From 03eaf9b461454e79bb4d9645cfcd093e4a32af8d Mon Sep 17 00:00:00 2001
From: historic_bruno <ben@wildfiregames.com>
Date: Sat, 18 Oct 2014 03:07:24 +0000
Subject: [PATCH] Fixes cpuid to work with i386 CPUs and PIE/PIC, based on old
 GCC cpuid.h source and patch by pstumpf, fixes #2675

This was SVN commit r15886.
---
 source/lib/sysdep/arch/x86_x64/x86_x64.cpp | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/source/lib/sysdep/arch/x86_x64/x86_x64.cpp b/source/lib/sysdep/arch/x86_x64/x86_x64.cpp
index 789cc89c85..5cca3d0ac9 100644
--- a/source/lib/sysdep/arch/x86_x64/x86_x64.cpp
+++ b/source/lib/sysdep/arch/x86_x64/x86_x64.cpp
@@ -49,10 +49,21 @@ namespace x86_x64 {
 #if defined(_MSC_FULL_VER) && _MSC_FULL_VER >= 150030729
 // VC10+ and VC9 SP1: __cpuidex is already available
 #elif GCC_VERSION
-# define __cpuidex(regsArray, level, index)\
-	__asm__ __volatile__ ("cpuid"\
-	: "=a" ((regsArray)[0]), "=b" ((regsArray)[1]), "=c" ((regsArray)[2]), "=d" ((regsArray)[3])\
-	: "0" (level), "2" (index));
+// Adapted from GPLv2 version of GCC's cpuid.h
+# if ARCH_IA32 && defined(__PIC__)
+// %ebx may be the PIC register
+#  define __cpuidex(regsArray, level, index)\
+	__asm__ ("xchgl\t%%ebx, %1\n\t"\
+		"cpuid\n\t"\
+		"xchgl\t%%ebx, %1\n\t"\
+		: "=a" ((regsArray)[0]), "=r" ((regsArray)[1]), "=c" ((regsArray)[2]), "=d" ((regsArray)[3])\
+		: "0" (level), "2" (index));
+# else
+#  define __cpuidex(regsArray, level, index)\
+	__asm__ ("cpuid\n\t"\
+		: "=a" ((regsArray)[0]), "=b" ((regsArray)[1]), "=c" ((regsArray)[2]), "=d" ((regsArray)[3])\
+		: "0" (level), "2" (index));
+# endif
 #else
 # error "compiler not supported"
 #endif