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Re: [PATCH][libm] Replace global constants with preprocessor defines

From: Andreas Jaeger <aj at suse dot com>
To: Siddhesh Poyarekar <siddhesh at redhat dot com>
Cc: libc-alpha at sourceware dot org
Date: Thu, 27 Dec 2012 10:01:38 +0100
Subject: Re: [PATCH][libm] Replace global constants with preprocessor defines
References: <20121226074532.GB10003@spoyarek.pnq.redhat.com>

On 12/26/2012 08:45 AM, Siddhesh Poyarekar wrote:

Hi,

A lot of constants (including 1.0 and 0.0) are encoded as `struct
number`.  This adds an extra dereference in the code and hence makes
it slower.  Attached patch replaces these with preprocessor defines.
I have only touched the multiprecision stuff for now and also only the
more straightforward ones to make reviewing easier.  I intend to clean
out all such variables during 2.18 development.  I have verified that
these changes do not break the testsuite on x86_64.

OK for 2.18?

Siddhesh

	* sysdeps/ieee754/dbl-64/mpa.c (norm): Define R as RADIXI.
	(norm): Likewise.
	* sysdeps/ieee754/dbl-64/mpa2.h: Remove all static const
	variables with preprocessor constants.
	* sysdeps/ieee754/dbl-64/mpatan.h: Likewise.
	* sysdeps/ieee754/dbl-64/mpexp.h: Likewise.
	* sysdeps/ieee754/dbl-64/mpsqrt.h: Likewise.


diff --git a/sysdeps/ieee754/dbl-64/mpa.c b/sysdeps/ieee754/dbl-64/mpa.c
index f17e0d3..1c93bdc 100644
--- a/sysdeps/ieee754/dbl-64/mpa.c
+++ b/sysdeps/ieee754/dbl-64/mpa.c
@@ -140,7 +140,7 @@ static void __cpymn(const mp_no *x, int m, mp_no *y, int n) {
  /* number *y, normalized case  (|x| >= 2**(-1022))) */
  static void norm(const mp_no *x, double *y, int p)
  {
-  #define R  radixi.d
+  #define R  RADIXI
    int i;
  #if 0
    int k;
@@ -200,7 +200,7 @@ static void denorm(const mp_no *x, double *y, int p)
    double a,v;
  #endif

-#define R  radixi.d
+#define R  RADIXI
    if (EX<-44 || (EX==-44 && X[1]<TWO5))
       { *y=ZERO; return; }

diff --git a/sysdeps/ieee754/dbl-64/mpa2.h b/sysdeps/ieee754/dbl-64/mpa2.h
index cfe22b8..1dd44ef 100644
--- a/sysdeps/ieee754/dbl-64/mpa2.h
+++ b/sysdeps/ieee754/dbl-64/mpa2.h
@@ -30,65 +30,21 @@
  #ifndef MPA2_H
  #define MPA2_H

