x86: Add defines / utilities for making ISA specific x86 builds

1. Factor out some of the ISA level defines in isa-level.c to
   standalone header isa-level.h

2. Add new headers with ISA level dependent macros for handling
   ifuncs.

Note, this file does not change any code.

Tested with and without multiarch on x86_64 for ISA levels:
{generic, x86-64-v2, x86-64-v3, x86-64-v4}

And m32 with and without multiarch.

4 files changed, 180 insertions, 13 deletions

diff --git a/sysdeps/x86/init-arch.h b/sysdeps/x86/init-arch.h
index 277c15f..a2886a2 100644
--- a/sysdeps/x86/init-arch.h
+++ b/sysdeps/x86/init-arch.h
@@ -19,7 +19,9 @@
 #include <ifunc-init.h>
 #include <isa.h>
 
-#ifndef __x86_64__
+#ifdef __x86_64__
+# include <isa-ifunc-macros.h>
+#else
 /* Due to the reordering and the other nifty extensions in i686, it is
    not really good to use heavily i586 optimized code on an i686.  It's
    better to use i486 code if it isn't an i586.  */
diff --git a/sysdeps/x86/isa-ifunc-macros.h b/sysdeps/x86/isa-ifunc-macros.h
new file mode 100644
index 0000000..ba6826d
--- /dev/null
+++ b/sysdeps/x86/isa-ifunc-macros.h
@@ -0,0 +1,70 @@
+/* Common ifunc selection utils
+   All versions must be listed in ifunc-impl-list.c.
+   Copyright (C) 2022 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 _ISA_IFUNC_MACROS_H
+#define _ISA_IFUNC_MACROS_H 1
+
+#include <isa-level.h>
+#include <sys/cdefs.h>
+#include <stdlib.h>
+
+/* Only include at the level of the minimum build ISA or higher. I.e
+   if built with ISA=V1, then include all implementations. On the
+   other hand if built with ISA=V3 only include V3/V4
+   implementations. If there is no implementation at or above the
+   minimum build ISA level, then include the highest ISA level
+   implementation.  */
+#if MINIMUM_X86_ISA_LEVEL <= 4
+# define X86_IFUNC_IMPL_ADD_V4(...) IFUNC_IMPL_ADD (__VA_ARGS__)
+#endif
+#if MINIMUM_X86_ISA_LEVEL <= 3
+# define X86_IFUNC_IMPL_ADD_V3(...) IFUNC_IMPL_ADD (__VA_ARGS__)
+#endif
+#if MINIMUM_X86_ISA_LEVEL <= 2
+# define X86_IFUNC_IMPL_ADD_V2(...) IFUNC_IMPL_ADD (__VA_ARGS__)
+#endif
+#if MINIMUM_X86_ISA_LEVEL <= 1
+# define X86_IFUNC_IMPL_ADD_V1(...) IFUNC_IMPL_ADD (__VA_ARGS__)
+#endif
+
+#ifndef X86_IFUNC_IMPL_ADD_V4
+# define X86_IFUNC_IMPL_ADD_V4(...)
+#endif
+#ifndef X86_IFUNC_IMPL_ADD_V3
+# define X86_IFUNC_IMPL_ADD_V3(...)
+#endif
+#ifndef X86_IFUNC_IMPL_ADD_V2
+# define X86_IFUNC_IMPL_ADD_V2(...)
+#endif
+#ifndef X86_IFUNC_IMPL_ADD_V1
+# define X86_IFUNC_IMPL_ADD_V1(...)
+#endif
+
+#define X86_ISA_CPU_FEATURE_CONST_CHECK_ENABLED(name)                  \
+  ((name##_X86_ISA_LEVEL) <= MINIMUM_X86_ISA_LEVEL)
+
+#define X86_ISA_CPU_FEATURE_USABLE_P(ptr, name)                        \
+  (X86_ISA_CPU_FEATURE_CONST_CHECK_ENABLED (name)                      \
+   || CPU_FEATURE_USABLE_P (ptr, name))
+
+#define X86_ISA_CPU_FEATURES_ARCH_P(ptr, name)                         \
+  (X86_ISA_CPU_FEATURE_CONST_CHECK_ENABLED (name)                      \
+   || CPU_FEATURES_ARCH_P (ptr, name))
+
+#endif
diff --git a/sysdeps/x86/isa-level.c b/sysdeps/x86/isa-level.c
index 09cd72a..5b7a2da 100644
--- a/sysdeps/x86/isa-level.c
+++ b/sysdeps/x86/isa-level.c
@@ -26,38 +26,31 @@
    <https://www.gnu.org/licenses/>.  */
 
 #include <elf.h>
-
+#include <sysdeps/x86/isa-level.h>
 /* ELF program property for x86 ISA level.  */
 #ifdef INCLUDE_X86_ISA_LEVEL
-# if defined __SSE__ && defined __SSE2__
+# if MINIMUM_X86_ISA_LEVEL >= 1
 /* NB: ISAs, excluding MMX, in x86-64 ISA level baseline are used.  */
 #  define ISA_BASELINE	GNU_PROPERTY_X86_ISA_1_BASELINE
 # else
 #  define ISA_BASELINE	0
 # endif
 
