Handle EM_ASM/EM_JS in LLVM wasm backend O0 output (#1888)

See emscripten-core/emscripten#7928 - we have been optimizing all wasms until now, and noticed this when the wasm object file path did not do so. When not optimizing, our methods of handling EM_ASM and EM_JS fail since the patterns are different.

Specifically, for EM_ASM we hunt for emscripten_asm_const(X, where X is a constant, but without opts it may be a get of a local. For EM_JS, the function body may not just contain a const, but a block with a set of the const and a return of a get later.

This adds logic to track gets and sets in basic blocks, which is sufficient to handle this.

6 files changed, 327 insertions, 18 deletions

diff --git a/src/tools/wasm-emscripten-finalize.cpp b/src/tools/wasm-emscripten-finalize.cpp
index 3ea3629c5..5c2e37ac3 100644
--- a/src/tools/wasm-emscripten-finalize.cpp
+++ b/src/tools/wasm-emscripten-finalize.cpp
@@ -173,14 +173,16 @@ int main(int argc, const char *argv[]) {
   EmscriptenGlueGenerator generator(wasm);
   generator.fixInvokeFunctionNames();
 
-  PassRunner passRunner(&wasm);
-  passRunner.setDebug(options.debug);
-  passRunner.setDebugInfo(debugInfo);
-  passRunner.add(ABI::getLegalizationPass(
-    legalizeJavaScriptFFI ? ABI::LegalizationLevel::Full
-                          : ABI::LegalizationLevel::Minimal
-  ));
-  passRunner.run();
+  {
+    PassRunner passRunner(&wasm);
+    passRunner.setDebug(options.debug);
+    passRunner.setDebugInfo(debugInfo);
+    passRunner.add(ABI::getLegalizationPass(
+      legalizeJavaScriptFFI ? ABI::LegalizationLevel::Full
+                            : ABI::LegalizationLevel::Minimal
+    ));
+    passRunner.run();
+  }
 
   std::vector<Name> initializerFunctions;
 
diff --git a/src/wasm/wasm-emscripten.cpp b/src/wasm/wasm-emscripten.cpp
index 88e66ea07..3dee642b1 100644
--- a/src/wasm/wasm-emscripten.cpp
+++ b/src/wasm/wasm-emscripten.cpp
@@ -443,18 +443,22 @@ std::string codeForConstAddr(Module& wasm,
   return escape(str);
 }
 
-struct AsmConstWalker : public PostWalker<AsmConstWalker> {
+struct AsmConstWalker : public LinearExecutionWalker<AsmConstWalker> {
   Module& wasm;
   std::vector<Address> segmentOffsets; // segment index => address offset
 
   std::map<std::string, std::set<std::string>> sigsForCode;
   std::map<std::string, Address> ids;
   std::set<std::string> allSigs;
+  std::map<Index, SetLocal*> sets; // last sets in the current basic block, per index
 
   AsmConstWalker(Module& _wasm)
     : wasm(_wasm),
       segmentOffsets(getSegmentOffsets(wasm)) { }
 
+  void noteNonLinear(Expression* curr);
+
+  void visitSetLocal(SetLocal* curr);
   void visitCall(Call* curr);
   void visitTable(Table* curr);
 
@@ -471,15 +475,33 @@ private:
   std::vector<std::unique_ptr<Function>> queuedImports;
 };
 
