diff mbox series

math: Fix float conversion regressions with gcc-12 [BZ #28713]

Message ID 20211231132455.2916708-1-szabolcs.nagy@arm.com
State New
Headers show
Series math: Fix float conversion regressions with gcc-12 [BZ #28713] | expand

Commit Message

Szabolcs Nagy Dec. 31, 2021, 1:24 p.m. UTC 
Converting double precision constants to float is now affected by the
runtime dynamic rounding mode instead of being evaluated at compile
time with default rounding mode (except static object initializers).

This can change the computed result and cause performance regression.
The known correctness issues (increased ulp errors) are already fixed,
this patch fixes remaining cases of unnecessary runtime conversions.

Add float M_* macros to math.h as new GNU extension API.  To avoid
conversions the new M_* macros are used and instead of casting double
literals to float, use float literals (only required if the conversion
is inexact).

The patch was tested on aarch64 where the following symbols had new
spurious conversion instructions that got fixed:

  __clog10f
  __gammaf_r_finite@GLIBC_2.17
  __j0f_finite@GLIBC_2.17
  __j1f_finite@GLIBC_2.17
  __jnf_finite@GLIBC_2.17
  __kernel_casinhf
  __lgamma_negf
  __log1pf
  __y0f_finite@GLIBC_2.17
  __y1f_finite@GLIBC_2.17
  cacosf
  cacoshf
  casinhf
  catanf
  catanhf
  clogf
  gammaf_positive

Fixes bug 28713.
---
 manual/math.texi                         |  7 ++++---
 math/k_casinh_template.c                 |  2 +-
 math/math.h                              | 17 +++++++++++++++++
 math/s_cacos_template.c                  |  2 +-
 math/s_catan_template.c                  |  2 +-
 math/s_catanh_template.c                 |  2 +-
 math/s_clog10_template.c                 |  8 ++++----
 math/s_clog_template.c                   |  4 ++--
 sysdeps/generic/math-type-macros-float.h |  5 ++---
 sysdeps/ieee754/flt-32/e_gammaf_r.c      | 12 ++++++------
 sysdeps/ieee754/flt-32/e_j0f.c           |  4 ++--
 sysdeps/ieee754/flt-32/e_j1f.c           |  4 ++--
 sysdeps/ieee754/flt-32/e_jnf.c           |  2 +-
 sysdeps/ieee754/flt-32/lgamma_negf.c     |  8 ++++----
 sysdeps/ieee754/flt-32/s_log1pf.c        |  2 +-
 15 files changed, 49 insertions(+), 32 deletions(-)

Comments

Joseph Myers Dec. 31, 2021, 5:48 p.m. UTC | #1 
On Fri, 31 Dec 2021, Szabolcs Nagy via Libc-alpha wrote:

> Add float M_* macros to math.h as new GNU extension API.  To avoid
> conversions the new M_* macros are used and instead of casting double
> literals to float, use float literals (only required if the conversion
> is inexact).

As a new user-visible feature, I think the new macros should get a NEWS 
entry.
Paul Zimmermann Jan. 1, 2022, 6:45 a.m. UTC | #2 
Dear Szabolcs,

+# define M_PI_2f	1.57079632679489661923f	/* pi/2 */

-      __real__ res = (FLOAT) M_MLIT (M_PI_2) - __real__ y;
+      __real__ res = M_MLIT (M_PI_2) - __real__ y;

I wonder why your patch never uses M_PI_2f. Should it be M_PI_2f above?

Best regards,
Paul
Szabolcs Nagy Jan. 2, 2022, 1:27 p.m. UTC | #3 
The 01/01/2022 07:45, Paul Zimmermann wrote:
>        Dear Szabolcs,
> 
> +# define M_PI_2f	1.57079632679489661923f	/* pi/2 */
> 
> -      __real__ res = (FLOAT) M_MLIT (M_PI_2) - __real__ y;
> +      __real__ res = M_MLIT (M_PI_2) - __real__ y;
> 
> I wonder why your patch never uses M_PI_2f. Should it be M_PI_2f above?

