[PATCH v4 4/6] linux-user/elfload: Introduce MIPS GET_FEATURE_REG_EQU() macro

[Philippe Mathieu-Daudé]

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.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 target/mips/cpu.h    |  1 +
 linux-user/elfload.c | 12 +++++++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/target/mips/cpu.h b/target/mips/cpu.h
index 23f8c6f96cd..2639b0ea06c 100644
--- a/target/mips/cpu.h
+++ b/target/mips/cpu.h
@@ -844,6 +844,7 @@ struct CPUMIPSState {
 #define CP0C0_MT   7     /*  9..7  */
 #define CP0C0_VI   3
 #define CP0C0_K0   0     /*  2..0  */
+#define CP0C0_AR_LENGTH 3
     int32_t CP0_Config1;
 #define CP0C1_M    31
 #define CP0C1_MMU  25    /* 30..25 */
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index b7c6d30723a..8f943f93ba7 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -7,6 +7,7 @@
 
 #include "qemu.h"
 #include "disas/disas.h"
+#include "qemu/bitops.h"
 #include "qemu/path.h"
 #include "qemu/queue.h"
 #include "qemu/guest-random.h"
@@ -995,17 +996,26 @@ 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, _start, _length, _val, _hwcap) \
+    do { \
+        if (extract32(cpu->env._reg, (_start), (_length)) == (_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, CP0C0_AR, CP0C0_AR_LENGTH,
+                        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
 
-- 
2.26.2