On Thursday 01 September 2011, Andrew Stubbs wrote:
> Hi all,
>
> I'm currently trying to get GCC to auto-detect what CPU to optimize for
> by finding out what CPU it's actually running on (the user would only
> have to pass -mcpu=native). It does this simply by reading /proc/cpuinfo.
>
> The problem is finding what magic numbers correspond to what CPU. I've
> found the numbers for A8 and A9 empirically, but I'd like a longer list
> than that!
>
> Does anybody have a list of such numbers?
>
> Or else, perhaps people could just post any number they happen to know?
>
> I do have a few devices other than A8 and A9 lying around I can look at,
> but the problem there is I don't actually know for certain what exact
> CPU model those numbers map to, so confirmed numbers only please.
This is what we use in the kernel: to find out the architecture level:
#define CPU_ARCH_UNKNOWN 0
#define CPU_ARCH_ARMv3 1
#define CPU_ARCH_ARMv4 2
#define CPU_ARCH_ARMv4T 3
#define CPU_ARCH_ARMv5 4
#define CPU_ARCH_ARMv5T 5
#define CPU_ARCH_ARMv5TE 6
#define CPU_ARCH_ARMv5TEJ 7
#define CPU_ARCH_ARMv6 8
#define CPU_ARCH_ARMv7 9
int cpu_architecture(void)
{
int cpu_arch;
if ((read_cpuid_id() & 0x0008f000) == 0) {
cpu_arch = CPU_ARCH_UNKNOWN;
} else if ((read_cpuid_id() & 0x0008f000) == 0x00007000) {
cpu_arch = (read_cpuid_id() & (1 << 23)) ? CPU_ARCH_ARMv4T :
CPU_ARCH_ARMv3;
} else if ((read_cpuid_id() & 0x00080000) == 0x00000000) {
cpu_arch = (read_cpuid_id() >> 16) & 7;
if (cpu_arch)
cpu_arch += CPU_ARCH_ARMv3;
} else if ((read_cpuid_id() & 0x000f0000) == 0x000f0000) {
unsigned int mmfr0;
/* Revised CPUID format. Read the Memory Model Feature
* Register 0 and check for VMSAv7 or PMSAv7 */
asm("mrc p15, 0, %0, c0, c1, 4"
: "=r" (mmfr0));
if ((mmfr0 & 0x0000000f) >= 0x00000003 ||
(mmfr0 & 0x000000f0) >= 0x00000030)
cpu_arch = CPU_ARCH_ARMv7;
else if ((mmfr0 & 0x0000000f) == 0x00000002 ||
(mmfr0 & 0x000000f0) == 0x00000020)
cpu_arch = CPU_ARCH_ARMv6;
else
cpu_arch = CPU_ARCH_UNKNOWN;
} else
cpu_arch = CPU_ARCH_UNKNOWN;
return cpu_arch;
}
[ within the /proc/cpuinfo code: ]
...
seq_printf(m, "\nCPU implementer\t: 0x%02x\n", read_cpuid_id() >> 24);
seq_printf(m, "CPU architecture: %s\n", proc_arch[cpu_architecture()]);
if ((read_cpuid_id() & 0x0008f000) == 0x00000000) {
/* pre-ARM7 */
seq_printf(m, "CPU part\t: %07x\n", read_cpuid_id() >> 4);
} else {
if ((read_cpuid_id() & 0x0008f000) == 0x00007000) {
/* ARM7 */
seq_printf(m, "CPU variant\t: 0x%02x\n",
(read_cpuid_id() >> 16) & 127);
} else {
/* post-ARM7 */
seq_printf(m, "CPU variant\t: 0x%x\n",
(read_cpuid_id() >> 20) & 15);
}
seq_printf(m, "CPU part\t: 0x%03x\n",
(read_cpuid_id() >> 4) & 0xfff);
}
seq_printf(m, "CPU revision\t: %d\n", read_cpuid_id() & 15);
...
Arnd
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