+void AsmConstWalker::noteNonLinear(Expression* curr) {
+  // End of this basic block; clear sets.
+  sets.clear();
+}
+
+void AsmConstWalker::visitSetLocal(SetLocal* curr) {
+  sets[curr->index] = curr;
+}
+
 void AsmConstWalker::visitCall(Call* curr) {
   auto* import = wasm.getFunction(curr->target);
   if (import->imported() && import->base.hasSubstring(EMSCRIPTEN_ASM_CONST)) {
     auto baseSig = getSig(curr);
     auto sig = fixupNameWithSig(curr->target, baseSig);
-
-    auto arg = curr->operands[0]->cast<Const>();
-    auto code = codeForConstAddr(wasm, segmentOffsets, arg);
-    arg->value = idLiteralForCode(code);
+    auto* arg = curr->operands[0];
+    // The argument may be a get, in which case, the last set in this basic block
+    // has the value.
+    if (auto* get = arg->dynCast<GetLocal>()) {
+      auto* set = sets[get->index];
+      if (set) {
+        assert(set->index == get->index);
+        arg = set->value;
+      }
+    }
+    auto* value = arg->cast<Const>();
+    auto code = codeForConstAddr(wasm, segmentOffsets, value);
+    value->value = idLiteralForCode(code);
     sigsForCode[code].insert(sig);
   }
 }
@@ -599,16 +621,31 @@ struct EmJsWalker : public PostWalker<EmJsWalker> {
     auto addrConst = curr->body->dynCast<Const>();
     if (addrConst == nullptr) {
       auto block = curr->body->dynCast<Block>();
-      Expression* first = nullptr;
+      Expression* value = nullptr;
       if (block && block->list.size() > 0) {
-        first = block->list[0];
+        value = block->list[0];
+        // first item may be a set of a local that we get later
+        auto* set = value->dynCast<SetLocal>();
+        if (set) {
+          value = block->list[1];
+        }
+        // look into a return value
+        if (auto* ret = value->dynCast<Return>()) {
+          value = ret->value;
+        }
+        // if it's a get of that set, use that value
+        if (auto* get = value->dynCast<GetLocal>()) {
+          if (set && get->index == set->index) {
+            value = set->value;
+          }
+        }
       }
-      if (first) {
-        addrConst = first->dynCast<Const>();
+      if (value) {
+        addrConst = value->dynCast<Const>();
       }
     }
     if (addrConst == nullptr) {
-      Fatal() << "Unexpected generated __em_js__ function body: " << curr;
+      Fatal() << "Unexpected generated __em_js__ function body: " << curr->name;
     }
     auto code = codeForConstAddr(wasm, segmentOffsets, addrConst);
     codeByName[funcName] = code;
diff --git a/test/lld/em_asm_O0.wast b/test/lld/em_asm_O0.wast
new file mode 100644
index 000000000..10511ca67
--- /dev/null
+++ b/test/lld/em_asm_O0.wast
@@ -0,0 +1,47 @@
+(module
+ (type $0 (func (param i32) (result i32)))
+ (type $1 (func (param i32 i32 i32) (result i32)))
+ (type $2 (func (param i32 i32) (result i32)))
+ (type $3 (func (result i32)))
+ (type $4 (func))
+ (import "env" "_Z24emscripten_asm_const_intIJEEiPKcDpT_" (func $_Z24emscripten_asm_const_intIJEEiPKcDpT_ (param i32) (result i32)))
+ (import "env" "_Z24emscripten_asm_const_intIJiiEEiPKcDpT_" (func $_Z24emscripten_asm_const_intIJiiEEiPKcDpT_ (param i32 i32 i32) (result i32)))
+ (import "env" "_Z24emscripten_asm_const_intIJiEEiPKcDpT_" (func $_Z24emscripten_asm_const_intIJiEEiPKcDpT_ (param i32 i32) (result i32)))
+ (global $global$0 (mut i32) (i32.const 66192))
+ (global $global$1 i32 (i32.const 66192))
+ (global $global$2 i32 (i32.const 652))
+ (table 1 1 funcref)
+ (memory $0 2)
+ (data (i32.const 568) "{ Module.print(\"Hello world\"); }\00{ return $0 + $1; }\00{ Module.print(\"Got \" + $0); }\00")
+ (export "memory" (memory $0))
+ (export "__wasm_call_ctors" (func $__wasm_call_ctors))
