[dart2wasm] Small improvements in FFI native tests:

- Document which target needs to be built for the test
  `web/wasm/ffi/ffi_native`.

- Add tests that passes and expects `double` and `float`s.
  (The `sqrt` native function was previous unused)

- Define inputs in `wasm_module` gn template so that the
  `ffi_native_test_wasm_module` target will rebuild the Wasm file when
  `tests/web/wasm/ffi/ffi_native_test_module.c` changes.

Change-Id: Iff642ff2cdee48a617e8f2cf4cca4053122a7e05
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/384263
Reviewed-by: Martin Kustermann <kustermann@google.com>
Commit-Queue: Ömer Ağacan <omersa@google.com>

tests/web/wasm/ffi/ffi_native_test.dart

@@ -5,6 +5,9 @@
 // dart2wasmOptions=--extra-compiler-option=--enable-experimental-ffi
 // SharedObjects=ffi_native_test_module
 
+// Build target `ffi_native_test_wasm_module` for the FFI module used in this
+// test.
+
 import 'dart:ffi';
 import 'dart:nativewrappers';
 
@@ -46,8 +49,11 @@ external bool boolReturn(int b);
 @Native<Void Function()>()
 external void toggleBool();
 
+@Native<Float Function(Float)>()
+external double sqrtFloat(double d);
+
 @Native<Double Function(Double)>()
-external double sqrt(double d);
+external double sqrtDouble(double d);
 
 @Native<Char Function(Char)>()
 external int incrementChar(int a);
@@ -173,6 +179,9 @@ void main() {
   Expect.equals(incrementUintPtr(25), 26);
   Expect.equals(incrementSize(27), 28);
   Expect.equals(incrementWchar(29), 30);
+
+  Expect.equals(sqrtDouble(1e300), 1e150);
+  Expect.equals(sqrtFloat(1e10), 1e5);
 }
 
 // Don't crash on an unused `Native.addressOf`.

tests/web/wasm/ffi/ffi_native_test_module.c

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #include <emscripten.h>
+#include <math.h>
 #include <stdbool.h>
 #include <stdint.h>
 #include <stdlib.h>
@@ -163,3 +164,13 @@ EMSCRIPTEN_KEEPALIVE
 wchar_t incrementWchar(wchar_t a) {
     return a + 1;
 }
+
+EMSCRIPTEN_KEEPALIVE
+double sqrtDouble(double d) {
+    return sqrt(d);
+}
+
+EMSCRIPTEN_KEEPALIVE
+float sqrtFloat(float d) {
+    return sqrtf(d);
+}

utils/dart2wasm/BUILD.gn

@@ -19,6 +19,7 @@ template("wasm_module") {
       rebase_path("$root_out_dir/wasm/${invoker.module_name}.wasm"),
       "-O",
     ]
+    inputs = [ "//tests/web/wasm/ffi/${invoker.module_name}.c" ]
     outputs = [ "$root_out_dir/wasm/${invoker.module_name}.wasm" ]
   }
 }