Harmony: implement Math.clz32

src/harmony-math.js

Index: src/harmony-math.js
diff --git a/src/harmony-math.js b/src/harmony-math.js
index ee426ef1191f417b2178b17581c1a516704ecaab..7b5883f8e93138301f1b5547baa6ad81460546e9 100644
--- a/src/harmony-math.js
+++ b/src/harmony-math.js
@@ -154,6 +154,20 @@ function MathHypot(x, y) {  // Function length is 2.
 }
 
 
+function MathClz32(x) {

[Sven Panne, 2014/02/18 07:21:24]

What TC39 seems to intend is basically exposing some form of intrinsics for
processor intstructions. AFAICT "count leading zeroes" has HW support for all
our platforms and boils down to a single CPU instructions, and I think this is
the expectation of people using such intrinsics. Therefore we should add
Crankshaft support, which shouldn't be too hard.

+  x = ToUint32(TO_NUMBER_INLINE(x));
+  if (x == 0) return 32;
+  var result = 0;
+  // Binary search.
+  if ((x & 0xFFFF0000) === 0) { x <<= 16; result += 16; };
+  if ((x & 0xFF000000) === 0) { x <<=  8; result +=  8; };
+  if ((x & 0xF0000000) === 0) { x <<=  4; result +=  4; };
+  if ((x & 0xC0000000) === 0) { x <<=  2; result +=  2; };
+  if ((x & 0x80000000) === 0) { x <<=  1; result +=  1; };
+  return result;
+}
+
+
 function ExtendMath() {
   %CheckIsBootstrapping();
 
@@ -169,8 +183,10 @@ function ExtendMath() {
     "atanh", MathAtanh,
     "log10", MathLog10,
     "log2", MathLog2,
-    "hypot", MathHypot
+    "hypot", MathHypot,
+    "clz32", MathClz32
   ));
 }
 
+
 ExtendMath();