+ (export "main" (func $main))
+ (export "__heap_base" (global $global$1))
+ (export "__data_end" (global $global$2))
+ (func $main (; 3 ;) (type $3) (result i32)
+  (local $t1 i32)
+  (local $t2 i32)
+  (drop
+   (call $_Z24emscripten_asm_const_intIJEEiPKcDpT_
+    (i32.const 568)
+   )
+  )
+  (local.set $t1 (i32.const 621))
+  (local.set $t2 (i32.const 601))
+  (drop
+   (call $_Z24emscripten_asm_const_intIJiEEiPKcDpT_
+    (local.get $t1)
+    (call $_Z24emscripten_asm_const_intIJiiEEiPKcDpT_
+     (local.get $t2)
+     (i32.const 13)
+     (i32.const 27)
+    )
+   )
+  )
+  (i32.const 0)
+ )
+ (func $__wasm_call_ctors (; 4 ;) (type $4)
+ )
+ ;; custom section "linking", size 3
+)
+
diff --git a/test/lld/em_asm_O0.wast.out b/test/lld/em_asm_O0.wast.out
new file mode 100644
index 000000000..cbc93c5cb
--- /dev/null
+++ b/test/lld/em_asm_O0.wast.out
@@ -0,0 +1,126 @@
+(module
+ (type $0 (func (param i32) (result i32)))
+ (type $1 (func (param i32 i32 i32) (result i32)))
+ (type $2 (func (param i32 i32) (result i32)))
+ (type $3 (func (result i32)))
+ (type $4 (func))
+ (type $FUNCSIG$ii (func (param i32) (result i32)))
+ (type $FUNCSIG$iiii (func (param i32 i32 i32) (result i32)))
+ (type $FUNCSIG$iii (func (param i32 i32) (result i32)))
+ (import "env" "emscripten_asm_const_i" (func $emscripten_asm_const_i (param i32) (result i32)))
+ (import "env" "emscripten_asm_const_iii" (func $emscripten_asm_const_iii (param i32 i32 i32) (result i32)))
+ (import "env" "emscripten_asm_const_ii" (func $emscripten_asm_const_ii (param i32 i32) (result i32)))
+ (memory $0 2)
+ (data (i32.const 568) "{ Module.print(\"Hello world\"); }\00{ return $0 + $1; }\00{ Module.print(\"Got \" + $0); }\00")
+ (table $0 1 1 funcref)
+ (global $global$0 (mut i32) (i32.const 16384))
+ (global $global$1 i32 (i32.const 66192))
+ (global $global$2 i32 (i32.const 652))
+ (export "memory" (memory $0))
+ (export "__post_instantiate" (func $__wasm_call_ctors))
+ (export "main" (func $main))
+ (export "__heap_base" (global $global$1))
+ (export "__data_end" (global $global$2))
+ (export "stackSave" (func $stackSave))
+ (export "stackAlloc" (func $stackAlloc))
+ (export "stackRestore" (func $stackRestore))
+ (export "__growWasmMemory" (func $__growWasmMemory))
+ (func $main (; 3 ;) (type $3) (result i32)
+  (local $t1 i32)
+  (local $t2 i32)
+  (drop
+   (call $emscripten_asm_const_i
+    (i32.const 0)
+   )
+  )
+  (local.set $t1
+   (i32.const 2)
+  )
+  (local.set $t2
+   (i32.const 1)
+  )
+  (drop
+   (call $emscripten_asm_const_ii
+    (local.get $t1)
+    (call $emscripten_asm_const_iii
+     (local.get $t2)
+     (i32.const 13)
+     (i32.const 27)
+    )
+   )
+  )
+  (i32.const 0)
+ )
+ (func $__wasm_call_ctors (; 4 ;) (type $4)
+  (nop)
+ )
+ (func $stackSave (; 5 ;) (result i32)
+  (global.get $global$0)
+ )
+ (func $stackAlloc (; 6 ;) (param $0 i32) (result i32)
+  (local $1 i32)
+  (global.set $global$0
+   (local.tee $1
+    (i32.and
+     (i32.sub
+      (global.get $global$0)
+      (local.get $0)
+     )
+     (i32.const -16)
+    )
+   )
+  )
+  (local.get $1)
+ )
+ (func $stackRestore (; 7 ;) (param $0 i32)
+  (global.set $global$0
+   (local.get $0)
+  )
+ )
+ (func $__growWasmMemory (; 8 ;) (param $newSize i32) (result i32)
+  (grow_memory
+   (local.get $newSize)
+  )
+ )
+)
+(;
+--BEGIN METADATA --
+{
+  "asmConsts": {
+    "2": ["{ Module.print(\"Got \" + $0); }", ["ii"], [""]],
+    "0": ["{ Module.print(\"Hello world\"); }", ["i"], [""]],
+    "1": ["{ return $0 + $1; }", ["iii"], [""]]
+  },
+  "staticBump": 84,
+  "tableSize": 1,
+  "initializers": [
+    "__post_instantiate"
+  ],
+  "declares": [
+  ],