this is template code under math/ and M_MLIT (M_PI_2) should
expand to M_PI_2f when it is used for the float variant.

see the change in
sysdeps/generic/math-type-macros-float.h
Paul Zimmermann Jan. 3, 2022, 10:24 a.m. UTC | #4 
Dear Szabolcs,

> > +# define M_PI_2f	1.57079632679489661923f	/* pi/2 */
> > 
> > -      __real__ res = (FLOAT) M_MLIT (M_PI_2) - __real__ y;
> > +      __real__ res = M_MLIT (M_PI_2) - __real__ y;
> > 
> > I wonder why your patch never uses M_PI_2f. Should it be M_PI_2f above?
> 
> this is template code under math/ and M_MLIT (M_PI_2) should
> expand to M_PI_2f when it is used for the float variant.
> 
> see the change in
> sysdeps/generic/math-type-macros-float.h

ok.

While looking at that patch, in math/math.h, I thought new constants should
be declared as hexadecimal values?

+# define M_Ef		2.7182818284590452354f	/* e */

Otherwise this patch seems good to me.

Paul
Szabolcs Nagy Jan. 4, 2022, 8:52 a.m. UTC | #5 
The 01/03/2022 11:24, Paul Zimmermann wrote:
>        Dear Szabolcs,
> 
> > > +# define M_PI_2f	1.57079632679489661923f	/* pi/2 */
> > > 
> > > -      __real__ res = (FLOAT) M_MLIT (M_PI_2) - __real__ y;
> > > +      __real__ res = M_MLIT (M_PI_2) - __real__ y;
> > > 
> > > I wonder why your patch never uses M_PI_2f. Should it be M_PI_2f above?
> > 
> > this is template code under math/ and M_MLIT (M_PI_2) should
> > expand to M_PI_2f when it is used for the float variant.
> > 
> > see the change in
> > sysdeps/generic/math-type-macros-float.h
> 
> ok.
> 
> While looking at that patch, in math/math.h, I thought new constants should
> be declared as hexadecimal values?
> 
> +# define M_Ef		2.7182818284590452354f	/* e */
> 
> Otherwise this patch seems good to me.

this is a public header, i think decimal consts
are used because hexadecimal is >=c99 only and
not c++ compatible (at least before c++17).
Paul Zimmermann Jan. 4, 2022, 9:52 a.m. UTC | #6 
Dear Szabolcs,

> > While looking at that patch, in math/math.h, I thought new constants should
> > be declared as hexadecimal values?
> > 
> > +# define M_Ef		2.7182818284590452354f	/* e */
> > 
> > Otherwise this patch seems good to me.
> 
> this is a public header, i think decimal consts
> are used because hexadecimal is >=c99 only and
> not c++ compatible (at least before c++17).

ok, this looks good to me, all test still pass with gcc 12 (on x86_64 linux),
except elf/tst-env-setuid, but I believe this is unrelated.

Reviewed-by: Paul Zimmermann <Paul.Zimmermann@inria.fr>

Thanks!
Paul
diff mbox series

Patch

diff --git a/manual/math.texi b/manual/math.texi
index 376306cfc5..e00871c303 100644
--- a/manual/math.texi
+++ b/manual/math.texi
@@ -131,9 +131,10 @@  defined.  The default set of features includes these constants.
 @xref{Feature Test Macros}.
 
 All values are of type @code{double}.  As an extension, @theglibc{}
-also defines these constants with type @code{long double}.  The
-@code{long double} macros have a lowercase @samp{l} appended to their
-names: @code{M_El}, @code{M_PIl}, and so forth.  These are only
+also defines these constants with type @code{long double} and
+@code{float}.  The @code{long double} macros have a lowercase @samp{l}
+while the @code{float} macros have a lowercase @samp{f} appended to
+their names: @code{M_El}, @code{M_PIl}, and so forth.  These are only
 available if @code{_GNU_SOURCE} is defined.
 
