powerpc64le: ifunc select *f128 routines in multiarch mode

Programatically generate simple wrappers for interesting libm *f128
objects.  Selected functions are transcendental functions or
those with trivial compiler builtins.  This can result in a 2-3x
speedup (e.g logf128 and expf128).

A second set of implementation files are generated which include
the first implementation encountered along the search path.  This
usually works, except when a wrapper is overriden and makefile
search order slightly diverges from include order.  Likewise,
wrapper object files are created for each generated file.  These
hold the ifunc selection routines which export ABI.

Next, several shared headers are intercepted to control renaming of
asm function redirects are used first, and sometimes macro renames
if the former is impractical.

Notably, if the request machine supports hardware IEEE128 (i.e POWER9
and newer) this ifunc machinery is disabled.  Likewise existing
ifunc support for float128 is consolidated into this (e.g sqrtf128
and fmaf128).

Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>

1 files changed, 166 insertions, 0 deletions

diff --git a/sysdeps/powerpc/powerpc64/le/fpu/multiarch/float128-ifunc.h b/sysdeps/powerpc/powerpc64/le/fpu/multiarch/float128-ifunc.h
new file mode 100644
index 0000000000..73099e0341
--- /dev/null
+++ b/sysdeps/powerpc/powerpc64/le/fpu/multiarch/float128-ifunc.h
@@ -0,0 +1,166 @@
+/* _Float128 ifunc ABI/ifunc generation macros.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _FLOAT128_IFUNC_H
+#define _FLOAT128_IFUNC_H 1
+
+/* Disable hidden prototypes.  These perform function renames which
+   prevent the ifunc functions from working.  */
+#undef hidden_proto
+#define hidden_proto(x)
+#define NO_MATH_REDIRECT 1
+
+/* Include the real math.h to avoid optimizations caused by include/math.h
+   (e.x fabsf128 prototype is masked by an inline definition).*/
+#include <math/math.h>
+#include <math_private.h>
+#include <complex.h>
+#include <first-versions.h>
+#include <shlib-compat.h>
+#include "init-arch.h"
+
+#include <libm-alias-float128.h>
+#include <libm-alias-finite.h>
+
+/* _F128_IFUNC2(func, from, r)
+      Generate an ifunc symbol func ## r from the symbols
+	from ## {power8, power9} ## r
+
+      We use the PPC hwcap bit HAS_IEEE128 to select between the two with
+      the assumption all P9 features are available on such targets.  */
+#define _F128_IFUNC2(func, from, r) \
+	libc_ifunc (func ## r, (hwcap2 & PPC_FEATURE2_HAS_IEEE128) \
+                                ? from ## _power9 ## r : from ## _power8 ## r)
+
+/* _F128_IFUNC(func, r)
+      Similar to above, except the exported symbol name trivially remaps from
+      func ## {cpu} ## r to func ## r.  */
+#define _F128_IFUNC(func, r) _F128_IFUNC2(func, func, r)
+
+/* MAKE_IMPL_IFUNC2(func, pfx1, pfx2, r)
+     Declare external symbols of type pfx1 ## func ## f128 ## r with the name
+                                      pfx2 ## func ## f128 ## _{cpu} ## r
+     which are exported as implementation specific symbols (i.e backing support
+     for type classification macros).  */
+#define MAKE_IMPL_IFUNC2(func, pfx1, pfx2, r) \
+	extern __typeof (pfx1 ## func ## f128 ## r) pfx2 ## func ## f128_power8 ## r; \
+	extern __typeof (pfx1 ## func ## f128 ## r) pfx2 ## func ## f128_power9 ## r; \
+        _F128_IFUNC2 (__ ## func ## f128, pfx2 ## func ## f128, r);
+
+/* GEN_COMPAT_R_e(f)
+     Generate a compatability symbol for finite alias of ieee function.  */
+#define GEN_COMPAT_R_e(f, r) \
+	libm_alias_finite (__ieee754_ ## f ## f128 ## r, __ ## f ## f128 ## r)
+
+#define GEN_COMPAT_e_acos(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_acosh(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_asin(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_sinh(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_atan2(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_atanh(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_cosh(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_exp10(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_exp2(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_exp(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_fmod(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_gamma_r(f) GEN_COMPAT_R_e(f,_r)