+  "externs": [
+  ],
+  "implementedFunctions": [
+    "___post_instantiate",
+    "_main",
+    "_stackSave",
+    "_stackAlloc",
+    "_stackRestore",
+    "___growWasmMemory"
+  ],
+  "exports": [
+    "memory",
+    "__post_instantiate",
+    "main",
+    "__heap_base",
+    "__data_end",
+    "stackSave",
+    "stackAlloc",
+    "stackRestore",
+    "__growWasmMemory"
+  ],
+  "invokeFuncs": [
+  ]
+}
+-- END METADATA --
+;)
diff --git a/test/lld/em_js_O0.wast b/test/lld/em_js_O0.wast
new file mode 100644
index 000000000..6d64c5b61
--- /dev/null
+++ b/test/lld/em_js_O0.wast
@@ -0,0 +1,22 @@
+(module
+ (import "env" "memory" (memory $0 256 256))
+ (data (i32.const 1024) "(void)<::>{ out(\"no args works\"); }\00(void)<::>{ out(\"no args returning int\"); return 12; }\00(void)<::>{ out(\"no args returning double\"); return 12.25; }\00(int x)<::>{ out(\"  takes ints: \" + x);}\00(double d)<::>{ out(\"  takes doubles: \" + d);}\00(char* str)<::>{ out(\"  takes strings: \" + UTF8ToString(str)); return 7.75; }\00(int x, int y)<::>{ out(\"  takes multiple ints: \" + x + \", \" + y); return 6; }\00(int x, const char* str, double d)<::>{ out(\"  mixed arg types: \" + x + \", \" + UTF8ToString(str) + \", \" + d); return 8.125; }\00(int unused)<::>{ out(\"  ignores unused args\"); return 5.5; }\00(int x, int y)<::>{ out(\"  skips unused args: \" + y); return 6; }\00(double x, double y, double z)<::>{ out(\"  \" + x + \" + \" + z); return x + z; }\00(void)<::>{ out(\"  can use <::> separator in user code\"); return 15; }\00(void)<::>{ var x, y; x = {}; y = 3; x[y] = [1, 2, 3]; out(\"  can have commas in user code: \" + x[y]); return x[y][1]; }\00(void)<::>{ var jsString = \'\e3\81\93\e3\82\93\e3\81\ab\e3\81\a1\e3\81\af\'; var lengthBytes = lengthBytesUTF8(jsString); var stringOnWasmHeap = _malloc(lengthBytes); stringToUTF8(jsString, stringOnWasmHeap, lengthBytes+1); return stringOnWasmHeap; }\00(void)<::>{ var jsString = \'hello from js\'; var lengthBytes = jsString.length+1; var stringOnWasmHeap = _malloc(lengthBytes); stringToUTF8(jsString, stringOnWasmHeap, lengthBytes+1); return stringOnWasmHeap; }\00BEGIN\n\00    noarg_int returned: %d\n\00    noarg_double returned: %f\n\00    stringarg returned: %f\n\00string arg\00    multi_intarg returned: %d\n\00    multi_mixedarg returned: %f\n\00hello\00    unused_args returned: %d\n\00    skip_args returned: %f\n\00    add_outer returned: %f\n\00    user_separator returned: %d\n\00    user_comma returned: %d\n\00    return_str returned: %s\n\00    return_utf8_str returned: %s\n\00END\n\00\00\cc\1a\00\00\00\00\00\00\00\00\00\00\00\00\00\00T!\"\19\0d\01\02\03\11K\1c\0c\10\04\0b\1d\12\1e\'hnopqb \05\06\0f\13\14\15\1a\08\16\07($\17\18\t\n\0e\1b\1f%#\83\82}&*+<=>?CGJMXYZ[\\]^_`acdefgijklrstyz{|\00\00\00\00\00\00\00\00\00Illegal byte sequence\00Domain error\00Result not representable\00Not a tty\00Permission denied\00Operation not permitted\00No such file or directory\00No such process\00File exists\00Value too large for data type\00No space left on device\00Out of memory\00Resource busy\00Interrupted system call\00Resource temporarily unavailable\00Invalid seek\00Cross-device link\00Read-only file system\00Directory not empty\00Connection reset by peer\00Operation timed out\00Connection refused\00Host is down\00Host is unreachable\00Address in use\00Broken pipe\00I/O error\00No such device or address\00Block device required\00No such device\00Not a directory\00Is a directory\00Text file busy\00Exec format error\00Invalid argument\00Argument list too long\00Symbolic link loop\00Filename too long\00Too many open files in system\00No file descriptors available\00Bad file descriptor\00No