-
-#ifdef BIG_ENDI
-static const number
-/**/ radix          = {{0x41700000, 0x00000000} }, /* 2**24  */
-/**/ radixi         = {{0x3e700000, 0x00000000} }, /* 2**-24 */
-/**/ cutter         = {{0x44b00000, 0x00000000} }, /* 2**76  */
-/**/ zero           = {{0x00000000, 0x00000000} }, /*  0     */
-/**/ one            = {{0x3ff00000, 0x00000000} }, /*  1     */
-/**/ mone           = {{0xbff00000, 0x00000000} }, /* -1     */
-/**/ two            = {{0x40000000, 0x00000000} }, /*  2     */
-/**/ two5           = {{0x40400000, 0x00000000} }, /* 2**5   */
-/**/ two10          = {{0x40900000, 0x00000000} }, /* 2**10  */
-/**/ two18          = {{0x41100000, 0x00000000} }, /* 2**18  */
-/**/ two19          = {{0x41200000, 0x00000000} }, /* 2**19  */
-/**/ two23          = {{0x41600000, 0x00000000} }, /* 2**23  */
-/**/ two52          = {{0x43300000, 0x00000000} }, /* 2**52  */
-/**/ two57          = {{0x43800000, 0x00000000} }, /* 2**57  */
-/**/ two71          = {{0x44600000, 0x00000000} }, /* 2**71  */
-/**/ twom1032       = {{0x00000400, 0x00000000} }; /* 2**-1032 */
-
-#else
-#ifdef LITTLE_ENDI
-static const number
-/**/ radix          = {{0x00000000, 0x41700000} }, /* 2**24  */
-/**/ radixi         = {{0x00000000, 0x3e700000} }, /* 2**-24 */
-/**/ cutter         = {{0x00000000, 0x44b00000} }, /* 2**76  */
-/**/ zero           = {{0x00000000, 0x00000000} }, /*  0     */
-/**/ one            = {{0x00000000, 0x3ff00000} }, /*  1     */
-/**/ mone           = {{0x00000000, 0xbff00000} }, /* -1     */
-/**/ two            = {{0x00000000, 0x40000000} }, /*  2     */
-/**/ two5           = {{0x00000000, 0x40400000} }, /* 2**5   */
-/**/ two10          = {{0x00000000, 0x40900000} }, /* 2**10  */
-/**/ two18          = {{0x00000000, 0x41100000} }, /* 2**18  */
-/**/ two19          = {{0x00000000, 0x41200000} }, /* 2**19  */
-/**/ two23          = {{0x00000000, 0x41600000} }, /* 2**23  */
-/**/ two52          = {{0x00000000, 0x43300000} }, /* 2**52  */
-/**/ two57          = {{0x00000000, 0x43800000} }, /* 2**57  */
-/**/ two71          = {{0x00000000, 0x44600000} }, /* 2**71  */
-/**/ twom1032       = {{0x00000000, 0x00000400} }; /* 2**-1032 */
-
-#endif
-#endif
-
-#define  RADIX     radix.d
-#define  RADIXI    radixi.d
-#define  CUTTER    cutter.d
-#define  ZERO      zero.d
-#define  ONE       one.d
-#define  MONE      mone.d
-#define  TWO       two.d
-#define  TWO5      two5.d
-#define  TWO10     two10.d
-#define  TWO18     two18.d
-#define  TWO19     two19.d
-#define  TWO23     two23.d
-#define  TWO52     two52.d
-#define  TWO57     two57.d
-#define  TWO71     two71.d
-#define  TWOM1032  twom1032.d
-
+#define  RADIX     0x1.0p24
+#define  RADIXI    0x1.0p-24
+#define  CUTTER    0x1.0p76
+#define  ZERO      0.0
+#define  ONE       1.0
+#define  MONE      -1.0
+#define  TWO       -2.0
+#define  TWO5      0x1.0p5
+#define  TWO10     0x1.0p10
+#define  TWO18     0x1.0p18
+#define  TWO19     0x1.0p19
+#define  TWO23     0x1.0p23
+#define  TWO52     0x1.0p52
+#define  TWO57     0x1.0p57
+#define  TWO71     0x1.0p71
+#define  TWOM1032  0x1.0p-1032

  #endif
diff --git a/sysdeps/ieee754/dbl-64/mpatan.h b/sysdeps/ieee754/dbl-64/mpatan.h
index c56b9b5..f920cc2 100644
--- a/sysdeps/ieee754/dbl-64/mpatan.h
+++ b/sysdeps/ieee754/dbl-64/mpatan.h
@@ -30,8 +30,6 @@
  extern const number __atan_xm[8] attribute_hidden;
  extern const number __atan_twonm1[33] attribute_hidden;
  extern const number __atan_twom[8] attribute_hidden;
-extern const number __atan_one attribute_hidden;
-extern const number __atan_two attribute_hidden;
  extern const int __atan_np[33] attribute_hidden;


@@ -97,10 +95,6 @@ extern const int __atan_np[33] attribute_hidden;
  /**/                  {{0x40600000, 0x00000000} }, /* 128.0  */
  		    };

-  const number
-/**/ __atan_one     = {{0x3ff00000, 0x00000000} }, /* 1      */
-/**/ __atan_two     = {{0x40000000, 0x00000000} }; /* 2      */
-
  #else
  #ifdef LITTLE_ENDI

@@ -164,10 +158,6 @@ __atan_twonm1[33] = {                             /* 2n-1   */
  /**/                  {{0x00000000, 0x40600000} }, /* 128.0  */
  		    };