-# if ISA_BASELINE && defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16 \
-     && defined HAVE_X86_LAHF_SAHF && defined __POPCNT__ \
-     && defined __SSE3__ && defined __SSSE3__ && defined __SSE4_1__ \
-     && defined __SSE4_2__
+# if MINIMUM_X86_ISA_LEVEL >= 2
 /* NB: ISAs in x86-64 ISA level v2 are used.  */
 #  define ISA_V2	GNU_PROPERTY_X86_ISA_1_V2
 # else
 #  define ISA_V2	0
 # endif
 
-# if ISA_V2 && defined __AVX__ && defined __AVX2__ && defined __F16C__ \
-     && defined __FMA__ && defined __LZCNT__ && defined HAVE_X86_MOVBE \
-     && defined __BMI__ && defined __BMI2__
+# if MINIMUM_X86_ISA_LEVEL >= 3
 /* NB: ISAs in x86-64 ISA level v3 are used.  */
 #  define ISA_V3	GNU_PROPERTY_X86_ISA_1_V3
 # else
 #  define ISA_V3	0
 # endif
 
-# if ISA_V3 && defined __AVX512F__ && defined __AVX512BW__ \
-     && defined __AVX512CD__ && defined __AVX512DQ__ \
-     && defined __AVX512VL__
+# if MINIMUM_X86_ISA_LEVEL >= 4
 /* NB: ISAs in x86-64 ISA level v4 are used.  */
 #  define ISA_V4	GNU_PROPERTY_X86_ISA_1_V4
 # else
diff --git a/sysdeps/x86/isa-level.h b/sysdeps/x86/isa-level.h
new file mode 100644
index 0000000..7cae11c
--- /dev/null
+++ b/sysdeps/x86/isa-level.h
@@ -0,0 +1,102 @@
+/* Header defining the minimum x86 ISA level
+   Copyright (C) 2022 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.
+
+   In addition to the permissions in the GNU Lesser General Public
+   License, the Free Software Foundation gives you unlimited
+   permission to link the compiled version of this file with other
+   programs, and to distribute those programs without any restriction
+   coming from the use of this file.  (The Lesser General Public
+   License restrictions do apply in other respects; for example, they
+   cover modification of the file, and distribution when not linked
+   into another program.)
+
+   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 _ISA_LEVEL_H
+#define _ISA_LEVEL_H
+
+#if defined __SSE__ && defined __SSE2__
+/* NB: ISAs, excluding MMX, in x86-64 ISA level baseline are used.  */
+# define __X86_ISA_V1 1
+#else
+# define __X86_ISA_V1 0
+#endif
+
+#if __X86_ISA_V1 && defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_16               \
+    && defined HAVE_X86_LAHF_SAHF && defined __POPCNT__ && defined __SSE3__   \
+    && defined __SSSE3__ && defined __SSE4_1__ && defined __SSE4_2__
+/* NB: ISAs in x86-64 ISA level v2 are used.  */
+# define __X86_ISA_V2 1
+#else
+# define __X86_ISA_V2 0
+#endif
+
+#if __X86_ISA_V2 && defined __AVX__ && defined __AVX2__ && defined __F16C__   \
+    && defined __FMA__ && defined __LZCNT__ && defined HAVE_X86_MOVBE         \
+    && defined __BMI__ && defined __BMI2__
+/* NB: ISAs in x86-64 ISA level v3 are used.  */
+# define __X86_ISA_V3 1
+#else
+# define __X86_ISA_V3 0
+#endif
+
+#if __X86_ISA_V3 && defined __AVX512F__ && defined __AVX512BW__               \
+    && defined __AVX512CD__ && defined __AVX512DQ__ && defined __AVX512VL__
+/* NB: ISAs in x86-64 ISA level v4 are used.  */
+# define __X86_ISA_V4 1
+#else
+# define __X86_ISA_V4 0
+#endif
+
+#define MINIMUM_X86_ISA_LEVEL                                                 \
+  (__X86_ISA_V1 + __X86_ISA_V2 + __X86_ISA_V3 + __X86_ISA_V4)
+
+
+/*
+ * CPU Features that are hard coded as enabled depending on ISA build
+ *   level.
+ *    - Values > 0 features are always ENABLED if:
+ *          Value >= MINIMUM_X86_ISA_LEVEL
+ */
+
+
+/* ISA level >= 4 guaranteed includes.  */
+#define AVX512VL_X86_ISA_LEVEL 4
+#define AVX512BW_X86_ISA_LEVEL 4
+
+/* ISA level >= 3 guaranteed includes.  */
+#define AVX2_X86_ISA_LEVEL 3
+#define BMI2_X86_ISA_LEVEL 3
+
+/*
+ * NB: This may not be fully assumable for ISA level >= 3. From
+ * looking over the architectures supported in cpu-features.h the
+ * following CPUs may have an issue with this being default set:
+ *      - AMD Excavator
+ */
+#define AVX_Fast_Unaligned_Load_X86_ISA_LEVEL 3
+
+/*
+ * KNL (the only cpu that sets this supported in cpu-features.h)
+ * builds with ISA V1 so this shouldn't harm any architectures.
+ */
+#define Prefer_No_VZEROUPPER_X86_ISA_LEVEL 3
+
+#define ISA_SHOULD_BUILD(isa_build_level)                              \
+  (MINIMUM_X86_ISA_LEVEL <= (isa_build_level) && IS_IN (libc))         \
+   || defined ISA_DEFAULT_IMPL
+
+#endif