child process\00Bad address\00File too large\00Too many links\00No locks available\00Resource deadlock would occur\00State not recoverable\00Previous owner died\00Operation canceled\00Function not implemented\00No message of desired type\00Identifier removed\00Device not a stream\00No data available\00Device timeout\00Out of streams resources\00Link has been severed\00Protocol error\00Bad message\00File descriptor in bad state\00Not a socket\00Destination address required\00Message too large\00Protocol wrong type for socket\00Protocol not available\00Protocol not supported\00Socket type not supported\00Not supported\00Protocol family not supported\00Address family not supported by protocol\00Address not available\00Network is down\00Network unreachable\00Connection reset by network\00Connection aborted\00No buffer space available\00Socket is connected\00Socket not connected\00Cannot send after socket shutdown\00Operation already in progress\00Operation in progress\00Stale file handle\00Remote I/O error\00Quota exceeded\00No medium found\00Wrong medium type\00No error information\00\00-+   0X0x\00(null)\00\00\00\00\11\00\n\00\11\11\11\00\00\00\00\05\00\00\00\00\00\00\t\00\00\00\00\0b\00\00\00\00\00\00\00\00\11\00\0f\n\11\11\11\03\n\07\00\01\13\t\0b\0b\00\00\t\06\0b\00\00\0b\00\06\11\00\00\00\11\11\11\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\0b\00\00\00\00\00\00\00\00\11\00\n\n\11\11\11\00\n\00\00\02\00\t\0b\00\00\00\t\00\0b\00\00\0b\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\0c\00\00\00\00\00\00\00\00\00\00\00\0c\00\00\00\00\0c\00\00\00\00\t\0c\00\00\00\00\00\0c\00\00\0c\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\0e\00\00\00\00\00\00\00\00\00\00\00\0d\00\00\00\04\0d\00\00\00\00\t\0e\00\00\00\00\00\0e\00\00\0e\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\10\00\00\00\00\00\00\00\00\00\00\00\0f\00\00\00\00\0f\00\00\00\00\t\10\00\00\00\00\00\10\00\00\10\00\00\12\00\00\00\12\12\12\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\12\00\00\00\12\12\12\00\00\00\00\00\00\t\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\0b\00\00\00\00\00\00\00\00\00\00\00\n\00\00\00\00\n\00\00\00\00\t\0b\00\00\00\00\00\0b\00\00\0b\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\0c\00\00\00\00\00\00\00\00\00\00\00\0c\00\00\00\00\0c\00\00\00\00\t\0c\00\00\00\00\00\0c\00\00\0c\00\000123456789ABCDEF-0X+0X 0X-0x+0x 0x\00inf\00INF\00nan\00NAN\00.\00")
+ (data (i32.const 5232) "\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00")
+ (data (i32.const 6860) "\05\00\00\00\00\00\00\00\00\00\00\00\02\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\03\00\00\00\04\00\00\00\88\14\00\00\00\04\00\00\00\00\00\00\00\00\00\00\01\00\00\00\00\00\00\00\00\00\00\00\00\00\00\n\ff\ff\ff\ff\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\cc\1a\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\b0\18\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00")
+ (global $global$0 (mut i32) (i32.const 5250112))
+ (global $global$1 i32 (i32.const 5250112))
+ (global $global$2 i32 (i32.const 7232))
+ (export "__em_js__noarg" (func $__em_js__noarg))
+ (export "__heap_base" (global $global$1))
+ (export "__data_end" (global $global$2))
+ (func $__em_js__noarg (result i32)
+  (local $0 i32)
+  (local.set $0
+   (i32.const 1024)
+  )
+  (return
+   (local.get $0)
+  )
+ )
+)
+
diff --git a/test/lld/em_js_O0.wast.out b/test/lld/em_js_O0.wast.out
new file mode 100644
index 000000000..9b3307d5e
--- /dev/null
+++ b/test/lld/em_js_O0.wast.out
@@ -0,0 +1,75 @@
+(module
+ (type $0 (func (result i32)))
+ (import "env" "memory" (memory $0 256 256))
