Fix splitI64 so it can be used to send values from JS libraries into wasm (#19575)

When a JS library calls into wasm and the function has an i64 argument, we must
legalize into two 32-bit integers if we lack BigInt support.

Note that we may be able to do more efficient things than splitI64 (assuming
the input uses only 53 bits, and is signed, can help simplify things a lot), but we
leave that for optimization later.

This removes the old/unused sendI64Argument.

Author: kripken

src/parseTools.js

@@ -213,6 +213,12 @@ function makeInlineCalculation(expression, value, tempVar) {
 // value, represented by a low and high i32 pair.
 // Will suffer from rounding and truncation.
 function splitI64(value) {
+  if (WASM_BIGINT) {
+    // Nothing to do: just make sure it is a BigInt (as it must be of that
+    // type, to be sent into wasm).
+    return `BigInt(${value})`;
+  }
+
   // general idea:
   //
   //  $1$0 = ~~$d >>> 0;
@@ -229,7 +235,6 @@ function splitI64(value) {
   // For negatives, we need to ensure a -1 if the value is overall negative,
   // even if not significant negative component
 
-  assert(!WASM_BIGINT, 'splitI64 should not be used when WASM_BIGINT is enabled');
   const low = value + '>>>0';
   const high = makeInlineCalculation(
       asmCoercion('Math.abs(VALUE)', 'double') + ' >= ' + asmEnsureFloat('1', 'double') + ' ? ' +
@@ -886,15 +891,10 @@ function receiveI64ParamAsI53(name, onError) {
 }
 
 function receiveI64ParamAsI53Unchecked(name) {
-  if (WASM_BIGINT) return `${name} = Number(${name});`;
-  return `var ${name} = convertI32PairToI53(${name}_low, ${name}_high);`;
-}
-
-function sendI64Argument(low, high) {
   if (WASM_BIGINT) {
-    return 'BigInt(low) | (BigInt(high) << 32n)';
+    return `${name} = Number(${name});`;
   }
-  return low + ', ' + high;
+  return `var ${name} = convertI32PairToI53(${name}_low, ${name}_high);`;
 }
 
 // Any function called from wasm64 may have bigint args, this function takes

test/core/js_library_i64_params.c

@@ -1,4 +1,5 @@
 #include <assert.h>
+#include <emscripten.h>
 #include <stdio.h>
 
 #define MAX_SAFE_INTEGER (1ll<<53)
@@ -8,6 +9,11 @@
 
 int64_t jscall(int64_t arg);
 
+EMSCRIPTEN_KEEPALIVE
+void called_from_js(uint64_t arg) {
+  printf("called_from_js with: %lld\n", arg);
+}
+
 void check_ok(int64_t val) {
   printf("checking: %lld\n", val);
   int64_t rtn = jscall(val);
@@ -25,7 +31,11 @@ void check_invalid(int64_t val) {
 }
 
 int main() {
+  check_ok(0);
+  check_ok(1);
+  check_ok(-1);
   check_ok(42);
+  check_ok(-42);
   check_ok(MAX_SAFE_INTEGER/2);
   check_ok(MIN_SAFE_INTEGER/2);
   check_ok(MAX_SAFE_INTEGER);

test/core/js_library_i64_params.js

@@ -4,6 +4,9 @@ TestLibrary = {
   jscall: function({{{ defineI64Param('foo') }}}) {
     {{{ receiveI64ParamAsI53('foo', `(err('overflow'), ${makeReturn64('42')})`) }}}
     err('js:got:       ' + foo);
+
+    _called_from_js({{{ splitI64("foo") }}});
+
     if (foo < 0)
       var rtn = Math.ceil(foo / 2);
     else

test/core/js_library_i64_params.out

@@ -1,25 +1,54 @@
+checking: 0
+js:got:       0
+called_from_js with: 0
+js:returning: 0
+got:      0
+expected: 0
+checking: 1
+js:got:       1
+called_from_js with: 1
+js:returning: 0
+got:      0
+expected: 0
+checking: -1
+js:got:       -1
+called_from_js with: -1
+js:returning: 0
+got:      0
+expected: 0
 checking: 42
 js:got:       42
+called_from_js with: 42
 js:returning: 21
 got:      21
 expected: 21
+checking: -42
+js:got:       -42
+called_from_js with: -42
+js:returning: -21
+got:      -21
+expected: -21
 checking: 4503599627370496
 js:got:       4503599627370496
+called_from_js with: 4503599627370496
 js:returning: 2251799813685248
 got:      2251799813685248
 expected: 2251799813685248
 checking: -4503599627370496
 js:got:       -4503599627370496
+called_from_js with: -4503599627370496
 js:returning: -2251799813685248
 got:      -2251799813685248
 expected: -2251799813685248
 checking: 9007199254740992
 js:got:       9007199254740992
+called_from_js with: 9007199254740992
 js:returning: 4503599627370496
 got:      4503599627370496
 expected: 4503599627370496
 checking: -9007199254740992
 js:got:       -9007199254740992
+called_from_js with: -9007199254740992
 js:returning: -4503599627370496
 got:      -4503599627370496
 expected: -4503599627370496