m4/ax_gcc_x86_cpuid.m4: update from autoconf-archive v2023.02.20

m4/ax_gcc_x86_cpuid.m4

@@ -1,17 +1,19 @@
 # ===========================================================================
-#        http://www.nongnu.org/autoconf-archive/ax_gcc_x86_cpuid.html
+#     https://www.gnu.org/software/autoconf-archive/ax_gcc_x86_cpuid.html
 # ===========================================================================
 #
 # SYNOPSIS
 #
 #   AX_GCC_X86_CPUID(OP)
+#   AX_GCC_X86_CPUID_COUNT(OP, COUNT)
 #
 # DESCRIPTION
 #
 #   On Pentium and later x86 processors, with gcc or a compiler that has a
 #   compatible syntax for inline assembly instructions, run a small program
 #   that executes the cpuid instruction with input OP. This can be used to
-#   detect the CPU type.
+#   detect the CPU type. AX_GCC_X86_CPUID_COUNT takes an additional COUNT
+#   parameter that gets passed into register ECX before calling cpuid.
 #
 #   On output, the values of the eax, ebx, ecx, and edx registers are stored
 #   as hexadecimal strings as "eax:ebx:ecx:edx" in the cache variable
@@ -28,6 +30,7 @@
 #
 #   Copyright (c) 2008 Steven G. Johnson <[email protected]>
 #   Copyright (c) 2008 Matteo Frigo
+#   Copyright (c) 2015 Michael Petch <[email protected]>
 #
 #   This program is free software: you can redistribute it and/or modify it
 #   under the terms of the GNU General Public License as published by the
@@ -40,7 +43,7 @@
 #   Public License for more details.
 #
 #   You should have received a copy of the GNU General Public License along
-#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
 #
 #   As a special exception, the respective Autoconf Macro's copyright owner
 #   gives unlimited permission to copy, distribute and modify the configure
@@ -55,16 +58,25 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
+#serial 10
+
 AC_DEFUN([AX_GCC_X86_CPUID],
+[AX_GCC_X86_CPUID_COUNT($1, 0)
+])
+
+AC_DEFUN([AX_GCC_X86_CPUID_COUNT],
 [AC_REQUIRE([AC_PROG_CC])
 AC_LANG_PUSH([C])
 AC_CACHE_CHECK(for x86 cpuid $1 output, ax_cv_gcc_x86_cpuid_$1,
  [AC_RUN_IFELSE([AC_LANG_PROGRAM([#include <stdio.h>], [
-     int op = $1, eax, ebx, ecx, edx;
+     int op = $1, level = $2, eax, ebx, ecx, edx;
      FILE *f;
-      __asm__("cpuid"
-        : "=a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx)
-        : "a" (op));
+      __asm__ __volatile__ ("xchg %%ebx, %1\n"
+        "cpuid\n"
+        "xchg %%ebx, %1\n"
+        : "=a" (eax), "=r" (ebx), "=c" (ecx), "=d" (edx)
+        : "a" (op), "2" (level));
+
      f = fopen("conftest_cpuid", "w"); if (!f) return 1;
      fprintf(f, "%x:%x:%x:%x\n", eax, ebx, ecx, edx);
      fclose(f);