Runtime: simplify logic converting between floats and bits

Author: hhugo

compiler/lib/reserved.ml

@@ -144,6 +144,7 @@ let provided =
     ; "require" (* only available in node *)
     ; "Symbol"
     ; "ArrayBuffer"
+    ; "DataView"
     ; "Float32Array"
     ; "Float64Array"
     ; "Int16Array"

compiler/tests-jsoo/test_marshal.ml

@@ -157,8 +157,9 @@ let%expect_test "test float" =
   Printf.printf "%f" (Marshal.from_string r1 0);
   [%expect
     {|
-      "\132\149\166\190\000\000\000\t\000\000\000\000\000\000\000\003\000\000\000\002\012\031\133\235Q\184\030\t@"
-      3.140000 |}];
+    "\132\149\166\190\000\000\000\t\000\000\000\000\000\000\000\003\000\000\000\002\012\031\133\235Q\184\030\t@"
+    3.140000
+    |}];
   let r2 = Marshal.to_string obj [] in
   Printf.printf "%S\n" r2;
   let a, b, c, d =
@@ -170,7 +171,8 @@ let%expect_test "test float" =
   [%expect
     {|
     "\132\149\166\190\000\000\000\017\000\000\000\004\000\000\000\012\000\000\000\011\160\160\012\031\133\235Q\184\030\t@\004\001\160\004\003@"
-    3.140000 3.140000 3.140000 3.140000 |}]
+    3.140000 3.140000 3.140000 3.140000
+    |}]
 
 let%expect_test "test input with offset" =
   let s = 3.14 in

compiler/tests-ocaml/lib-hashtbl/hfun_js.expected

@@ -12,9 +12,9 @@
 -0.0		07be548a
 +infty		23ea56fb
 -infty		059f7872
-NaN		3228858d
-NaN#2		3228858d
-NaN#3		3228858d
+NaN		23498e72
+NaN#2		23498e72
+NaN#3		23498e72
 -- Native integers:
 0		07be548a
 -1		3653e015

runtime/js/ieee_754.js

@@ -17,74 +17,27 @@
 // along with this program; if not, write to the Free Software
 // Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 
-//Provides: jsoo_floor_log2
-var log2_ok = Math.log2 && Math.log2(1.1235582092889474e307) === 1020;
-function jsoo_floor_log2(x) {
-  if (log2_ok) return Math.floor(Math.log2(x));
-  var i = 0;
-  if (x === 0) return Number.NEGATIVE_INFINITY;
-  if (x >= 1) {
-    while (x >= 2) {
-      x /= 2;
-      i++;
-    }
-  } else {
-    while (x < 1) {
-      x *= 2;
-      i--;
-    }
-  }
-  return i;
-}
+//Provides: jsoo_dataview
+var jsoo_dataview = new DataView(new ArrayBuffer(8));
 
 //Provides: caml_int64_bits_of_float const
-//Requires: jsoo_floor_log2, caml_int64_create_lo_mi_hi
+//Requires: caml_int64_create_lo_mi_hi
+//Requires: jsoo_dataview
 function caml_int64_bits_of_float(x) {
-  if (!Number.isFinite(x)) {
-    if (Number.isNaN(x)) return caml_int64_create_lo_mi_hi(1, 0, 0x7ff0);
-    if (x > 0) return caml_int64_create_lo_mi_hi(0, 0, 0x7ff0);
-    else return caml_int64_create_lo_mi_hi(0, 0, 0xfff0);
-  }
-  var sign =
-    x === 0 && 1 / x === Number.NEGATIVE_INFINITY
-      ? 0x8000
-      : x >= 0
-        ? 0
-        : 0x8000;
-  if (sign) x = -x;
-  // Int64.bits_of_float 1.1235582092889474E+307 = 0x7fb0000000000000L
-  // using Math.LOG2E*Math.log(x) in place of Math.log2 result in precision lost
-  var exp = jsoo_floor_log2(x) + 1023;
-  if (exp <= 0) {
-    exp = 0;
-    x /= Math.pow(2, -1026);
-  } else {
-    x /= Math.pow(2, exp - 1027);
-    if (x < 16) {
-      x *= 2;
-      exp -= 1;
-    }
-    if (exp === 0) {
-      x /= 2;
-    }
-  }
-  var k = Math.pow(2, 24);
-  var r3 = x | 0;
-  x = (x - r3) * k;
-  var r2 = x | 0;
-  x = (x - r2) * k;
-  var r1 = x | 0;
-  r3 = (r3 & 0xf) | sign | (exp << 4);
+  jsoo_dataview.setFloat64(0, x, true);
+  var lo32 = jsoo_dataview.getUint32(0, true);
+  var hi32 = jsoo_dataview.getUint32(4, true);
+  var r1 = lo32 & 0xffffff;
+  var r2 = (lo32 >>> 24) | ((hi32 << 8) & 0xffffff);
+  var r3 = (hi32 >>> 16) & 0xffff;
   return caml_int64_create_lo_mi_hi(r1, r2, r3);
 }
 
