasm_call_ctors", WASM_SYMBOL_VISIBILITY_HIDDEN,
make<SyntheticFunction>(NullSignature, "__wasm_call_ctors"));
if (Config->PassiveSegments) {
// Passive segments are used to avoid memory being reinitialized on each
// thread's instantiation. These passive segments are initialized and
// dropped in __wasm_init_memory, which is the first function called from
// __wasm_call_ctors.
WasmSym::InitMemory = Symtab->addSyntheticFunction(
"__wasm_init_memory", WASM_SYMBOL_VISIBILITY_HIDDEN,
make<SyntheticFunction>(NullSignature, "__wasm_init_memory"));
}
if (Config->Pic) {
// For PIC code we create a synthetic function call __wasm_apply_relocs
// and add this as the first call in __wasm_call_ctors.
// We also unconditionally export
// For PIC code we create a synthetic function __wasm_apply_relocs which
// is called from __wasm_call_ctors before the user-level constructors.
WasmSym::ApplyRelocs = Symtab->addSyntheticFunction(
"__wasm_apply_relocs", WASM_SYMBOL_VISIBILITY_HIDDEN,
make<SyntheticFunction>(NullSignature, "__wasm_apply_relocs"));

8
lld/wasm/MarkLive.cpp
View File

@ -50,6 +50,10 @@ void lld::wasm::markLive() {
// function. However, this function does not contain relocations so we
// have to manually mark the ctors as live if CallCtors itself is live.
if (Sym == WasmSym::CallCtors) {
if (Config->PassiveSegments)
Enqueue(WasmSym::InitMemory);
if (Config->Pic)
Enqueue(WasmSym::ApplyRelocs);
for (const ObjFile *Obj : Symtab->ObjectFiles) {
const WasmLinkingData &L = Obj->getWasmObj()->linkingData();
for (const WasmInitFunc &F : L.InitFunctions) {
@ -79,10 +83,8 @@ void lld::wasm::markLive() {
}
}
if (Config->Pic) {
if (Config->Pic)
Enqueue(WasmSym::CallCtors);
Enqueue(WasmSym::ApplyRelocs);
}
// Follow relocations to mark all reachable chunks.
while (!Q.empty()) {

6
lld/wasm/Options.td
View File

@ -143,6 +143,12 @@ def import_memory: F<"import-memory">,
def shared_memory: F<"shared-memory">,
HelpText<"Use shared linear memory">;
def active_segments: F<"active-segments">,
HelpText<"Force segments to be active">;
def passive_segments: F<"passive-segments">,
HelpText<"Force segments to be passive">;
def import_table: F<"import-table">,
HelpText<"Import function table from the environment">;

28
lld/wasm/OutputSections.cpp
View File

@ -132,20 +132,26 @@ void DataSection::finalizeContents() {
OS.flush();
BodySize = DataSectionHeader.size();
assert(!Config->Pic ||
Segments.size() <= 1 &&
"Currenly only a single data segment is supported in PIC mode");
for (OutputSegment *Segment : Segments) {
raw_string_ostream OS(Segment->Header);
writeUleb128(OS, 0, "memory index");
WasmInitExpr InitExpr;
if (Config->Pic) {
assert(Segments.size() <= 1 &&
"Currenly only a single data segment is supported in PIC mode");
InitExpr.Opcode = WASM_OPCODE_GLOBAL_GET;
InitExpr.Value.Global = WasmSym::MemoryBase->getGlobalIndex();
} else {
InitExpr.Opcode = WASM_OPCODE_I32_CONST;
InitExpr.Value.Int32 = Segment->StartVA;
writeUleb128(OS, Segment->InitFlags, "init flags");
if (Segment->InitFlags & WASM_SEGMENT_HAS_MEMINDEX)
writeUleb128(OS, 0, "memory index");
if ((Segment->InitFlags & WASM_SEGMENT_IS_PASSIVE) == 0) {
WasmInitExpr InitExpr;
if (Config->Pic) {
InitExpr.Opcode = WASM_OPCODE_GLOBAL_GET;
InitExpr.Value.Global = WasmSym::MemoryBase->getGlobalIndex();
} else {
InitExpr.Opcode = WASM_OPCODE_I32_CONST;
InitExpr.Value.Int32 = Segment->StartVA;
}
writeInitExpr(OS, InitExpr);
}
writeInitExpr(OS, InitExpr);
writeUleb128(OS, Segment->Size, "segment size");
OS.flush();

