Add a --standalone-wasm flag to wasm-emscripten-finalize (#2333)

The flag indicates that we want to run the wasm by itself, without JS support. In that case we don't emit JS dynCalls etc., and we also emit a wasi _start if there is a main, i.e., we try to use the current conventions in the wasm-only space.

10 files changed, 367 insertions, 1 deletions

diff --git a/scripts/test/lld.py b/scripts/test/lld.py
index 4aafd9549..7372698cd 100755
--- a/scripts/test/lld.py
+++ b/scripts/test/lld.py
@@ -26,6 +26,8 @@ def args_for_finalize(filename):
         return ['--check-stack-overflow', '--global-base=568']
     elif 'shared' in filename:
         return ['--side-module']
+    elif 'standalone-wasm' in filename:
+        return ['--standalone-wasm', '--global-base=568']
     else:
         return ['--global-base=568']
 
diff --git a/src/tools/wasm-emscripten-finalize.cpp b/src/tools/wasm-emscripten-finalize.cpp
index ea69cabbc..8a246e5d2 100644
--- a/src/tools/wasm-emscripten-finalize.cpp
+++ b/src/tools/wasm-emscripten-finalize.cpp
@@ -50,6 +50,8 @@ int main(int argc, const char* argv[]) {
   bool legalizeJavaScriptFFI = true;
   bool checkStackOverflow = false;
   uint64_t globalBase = INVALID_BASE;
+  bool standaloneWasm = false;
+
   ToolOptions options("wasm-emscripten-finalize",
                       "Performs Emscripten-specific transforms on .wasm files");
   options
@@ -135,6 +137,14 @@ int main(int argc, const char* argv[]) {
          [&checkStackOverflow](Options* o, const std::string&) {
            checkStackOverflow = true;
          })
+    .add("--standalone-wasm",
+         "",
+         "Emit a wasm file that does not depend on JS, as much as possible,"
+         " using wasi and other standard conventions etc. where possible",
+         Options::Arguments::Zero,
+         [&standaloneWasm](Options* o, const std::string&) {
+           standaloneWasm = true;
+         })
     .add_positional("INFILE",
                     Options::Arguments::One,
                     [&infile](Options* o, const std::string& argument) {
@@ -233,7 +243,13 @@ int main(int argc, const char* argv[]) {
     }
   }
 
-  generator.generateDynCallThunks();
+  if (standaloneWasm) {
+    // Export a standard wasi "_start" method.
+    generator.exportWasiStart();
+  } else {
+    // If not standalone wasm then JS is relevant and we need dynCalls.
+    generator.generateDynCallThunks();
+  }
 
   // Legalize the wasm.
   {
diff --git a/src/wasm-emscripten.h b/src/wasm-emscripten.h
index 1758aa23a..9dc82bc1a 100644
--- a/src/wasm-emscripten.h
+++ b/src/wasm-emscripten.h
@@ -56,6 +56,8 @@ public:
 
   void enforceStackLimit();
 
+  void exportWasiStart();
+
   // Emits the data segments to a file. The file contains data from address base
   // onwards (we must pass in base, as we can't tell it from the wasm - the
   // first segment may start after a run of zeros, but we need those zeros in
diff --git a/src/wasm/wasm-emscripten.cpp b/src/wasm/wasm-emscripten.cpp
index 978afa296..3aa6f5647 100644
--- a/src/wasm/wasm-emscripten.cpp
+++ b/src/wasm/wasm-emscripten.cpp
@@ -22,6 +22,7 @@
 #include "asmjs/shared-constants.h"
 #include "ir/function-type-utils.h"
 #include "ir/import-utils.h"
+#include "ir/literal-utils.h"
 #include "ir/module-utils.h"
 #include "shared-constants.h"
 #include "wasm-builder.h"
@@ -1210,4 +1211,22 @@ void EmscriptenGlueGenerator::separateDataSegments(Output* outfile,
   wasm.memory.segments.clear();
 }
 
