diff options
Diffstat (limited to 'wasm/MarkLive.cpp')
| -rw-r--r-- | wasm/MarkLive.cpp | 120 | 
1 files changed, 0 insertions, 120 deletions
diff --git a/wasm/MarkLive.cpp b/wasm/MarkLive.cpp deleted file mode 100644 index 3bbd1148f6ad..000000000000 --- a/wasm/MarkLive.cpp +++ /dev/null @@ -1,120 +0,0 @@ -//===- MarkLive.cpp -------------------------------------------------------===// -// -//                             The LLVM Linker -// -// This file is distributed under the University of Illinois Open Source -// License. See LICENSE.TXT for details. -// -//===----------------------------------------------------------------------===// -// -// This file implements --gc-sections, which is a feature to remove unused -// chunks from the output. Unused chunks are those that are not reachable from -// known root symbols or chunks. This feature is implemented as a mark-sweep -// garbage collector. -// -// Here's how it works. Each InputChunk has a "Live" bit. The bit is off by -// default. Starting with the GC-roots, visit all reachable chunks and set their -// Live bits. The Writer will then ignore chunks whose Live bits are off, so -// that such chunk are not appear in the output. -// -//===----------------------------------------------------------------------===// - -#include "MarkLive.h" -#include "Config.h" -#include "InputChunks.h" -#include "InputEvent.h" -#include "InputGlobal.h" -#include "SymbolTable.h" -#include "Symbols.h" - -#define DEBUG_TYPE "lld" - -using namespace llvm; -using namespace llvm::wasm; - -void lld::wasm::markLive() { -  if (!Config->GcSections) -    return; - -  LLVM_DEBUG(dbgs() << "markLive\n"); -  SmallVector<InputChunk *, 256> Q; - -  auto Enqueue = [&](Symbol *Sym) { -    if (!Sym || Sym->isLive()) -      return; -    LLVM_DEBUG(dbgs() << "markLive: " << Sym->getName() << "\n"); -    Sym->markLive(); -    if (InputChunk *Chunk = Sym->getChunk()) -      Q.push_back(Chunk); -  }; - -  // Add GC root symbols. -  if (!Config->Entry.empty()) -    Enqueue(Symtab->find(Config->Entry)); -  Enqueue(WasmSym::CallCtors); - -  // We need to preserve any exported symbol -  for (Symbol *Sym : Symtab->getSymbols()) -    if (Sym->isExported()) -      Enqueue(Sym); - -  // The ctor functions are all used in the synthetic __wasm_call_ctors -  // function, but since this function is created in-place it doesn't contain -  // relocations which mean we have to manually mark the ctors. -  for (const ObjFile *Obj : Symtab->ObjectFiles) { -    const WasmLinkingData &L = Obj->getWasmObj()->linkingData(); -    for (const WasmInitFunc &F : L.InitFunctions) -      Enqueue(Obj->getFunctionSymbol(F.Symbol)); -  } - -  // Follow relocations to mark all reachable chunks. -  while (!Q.empty()) { -    InputChunk *C = Q.pop_back_val(); - -    for (const WasmRelocation Reloc : C->getRelocations()) { -      if (Reloc.Type == R_WEBASSEMBLY_TYPE_INDEX_LEB) -        continue; -      Symbol *Sym = C->File->getSymbol(Reloc.Index); - -      // If the function has been assigned the special index zero in the table, -      // the relocation doesn't pull in the function body, since the function -      // won't actually go in the table (the runtime will trap attempts to call -      // that index, since we don't use it).  A function with a table index of -      // zero is only reachable via "call", not via "call_indirect".  The stub -      // functions used for weak-undefined symbols have this behaviour (compare -      // equal to null pointer, only reachable via direct call). -      if (Reloc.Type == R_WEBASSEMBLY_TABLE_INDEX_SLEB || -          Reloc.Type == R_WEBASSEMBLY_TABLE_INDEX_I32) { -        FunctionSymbol *FuncSym = cast<FunctionSymbol>(Sym); -        if (FuncSym->hasTableIndex() && FuncSym->getTableIndex() == 0) -          continue; -      } - -      Enqueue(Sym); -    } -  } - -  // Report garbage-collected sections. -  if (Config->PrintGcSections) { -    for (const ObjFile *Obj : Symtab->ObjectFiles) { -      for (InputChunk *C : Obj->Functions) -        if (!C->Live) -          message("removing unused section " + toString(C)); -      for (InputChunk *C : Obj->Segments) -        if (!C->Live) -          message("removing unused section " + toString(C)); -      for (InputGlobal *G : Obj->Globals) -        if (!G->Live) -          message("removing unused section " + toString(G)); -      for (InputEvent *E : Obj->Events) -        if (!E->Live) -          message("removing unused section " + toString(E)); -    } -    for (InputChunk *C : Symtab->SyntheticFunctions) -      if (!C->Live) -        message("removing unused section " + toString(C)); -    for (InputGlobal *G : Symtab->SyntheticGlobals) -      if (!G->Live) -        message("removing unused section " + toString(G)); -  } -}  | 
