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[WebAssembly] Reorder Symbol fields to make it smaller 

On 64-bit systems, this decreases sizeof(SymbolUnion) from 112 to 96.

Add a static_assert to avoid accidental increases in future.

Reviewed By: sbc100

Differential Revision: https://reviews.llvm.org/D64208

llvm-svn: 365169
This commit is contained in:
Fangrui Song 2019-07-05 01:27:39 +00:00
parent f0e5aa035e
commit 3d0193909b
1 changed files with 33 additions and 27 deletions
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60
lld/wasm/Symbols.h
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@ -41,7 +41,7 @@ class OutputSection;
// The base class for real symbol classes. // The base class for real symbol classes.
class Symbol { class Symbol {
public: public:
enum Kind { enum Kind : uint8_t {
DefinedFunctionKind, DefinedFunctionKind,
DefinedDataKind, DefinedDataKind,
DefinedGlobalKind, DefinedGlobalKind,
@ -107,6 +107,33 @@ public:
WasmSymbolType getWasmType() const; WasmSymbolType getWasmType() const;
bool isExported() const; bool isExported() const;
const WasmSignature* getSignature() const;
bool isInGOT() const { return GOTIndex != INVALID_INDEX; }
uint32_t getGOTIndex() const {
assert(GOTIndex != INVALID_INDEX);
return GOTIndex;
}
void setGOTIndex(uint32_t Index);
bool hasGOTIndex() const { return GOTIndex != INVALID_INDEX; }
protected:
Symbol(StringRef Name, Kind K, uint32_t Flags, InputFile *F)
: Name(Name), File(F), Flags(Flags), SymbolKind(K),
Referenced(!Config->GcSections), IsUsedInRegularObj(false),
ForceExport(false), CanInline(false), Traced(false) {}
StringRef Name;
InputFile *File;
uint32_t Flags;
uint32_t OutputSymbolIndex = INVALID_INDEX;
uint32_t GOTIndex = INVALID_INDEX;
Kind SymbolKind;
unsigned Referenced : 1;
public:
// True if the symbol was used for linking and thus need to be added to the // True if the symbol was used for linking and thus need to be added to the
// output file's symbol table. This is true for all symbols except for // output file's symbol table. This is true for all symbols except for
// unreferenced DSO symbols, lazy (archive) symbols, and bitcode symbols that // unreferenced DSO symbols, lazy (archive) symbols, and bitcode symbols that
@ -124,32 +151,6 @@ public:
// True if this symbol is specified by --trace-symbol option. // True if this symbol is specified by --trace-symbol option.
unsigned Traced : 1; unsigned Traced : 1;
const WasmSignature* getSignature() const;
bool isInGOT() const { return GOTIndex != INVALID_INDEX; }
uint32_t getGOTIndex() const {
assert(GOTIndex != INVALID_INDEX);
return GOTIndex;
}
void setGOTIndex(uint32_t Index);
bool hasGOTIndex() const { return GOTIndex != INVALID_INDEX; }
protected:
Symbol(StringRef Name, Kind K, uint32_t Flags, InputFile *F)
: IsUsedInRegularObj(false), ForceExport(false), CanInline(false),
Traced(false), Name(Name), SymbolKind(K), Flags(Flags), File(F),
Referenced(!Config->GcSections) {}
StringRef Name;
Kind SymbolKind;
uint32_t Flags;
InputFile *File;
uint32_t OutputSymbolIndex = INVALID_INDEX;
uint32_t GOTIndex = INVALID_INDEX;
bool Referenced;
}; };
class FunctionSymbol : public Symbol { class FunctionSymbol : public Symbol {
@ -474,6 +475,11 @@ union SymbolUnion {
alignas(SectionSymbol) char I[sizeof(SectionSymbol)]; alignas(SectionSymbol) char I[sizeof(SectionSymbol)];
}; };
// It is important to keep the size of SymbolUnion small for performance and
// memory usage reasons. 96 bytes is a soft limit based on the size of
// UndefinedFunction on a 64-bit system.
static_assert(sizeof(SymbolUnion) <= 96, "SymbolUnion too large");
void printTraceSymbol(Symbol *Sym); void printTraceSymbol(Symbol *Sym);
void printTraceSymbolUndefined(StringRef Name, const InputFile* File); void printTraceSymbolUndefined(StringRef Name, const InputFile* File);