+ (data (i32.const 1024) "(void)<::>{ out(\"no args works\"); }\00(void)<::>{ out(\"no args returning int\"); return 12; }\00(void)<::>{ out(\"no args returning double\"); return 12.25; }\00(int x)<::>{ out(\"  takes ints: \" + x);}\00(double d)<::>{ out(\"  takes doubles: \" + d);}\00(char* str)<::>{ out(\"  takes strings: \" + UTF8ToString(str)); return 7.75; }\00(int x, int y)<::>{ out(\"  takes multiple ints: \" + x + \", \" + y); return 6; }\00(int x, const char* str, double d)<::>{ out(\"  mixed arg types: \" + x + \", \" + UTF8ToString(str) + \", \" + d); return 8.125; }\00(int unused)<::>{ out(\"  ignores unused args\"); return 5.5; }\00(int x, int y)<::>{ out(\"  skips unused args: \" + y); return 6; }\00(double x, double y, double z)<::>{ out(\"  \" + x + \" + \" + z); return x + z; }\00(void)<::>{ out(\"  can use <::> separator in user code\"); return 15; }\00(void)<::>{ var x, y; x = {}; y = 3; x[y] = [1, 2, 3]; out(\"  can have commas in user code: \" + x[y]); return x[y][1]; }\00(void)<::>{ var jsString = \'\e3\81\93\e3\82\93\e3\81\ab\e3\81\a1\e3\81\af\'; var lengthBytes = lengthBytesUTF8(jsString); var stringOnWasmHeap = _malloc(lengthBytes); stringToUTF8(jsString, stringOnWasmHeap, lengthBytes+1); return stringOnWasmHeap; }\00(void)<::>{ var jsString = \'hello from js\'; var lengthBytes = jsString.length+1; var stringOnWasmHeap = _malloc(lengthBytes); stringToUTF8(jsString, stringOnWasmHeap, lengthBytes+1); return stringOnWasmHeap; }\00BEGIN\n\00    noarg_int returned: %d\n\00    noarg_double returned: %f\n\00    stringarg returned: %f\n\00string arg\00    multi_intarg returned: %d\n\00    multi_mixedarg returned: %f\n\00hello\00    unused_args returned: %d\n\00    skip_args returned: %f\n\00    add_outer returned: %f\n\00    user_separator returned: %d\n\00    user_comma returned: %d\n\00    return_str returned: %s\n\00    return_utf8_str returned: %s\n\00END\n\00\00\cc\1a\00\00\00\00\00\00\00\00\00\00\00\00\00\00T!\"\19\0d\01\02\03\11K\1c\0c\10\04\0b\1d\12\1e\'hnopqb \05\06\0f\13\14\15\1a\08\16\07($\17\18\t\n\0e\1b\1f%#\83\82}&*+<=>?CGJMXYZ[\\]^_`acdefgijklrstyz{|\00\00\00\00\00\00\00\00\00Illegal byte sequence\00Domain error\00Result not representable\00Not a tty\00Permission denied\00Operation not permitted\00No such file or directory\00No such process\00File exists\00Value too large for data type\00No space left on device\00Out of memory\00Resource busy\00Interrupted system call\00Resource temporarily unavailable\00Invalid seek\00Cross-device link\00Read-only file system\00Directory not empty\00Connection reset by peer\00Operation timed out\00Connection refused\00Host is down\00Host is unreachable\00Address in use\00Broken pipe\00I/O error\00No such device or address\00Block device required\00No such device\00Not a directory\00Is a directory\00Text file busy\00Exec format error\00Invalid argument\00Argument list too long\00Symbolic link loop\00Filename too long\00Too many open files in system\00No file descriptors available\00Bad file descriptor\00No child process\00Bad address\00File too large\00Too many links\00No locks available\00Resource deadlock would occur\00State not recoverable\00Previous owner died\00Operation canceled\00Function not implemented\00No message of desired type\00Identifier removed\00Device not a stream\00No data available\00Device timeout\00Out of streams resources\00Link has been severed\00Protocol error\00Bad message\00File descriptor in bad state\00Not a socket\00Destination address required\00Message too large\00Protocol wrong type for socket\00Protocol not available\00Protocol not supported\00Socket type not supported\00Not supported\00Protocol family not supported\00Address family not supported by protocol\00Address not available\00Network