 Likewise, @theglibc{} also defines these constants with the types
diff --git a/math/k_casinh_template.c b/math/k_casinh_template.c
index d6ea6556b9..7bb575924b 100644
--- a/math/k_casinh_template.c
+++ b/math/k_casinh_template.c
@@ -56,7 +56,7 @@  M_DECL_FUNC (__kernel_casinh) (CFLOAT x, int adj)
 	}
 
       res = M_SUF (__clog) (y);
-      __real__ res += (FLOAT) M_MLIT (M_LN2);
+      __real__ res += M_MLIT (M_LN2);
     }
   else if (rx >= M_LIT (0.5) && ix < M_EPSILON / 8)
     {
diff --git a/math/math.h b/math/math.h
index 404d24dae6..47f737b9bc 100644
--- a/math/math.h
+++ b/math/math.h
@@ -1158,6 +1158,23 @@  iszero (__T __val)
 # define M_SQRT1_2	0.70710678118654752440	/* 1/sqrt(2) */
 #endif
 
+/* GNU extension to provide float constants with similar names.  */
+#ifdef __USE_GNU
+# define M_Ef		2.7182818284590452354f	/* e */
+# define M_LOG2Ef	1.4426950408889634074f	/* log_2 e */
+# define M_LOG10Ef	0.43429448190325182765f	/* log_10 e */
+# define M_LN2f		0.69314718055994530942f	/* log_e 2 */
+# define M_LN10f	2.30258509299404568402f	/* log_e 10 */
+# define M_PIf		3.14159265358979323846f	/* pi */
+# define M_PI_2f	1.57079632679489661923f	/* pi/2 */
+# define M_PI_4f	0.78539816339744830962f	/* pi/4 */
+# define M_1_PIf	0.31830988618379067154f	/* 1/pi */
+# define M_2_PIf	0.63661977236758134308f	/* 2/pi */
+# define M_2_SQRTPIf	1.12837916709551257390f	/* 2/sqrt(pi) */
+# define M_SQRT2f	1.41421356237309504880f	/* sqrt(2) */
+# define M_SQRT1_2f	0.70710678118654752440f	/* 1/sqrt(2) */
+#endif
+
 /* The above constants are not adequate for computation using `long double's.
    Therefore we provide as an extension constants with similar names as a
    GNU extension.  Provide enough digits for the 128-bit IEEE quad.  */
diff --git a/math/s_cacos_template.c b/math/s_cacos_template.c
index 8c014ecf29..e0d6654c46 100644
--- a/math/s_cacos_template.c
+++ b/math/s_cacos_template.c
@@ -32,7 +32,7 @@  M_DECL_FUNC (__cacos) (CFLOAT x)
     {
       y = M_SUF (__casin) (x);
 
