util: use faster -0 check

mscdex · MylesBorins · commit 58c68c2fcb37 · 2017-10-11T02:05:41.000-04:00
PR-URL: #15726 Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: Benedikt Meurer <benedikt.meurer@gmail.com> Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
diff --git a/benchmark/util/inspect.js b/benchmark/util/inspect.js
@@ -22,7 +22,8 @@ const bench = common.createBenchmark(main, {
     'Error',
     'Array',
     'TypedArray',
-    'TypedArray_extra'
+    'TypedArray_extra',
+    'Number'
   ],
   option: Object.keys(opts)
 });
@@ -92,6 +93,9 @@ function main({ method, n, option }) {
       obj[Symbol('baz')] = 5;
       benchmark(n, obj, options);
       break;
+    case 'Number':
+      benchmark(n, 0, options);
+      break;
     default:
       throw new Error(`Unsupported method "${method}"`);
   }
diff --git a/lib/util.js b/lib/util.js
@@ -614,8 +614,10 @@ function formatValue(ctx, value, recurseTimes, ln) {
 }
 
 function formatNumber(fn, value) {
-  // Format -0 as '-0'. Strict equality won't distinguish 0 from -0.
-  if (Object.is(value, -0))
+  // Format -0 as '-0'. A `value === -0` check won't distinguish 0 from -0.
+  // Using a division check is currently faster than `Object.is(value, -0)`
+  // as of V8 6.1.
+  if (1 / value === -Infinity)
     return fn('-0', 'number');
   return fn(`${value}`, 'number');
 }

Original file line number	Diff line number	Diff line change
`@@ -614,8 +614,10 @@ function formatValue(ctx, value, recurseTimes, ln) {`
`614`	`614`	`}`
`615`	`615`
`616`	`616`	`function formatNumber(fn, value) {`
`617`		`- // Format -0 as '-0'. Strict equality won't distinguish 0 from -0.`
`618`		`- if (Object.is(value, -0))`
	`617`	+ // Format -0 as '-0'. A `value === -0` check won't distinguish 0 from -0.
	`618`	+ // Using a division check is currently faster than `Object.is(value, -0)`
	`619`	`+ // as of V8 6.1.`
	`620`	`+ if (1 / value === -Infinity)`
`619`	`621`	`return fn('-0', 'number');`
`620`	`622`	return fn(`${value}`, 'number');
`621`	`623`	`}`