From e1ce400d1fe432e5eee562ec4d000082e0189a0e Mon Sep 17 00:00:00 2001
From: gns <infiwang@proton.me>
Date: Wed, 6 Mar 2024 09:27:26 +0800
Subject: [PATCH] riscv(support): add extension detection

---
 src/lib_jit.c | 123 ++++++++++++++++++++++++++++++++++++++++++++++++++
 src/lj_jit.h  |  11 +++++
 2 files changed, 134 insertions(+)

diff --git a/src/lib_jit.c b/src/lib_jit.c
index fd8e585b..e97e4d45 100644
--- a/src/lib_jit.c
+++ b/src/lib_jit.c
@@ -631,6 +631,111 @@ JIT_PARAMDEF(JIT_PARAMINIT)
 #include <sys/utsname.h>
 #endif
 
+#if LJ_TARGET_RISCV64 && LJ_TARGET_POSIX
+#include <setjmp.h>
+#include <signal.h>
+static sigjmp_buf sigbuf = {0};
+static void detect_sigill(int sig)
+{
+  siglongjmp(sigbuf, 1);
+}
+
+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 defined(__GNUC__)
+  /* c.nop; c.nop; */
+  __asm__(".4byte 0x00010001");
+  return 1;
+#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 defined(__GNUC__)
+  /* Don't bother verifying the result, just check if the instruction exists. */
+  /* add.uw zero, zero, zero */
+  __asm__(".4byte 0x0800003b");
+  return 1;
+#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 defined(__GNUC__)
+  register int t asm ("a0");
+  /* addi a0, zero, 255; sext.b a0, a0; */
+  __asm__("addi a0, zero, 255\n\t.4byte 0x60451513");
+  return t < 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 defined(__GNUC__)
+  /* czero.eqz zero, zero, zero; */
+  __asm__(".4byte 0x0e005033");
+  return 1;
+#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;
+#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;
+#elif defined(__GNUC__)
+    register int t asm ("a0");
+    /* C906 & C910 & C908 all have "xtheadc", XTheadBb subset "xtheadc". */
+    /* Therefore assume XThead* are present if XTheadBb is present. */
+    /* addi a0, zero, 255; th.ext a0, a0, 7, 0; */
+    __asm__("addi a0, zero, 255\n\t.4byte 0x1c05250b");
+    return t == -1;		/* In case of collision with other vendor extensions. */
+#else
+    return 0;
+#endif
+}
+
+static uint32_t riscv_probe(int (*func)(void), uint32_t flag)
+{
+    if (sigsetjmp(sigbuf, 1) == 0) {
+        return func() ? flag : 0;
+    } else return 0;
+}
+#endif
+
 /* Arch-dependent CPU feature detection. */
 static uint32_t jit_cpudetect(void)
 {
@@ -702,6 +807,24 @@ static uint32_t jit_cpudetect(void)
   }
 #endif
 
+#elif LJ_TARGET_RISCV64
+#if LJ_HASJIT
+  /* SIGILL-based detection of RVC, Zba, Zbb and XThead. Welcome to the future. */
+  struct sigaction old = {0}, act = {0};
+  act.sa_handler = detect_sigill;
+  sigaction(SIGILL, &act, &old);
+  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);
+  sigaction(SIGILL, &old, NULL);
+
+  /* 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 102ba0b4..e61d99ff 100644
--- a/src/lj_jit.h
+++ b/src/lj_jit.h
@@ -67,6 +67,17 @@
 #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"
+
 #else
 
 #define JIT_F_CPUSTRING		""