is down\00Network unreachable\00Connection reset by network\00Connection aborted\00No buffer space available\00Socket is connected\00Socket not connected\00Cannot send after socket shutdown\00Operation already in progress\00Operation in progress\00Stale file handle\00Remote I/O error\00Quota exceeded\00No medium found\00Wrong medium type\00No error information\00\00-+   0X0x\00(null)\00\00\00\00\11\00\n\00\11\11\11\00\00\00\00\05\00\00\00\00\00\00\t\00\00\00\00\0b\00\00\00\00\00\00\00\00\11\00\0f\n\11\11\11\03\n\07\00\01\13\t\0b\0b\00\00\t\06\0b\00\00\0b\00\06\11\00\00\00\11\11\11\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\0b\00\00\00\00\00\00\00\00\11\00\n\n\11\11\11\00\n\00\00\02\00\t\0b\00\00\00\t\00\0b\00\00\0b\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\0c\00\00\00\00\00\00\00\00\00\00\00\0c\00\00\00\00\0c\00\00\00\00\t\0c\00\00\00\00\00\0c\00\00\0c\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\0e\00\00\00\00\00\00\00\00\00\00\00\0d\00\00\00\04\0d\00\00\00\00\t\0e\00\00\00\00\00\0e\00\00\0e\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\10\00\00\00\00\00\00\00\00\00\00\00\0f\00\00\00\00\0f\00\00\00\00\t\10\00\00\00\00\00\10\00\00\10\00\00\12\00\00\00\12\12\12\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\12\00\00\00\12\12\12\00\00\00\00\00\00\t\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\0b\00\00\00\00\00\00\00\00\00\00\00\n\00\00\00\00\n\00\00\00\00\t\0b\00\00\00\00\00\0b\00\00\0b\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\0c\00\00\00\00\00\00\00\00\00\00\00\0c\00\00\00\00\0c\00\00\00\00\t\0c\00\00\00\00\00\0c\00\00\0c\00\000123456789ABCDEF-0X+0X 0X-0x+0x 0x\00inf\00INF\00nan\00NAN\00.\00")
+ (data (i32.const 5232) "\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00")
+ (data (i32.const 6860) "\05\00\00\00\00\00\00\00\00\00\00\00\02\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\03\00\00\00\04\00\00\00\88\14\00\00\00\04\00\00\00\00\00\00\00\00\00\00\01\00\00\00\00\00\00\00\00\00\00\00\00\00\00\n\ff\ff\ff\ff\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\cc\1a\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\b0\18\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00\00")
+ (global $global$0 (mut i32) (i32.const 16384))
+ (global $global$1 i32 (i32.const 5250112))
+ (global $global$2 i32 (i32.const 7232))
+ (export "__heap_base" (global $global$1))
+ (export "__data_end" (global $global$2))
+ (export "stackSave" (func $stackSave))
+ (export "stackAlloc" (func $stackAlloc))
+ (export "stackRestore" (func $stackRestore))
+ (export "__growWasmMemory" (func $__growWasmMemory))
+ (func $stackSave (; 0 ;) (result i32)
+  (global.get $global$0)
+ )
+ (func $stackAlloc (; 1 ;) (param $0 i32) (result i32)
+  (local $1 i32)
+  (global.set $global$0
+   (local.tee $1
+    (i32.and
+     (i32.sub
+      (global.get $global$0)
+      (local.get $0)
+     )
+     (i32.const -16)
+    )
+   )
+  )
+  (local.get $1)
+ )
+ (func $stackRestore (; 2 ;) (param $0 i32)
+  (global.set $global$0
+   (local.get $0)
+  )
+ )
+ (func $__growWasmMemory (; 3 ;) (param $newSize i32) (result i32)
+  (grow_memory
+   (local.get $newSize)
+  )
+ )
+)
+(;
+--BEGIN METADATA --
+{
+  "emJsFuncs": {
+    "noarg": "(void)<::>{ out(\"no args works\"); }"
+  },
+  "staticBump": 6664,
+  "tableSize": 0,
+  "declares": [
+  ],
+  "externs": [
+  ],
+  "implementedFunctions": [
+    "_stackSave",
+    "_stackAlloc",
+    "_stackRestore",
+    "___growWasmMemory"
+  ],
+  "exports": [
+    "__heap_base",
+    "__data_end",
+    "stackSave",
+    "stackAlloc",
+    "stackRestore",
+    "__growWasmMemory"
+  ],
+  "invokeFuncs": [
+  ]
+}
+-- END METADATA --
+;)