1
lld/wasm/OutputSegment.h
View File

@ -33,6 +33,7 @@ public:
StringRef Name;
const uint32_t Index;
uint32_t InitFlags = 0;
uint32_t SectionOffset = 0;
uint32_t Alignment = 0;
uint32_t StartVA = 0;

1
lld/wasm/Symbols.cpp
View File

@ -25,6 +25,7 @@ using namespace lld;
using namespace lld::wasm;
DefinedFunction *WasmSym::CallCtors;
DefinedFunction *WasmSym::InitMemory;
DefinedFunction *WasmSym::ApplyRelocs;
DefinedData *WasmSym::DsoHandle;
DefinedData *WasmSym::DataEnd;

4
lld/wasm/Symbols.h
View File

@ -438,6 +438,10 @@ struct WasmSym {
// Function that directly calls all ctors in priority order.
static DefinedFunction *CallCtors;
// __wasm_init_memory
// Function that initializes passive data segments post-instantiation.
static DefinedFunction *InitMemory;
// __wasm_apply_relocs
// Function that applies relocations to data segment post-instantiation.
static DefinedFunction *ApplyRelocs;

2
lld/wasm/SyntheticSections.cpp
View File

@ -323,7 +323,7 @@ void DataCountSection::writeBody() {
}
bool DataCountSection::isNeeded() const {
return NumSegments && Out.TargetFeaturesSec->Features.count("bulk-memory");
return NumSegments && Config->PassiveSegments;
}
static uint32_t getWasmFlags(const Symbol *Sym) {

