Hello!
Now that %ebx is also allocatable in PIC modes, we can cleanup
config/i386/cpuid considerably. I propose to remove all PIC related
specializations of __cpuid and __cpuid_count and protect the
compilation with "#if __GNUC__ >= 5".
The only drawback would be that non-bootstrapped build with gcc < 5.0
will ignore -march=native, but I think this should be acceptable.
Bootstrapped build will still work as expected.
2014-10-16 Uros Bizjak <ubiz...@gmail.com>
* config/i386/cpuid.h (__cpuid): Remove definitions that handle %ebx
register in a special way.
(__cpuid_count): Ditto.
* config/i386/driver-i386.h: Protect with #if __GNUC__ >= 5.
(host_detect_local_cpu): Mention that GCC that is able to handle
%ebx register in PIC and non-PIC modes is required to compile the
function.
Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.
Any comments?
Uros.
Index: config/i386/cpuid.h
===================================================================
--- config/i386/cpuid.h (revision 216282)
+++ config/i386/cpuid.h (working copy)
@@ -146,56 +146,7 @@
#define signature_VORTEX_ecx 0x436f5320
#define signature_VORTEX_edx 0x36387865
-#if defined(__i386__) && defined(__PIC__)
-/* %ebx may be the PIC register. */
-#if __GNUC__ >= 3
#define __cpuid(level, a, b, c, d) \
- __asm__ ("xchg{l}\t{%%}ebx, %k1\n\t" \
- "cpuid\n\t" \
- "xchg{l}\t{%%}ebx, %k1\n\t" \
- : "=a" (a), "=&r" (b), "=c" (c), "=d" (d) \
- : "0" (level))
-
-#define __cpuid_count(level, count, a, b, c, d) \
- __asm__ ("xchg{l}\t{%%}ebx, %k1\n\t" \
- "cpuid\n\t" \
- "xchg{l}\t{%%}ebx, %k1\n\t" \
- : "=a" (a), "=&r" (b), "=c" (c), "=d" (d) \
- : "0" (level), "2" (count))
-#else
-/* Host GCCs older than 3.0 weren't supporting Intel asm syntax
- nor alternatives in i386 code. */
-#define __cpuid(level, a, b, c, d) \
- __asm__ ("xchgl\t%%ebx, %k1\n\t" \
- "cpuid\n\t" \
- "xchgl\t%%ebx, %k1\n\t" \
- : "=a" (a), "=&r" (b), "=c" (c), "=d" (d) \
- : "0" (level))
-
-#define __cpuid_count(level, count, a, b, c, d) \
- __asm__ ("xchgl\t%%ebx, %k1\n\t" \
- "cpuid\n\t" \
- "xchgl\t%%ebx, %k1\n\t" \
- : "=a" (a), "=&r" (b), "=c" (c), "=d" (d) \
- : "0" (level), "2" (count))
-#endif
-#elif defined(__x86_64__) && (defined(__code_model_medium__) ||
defined(__code_model_large__)) && defined(__PIC__)
-/* %rbx may be the PIC register. */
-#define __cpuid(level, a, b, c, d) \
- __asm__ ("xchg{q}\t{%%}rbx, %q1\n\t" \
- "cpuid\n\t" \
- "xchg{q}\t{%%}rbx, %q1\n\t" \
- : "=a" (a), "=&r" (b), "=c" (c), "=d" (d) \
- : "0" (level))
-
-#define __cpuid_count(level, count, a, b, c, d) \
- __asm__ ("xchg{q}\t{%%}rbx, %q1\n\t" \
- "cpuid\n\t" \
- "xchg{q}\t{%%}rbx, %q1\n\t" \
- : "=a" (a), "=&r" (b), "=c" (c), "=d" (d) \
- : "0" (level), "2" (count))
-#else
-#define __cpuid(level, a, b, c, d) \
__asm__ ("cpuid\n\t" \
: "=a" (a), "=b" (b), "=c" (c), "=d" (d) \
: "0" (level))
@@ -204,8 +155,8 @@
__asm__ ("cpuid\n\t" \
: "=a" (a), "=b" (b), "=c" (c), "=d" (d) \
: "0" (level), "2" (count))
-#endif
+
/* Return highest supported input value for cpuid instruction. ext can
be either 0x0 or 0x8000000 to return highest supported value for
basic or extended cpuid information. Function returns 0 if cpuid
Index: config/i386/driver-i386.c
===================================================================
--- config/i386/driver-i386.c (revision 216282)
+++ config/i386/driver-i386.c (working copy)
@@ -24,7 +24,7 @@ along with GCC; see the file COPYING3. If not see
const char *host_detect_local_cpu (int argc, const char **argv);
-#ifdef __GNUC__
+#if __GNUC__ >= 5
#include "cpuid.h"
struct cache_desc
@@ -942,9 +942,10 @@ done:
}
#else
-/* If we aren't compiling with GCC then the driver will just ignore
- -march and -mtune "native" target and will leave to the newly
- built compiler to generate code for its default target. */
+/* If we aren't compiling with GCC that is able to handle %EBX
+ register in PIC and non-PIC modes, then the driver will just
+ ignore -march and -mtune "native" target and will leave to the
+ newly built compiler to generate code for its default target. */
const char *host_detect_local_cpu (int, const char **)
{