+#define GEN_COMPAT_e_hypot(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_j0(f) GEN_COMPAT_R_e(f,) GEN_COMPAT_R_e(y0,)
+#define GEN_COMPAT_e_j1(f) GEN_COMPAT_R_e(f,) GEN_COMPAT_R_e(y1,)
+#define GEN_COMPAT_e_jn(f) GEN_COMPAT_R_e(f,) GEN_COMPAT_R_e(yn,)
+#define GEN_COMPAT_e_lgamma_r(f) GEN_COMPAT_R_e(f,_r)
+#define GEN_COMPAT_e_log10(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_log2(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_log(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_pow(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_remainder(f) GEN_COMPAT_R_e(f,)
+#define GEN_COMPAT_e_sqrt(f) GEN_COMPAT_R_e(f,)
+
+/* MAKE_IEEE_IFUNC_R(func, pfx, r)
+    Declare an ieee ifunc symbol used internally by libm.  E.g __ieee754_sinf128  */
+#define MAKE_IEEE_IFUNC_R(func, r) \
+	extern __typeof (__ieee754_ ## func ## f128 ## r) __ieee754_ ## func ## f128_power8 ## r; \
+	extern __typeof (__ieee754_ ## func ## f128 ## r) __ieee754_ ## func ## f128_power9 ## r; \
+        _F128_IFUNC2 (__ieee754_ ## func ## f128, __ieee754_ ## func ## f128, r);
+
+/* MAKE_IFUNCP_WRAP_R(w, func, r)
+      Export a function which the implementation wraps with prefix w to
+      to func ## r.  */
+#define MAKE_IFUNCP_WRAP_R(w, func, r) \
+	extern __typeof (func ## f128 ## r) __ ## func ## f128 ## r; \
+	MAKE_IMPL_IFUNC2 (func,__,__ ## w, r) \
+	weak_alias (__ ## func ## f128 ## r, func ## f128 ## r); \
+	libm_alias_float128_other_r (__ ## func, func, r);
+
+/* MAKE_IFUNCP_R(func, r)
+    The default IFUNC generator for all libm _Float128 ABI except
+    when specifically overwritten.  This is a convenience wrapper
+    around MAKE_IFUNCP_R where w is not used.  */
+#define MAKE_IFUNCP_R(func,r) MAKE_IFUNCP_WRAP_R (,func,r)
+
+/* Generic aliasing functions.  */
+#define DECL_ALIAS(f) MAKE_IFUNCP_R (f,)
+#define DECL_ALIAS_s(f) MAKE_IFUNCP_R (f,)
+#define DECL_ALIAS_w(f) MAKE_IFUNCP_R (f,)
+#define DECL_ALIAS_e(f) MAKE_IEEE_IFUNC_R (f,)
+#define DECL_ALIAS_k(f)
+#define DECL_ALIAS_R_w(f) MAKE_IFUNCP_R (f, _r)
+#define DECL_ALIAS_R_e(f) MAKE_IEEE_IFUNC_R (f,_r)
+
+/* No symbols are defined in these helper/wrapper objects. */
+#define DECL_ALIAS_lgamma_neg(x)
+#define DECL_ALIAS_lgamma_product(x)
+#define DECL_ALIAS_gamma_product(x)
+#define DECL_ALIAS_x2y2m1(x)
+#define DECL_ALIAS_s_log1p(x)
+#define DECL_ALIAS_s_scalbln(x)
+#define DECL_ALIAS_s_scalbn(x)
+
+/* Ensure the wrapper functions get exposed via IFUNC, not the
+   wrappee (e.g __w_log1pf128_power8 instead of __log1pf128_power8.  */
+#define DECL_ALIAS_w_log1p(x) MAKE_IFUNCP_WRAP_R(w_,x,)
+#define DECL_ALIAS_w_scalbln(x) MAKE_IFUNCP_WRAP_R(w_,x,)
+
+/* These are declared in their respective jX objects.  */
+#define DECL_ALIAS_w_j0(f) MAKE_IFUNCP_R (f,) MAKE_IFUNCP_R (y0,)
+#define DECL_ALIAS_w_j1(f) MAKE_IFUNCP_R (f,) MAKE_IFUNCP_R (y1,)
+#define DECL_ALIAS_w_jn(f) MAKE_IFUNCP_R (f,) MAKE_IFUNCP_R (yn,)
+#define DECL_ALIAS_e_j0(f) MAKE_IEEE_IFUNC_R (f,) MAKE_IEEE_IFUNC_R (y0,)
+#define DECL_ALIAS_e_j1(f) MAKE_IEEE_IFUNC_R (f,) MAKE_IEEE_IFUNC_R (y1,)
+#define DECL_ALIAS_e_jn(f) MAKE_IEEE_IFUNC_R (f,) MAKE_IEEE_IFUNC_R (yn,)
+
+#define DECL_ALIAS_s_erf(f) MAKE_IFUNCP_R (f,) MAKE_IFUNCP_R (erfc,)
+
+/* scalbnf128 is an alias of ldexpf128.  */
+#define DECL_ALIAS_s_ldexp(f) MAKE_IFUNCP_R (f,) MAKE_IFUNCP_WRAP_R (wrap_, scalbn,)
+
+/* Declare an IFUNC for a symbol which only exists
+   to provide long double == ieee128 ABI.  */
+#define DECL_LDOUBLE_ALIAS(func, RTYPE, ARGS) \
+	extern RTYPE func ARGS; \
+	extern __typeof (func) func ## _power8; \
+	extern __typeof (func) func ## _power9; \
+	_F128_IFUNC ( func,)
+
+/* Handle the special case functions which exist only to support
+   ldouble == ieee128.  */
+#define DECL_ALIAS_w_scalb(x) \
+	DECL_LDOUBLE_ALIAS (__scalbf128,_Float128, (_Float128, _Float128)) \
+	libm_alias_float128_other_r_ldbl (__scalb, scalb,)
+
+#endif /* ifndef _FLOAT128_IFUNC_H  */