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runtime: rename float64 constants to avoid name space pollution

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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>
This commit is contained in:
Russ Cox 2015-01-16 14:33:27 -05:00
parent e12b1ddc99
commit 7ef59e4ed8
1 changed files with 12 additions and 12 deletions
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24
src/runtime/sqrt.go
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@ -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)
}