Add loongarch support

tests/checkasm/checkasm.c

@@ -104,6 +104,9 @@ static const struct {
     { "NEON",               "neon",      DAV1D_ARM_CPU_FLAG_NEON },
 #elif ARCH_PPC64LE
     { "VSX",                "vsx",       DAV1D_PPC_CPU_FLAG_VSX },
+#elif ARCH_LOONGARCH
+    { "LSX",                "lsx",       DAV1D_LOONGARCH_CPU_FLAG_LSX },
+    { "LASX",               "lasx",      DAV1D_LOONGARCH_CPU_FLAG_LASX },
 #endif
     { 0 }
 };

tests/checkasm/checkasm.h

@@ -197,6 +197,23 @@ static inline uint64_t readtime(void) {
     return (((uint64_t)tbu) << 32) | (uint64_t)tbl;
 }
 #define readtime readtime
+#elif ARCH_LOONGARCH
+static inline uint64_t readtime(void) {
+#if ARCH_LOONGARCH64
+    uint64_t a, id;
+    __asm__ __volatile__("rdtime.d  %0, %1"
+                         : "=r"(a), "=r"(id)
+                         :: );
+    return a;
+#else
+    uint32_t a, id;
+    __asm__ __volatile__("rdtimel.w  %0, %1"
+                         : "=r"(a), "=r"(id)
+                         :: );
+    return (uint64_t)a;
+#endif
+}
+#define readtime readtime
 #endif
 
 /* Verifies that clobbered callee-saved registers