runtime: rename float64 constants to avoid name space pollution

Otherwise, if you mistakenly refer to an undeclared 'shift' variable, you get 52.

Change-Id: I845fb29f23baee1d8e17b37bde0239872eb54316
Reviewed-on: https://go-review.googlesource.com/2909
Reviewed-by: Austin Clements <austin@google.com>

diff --git a/src/runtime/sqrt.go b/src/runtime/sqrt.go
index e3a27014b5cf3fd224e11020cda8efd9a4395f13..d483f8a01f917f43adaed5e513c6818cef7bdc79 100644 (file)
--- a/src/runtime/sqrt.go
+++ b/src/runtime/sqrt.go
@@ -86,10 +86,10 @@ import "unsafe"
 // Notes:  Rounding mode detection omitted.
 
 const (
-       mask       = 0x7FF
-       shift      = 64 - 11 - 1
-       bias       = 1023
-       maxFloat64 = 1.797693134862315708145274237317043567981e+308 // 2**1023 * (2**53 - 1) / 2**52
+       float64Mask  = 0x7FF
+       float64Shift = 64 - 11 - 1
+       float64Bias  = 1023
+       maxFloat64   = 1.797693134862315708145274237317043567981e+308 // 2**1023 * (2**53 - 1) / 2**52
 )
 
 func float64bits(f float64) uint64     { return *(*uint64)(unsafe.Pointer(&f)) }
@@ -105,25 +105,25 @@ func sqrt(x float64) float64 {
        }
        ix := float64bits(x)
        // normalize x
-       exp := int((ix >> shift) & mask)
+       exp := int((ix >> float64Shift) & float64Mask)
        if exp == 0 { // subnormal x
-               for ix&1<<shift == 0 {
+               for ix&1<<float64Shift == 0 {
                        ix <<= 1
                        exp--
                }
                exp++
        }
-       exp -= bias // unbias exponent
-       ix &^= mask << shift
-       ix |= 1 << shift
+       exp -= float64Bias // unbias exponent
+       ix &^= float64Mask << float64Shift
+       ix |= 1 << float64Shift
        if exp&1 == 1 { // odd exp, double x to make it even
                ix <<= 1
        }
        exp >>= 1 // exp = exp/2, exponent of square root
        // generate sqrt(x) bit by bit
        ix <<= 1
-       var q, s uint64               // q = sqrt(x)
-       r := uint64(1 << (shift + 1)) // r = moving bit from MSB to LSB
+       var q, s uint64                      // q = sqrt(x)
+       r := uint64(1 << (float64Shift + 1)) // r = moving bit from MSB to LSB
        for r != 0 {
                t := s + r
                if t <= ix {
@@ -138,6 +138,6 @@ func sqrt(x float64) float64 {
        if ix != 0 { // remainder, result not exact
                q += q & 1 // round according to extra bit
        }
-       ix = q>>1 + uint64(exp-1+bias)<<shift // significand + biased exponent
+       ix = q>>1 + uint64(exp-1+float64Bias)<<float64Shift // significand + biased exponent
        return float64frombits(ix)
 }