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[v2,4/6] linux-user/elfload: Introduce MIPS GET_FEATURE_REG_EQU() macro

Message ID 20201201133525.2866838-5-f4bug@amsat.org
State New
Headers show
Series linux-user: Rework get_elf_hwcap() and support MIPS Loongson 2F/3E | expand

Commit Message

Philippe Mathieu-Daudé Dec. 1, 2020, 1:35 p.m. UTC 
ISA features are usually denoted in read-only bits from
CPU registers. Add the GET_FEATURE_REG_EQU() macro which
checks if a CPU register has bits set to a specific value.

Use the macro to check the 'Architecture Revision' level
of the Config0 register, which is '2' when the Release 6
ISA is implemented.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 linux-user/elfload.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

Comments

Richard Henderson Dec. 1, 2020, 5:36 p.m. UTC | #1 
On 12/1/20 7:35 AM, Philippe Mathieu-Daudé wrote:
> +#define GET_FEATURE_REG_EQU(_reg, _mask, _val, _hwcap) \
> +    do { \
> +        if ((cpu->env._reg & (_mask)) == _val) { \
> +            hwcaps |= _hwcap; \
> +        } \
> +    } while (0)
> +
>  static uint32_t get_elf_hwcap(void)
>  {
>      MIPSCPU *cpu = MIPS_CPU(thread_cpu);
>      uint32_t hwcaps = 0;
>  
> -    GET_FEATURE_INSN(ISA_MIPS32R6 | ISA_MIPS64R6, HWCAP_MIPS_R6);
> +    GET_FEATURE_REG_EQU(CP0_Config0, 7 << CP0C0_AR, 2, HWCAP_MIPS_R6);

You'd need 2 << CP0C0_AR for the equality to match.
Would it be better to have the shift as a separate argument?


r~
Philippe Mathieu-Daudé Dec. 1, 2020, 7 p.m. UTC | #2 
On 12/1/20 6:36 PM, Richard Henderson wrote:
> On 12/1/20 7:35 AM, Philippe Mathieu-Daudé wrote:
>> +#define GET_FEATURE_REG_EQU(_reg, _mask, _val, _hwcap) \
>> +    do { \
>> +        if ((cpu->env._reg & (_mask)) == _val) { \
>> +            hwcaps |= _hwcap; \
>> +        } \
>> +    } while (0)
>> +
>>  static uint32_t get_elf_hwcap(void)
>>  {
>>      MIPSCPU *cpu = MIPS_CPU(thread_cpu);
>>      uint32_t hwcaps = 0;
>>  
>> -    GET_FEATURE_INSN(ISA_MIPS32R6 | ISA_MIPS64R6, HWCAP_MIPS_R6);
>> +    GET_FEATURE_REG_EQU(CP0_Config0, 7 << CP0C0_AR, 2, HWCAP_MIPS_R6);
> 
> You'd need 2 << CP0C0_AR for the equality to match.

Oops...

> Would it be better to have the shift as a separate argument?

Yes, thanks!

Phil.
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Patch

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index b7c6d30723a..73c1972183b 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -995,17 +995,25 @@  enum {
 #define GET_FEATURE_REG_SET(_reg, _mask, _hwcap) \
     do { if (cpu->env._reg & (_mask)) { hwcaps |= _hwcap; } } while (0)
 
+#define GET_FEATURE_REG_EQU(_reg, _mask, _val, _hwcap) \
+    do { \
+        if ((cpu->env._reg & (_mask)) == _val) { \
+            hwcaps |= _hwcap; \
+        } \
+    } while (0)
+
 static uint32_t get_elf_hwcap(void)
 {
     MIPSCPU *cpu = MIPS_CPU(thread_cpu);
     uint32_t hwcaps = 0;
 
-    GET_FEATURE_INSN(ISA_MIPS32R6 | ISA_MIPS64R6, HWCAP_MIPS_R6);
+    GET_FEATURE_REG_EQU(CP0_Config0, 7 << CP0C0_AR, 2, HWCAP_MIPS_R6);
     GET_FEATURE_REG_SET(CP0_Config3, 1 << CP0C3_MSAP, HWCAP_MIPS_MSA);
 
     return hwcaps;
 }
 
+#undef GET_FEATURE_REG_EQU
 #undef GET_FEATURE_REG_SET
 #undef GET_FEATURE_INSN