RISCV64: Add FFI and JIT support

Contributed by infiWang.

src/jit/dis_riscv64.lua

@@ -0,0 +1,16 @@
+----------------------------------------------------------------------------
+-- LuaJIT RISC-V 64 disassembler wrapper module.
+--
+-- Copyright (C) 2005-2023 Mike Pall. All rights reserved.
+-- Released under the MIT license. See Copyright Notice in luajit.h
+----------------------------------------------------------------------------
+-- This module just exports the default riscv little-endian functions from the
+-- RISC-V disassembler module. All the interesting stuff is there.
+------------------------------------------------------------------------------
+
+local dis_riscv = require((string.match(..., ".*%.") or "").."dis_riscv")
+return {
+  create = dis_riscv.create,
+  disass = dis_riscv.disass,
+  regname = dis_riscv.regname
+}

src/lib_jit.c

@@ -642,6 +642,84 @@ JIT_PARAMDEF(JIT_PARAMINIT)
 #include <sys/utsname.h>
 #endif
 
+#if LJ_TARGET_RISCV64 && LJ_TARGET_POSIX
+
+#if LJ_TARGET_LINUX
+#include <unistd.h>
+
+struct riscv_hwprobe hwprobe_requests[] = {
+	{RISCV_HWPROBE_KEY_IMA_EXT_0}
+};
+
+const uint64_t *hwprobe_ext = &hwprobe_requests[0].value;
+
+int hwprobe_ret = 0;
+#endif
+
+static int riscv_compressed()
+{
+#if defined(__riscv_c) || defined(__riscv_compressed)
+  /* Don't bother checking for RVC -- would crash before getting here. */
+  return 1;
+#elif LJ_TARGET_LINUX
+  return (hwprobe_ret == 0 && ((*hwprobe_ext) & RISCV_HWPROBE_IMA_C)) ? 1 : 0;
+#else
+  return 0;
+#endif
+}
+
+static int riscv_zba()
+{
+#if defined(__riscv_b) || defined(__riscv_zba)
+  /* Don't bother checking for Zba -- would crash before getting here. */
+  return 1;
+#elif LJ_TARGET_LINUX
+  return (hwprobe_ret == 0 && ((*hwprobe_ext) & RISCV_HWPROBE_EXT_ZBA)) ? 1 : 0;
+#else
+  return 0;
+#endif
+}
+
+static int riscv_zbb()
+{
+#if defined(__riscv_b) || defined(__riscv_zbb)
+  /* Don't bother checking for Zbb -- would crash before getting here. */
+  return 1;
+#elif LJ_TARGET_LINUX
+  return (hwprobe_ret == 0 && ((*hwprobe_ext) & RISCV_HWPROBE_EXT_ZBB)) ? 1 : 0;
+#else
+  return 0;
+#endif
+}
+
+static int riscv_zicond()
+{
+#if defined(__riscv_zicond)
+  /* Don't bother checking for Zicond -- would crash before getting here. */
+  return 1;
+#elif LJ_TARGET_LINUX
+  return (hwprobe_ret == 0 && ((*hwprobe_ext) & RISCV_HWPROBE_EXT_ZICOND)) ? 1 : 0;
+#else
+  return 0;
+#endif
+}
+
+static int riscv_xthead()
+{
+/*
+** Hardcoded as there's no easy way of detection:
+** - SIGILL have some trouble with libluajit as we speak
+** - Checking mvendorid looks good, but might not be reliable.
+*/
+  return 0;
+}
+
+static uint32_t riscv_probe(int (*func)(void), uint32_t flag)
+{
+    return func() ? flag : 0;
+}
+#endif
+
 /* Arch-dependent CPU detection. */
 static uint32_t jit_cpudetect(lua_State *L)
 {
@@ -729,7 +807,26 @@ static uint32_t jit_cpudetect(lua_State *L)
 #endif
 #endif
 #elif LJ_TARGET_RISCV64
-  /* No optional CPU features to detect (for now). */
+#if LJ_HASJIT
+
+#if LJ_TARGET_LINUX
+  /* HWPROBE-based detection of RVC, Zba, Zbb and Zicond. */
+  hwprobe_ret = syscall(__NR_riscv_hwprobe, &hwprobe_requests,
+                sizeof(hwprobe_requests) / sizeof(struct riscv_hwprobe), 0,
+			          NULL, 0);
+
+  flags |= riscv_probe(riscv_compressed, JIT_F_RVC);
+  flags |= riscv_probe(riscv_zba, JIT_F_RVZba);
+  flags |= riscv_probe(riscv_zbb, JIT_F_RVZbb);
+  flags |= riscv_probe(riscv_zicond, JIT_F_RVZicond);
+  flags |= riscv_probe(riscv_xthead, JIT_F_RVXThead);
+
+#endif
+
+  /* Detect V/P? */
+  /* V have no hardware available, P not ratified yet. */
+#endif
+
 #else
 #error "Missing CPU detection for this architecture"
 #endif

src/lj_arch.h

@@ -439,7 +439,6 @@
 #define LJ_TARGET_MASKSHIFT	1
 #define LJ_TARGET_MASKROT	1
 #define LJ_ARCH_NUMMODE		LJ_NUMMODE_DUAL
-#define LJ_ARCH_NOJIT		1       /* NYI */
 
 #define LJ_ARCH_NOMEMPROF	1
 #define LJ_ARCH_NOSYSPROF	1

src/lj_asm.c

@@ -185,6 +185,8 @@ IRFLDEF(FLOFS)
 #include "lj_emit_ppc.h"
 #elif LJ_TARGET_MIPS
 #include "lj_emit_mips.h"
+#elif LJ_TARGET_RISCV64
+#include "lj_emit_riscv.h"
 #else
 #error "Missing instruction emitter for target CPU"
 #endif
@@ -1641,6 +1643,8 @@ static void asm_loop(ASMState *as)
 #include "lj_asm_ppc.h"
 #elif LJ_TARGET_MIPS
 #include "lj_asm_mips.h"
+#elif LJ_TARGET_RISCV64
+#include "lj_asm_riscv64.h"
 #else
 #error "Missing assembler for target CPU"
 #endif