-  const number
-/**/ __atan_one    = {{0x00000000, 0x3ff00000} }, /* 1      */
-/**/ __atan_two    = {{0x00000000, 0x40000000} }; /* 2      */
-
  #endif
  #endif

@@ -178,5 +168,5 @@ __atan_twonm1[33] = {                             /* 2n-1   */
  #endif
  #endif

-#define  ONE       __atan_one.d
-#define  TWO       __atan_two.d
+#define  ONE       1.0
+#define  TWO       2.0
diff --git a/sysdeps/ieee754/dbl-64/mpexp.h b/sysdeps/ieee754/dbl-64/mpexp.h
index 758255b..efa629d 100644
--- a/sysdeps/ieee754/dbl-64/mpexp.h
+++ b/sysdeps/ieee754/dbl-64/mpexp.h
@@ -28,13 +28,6 @@
  #define MPEXP_H

  extern const number __mpexp_twomm1[33] attribute_hidden;
-extern const number __mpexp_radix attribute_hidden;
-extern const number __mpexp_radixi attribute_hidden;
-extern const number __mpexp_zero attribute_hidden;
-extern const number __mpexp_one attribute_hidden;
-extern const number __mpexp_two attribute_hidden;
-extern const number __mpexp_half attribute_hidden;
-

  #ifndef AVOID_MPEXP_H
  #ifdef BIG_ENDI
@@ -75,14 +68,6 @@ extern const number __mpexp_half attribute_hidden;
  /**/                  {{0x3ae00000, 0x00000000} }, /* 2**-81 */
    };

-  const number
-/**/ __mpexp_radix    = {{0x41700000, 0x00000000} }, /* 2**24  */
-/**/ __mpexp_radixi   = {{0x3e700000, 0x00000000} }, /* 2**-24 */
-/**/ __mpexp_zero     = {{0x00000000, 0x00000000} }, /* 0      */
-/**/ __mpexp_one      = {{0x3ff00000, 0x00000000} }, /* 1      */
-/**/ __mpexp_two      = {{0x40000000, 0x00000000} }, /* 2      */
-/**/ __mpexp_half     = {{0x3fe00000, 0x00000000} }; /* 1/2    */
-
  #else
  #ifdef LITTLE_ENDI
    const number
@@ -121,23 +106,16 @@ extern const number __mpexp_half attribute_hidden;
  /**/                  {{0x00000000, 0x3b100000} }, /* 2**-78 */
  /**/                  {{0x00000000, 0x3ae00000} }, /* 2**-81 */
    };
-  const number
-/**/ __mpexp_radix    = {{0x00000000, 0x41700000} }, /* 2**24  */
-/**/ __mpexp_radixi   = {{0x00000000, 0x3e700000} }, /* 2**-24 */
-/**/ __mpexp_zero     = {{0x00000000, 0x00000000} }, /* 0      */
-/**/ __mpexp_one      = {{0x00000000, 0x3ff00000} }, /* 1      */
-/**/ __mpexp_two      = {{0x00000000, 0x40000000} }, /* 2      */
-/**/ __mpexp_half     = {{0x00000000, 0x3fe00000} }; /* 1/2    */

  #endif
  #endif
  #endif

-#define  RADIX     __mpexp_radix.d
-#define  RADIXI    __mpexp_radixi.d
-#define  ZERO      __mpexp_zero.d
-#define  ONE       __mpexp_one.d
-#define  TWO       __mpexp_two.d
-#define  HALF      __mpexp_half.d
+#define  RADIX     0x1.0p24
+#define  RADIXI    0x1.0p-24
+#define  ZERO      0.0
+#define  ONE       1.0
+#define  TWO       2.0
+#define  HALF      0x1.0p-1

Previously these had some comments (but were in hex, so this was really needed). For some of them it is obvious but I suggest to stay with the comments.

Let's say explictily "1/2" for HALF and 2^24 for RADIX etc.

Similar above for TWO5 etc. Either add a comment before that the following are TWOX with 2^X or add it for each comment...

Andreas
--
 Andreas Jaeger aj@{suse.com,opensuse.org} Twitter/Identica: jaegerandi
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Follow-Ups:
- Re: [PATCH][libm] Replace global constants with preprocessor defines
  - From: Siddhesh Poyarekar

References:
- [PATCH][libm] Replace global constants with preprocessor defines
  - From: Siddhesh Poyarekar

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