-      __real__ res = (FLOAT) M_MLIT (M_PI_2) - __real__ y;
+      __real__ res = M_MLIT (M_PI_2) - __real__ y;
       if (__real__ res == 0)
 	__real__ res = 0;
       __imag__ res = -__imag__ y;
diff --git a/math/s_catan_template.c b/math/s_catan_template.c
index b9f8277511..b5307b3c51 100644
--- a/math/s_catan_template.c
+++ b/math/s_catan_template.c
@@ -106,7 +106,7 @@  M_DECL_FUNC (__catan) (CFLOAT x)
 	  if (M_FABS (__imag__ x) == 1
 	      && M_FABS (__real__ x) < M_EPSILON * M_EPSILON)
 	    __imag__ res = (M_COPYSIGN (M_LIT (0.5), __imag__ x)
-			    * ((FLOAT) M_MLIT (M_LN2)
+			    * (M_MLIT (M_LN2)
 			       - M_LOG (M_FABS (__real__ x))));
 	  else
 	    {
diff --git a/math/s_catanh_template.c b/math/s_catanh_template.c
index 63c14731ba..2327e48ca9 100644
--- a/math/s_catanh_template.c
+++ b/math/s_catanh_template.c
@@ -75,7 +75,7 @@  M_DECL_FUNC (__catanh) (CFLOAT x)
 	  if (M_FABS (__real__ x) == 1
 	      && M_FABS (__imag__ x) < M_EPSILON * M_EPSILON)
 	    __real__ res = (M_COPYSIGN (M_LIT (0.5), __real__ x)
-			    * ((FLOAT) M_MLIT (M_LN2)
+			    * (M_MLIT (M_LN2)
 			       - M_LOG (M_FABS (__imag__ x))));
 	  else
 	    {
diff --git a/math/s_clog10_template.c b/math/s_clog10_template.c
index 77b714a6c0..0c72db0b2e 100644
--- a/math/s_clog10_template.c
+++ b/math/s_clog10_template.c
@@ -72,7 +72,7 @@  M_DECL_FUNC (__clog10) (CFLOAT x)
       if (absx == 1 && scale == 0)
 	{
 	  __real__ result = (M_LOG1P (absy * absy)
-			     * ((FLOAT) M_MLIT (M_LOG10E) / 2));
+			     * (M_MLIT (M_LOG10E) / 2));
 	  math_check_force_underflow_nonneg (__real__ result);
 	}
       else if (absx > 1 && absx < 2 && absy < 1 && scale == 0)
@@ -80,7 +80,7 @@  M_DECL_FUNC (__clog10) (CFLOAT x)
 	  FLOAT d2m1 = (absx - 1) * (absx + 1);
 	  if (absy >= M_EPSILON)
 	    d2m1 += absy * absy;
-	  __real__ result = M_LOG1P (d2m1) * ((FLOAT) M_MLIT (M_LOG10E) / 2);
+	  __real__ result = M_LOG1P (d2m1) * (M_MLIT (M_LOG10E) / 2);
 	}
       else if (absx < 1
 	       && absx >= M_LIT (0.5)
@@ -88,7 +88,7 @@  M_DECL_FUNC (__clog10) (CFLOAT x)
 	       && scale == 0)
 	{
 	  FLOAT d2m1 = (absx - 1) * (absx + 1);
-	  __real__ result = M_LOG1P (d2m1) * ((FLOAT) M_MLIT (M_LOG10E) / 2);
+	  __real__ result = M_LOG1P (d2m1) * (M_MLIT (M_LOG10E) / 2);
 	}
       else if (absx < 1
 	       && absx >= M_LIT (0.5)
@@ -96,7 +96,7 @@  M_DECL_FUNC (__clog10) (CFLOAT x)
 	       && absx * absx + absy * absy >= M_LIT (0.5))
 	{
 	  FLOAT d2m1 = M_SUF (__x2y2m1) (absx, absy);
-	  __real__ result = M_LOG1P (d2m1) * ((FLOAT) M_MLIT (M_LOG10E) / 2);
+	  __real__ result = M_LOG1P (d2m1) * (M_MLIT (M_LOG10E) / 2);
 	}
       else
 	{
diff --git a/math/s_clog_template.c b/math/s_clog_template.c
index 0f6360cdc8..72414a812b 100644
--- a/math/s_clog_template.c
+++ b/math/s_clog_template.c
@@ -32,7 +32,7 @@  M_DECL_FUNC (__clog) (CFLOAT x)
   if (__glibc_unlikely (rcls == FP_ZERO && icls == FP_ZERO))
     {
       /* Real and imaginary part are 0.0.  */
-      __imag__ result = signbit (__real__ x) ? (FLOAT) M_MLIT (M_PI) : 0;
+      __imag__ result = signbit (__real__ x) ? M_MLIT (M_PI) : 0;
       __imag__ result = M_COPYSIGN (__imag__ result, __imag__ x);
       /* Yes, the following line raises an exception.  */
       __real__ result = -1 / M_FABS (__real__ x);
@@ -94,7 +94,7 @@  M_DECL_FUNC (__clog) (CFLOAT x)
       else
 	{
 	  FLOAT d = M_HYPOT (absx, absy);
-	  __real__ result = M_LOG (d) - scale * (FLOAT) M_MLIT (M_LN2);
+	  __real__ result = M_LOG (d) - scale * M_MLIT (M_LN2);
 	}
 
