cpuid: cache processor brand string

[ccan] / ccan / cpuid / cpuid.c

diff --git a/ccan/cpuid/cpuid.c b/ccan/cpuid/cpuid.c
index 6133e13f03c420144348f8d08ea9901d643985f9..1a09c5e666cb9457041bb0ae524fdd579677c07d 100644 (file)
--- a/ccan/cpuid/cpuid.c
+++ b/ccan/cpuid/cpuid.c
@@ -90,45 +90,60 @@ static struct {
        { CEF_XOP,              1 << 11,        false }
 };
 
-static bool has_feature(int feature, uint32_t ecx, uint32_t edx)
-{
-       int i;
-
-       for (i = 0; i < sizeof(features) / sizeof(features[0]); ++i) {
-               if (features[i].feature == feature) {
-                       if (features[i].use_edx)
-                               return (edx & features[i].mask);
-                       else
-                               return (ecx & features[i].mask);
-               }
-       }
-
-       return false;
-}
-
 bool cpuid_is_supported(void)
 {
-       int ret = 0;
+       /* The following assembly code uses EAX as the return value,
+        * but we store the value of EAX into ret since GCC uses EAX
+        * as the return register for every C function.  That's a double
+        * operation, but there's no other way to do this unless doing this
+        * function entirely in assembly.  */
+
+       /* This check is to make sure that the compiler is actually compiling
+        * for 64-bit.
+        *
+        * The compiler can be 32-bit and the system 64-bit so the 
+        * following would be true:
+        *      #if defined(__x86_64) ...
+        */
+
+#if UINTPTR_MAX == 0xffffffffffffffff
+#define ASM_PUSHF      "pushfq\n\t"
+#define ASM_POPF       "popfq\n\t"
+#define ASM_PUSHEAX    "pushq %%rax\n\t"
+#define ASM_POPEAX     "popq %%rax\n\t"
+#define ASM_PUSHECX    "popq %%rcx\n\t"
+#elif UINTPTR_MAX == 0xffffffff
+#define ASM_PUSHF      "pushfl\n\t"
+#define ASM_POPF       "popfl\n\t"
+#define ASM_PUSHEAX    "pushl %%eax\n\t"
+#define ASM_POPEAX     "popl %%eax\n\t"
+#define ASM_PUSHECX    "popl %%ecx\n\t"
+#endif
 
+       int ret = 0;
        asm volatile(
-               "pushfl\n\t"
-               "popl %%eax\n\t"
+               ASM_PUSHF
+               ASM_POPEAX
                "movl %%eax, %%ecx\n\t"
                "xorl $0x200000, %%eax\n\t"
-               "pushl %%eax\n\t"
-               "popfl\n\t"
-
-               "pushfl\n\t"
-               "popl %%eax\n\t"
+               ASM_PUSHEAX
+               ASM_POPF
+               ASM_PUSHF
+               ASM_POPEAX
                "xorl %%ecx, %%eax\n\t"
                "shrl $21, %%eax\n\t"
                "andl $1, %%eax\n\t"
-               "pushl %%ecx\n\t"
-               "popfl\n\t"
-
+               ASM_PUSHECX
+               ASM_POPF
                : "=a" (ret)
        );
 
+#undef ASM_PUSHF
+#undef ASM_POPF
+#undef ASM_PUSHEAX
+#undef ASM_POPEAX
+#undef ASM_PUSHECX
+
        return !!ret;
 }
 
@@ -149,7 +164,15 @@ bool cpuid_has_feature(int feature, bool extended)
        else
                ___cpuid(CPU_EXTENDED_PROC_INFO_FEATURE_BITS, &eax, &ebx, &ecx, &edx);
 
-       return has_feature(feature, ecx, edx);
+       for (i = 0; i < sizeof(features) / sizeof(features[0]); ++i) {
+               if (features[i].feature == feature) {
+                       if (features[i].use_edx)
+                               return (edx & features[i].mask);
+                       else
+                               return (ecx & features[i].mask);
+               }
+       }
+       return false;
 }
 
 static const char *const cpuids[] = {
@@ -225,9 +248,16 @@ void cpuid(cpuid_t info, uint32_t *buf)
                return;
 
        if (info == CPU_PROC_BRAND_STRING) {
-               ___cpuid(CPU_PROC_BRAND_STRING,           &buf[0], &buf[1], &buf[2],  &buf[3]);
-               ___cpuid(CPU_PROC_BRAND_STRING_INTERNAL0, &buf[4], &buf[5], &buf[6],  &buf[7]);
-               ___cpuid(CPU_PROC_BRAND_STRING_INTERNAL1, &buf[8], &buf[9], &buf[10], &buf[11]);
+               static char cached[48] = { 0 };
+               if (cached[0] == '\0') {
+                       ___cpuid(CPU_PROC_BRAND_STRING,           &buf[0], &buf[1], &buf[2],  &buf[3]);
+                       ___cpuid(CPU_PROC_BRAND_STRING_INTERNAL0, &buf[4], &buf[5], &buf[6],  &buf[7]);
+                       ___cpuid(CPU_PROC_BRAND_STRING_INTERNAL1, &buf[8], &buf[9], &buf[10], &buf[11]);
+
+                       memcpy(cached, buf, sizeof cached);
+               } else
+                       buf = (uint32_t *)cached;
+
                return;
        } else if (info == CPU_HIGHEST_EXTENDED_FUNCTION_SUPPORTED) {
                *buf = cpuid_highest_ext_func_supported();