 //Provides: caml_int32_bits_of_float const
-//Requires: jsoo_floor_log2
+//Requires: jsoo_dataview
 function caml_int32_bits_of_float(x) {
-  var float32a = new Float32Array(1);
-  float32a[0] = x;
-  var int32a = new Int32Array(float32a.buffer);
-  return int32a[0] | 0;
+  jsoo_dataview.setFloat32(0, x, true);
+  return jsoo_dataview.getUint32(0, true) | 0;
 }
 
 //FP literals can be written using the hexadecimal
@@ -150,24 +103,14 @@ function caml_hexstring_of_float(x, prec, style) {
 }
 
 //Provides: caml_int64_float_of_bits const
+//Requires: jsoo_dataview
 function caml_int64_float_of_bits(x) {
   var lo = x.lo;
   var mi = x.mi;
   var hi = x.hi;
-  var exp = (hi & 0x7fff) >> 4;
-  if (exp === 2047) {
-    if ((lo | mi | (hi & 0xf)) === 0)
-      return hi & 0x8000 ? Number.NEGATIVE_INFINITY : Number.POSITIVE_INFINITY;
-    else return Number.NaN;
-  }
-  var k = Math.pow(2, -24);
-  var res = (lo * k + mi) * k + (hi & 0xf);
-  if (exp > 0) {
-    res += 16;
-    res *= Math.pow(2, exp - 1027);
-  } else res *= Math.pow(2, -1026);
-  if (hi & 0x8000) res = -res;
-  return res;
+  jsoo_dataview.setUint32(0, lo | (mi << 24), true);
+  jsoo_dataview.setUint32(4, (mi >>> 8) | (hi << 16), true);
+  return jsoo_dataview.getFloat64(0, true);
 }
 
 //Provides: caml_nextafter_float const
@@ -192,11 +135,10 @@ function caml_trunc_float(x) {
 }
 
 //Provides: caml_int32_float_of_bits const
+//Requires: jsoo_dataview
 function caml_int32_float_of_bits(x) {
-  var int32a = new Int32Array(1);
-  int32a[0] = x;
-  var float32a = new Float32Array(int32a.buffer);
-  return float32a[0];
+  jsoo_dataview.setUint32(0, x, true);
+  return jsoo_dataview.getFloat32(0, true);
 }
 
 //Provides: caml_classify_float const
@@ -244,12 +186,11 @@ function caml_ldexp_float(x, exp) {
   return x;
 }
 //Provides: caml_frexp_float const
-//Requires: jsoo_floor_log2
 function caml_frexp_float(x) {
   if (x === 0 || !Number.isFinite(x)) return [0, x, 0];
   var neg = x < 0;
   if (neg) x = -x;
-  var exp = Math.max(-1023, jsoo_floor_log2(x) + 1);
+  var exp = Math.max(-1023, Math.floor(Math.log2(x)) + 1);
   x *= Math.pow(2, -exp);
   while (x < 0.5) {
     x *= 2;