       __imag__ result = M_ATAN2 (__imag__ x, __real__ x);
diff --git a/sysdeps/generic/math-type-macros-float.h b/sysdeps/generic/math-type-macros-float.h
index 5ba7615500..cf7ba5d6a3 100644
--- a/sysdeps/generic/math-type-macros-float.h
+++ b/sysdeps/generic/math-type-macros-float.h
@@ -27,9 +27,8 @@ 
 #define M_STRTO_NAN __strtof_nan
 #define M_USE_BUILTIN(c) USE_ ##c ##F_BUILTIN
 
-/* Standard/GNU macro literals do not exist for the float type.  Use
-   the double macro constants.  */
-#define M_MLIT(c) c
+/* GNU extension float constant macros.  */
+#define M_MLIT(c) c ## f
 
 #include <libm-alias-float.h>
 #include <math-nan-payload-float.h>
diff --git a/sysdeps/ieee754/flt-32/e_gammaf_r.c b/sysdeps/ieee754/flt-32/e_gammaf_r.c
index 974ed67c96..3fcfc581b3 100644
--- a/sysdeps/ieee754/flt-32/e_gammaf_r.c
+++ b/sysdeps/ieee754/flt-32/e_gammaf_r.c
@@ -85,7 +85,7 @@  gammaf_positive (float x, int *exp2_adj)
       float x_adj_frac = x_adj - x_adj_int;
       int x_adj_log2;
       float x_adj_mant = __frexpf (x_adj, &x_adj_log2);
-      if (x_adj_mant < (float) M_SQRT1_2)
+      if (x_adj_mant < M_SQRT1_2f)
 	{
 	  x_adj_log2--;
 	  x_adj_mant *= 2.0f;
@@ -94,7 +94,7 @@  gammaf_positive (float x, int *exp2_adj)
       float ret = (__ieee754_powf (x_adj_mant, x_adj)
 		   * __ieee754_exp2f (x_adj_log2 * x_adj_frac)
 		   * __ieee754_expf (-x_adj)
-		   * sqrtf (2 * (float) M_PI / x_adj)
+		   * sqrtf (2 * M_PIf / x_adj)
 		   / prod);
       exp_adj += x_eps * __ieee754_logf (x_adj);
       float bsum = gamma_coeff[NCOEFF - 1];
@@ -176,11 +176,11 @@  __ieee754_gammaf_r (float x, int *signgamp)
 	      if (frac > 0.5f)
 		frac = 1.0f - frac;
 	      float sinpix = (frac <= 0.25f
-			      ? __sinf ((float) M_PI * frac)
-			      : __cosf ((float) M_PI * (0.5f - frac)));
+			      ? __sinf (M_PIf * frac)
+			      : __cosf (M_PIf * (0.5f - frac)));
 	      int exp2_adj;
-	      float tret = (float) M_PI / (-x * sinpix
-					   * gammaf_positive (-x, &exp2_adj));
+	      float tret = M_PIf / (-x * sinpix
+				    * gammaf_positive (-x, &exp2_adj));
 	      ret = __scalbnf (tret, -exp2_adj);
 	      math_check_force_underflow_nonneg (ret);
 	    }
diff --git a/sysdeps/ieee754/flt-32/e_j0f.c b/sysdeps/ieee754/flt-32/e_j0f.c
index 0453a30109..9ae91a9dcc 100644
--- a/sysdeps/ieee754/flt-32/e_j0f.c
+++ b/sysdeps/ieee754/flt-32/e_j0f.c
@@ -233,7 +233,7 @@  j0f_near_root (float x, float z)
   float index_f;
   int index;
 
-  index_f = roundf ((x - FIRST_ZERO_J0) / (float) M_PI);
+  index_f = roundf ((x - FIRST_ZERO_J0) / M_PIf);
   /* j0f_asympt fails to give an error <= 9 ulps for x=0x1.324e92p+7
      (index 48) thus we can't reduce SMALL_SIZE below 49.  */
   if (index_f >= SMALL_SIZE)
@@ -514,7 +514,7 @@  y0f_near_root (float x, float z)
   float index_f;
   int index;
 
