finalize: Refactor C string extraction code. NFC.
This is a pure refactor in preparation for change that will
enable stripping or at least zeroing segments that only contain
EM_JS/EM_ASM strings.
diff --git a/src/wasm/wasm-emscripten.cpp b/src/wasm/wasm-emscripten.cpp
index 96263f5..1fd35de 100644
--- a/src/wasm/wasm-emscripten.cpp
+++ b/src/wasm/wasm-emscripten.cpp
@@ -76,62 +76,6 @@
const Address UNKNOWN_OFFSET(uint32_t(-1));
-std::vector<Address> getSegmentOffsets(Module& wasm) {
- std::unordered_map<Index, Address> passiveOffsets;
- if (wasm.features.hasBulkMemory()) {
- // Fetch passive segment offsets out of memory.init instructions
- struct OffsetSearcher : PostWalker<OffsetSearcher> {
- std::unordered_map<Index, Address>& offsets;
- OffsetSearcher(std::unordered_map<unsigned, Address>& offsets)
- : offsets(offsets) {}
- void visitMemoryInit(MemoryInit* curr) {
- // The desitination of the memory.init is either a constant
- // or the result of an addition with __memory_base in the
- // case of PIC code.
- auto* dest = curr->dest->dynCast<Const>();
- if (!dest) {
- auto* add = curr->dest->dynCast<Binary>();
- if (!add) {
- return;
- }
- dest = add->left->dynCast<Const>();
- if (!dest) {
- return;
- }
- }
- auto it = offsets.find(curr->segment);
- if (it != offsets.end()) {
- Fatal() << "Cannot get offset of passive segment initialized "
- "multiple times";
- }
- offsets[curr->segment] = dest->value.geti32();
- }
- } searcher(passiveOffsets);
- searcher.walkModule(&wasm);
- }
- std::vector<Address> segmentOffsets;
- for (unsigned i = 0; i < wasm.memory.segments.size(); ++i) {
- auto& segment = wasm.memory.segments[i];
- if (segment.isPassive) {
- auto it = passiveOffsets.find(i);
- if (it != passiveOffsets.end()) {
- segmentOffsets.push_back(it->second);
- } else {
- // This was a non-constant offset (perhaps TLS)
- segmentOffsets.push_back(UNKNOWN_OFFSET);
- }
- } else if (auto* addrConst = segment.offset->dynCast<Const>()) {
- auto address = addrConst->value.geti32();
- segmentOffsets.push_back(address);
- } else {
- // TODO(sbc): Wasm shared libraries have data segments with non-const
- // offset.
- segmentOffsets.push_back(0);
- }
- }
- return segmentOffsets;
-}
-
std::string escape(const char* input) {
std::string code = input;
// replace newlines quotes with escaped newlines
@@ -161,29 +105,88 @@
return code;
}
-const char* stringAtAddr(Module& wasm,
- std::vector<Address> const& segmentOffsets,
- Address address) {
- for (unsigned i = 0; i < wasm.memory.segments.size(); ++i) {
- Memory::Segment& segment = wasm.memory.segments[i];
- Address offset = segmentOffsets[i];
- if (offset != UNKNOWN_OFFSET && address >= offset &&
- address < offset + segment.data.size()) {
- return &segment.data[address - offset];
+class StringConstantTracker {
+public:
+ StringConstantTracker(Module& wasm) : wasm(wasm) { calcSegmentOffsets(); }
+
+ std::string codeForConstAddr(int64_t address) {
+ const char* str = stringAtAddr(address);
+ if (!str) {
+ Fatal() << "unable to find data for ASM/EM_JS const at: " << address;
+ }
+ return escape(str);
+ }
+
+private:
+ void calcSegmentOffsets() {
+ std::unordered_map<Index, Address> passiveOffsets;
+ if (wasm.features.hasBulkMemory()) {
+ // Fetch passive segment offsets out of memory.init instructions
+ struct OffsetSearcher : PostWalker<OffsetSearcher> {
+ std::unordered_map<Index, Address>& offsets;
+ OffsetSearcher(std::unordered_map<unsigned, Address>& offsets)
+ : offsets(offsets) {}
+ void visitMemoryInit(MemoryInit* curr) {
+ // The desitination of the memory.init is either a constant
+ // or the result of an addition with __memory_base in the
+ // case of PIC code.