+void EmscriptenGlueGenerator::exportWasiStart() {
+  // If main exists, export a function to call it per the wasi standard.
+  Name main = "main";
+  if (!wasm.getFunctionOrNull(main)) {
+    return;
+  }
+  Name _start = "_start";
+  Builder builder(wasm);
+  auto* body = builder.makeDrop(builder.makeCall(
+    main,
+    {LiteralUtils::makeZero(i32, wasm), LiteralUtils::makeZero(i32, wasm)},
+    i32));
+  auto* func =
+    builder.makeFunction(_start, std::vector<wasm::Type>{}, none, {}, body);
+  wasm.addFunction(func);
+  wasm.addExport(builder.makeExport(_start, _start, ExternalKind::Function));
+}
+
 } // namespace wasm
diff --git a/test/lld/standalone-wasm.wast b/test/lld/standalone-wasm.wast
new file mode 100644
index 000000000..2ccbf3f29
--- /dev/null
+++ b/test/lld/standalone-wasm.wast
@@ -0,0 +1,20 @@
+(module
+ (memory $0 2)
+ (table $0 1 1 funcref)
+ (elem (i32.const 0) $foo)
+ (global $global$0 (mut i32) (i32.const 66112))
+ (global $global$1 i32 (i32.const 66112))
+ (global $global$2 i32 (i32.const 576))
+ (export "memory" (memory $0))
+ (export "main" (func $main))
+ (export "__heap_base" (global $global$1))
+ (export "__data_end" (global $global$2))
+ (func $__original_main (result i32)
+  (nop)
+ )
+ (func $main (param $0 i32) (param $1 i32) (result i32)
+  (call $__original_main)
+ )
+ (func $foo (result i32))
+)
+
diff --git a/test/lld/standalone-wasm.wast.out b/test/lld/standalone-wasm.wast.out
new file mode 100644
index 000000000..5e9fa4c91
--- /dev/null
+++ b/test/lld/standalone-wasm.wast.out
@@ -0,0 +1,101 @@
+(module
+ (type $FUNCSIG$i (func (result i32)))
+ (type $FUNCSIG$iii (func (param i32 i32) (result i32)))
+ (memory $0 2)
+ (table $0 1 1 funcref)
+ (elem (i32.const 0) $foo)
+ (global $global$0 (mut i32) (i32.const 66112))
+ (global $global$1 i32 (i32.const 66112))
+ (global $global$2 i32 (i32.const 576))
+ (export "memory" (memory $0))
+ (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))
+ (export "_start" (func $_start))
+ (func $__original_main (; 0 ;) (type $FUNCSIG$i) (result i32)
+  (nop)
+ )
+ (func $main (; 1 ;) (type $FUNCSIG$iii) (param $0 i32) (param $1 i32) (result i32)
+  (call $__original_main)
+ )
+ (func $foo (; 2 ;) (type $FUNCSIG$i) (result i32)
+  (nop)
+ )
+ (func $stackSave (; 3 ;) (result i32)
+  (global.get $global$0)
+ )
+ (func $stackAlloc (; 4 ;) (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 (; 5 ;) (param $0 i32)
+  (global.set $global$0
+   (local.get $0)
+  )
+ )
+ (func $__growWasmMemory (; 6 ;) (param $newSize i32) (result i32)
+  (memory.grow
+   (local.get $newSize)
+  )
+ )
+ (func $_start (; 7 ;)
+  (drop
+   (call $main
+    (i32.const 0)
+    (i32.const 0)
+   )
+  )
+ )
+)
+(;
+--BEGIN METADATA --
+{
+  "staticBump": 8,
+  "tableSize": 1,
+  "declares": [
+  ],
+  "externs": [
+  ],
+  "implementedFunctions": [
+    "_main",
+    "_stackSave",
+    "_stackAlloc",
+    "_stackRestore",
+    "___growWasmMemory",
+    "__start"
+  ],
+  "exports": [
+    "main",
+    "stackSave",
+    "stackAlloc",
+    "stackRestore",
+    "__growWasmMemory",
+    "_start"
+  ],
+  "namedGlobals": {
+    "__heap_base" : "66112",
+    "__data_end" : "576"
+  },
+  "invokeFuncs": [
+  ],
+  "features": [
+  ],
+  "mainReadsParams": 0
+}
+-- END METADATA --
+;)
diff --git a/test/lld/standalone-wasm2.wast b/test/lld/standalone-wasm2.wast
new file mode 100644
index 000000000..f4c7843b6
--- /dev/null
+++ b/test/lld/standalone-wasm2.wast
@@ -0,0 +1,17 @@
+(module
+ (memory $0 2)
+ (global $global$0 (mut i32) (i32.const 66112))
+ (global $global$1 i32 (i32.const 66112))
+ (global $global$2 i32 (i32.const 576))
+ (export "memory" (memory $0))
+ (export "main" (func $main))
+ (export "__heap_base" (global $global$1))
+ (export "__data_end" (global $global$2))
+ (func $__original_main (param $0 i32) (param $1 i32) (result i32)
+  (nop)
+ )
+ (func $main (param $0 i32) (param $1 i32) (result i32)