-  index_f = roundf ((x - FIRST_ZERO_Y0) / (float) M_PI);
+  index_f = roundf ((x - FIRST_ZERO_Y0) / M_PIf);
   if (index_f >= SMALL_SIZE)
     return y0f_asympt (x);
   index = (int) index_f;
diff --git a/sysdeps/ieee754/flt-32/e_j1f.c b/sysdeps/ieee754/flt-32/e_j1f.c
index 052c661db9..ade10402fd 100644
--- a/sysdeps/ieee754/flt-32/e_j1f.c
+++ b/sysdeps/ieee754/flt-32/e_j1f.c
@@ -243,7 +243,7 @@  j1f_near_root (float x, float z)
       x = -x;
       sign = -1.0f;
     }
-  index_f = roundf ((x - FIRST_ZERO_J1) / (float) M_PI);
+  index_f = roundf ((x - FIRST_ZERO_J1) / M_PIf);
   if (index_f >= SMALL_SIZE)
     return sign * j1f_asympt (x);
   index = (int) index_f;
@@ -525,7 +525,7 @@  y1f_near_root (float x, float z)
   float index_f;
   int index;
 
-  index_f = roundf ((x - FIRST_ZERO_Y1) / (float) M_PI);
+  index_f = roundf ((x - FIRST_ZERO_Y1) / M_PIf);
   if (index_f >= SMALL_SIZE)
     return y1f_asympt (x);
   index = (int) index_f;
diff --git a/sysdeps/ieee754/flt-32/e_jnf.c b/sysdeps/ieee754/flt-32/e_jnf.c
index 80b684dd97..ff0a9d7c63 100644
--- a/sysdeps/ieee754/flt-32/e_jnf.c
+++ b/sysdeps/ieee754/flt-32/e_jnf.c
@@ -134,7 +134,7 @@  __ieee754_jnf(int n, float x)
 		tmp = n;
 		v = two/x;
 		tmp = tmp*__ieee754_logf(fabsf(v*tmp));
-		if(tmp<(float)8.8721679688e+01) {
+		if(tmp<8.8721679688e+01f) {
 		    for(i=n-1,di=(float)(i+i);i>0;i--){
 			temp = b;
 			b *= di;
diff --git a/sysdeps/ieee754/flt-32/lgamma_negf.c b/sysdeps/ieee754/flt-32/lgamma_negf.c
index ba6ada8f7e..d1128cc91c 100644
--- a/sysdeps/ieee754/flt-32/lgamma_negf.c
+++ b/sysdeps/ieee754/flt-32/lgamma_negf.c
@@ -165,9 +165,9 @@  static float
 lg_sinpi (float x)
 {
   if (x <= 0.25f)
-    return __sinf ((float) M_PI * x);
+    return __sinf (M_PIf * x);
   else
-    return __cosf ((float) M_PI * (0.5f - x));
+    return __cosf (M_PIf * (0.5f - x));
 }
 
 /* Compute cos (pi * X) for -0.25 <= X <= 0.5.  */
@@ -176,9 +176,9 @@  static float
 lg_cospi (float x)
 {
   if (x <= 0.25f)
-    return __cosf ((float) M_PI * x);
+    return __cosf (M_PIf * x);
   else
-    return __sinf ((float) M_PI * (0.5f - x));
+    return __sinf (M_PIf * (0.5f - x));
 }
 
 /* Compute cot (pi * X) for -0.25 <= X <= 0.5.  */
diff --git a/sysdeps/ieee754/flt-32/s_log1pf.c b/sysdeps/ieee754/flt-32/s_log1pf.c
index 6630f5a78e..555f0f82c8 100644
--- a/sysdeps/ieee754/flt-32/s_log1pf.c
+++ b/sysdeps/ieee754/flt-32/s_log1pf.c
@@ -92,7 +92,7 @@  __log1pf(float x)
 		if(k==0) return zero;
 		else {c += k*ln2_lo; return k*ln2_hi+c;}
 	    }
-	    R = hfsq*((float)1.0-(float)0.66666666666666666*f);
+	    R = hfsq*(1.0f-0.66666666666666666f*f);
 	    if(k==0) return f-R; else
 		     return k*ln2_hi-((R-(k*ln2_lo+c))-f);
 	}