ppc: Add pwr9 flag

Will be used to gate code using vec_absd and other useful instructions.

src/cpu.h

@@ -82,6 +82,9 @@ static ALWAYS_INLINE unsigned dav1d_get_cpu_flags(void) {
 #if defined(__VSX__)
     flags |= DAV1D_PPC_CPU_FLAG_VSX;
 #endif
+#if defined(__POWER9_VECTOR__)
+    flags |= DAV1D_PPC_CPU_FLAG_PWR9;
+#endif
 #elif ARCH_RISCV
 #if defined(__riscv_v)
     flags |= DAV1D_RISCV_CPU_FLAG_V;

src/ppc/cpu.c

@@ -40,12 +40,16 @@ COLD unsigned dav1d_get_cpu_flags_ppc(void) {
     unsigned flags = 0;
 #if defined(HAVE_GETAUXVAL) && ARCH_PPC64LE
     unsigned long hw_cap = getauxval(AT_HWCAP);
+    unsigned long hw_cap2 = getauxval(AT_HWCAP2);
 #elif defined(HAVE_ELF_AUX_INFO) && ARCH_PPC64LE
     unsigned long hw_cap = 0;
+    unsigned long hw_cap2 = 0;
     elf_aux_info(AT_HWCAP, &hw_cap, sizeof(hw_cap));
+    elf_aux_info(AT_HWCAP2, &hw_cap2, sizeof(hw_cap2));
 #endif
 #ifdef HAVE_AUX
     flags |= (hw_cap & PPC_FEATURE_HAS_VSX) ? DAV1D_PPC_CPU_FLAG_VSX : 0;
+    flags |= (hw_cap2 & PPC_FEATURE2_ARCH_3_00) ? DAV1D_PPC_CPU_FLAG_PWR9 : 0;
 #endif
     return flags;
 }

src/ppc/cpu.h

@@ -30,6 +30,7 @@
 
 enum CpuFlags {
     DAV1D_PPC_CPU_FLAG_VSX = 1 << 0,
+    DAV1D_PPC_CPU_FLAG_PWR9 = 1 << 1,
 };
 
 unsigned dav1d_get_cpu_flags_ppc(void);

tests/checkasm/checkasm.c

@@ -116,6 +116,7 @@ static const struct {
     { "LASX",               "lasx",      DAV1D_LOONGARCH_CPU_FLAG_LASX },
 #elif ARCH_PPC64LE
     { "VSX",                "vsx",       DAV1D_PPC_CPU_FLAG_VSX },
+    { "PWR9",               "pwr9",      DAV1D_PPC_CPU_FLAG_PWR9 },
 #elif ARCH_RISCV
     { "RVV",                "rvv",       DAV1D_RISCV_CPU_FLAG_V },
 #endif

tools/dav1d_cli_parse.c

@@ -104,7 +104,7 @@ static const struct option long_opts[] = {
 #elif ARCH_LOONGARCH
 #define ALLOWED_CPU_MASKS ", 'lsx' or 'lasx'"
 #elif ARCH_PPC64LE
-#define ALLOWED_CPU_MASKS " or 'vsx'"
+#define ALLOWED_CPU_MASKS ", 'vsx' or 'pwr9'"
 #elif ARCH_RISCV
 #define ALLOWED_CPU_MASKS " or 'rvv'"
 #elif ARCH_X86
@@ -243,6 +243,7 @@ static const EnumParseTable cpu_mask_tbl[] = {
     { "lasx", DAV1D_LOONGARCH_CPU_FLAG_LASX },
 #elif ARCH_PPC64LE
     { "vsx", DAV1D_PPC_CPU_FLAG_VSX },
+    { "pwr9", DAV1D_PPC_CPU_FLAG_PWR9 },
 #elif ARCH_RISCV
     { "rvv", DAV1D_RISCV_CPU_FLAG_V },
 #elif ARCH_X86