Re: [PATCH] Speed up libm on MIPS

[Steve Ellcey <sellcey@mips.com>]

On Thu, 2013-09-19 at 23:32 -0400, Carlos O'Donell wrote:

> > +
> > +  /* Set rounding bits.  */
> > +  cw &= ~0x3;
> 
> What's the magic ~0x3? Should it be a new macro?

0x3 is a mask to access the two bits in the FPU control register that
define the rounding mode.  It probably should be a macro and it seems
like it should go into fpu_control.h where it could be used by the
'real' fegetround and fesetround as well these new routines.  What do
you think of this patch as a precursor to my original patch so that I
can change all the code to use _FPU_RC_MASK instead of 0x3?

Steve Ellcey
sellcey@mips.com



2013-09-19  Steve Ellcey  <sellcey@mips.com>

	* sysdeps/mips/fpu_control.h (_FPU_RC_MASK): New.
	* sysdeps/mips/fpu/fegetround.c (fegetround): Use _FPU_RC_MASK.
	* sysdeps/mips/fpu/fesetround.c (fesetround): Use _FPU_RC_MASK.



diff --git a/ports/sysdeps/mips/fpu/fegetround.c b/ports/sysdeps/mips/fpu/fegetround.c
index 61217a7..17cd3e9 100644
--- a/ports/sysdeps/mips/fpu/fegetround.c
+++ b/ports/sysdeps/mips/fpu/fegetround.c
@@ -28,5 +28,5 @@ fegetround (void)
   /* Get control word.  */
   _FPU_GETCW (cw);
 
-  return cw & 0x3;
+  return cw & _FPU_RC_MASK;
 }
diff --git a/ports/sysdeps/mips/fpu/fesetround.c b/ports/sysdeps/mips/fpu/fesetround.c
index 7c25f43..c6fdd66 100644
--- a/ports/sysdeps/mips/fpu/fesetround.c
+++ b/ports/sysdeps/mips/fpu/fesetround.c
@@ -25,7 +25,7 @@ fesetround (int round)
 {
   fpu_control_t cw;
 
-  if ((round & ~0x3) != 0)
+  if ((round & ~_FPU_RC_MASK) != 0)
     /* ROUND is no valid rounding mode.  */
     return 1;
 
@@ -33,7 +33,7 @@ fesetround (int round)
   _FPU_GETCW (cw);
 
   /* Set rounding bits.  */
-  cw &= ~0x3;
+  cw &= ~_FPU_RC_MASK;
   cw |= round;
   /* Set new state.  */
   _FPU_SETCW (cw);
diff --git a/ports/sysdeps/mips/fpu_control.h b/ports/sysdeps/mips/fpu_control.h
index 4046962..f26b736 100644
--- a/ports/sysdeps/mips/fpu_control.h
+++ b/ports/sysdeps/mips/fpu_control.h
@@ -90,6 +90,8 @@ extern fpu_control_t __fpu_control;
 #define _FPU_RC_ZERO    0x1
 #define _FPU_RC_UP      0x2
 #define _FPU_RC_DOWN    0x3
+/* mask for rounding control */
+#define _FPU_RC_MASK    0x3
 
 #define _FPU_RESERVED 0xfe840000  /* Reserved bits in cw, incl NAN2008.  */