svn commit: r336412 - head/lib/msun/src

[Bruce Evans]

Author: bde
Date: Tue Jul 17 12:01:59 2018
New Revision: 336412
URL: https://svnweb.freebsd.org/changeset/base/336412

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

Modified:
  head/lib/msun/src/s_csqrt.c
  head/lib/msun/src/s_csqrtf.c
  head/lib/msun/src/s_csqrtl.c

Modified: head/lib/msun/src/s_csqrt.c
==============================================================================
--- head/lib/msun/src/s_csqrt.c	Tue Jul 17 11:53:37 2018	(r336411)
+++ head/lib/msun/src/s_csqrt.c	Tue Jul 17 12:01:59 2018	(r336412)
@@ -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

Modified: head/lib/msun/src/s_csqrtf.c
==============================================================================
--- head/lib/msun/src/s_csqrtf.c	Tue Jul 17 11:53:37 2018	(r336411)
+++ head/lib/msun/src/s_csqrtf.c	Tue Jul 17 12:01:59 2018	(r336412)
@@ -34,21 +34,15 @@ __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)
 		return (CMPLXF(0, b));
@@ -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)));
 	}
 }

Modified: head/lib/msun/src/s_csqrtl.c
==============================================================================
--- head/lib/msun/src/s_csqrtl.c	Tue Jul 17 11:53:37 2018	(r336411)
+++ head/lib/msun/src/s_csqrtl.c	Tue Jul 17 12:01:59 2018	(r336412)
@@ -36,24 +36,17 @@ __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.
+ * 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.
  */
-#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.
- */
 #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)