91
lld/wasm/Writer.cpp
View File

@ -54,6 +54,7 @@ public:
private:
void openFile();
void createInitMemoryFunction();
void createApplyRelocationsFunction();
void createCallCtorsFunction();
@ -407,6 +408,10 @@ void Writer::populateTargetFeatures() {
error("'atomics' feature is disallowed by " + Disallowed["atomics"] +
", so --shared-memory must not be used");
if (!Used.count("bulk-memory") && Config->PassiveSegments)
error("'bulk-memory' feature must be used in order to emit passive "
"segments");
// Validate that used features are allowed in output
if (!InferFeatures) {
for (auto &Feature : Used.keys()) {
@ -621,6 +626,8 @@ void Writer::createOutputSegments() {
if (S == nullptr) {
LLVM_DEBUG(dbgs() << "new segment: " << Name << "\n");
S = make<OutputSegment>(Name, Segments.size());
if (Config->PassiveSegments)
S->InitFlags = WASM_SEGMENT_IS_PASSIVE;
Segments.push_back(S);
}
S->addInputSegment(Segment);
@ -629,10 +636,57 @@ void Writer::createOutputSegments() {
}
}
static void CreateFunction(DefinedFunction *Func, StringRef BodyContent) {
std::string FunctionBody;
{
raw_string_ostream OS(FunctionBody);
writeUleb128(OS, BodyContent.size(), "function size");
OS << BodyContent;
}
ArrayRef<uint8_t> Body = arrayRefFromStringRef(Saver.save(FunctionBody));
cast<SyntheticFunction>(Func->Function)->setBody(Body);
}
void Writer::createInitMemoryFunction() {
LLVM_DEBUG(dbgs() << "createInitMemoryFunction\n");
std::string BodyContent;
{
raw_string_ostream OS(BodyContent);
writeUleb128(OS, 0, "num locals");
// initialize passive data segments
for (const OutputSegment *S : Segments) {
if (S->InitFlags & WASM_SEGMENT_IS_PASSIVE) {
// destination address
writeU8(OS, WASM_OPCODE_I32_CONST, "i32.const");
writeUleb128(OS, S->StartVA, "destination address");
// source segment offset
writeU8(OS, WASM_OPCODE_I32_CONST, "i32.const");
writeUleb128(OS, 0, "segment offset");
// memory region size
writeU8(OS, WASM_OPCODE_I32_CONST, "i32.const");
writeUleb128(OS, S->Size, "memory region size");
// memory.init instruction
writeU8(OS, WASM_OPCODE_MISC_PREFIX, "bulk-memory prefix");
writeUleb128(OS, WASM_OPCODE_MEMORY_INIT, "MEMORY.INIT");
writeUleb128(OS, S->Index, "segment index immediate");
writeU8(OS, 0, "memory index immediate");
// data.drop instruction
writeU8(OS, WASM_OPCODE_MISC_PREFIX, "bulk-memory prefix");
writeUleb128(OS, WASM_OPCODE_DATA_DROP, "DATA.DROP");
writeUleb128(OS, S->Index, "segment index immediate");
}
}
writeU8(OS, WASM_OPCODE_END, "END");
}
CreateFunction(WasmSym::InitMemory, BodyContent);
}
// For -shared (PIC) output, we create create a synthetic function which will
// apply any relocations to the data segments on startup. This function is
// called __wasm_apply_relocs and is added at the very beginning of
// __wasm_call_ctors before any of the constructors run.
// called __wasm_apply_relocs and is added at the beginning of __wasm_call_ctors
// before any of the constructors run.
void Writer::createApplyRelocationsFunction() {
LLVM_DEBUG(dbgs() << "createApplyRelocationsFunction\n");
// First write the body's contents to a string.
@ -646,16 +700,7 @@ void Writer::createApplyRelocationsFunction() {
writeU8(OS, WASM_OPCODE_END, "END");
}
// Once we know the size of the body we can create the final function body
std::string FunctionBody;
{
raw_string_ostream OS(FunctionBody);
writeUleb128(OS, BodyContent.size(), "function size");
OS << BodyContent;
}
ArrayRef<uint8_t> Body = arrayRefFromStringRef(Saver.save(FunctionBody));
cast<SyntheticFunction>(WasmSym::ApplyRelocs->Function)->setBody(Body);
CreateFunction(WasmSym::ApplyRelocs, BodyContent);
}
// Create synthetic "__wasm_call_ctors" function based on ctor functions
@ -669,11 +714,20 @@ void Writer::createCallCtorsFunction() {
{
raw_string_ostream OS(BodyContent);
writeUleb128(OS, 0, "num locals");
if (Config->PassiveSegments) {
writeU8(OS, WASM_OPCODE_CALL, "CALL");
writeUleb128(OS, WasmSym::InitMemory->getFunctionIndex(),
"function index");
}
if (Config->Pic) {
writeU8(OS, WASM_OPCODE_CALL, "CALL");
writeUleb128(OS, WasmSym::ApplyRelocs->getFunctionIndex(),
"function index");
}
// Call constructors
for (const WasmInitEntry &F : InitFunctions) {
writeU8(OS, WASM_OPCODE_CALL, "CALL");
writeUleb128(OS, F.Sym->getFunctionIndex(), "function index");
@ -681,16 +735,7 @@ void Writer::createCallCtorsFunction() {
writeU8(OS, WASM_OPCODE_END, "END");
}
// Once we know the size of the body we can create the final function body
std::string FunctionBody;
{
raw_string_ostream OS(FunctionBody);
writeUleb128(OS, BodyContent.size(), "function size");
OS << BodyContent;
}
ArrayRef<uint8_t> Body = arrayRefFromStringRef(Saver.save(FunctionBody));
cast<SyntheticFunction>(WasmSym::CallCtors->Function)->setBody(Body);
CreateFunction(WasmSym::CallCtors, BodyContent);
}
// Populate InitFunctions vector with init functions from all input objects.
@ -779,6 +824,8 @@ void Writer::run() {
if (!Config->Relocatable) {
// Create linker synthesized functions
if (Config->PassiveSegments)
createInitMemoryFunction();
if (Config->Pic)
createApplyRelocationsFunction();
createCallCtorsFunction();

3
llvm/include/llvm/BinaryFormat/Wasm.h
View File

@ -249,6 +249,9 @@ enum : unsigned {
WASM_OPCODE_F32_CONST = 0x43,
WASM_OPCODE_F64_CONST = 0x44,
WASM_OPCODE_I32_ADD = 0x6a,
WASM_OPCODE_MISC_PREFIX = 0xfc,
WASM_OPCODE_MEMORY_INIT = 0x08,
WASM_OPCODE_DATA_DROP = 0x09,
};
enum : unsigned {