+  (call $__original_main (local.get $0) (local.get $1))
+ )
+)
+
diff --git a/test/lld/standalone-wasm2.wast.out b/test/lld/standalone-wasm2.wast.out
new file mode 100644
index 000000000..fe669b414
--- /dev/null
+++ b/test/lld/standalone-wasm2.wast.out
@@ -0,0 +1,98 @@
+(module
+ (type $FUNCSIG$iii (func (param i32 i32) (result i32)))
+ (memory $0 2)
+ (global $global$0 (mut i32) (i32.const 66112))
+ (global $global$1 i32 (i32.const 66112))
+ (global $global$2 i32 (i32.const 576))
+ (export "memory" (memory $0))
+ (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))
+ (export "_start" (func $_start))
+ (func $__original_main (; 0 ;) (type $FUNCSIG$iii) (param $0 i32) (param $1 i32) (result i32)
+  (nop)
+ )
+ (func $main (; 1 ;) (type $FUNCSIG$iii) (param $0 i32) (param $1 i32) (result i32)
+  (call $__original_main
+   (local.get $0)
+   (local.get $1)
+  )
+ )
+ (func $stackSave (; 2 ;) (result i32)
+  (global.get $global$0)
+ )
+ (func $stackAlloc (; 3 ;) (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 (; 4 ;) (param $0 i32)
+  (global.set $global$0
+   (local.get $0)
+  )
+ )
+ (func $__growWasmMemory (; 5 ;) (param $newSize i32) (result i32)
+  (memory.grow
+   (local.get $newSize)
+  )
+ )
+ (func $_start (; 6 ;)
+  (drop
+   (call $main
+    (i32.const 0)
+    (i32.const 0)
+   )
+  )
+ )
+)
+(;
+--BEGIN METADATA --
+{
+  "staticBump": 8,
+  "tableSize": 0,
+  "declares": [
+  ],
+  "externs": [
+  ],
+  "implementedFunctions": [
+    "_main",
+    "_stackSave",
+    "_stackAlloc",
+    "_stackRestore",
+    "___growWasmMemory",
+    "__start"
+  ],
+  "exports": [
+    "main",
+    "stackSave",
+    "stackAlloc",
+    "stackRestore",
+    "__growWasmMemory",
+    "_start"
+  ],
+  "namedGlobals": {
+    "__heap_base" : "66112",
+    "__data_end" : "576"
+  },
+  "invokeFuncs": [
+  ],
+  "features": [
+  ],
+  "mainReadsParams": 1
+}
+-- END METADATA --
+;)
diff --git a/test/lld/standalone-wasm3.wast b/test/lld/standalone-wasm3.wast
new file mode 100644
index 000000000..45c0bed35
--- /dev/null
+++ b/test/lld/standalone-wasm3.wast
@@ -0,0 +1,13 @@
+(module
+ (memory $0 2)
+ (global $global$0 (mut i32) (i32.const 66112))
+ (global $global$1 i32 (i32.const 66112))
+ (global $global$2 i32 (i32.const 576))
+ (export "memory" (memory $0))
+ (export "__heap_base" (global $global$1))
+ (export "__data_end" (global $global$2))
+ (func $__original_main (param $0 i32) (param $1 i32) (result i32)
+  (nop)
+ )
+)
+
diff --git a/test/lld/standalone-wasm3.wast.out b/test/lld/standalone-wasm3.wast.out
new file mode 100644
index 000000000..a334d96e4
--- /dev/null
+++ b/test/lld/standalone-wasm3.wast.out
@@ -0,0 +1,78 @@
+(module
+ (type $FUNCSIG$iii (func (param i32 i32) (result i32)))
+ (memory $0 2)
+ (global $global$0 (mut i32) (i32.const 66112))
+ (global $global$1 i32 (i32.const 66112))
+ (global $global$2 i32 (i32.const 576))
+ (export "memory" (memory $0))
+ (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 $__original_main (; 0 ;) (type $FUNCSIG$iii) (param $0 i32) (param $1 i32) (result i32)
+  (nop)
+ )
+ (func $stackSave (; 1 ;) (result i32)
+  (global.get $global$0)
+ )
+ (func $stackAlloc (; 2 ;) (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 (; 3 ;) (param $0 i32)
+  (global.set $global$0
+   (local.get $0)
+  )
+ )
+ (func $__growWasmMemory (; 4 ;) (param $newSize i32) (result i32)
+  (memory.grow
+   (local.get $newSize)
+  )
+ )
+)
+(;
+--BEGIN METADATA --
+{
+  "staticBump": 8,
+  "tableSize": 0,
+  "declares": [
+  ],
+  "externs": [
+  ],
+  "implementedFunctions": [
+    "_stackSave",
+    "_stackAlloc",
+    "_stackRestore",
+    "___growWasmMemory"
+  ],
+  "exports": [
+    "stackSave",
+    "stackAlloc",
+    "stackRestore",
+    "__growWasmMemory"
+  ],
+  "namedGlobals": {
+    "__heap_base" : "66112",
+    "__data_end" : "576"
+  },
+  "invokeFuncs": [
+  ],
+  "features": [
+  ],
+  "mainReadsParams": 0
+}
+-- END METADATA --
+;)