[WebAssembly] Initialize memory in start function
Summary:
- `__wasm_init_memory` is now the WebAssembly start function instead
of being called from `__wasm_call_ctors` or called directly by the
runtime.
- Adds a new synthetic data symbol `__wasm_init_memory_flag` that is
atomically incremented from zero to one by the thread responsible
for initializing memory.
- All threads now unconditionally perform data.drop on all passive
segments.
- Removes --passive-segments and --active-segments flags and controls
segment type based on --shared-memory instead. The deleted flags
were only present to ameliorate the upgrade path in Emscripten.
Reviewers: sbc100, aheejin
Subscribers: dschuff, jgravelle-google, sunfish, jfb, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D65783
llvm-svn: 370965
diff --git a/lld/wasm/MarkLive.cpp b/lld/wasm/MarkLive.cpp
index 7656689..98267d1 100644
--- a/lld/wasm/MarkLive.cpp
+++ b/lld/wasm/MarkLive.cpp
@@ -50,8 +50,6 @@
// 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->isPic)
enqueue(WasmSym::applyRelocs);
for (const ObjFile *obj : symtab->objectFiles) {
@@ -86,6 +84,9 @@
if (config->isPic)
enqueue(WasmSym::callCtors);
+ if (config->sharedMemory && !config->shared)
+ enqueue(WasmSym::initMemory);
+
// Follow relocations to mark all reachable chunks.
while (!q.empty()) {
InputChunk *c = q.pop_back_val();