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[WebAssembly] Make stack-pointer imports mutable.

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This is not currently valid by the wasm spec, however:
 - It replaces doing set_global on an immutable global, which is also
   not valid.
 - It's expected be valid in the near future:
   https://github.com/WebAssembly/threads/blob/master/proposals/threads/Globals.md
 - This only occurs before linking, so a fully linked object will be
   valid.

llvm-svn: 319810
This commit is contained in:
Dan Gohman 2017-12-05 18:29:48 +00:00
parent 12cba944e4
commit 28436b67e8
1 changed files with 47 additions and 40 deletions
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87
lib/MC/WasmObjectWriter.cpp
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@ -115,6 +115,7 @@ struct WasmImport {
StringRef FieldName;
unsigned Kind;
int32_t Type;
bool IsMutable;
};
// A wasm function to be written into the function section.
@ -681,7 +682,7 @@ void WasmObjectWriter::writeImportSection(ArrayRef<WasmImport> Imports) {
break;
case wasm::WASM_EXTERNAL_GLOBAL:
encodeSLEB128(int32_t(Import.Type), getStream());
encodeULEB128(0, getStream()); // mutability
encodeULEB128(int32_t(Import.IsMutable), getStream());
break;
default:
llvm_unreachable("unsupported import kind");
@ -1036,41 +1037,6 @@ void WasmObjectWriter::writeObject(MCAssembler &Asm,
}
}
// Populate FunctionTypeIndices and Imports.
for (const MCSymbol &S : Asm.symbols()) {
const auto &WS = static_cast<const MCSymbolWasm &>(S);
// Register types for all functions, including those with private linkage
// (making them
// because wasm always needs a type signature.
if (WS.isFunction())
registerFunctionType(WS);
if (WS.isTemporary())
continue;
// If the symbol is not defined in this translation unit, import it.
if (!WS.isDefined(/*SetUsed=*/false)) {
WasmImport Import;
Import.ModuleName = WS.getModuleName();
Import.FieldName = WS.getName();
if (WS.isFunction()) {
Import.Kind = wasm::WASM_EXTERNAL_FUNCTION;
Import.Type = getFunctionType(WS);
SymbolIndices[&WS] = NumFuncImports;
++NumFuncImports;
} else {
Import.Kind = wasm::WASM_EXTERNAL_GLOBAL;
Import.Type = int32_t(PtrType);
SymbolIndices[&WS] = NumGlobalImports;
++NumGlobalImports;
}
Imports.push_back(Import);
}
}
// In the special .global_variables section, we've encoded global
// variables used by the function. Translate them into the Globals
// list.
@ -1146,6 +1112,51 @@ void WasmObjectWriter::writeObject(MCAssembler &Asm,
StackPointerGlobalName = StringRef(Contents.data(), Contents.size());
}
// Populate FunctionTypeIndices and Imports.
for (const MCSymbol &S : Asm.symbols()) {
const auto &WS = static_cast<const MCSymbolWasm &>(S);
// Register types for all functions, including those with private linkage
// (making them
// because wasm always needs a type signature.
if (WS.isFunction())
registerFunctionType(WS);
if (WS.isTemporary())
continue;
// If the symbol is not defined in this translation unit, import it.
if (!WS.isDefined(/*SetUsed=*/false)) {
WasmImport Import;
Import.ModuleName = WS.getModuleName();
Import.FieldName = WS.getName();
if (WS.isFunction()) {
Import.Kind = wasm::WASM_EXTERNAL_FUNCTION;
Import.Type = getFunctionType(WS);
SymbolIndices[&WS] = NumFuncImports;
++NumFuncImports;
} else {
Import.Kind = wasm::WASM_EXTERNAL_GLOBAL;
Import.Type = int32_t(PtrType);
Import.IsMutable = false;
SymbolIndices[&WS] = NumGlobalImports;
// If this global is the stack pointer, make it mutable and remember it
// so that we can emit metadata for it.
if (StackPointerGlobalName.hasValue() &&
WS.getName() == StackPointerGlobalName.getValue()) {
Import.IsMutable = true;
StackPointerGlobal = NumGlobalImports;
}
++NumGlobalImports;
}
Imports.push_back(Import);
}
}
for (MCSection &Sec : Asm) {
auto &Section = static_cast<MCSectionWasm &>(Sec);
if (!Section.isWasmData())
@ -1252,10 +1263,6 @@ void WasmObjectWriter::writeObject(MCAssembler &Asm,
SymbolIndices[&WS] = Index;
DEBUG(dbgs() << " -> global index: " << Index << "\n");
Globals.push_back(Global);
if (StackPointerGlobalName.hasValue() &&
WS.getName() == StackPointerGlobalName.getValue())
StackPointerGlobal = Index;
}
// If the symbol is visible outside this translation unit, export it.