From 89e0d60ad01107d9b0851718429c6ec882e749cc Mon Sep 17 00:00:00 2001
From: gns <wangbingzhen.riscv@isrc.iscas.ac.cn>
Date: Tue, 11 Aug 2026 20:36:09 +0800
Subject: [PATCH] riscv(support): add extension detection

---
 src/lib_jit.c | 120 ++++++++++++++++++++++++++++++++++++++++++++++++++
 src/lj_jit.h  |  40 +++++++++++++++++
 2 files changed, 160 insertions(+)

diff --git a/src/lib_jit.c b/src/lib_jit.c
index 6e01e374..1caf92ba 100644
--- a/src/lib_jit.c
+++ b/src/lib_jit.c
@@ -647,6 +647,104 @@ 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_zfa()
+{
+#if defined(__riscv_zfa)
+  /* Don't bother checking for Zfa -- would crash before getting here. */
+  return 1;
+#elif LJ_TARGET_LINUX
+  return (hwprobe_ret == 0 && ((*hwprobe_ext) & RISCV_HWPROBE_EXT_ZFA)) ? 1 : 0;
+#else
+  return 0;
+#endif
+}
+
+static int riscv_xthead()
+{
+#if (defined(__riscv_xtheadba) \
+  && defined(__riscv_xtheadbb) \
+  && defined(__riscv_xtheadcondmov) \
+  && defined(__riscv_xtheadmac))
+  /* Don't bother checking for XThead -- would crash before getting here. */
+  return 1;
+#else
+/*
+** 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;
+#endif
+}
+
+static uint32_t riscv_probe(int (*func)(void), uint32_t flag)
+{
+    return func() ? flag : 0;
+}
+#endif
+
 /* Arch-dependent CPU feature detection. */
 static uint32_t jit_cpudetect(void)
 {
@@ -724,6 +822,28 @@ static uint32_t jit_cpudetect(void)
   }
 #endif
 
+#elif LJ_TARGET_RISCV64
+#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_zfa, JIT_F_RVZfa);
+  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
diff --git a/src/lj_jit.h b/src/lj_jit.h
index af50e5c1..b0e28703 100644
--- a/src/lj_jit.h
+++ b/src/lj_jit.h
@@ -67,6 +67,46 @@
 #endif
 #endif
 
+#elif LJ_TARGET_RISCV64
+
+#define JIT_F_RVC		(JIT_F_CPU << 0)
+#define JIT_F_RVZba		(JIT_F_CPU << 1)
+#define JIT_F_RVZbb		(JIT_F_CPU << 2)
+#define JIT_F_RVZicond		(JIT_F_CPU << 3)
+#define JIT_F_RVZfa		(JIT_F_CPU << 4)
+#define JIT_F_RVXThead		(JIT_F_CPU << 5)
+
+#define JIT_F_CPUSTRING		"\003RVC\003Zba\003Zbb\006Zicond\003Zfa\006XThead"
+
+#if LJ_TARGET_LINUX
+#include <sys/syscall.h>
+
+#ifndef __NR_riscv_hwprobe
+#ifndef __NR_arch_specific_syscall
+#define __NR_arch_specific_syscall 244
+#endif
+#define __NR_riscv_hwprobe (__NR_arch_specific_syscall + 14)
+#endif
+
+struct riscv_hwprobe {
+    int64_t key;
+    uint64_t value;
+};
+
+#define RISCV_HWPROBE_KEY_MVENDORID     0
+#define RISCV_HWPROBE_KEY_MARCHID       1
+#define RISCV_HWPROBE_KEY_MIMPID        2
+#define RISCV_HWPROBE_KEY_BASE_BEHAVIOR 3
+#define RISCV_HWPROBE_KEY_IMA_EXT_0     4
+
+#define RISCV_HWPROBE_IMA_C      (1 << 1)
+#define RISCV_HWPROBE_EXT_ZBA    (1 << 3)
+#define RISCV_HWPROBE_EXT_ZBB    (1 << 4)
+#define RISCV_HWPROBE_EXT_ZFA    (1ULL << 32)
+#define RISCV_HWPROBE_EXT_ZICOND (1ULL << 35)
+
+#endif
+
 #else
 
 #define JIT_F_CPUSTRING		""