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Minor cleanups to csqrt*(), mostly in comments.

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Remove the STDC CX_LIMITED_RANGE pragma and its verbose comment.  We still
don't have any C99 compilers (that support fenv pragmas), and if we did
then there are thousands of other places in libm that would need to use
them more than here.

The other cleanups are smaller.
This commit is contained in:
Bruce Evans 2018-07-17 12:01:59 +00:00
parent 90c8e44125
commit 1693fd03d9
3 changed files with 14 additions and 36 deletions
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11
lib/msun/src/s_csqrt.c
View File

@ -35,16 +35,7 @@ __FBSDID("$FreeBSD$");
#include "math_private.h"
/*
* gcc doesn't implement complex multiplication or division correctly,
* so we need to handle infinities specially. We turn on this pragma to
* notify conforming c99 compilers that the fast-but-incorrect code that
* gcc generates is acceptable, since the special cases have already been
* handled.
*/
#pragma STDC CX_LIMITED_RANGE ON
/* We risk spurious overflow for components >= DBL_MAX / (1 + sqrt(2)). */
/* For avoiding overflow for components >= DBL_MAX / (1 + sqrt(2)). */
#define THRESH 0x1.a827999fcef32p+1022
double complex

18
lib/msun/src/s_csqrtf.c
View File

@ -34,20 +34,14 @@ __FBSDID("$FreeBSD$");
#include "math_private.h"
/*
* gcc doesn't implement complex multiplication or division correctly,
* so we need to handle infinities specially. We turn on this pragma to
* notify conforming c99 compilers that the fast-but-incorrect code that
* gcc generates is acceptable, since the special cases have already been
* handled.
*/
#pragma STDC CX_LIMITED_RANGE ON
float complex
csqrtf(float complex z)
{
float a = crealf(z), b = cimagf(z);
double t;
float a, b;
a = creal(z);
b = cimag(z);
/* Handle special cases. */
if (z == 0)
@ -82,9 +76,9 @@ csqrtf(float complex z)
*/
if (a >= 0) {
t = sqrt((a + hypot(a, b)) * 0.5);
return (CMPLXF(t, b / (2.0 * t)));
return (CMPLXF(t, b / (2 * t)));
} else {
t = sqrt((-a + hypot(a, b)) * 0.5);
return (CMPLXF(fabsf(b) / (2.0 * t), copysignf(t, b)));
return (CMPLXF(fabsf(b) / (2 * t), copysignf(t, b)));
}
}

21
lib/msun/src/s_csqrtl.c
View File

@ -36,25 +36,18 @@ __FBSDID("$FreeBSD$");
#include "math_private.h"
/*
* gcc doesn't implement complex multiplication or division correctly,
* so we need to handle infinities specially. We turn on this pragma to
* notify conforming c99 compilers that the fast-but-incorrect code that
* gcc generates is acceptable, since the special cases have already been
* handled.
*/
#pragma STDC CX_LIMITED_RANGE ON
/*
* We risk spurious overflow for components >= LDBL_MAX / (1 + sqrt(2)).
* Rather than determining the fully precise value at which we might
* overflow, just use a threshold of approximately LDBL_MAX / 4.
* THRESH is now calculated portably (up to 113-bit precision). However,
* the denormal threshold is hard-coded for a 15-bit exponent with the usual
* bias. s_logl.c and e_hypotl have less hard-coding but end up requiring
* the same for the exponent and more for the mantissa.
*/
#if LDBL_MAX_EXP != 0x4000
#error "Unsupported long double format"
#else
#define THRESH 0x1p16382L
#endif
/* For avoiding overflow for components >= LDBL_MAX / (1 + sqrt(2)). */
#define THRESH (LDBL_MAX / 2.414213562373095048801688724209698L)
long double complex
csqrtl(long double complex z)
{