+ auto* dest = curr->dest->dynCast<Const>();
+ if (!dest) {
+ auto* add = curr->dest->dynCast<Binary>();
+ if (!add) {
+ return;
+ }
+ dest = add->left->dynCast<Const>();
+ if (!dest) {
+ return;
+ }
+ }
+ auto it = offsets.find(curr->segment);
+ if (it != offsets.end()) {
+ Fatal() << "Cannot get offset of passive segment initialized "
+ "multiple times";
+ }
+ offsets[curr->segment] = dest->value.geti32();
+ }
+ } searcher(passiveOffsets);
+ searcher.walkModule(&wasm);
+ }
+ for (unsigned i = 0; i < wasm.memory.segments.size(); ++i) {
+ auto& segment = wasm.memory.segments[i];
+ if (segment.isPassive) {
+ auto it = passiveOffsets.find(i);
+ if (it != passiveOffsets.end()) {
+ segmentOffsets.push_back(it->second);
+ } else {
+ // This was a non-constant offset (perhaps TLS)
+ segmentOffsets.push_back(UNKNOWN_OFFSET);
+ }
+ } else if (auto* addrConst = segment.offset->dynCast<Const>()) {
+ auto address = addrConst->value.geti32();
+ segmentOffsets.push_back(address);
+ } else {
+ // TODO(sbc): Wasm shared libraries have data segments with non-const
+ // offset.
+ segmentOffsets.push_back(0);
+ }
}
}
- return nullptr;
-}
-std::string codeForConstAddr(Module& wasm,
- std::vector<Address> const& segmentOffsets,
- int64_t address) {
- const char* str = stringAtAddr(wasm, segmentOffsets, address);
- if (!str) {
- Fatal() << "unable to find data for ASM/EM_JS const at: " << address;
+ const char* stringAtAddr(Address address) {
+ for (unsigned i = 0; i < wasm.memory.segments.size(); ++i) {
+ Memory::Segment& segment = wasm.memory.segments[i];
+ Address offset = segmentOffsets[i];
+ if (offset != UNKNOWN_OFFSET && address >= offset &&
+ address < offset + segment.data.size()) {
+ return &segment.data[address - offset];
+ }
+ }
+ return nullptr;
}
- return escape(str);
-}
+
+ Module& wasm;
+ std::vector<Address> segmentOffsets; // segment index => address offset
+};
enum class Proxying {
None,
@@ -206,7 +209,7 @@
struct AsmConstWalker : public LinearExecutionWalker<AsmConstWalker> {
Module& wasm;
bool minimizeWasmChanges;
- std::vector<Address> segmentOffsets; // segment index => address offset
+ StringConstantTracker stringTracker;
struct AsmConst {
std::set<Signature> sigs;
@@ -222,7 +225,7 @@
AsmConstWalker(Module& _wasm, bool minimizeWasmChanges)
: wasm(_wasm), minimizeWasmChanges(minimizeWasmChanges),
- segmentOffsets(getSegmentOffsets(wasm)) {}
+ stringTracker(_wasm) {}
void noteNonLinear(Expression* curr);
@@ -316,7 +319,7 @@
auto* value = arg->cast<Const>();
int64_t address = value->value.getInteger();
- auto code = codeForConstAddr(wasm, segmentOffsets, address);
+ auto code = stringTracker.codeForConstAddr(address);
createAsmConst(address, code, sig, importName);
}
@@ -373,13 +376,12 @@
struct EmJsWalker : public PostWalker<EmJsWalker> {
Module& wasm;
- std::vector<Address> segmentOffsets; // segment index => address offset
+ StringConstantTracker stringTracker;
std::vector<Export> toRemove;
std::map<std::string, std::string> codeByName;
- EmJsWalker(Module& _wasm)
- : wasm(_wasm), segmentOffsets(getSegmentOffsets(wasm)) {}
+ EmJsWalker(Module& _wasm) : wasm(_wasm), stringTracker(_wasm) {}
void visitExport(Export* curr) {
if (curr->kind != ExternalKind::Function) {
@@ -400,7 +402,7 @@
}
auto* addrConst = consts.list[0];
int64_t address = addrConst->value.getInteger();
- auto code = codeForConstAddr(wasm, segmentOffsets, address);
+ auto code = stringTracker.codeForConstAddr(address);
codeByName[funcName] = code;
}
};
