[PATCH v3 02/14] util: Add RISC-V vector extension probe in cpuinfo

[LIU Zhiwei]

From: TANG Tiancheng <tangtiancheng.ttc@alibaba-inc.com>

Add support for probing RISC-V vector extension availability in
the backend. This information will be used when deciding whether
to use vector instructions in code generation.

While the compiler doesn't support RISCV_HWPROBE_EXT_ZVE64X,
we use RISCV_HWPROBE_IMA_V instead.

Signed-off-by: TANG Tiancheng <tangtiancheng.ttc@alibaba-inc.com>
Reviewed-by: Liu Zhiwei <zhiwei_liu@linux.alibaba.com>
---
 host/include/riscv/host/cpuinfo.h |  3 +++
 util/cpuinfo-riscv.c              | 26 ++++++++++++++++++++++++--
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/host/include/riscv/host/cpuinfo.h 
b/host/include/riscv/host/cpuinfo.h
index 2b00660e36..727cb3204b 100644
--- a/host/include/riscv/host/cpuinfo.h
+++ b/host/include/riscv/host/cpuinfo.h
@@ -10,9 +10,12 @@
 #define CPUINFO_ZBA             (1u << 1)
 #define CPUINFO_ZBB             (1u << 2)
 #define CPUINFO_ZICOND          (1u << 3)
+#define CPUINFO_ZVE64X          (1u << 4)
 
 /* Initialized with a constructor. */
 extern unsigned cpuinfo;
+extern unsigned riscv_vlenb;
+#define riscv_vlen (riscv_vlenb * 8)
 
 /*
  * We cannot rely on constructor ordering, so other constructors must
diff --git a/util/cpuinfo-riscv.c b/util/cpuinfo-riscv.c
index 497ce12680..05917c42d8 100644
--- a/util/cpuinfo-riscv.c
+++ b/util/cpuinfo-riscv.c
@@ -12,6 +12,7 @@
 #endif
 
 unsigned cpuinfo;
+unsigned riscv_vlenb;
 static volatile sig_atomic_t got_sigill;
 
 static void sigill_handler(int signo, siginfo_t *si, void *data)
@@ -33,7 +34,7 @@ static void sigill_handler(int signo, siginfo_t *si, void 
*data)
 /* Called both as constructor and (possibly) via other constructors. */
 unsigned __attribute__((constructor)) cpuinfo_init(void)
 {
-    unsigned left = CPUINFO_ZBA | CPUINFO_ZBB | CPUINFO_ZICOND;
+    unsigned left = CPUINFO_ZBA | CPUINFO_ZBB | CPUINFO_ZICOND | 
CPUINFO_ZVE64X;
     unsigned info = cpuinfo;
 
     if (info) {
@@ -49,6 +50,9 @@ unsigned __attribute__((constructor)) cpuinfo_init(void)
 #endif
 #if defined(__riscv_arch_test) && defined(__riscv_zicond)
     info |= CPUINFO_ZICOND;
+#endif
+#if defined(__riscv_arch_test) && defined(__riscv_zve64x)
+    info |= CPUINFO_ZVE64X;
 #endif
     left &= ~info;
 
@@ -64,7 +68,8 @@ unsigned __attribute__((constructor)) cpuinfo_init(void)
             && pair.key >= 0) {
             info |= pair.value & RISCV_HWPROBE_EXT_ZBA ? CPUINFO_ZBA : 0;
             info |= pair.value & RISCV_HWPROBE_EXT_ZBB ? CPUINFO_ZBB : 0;
-            left &= ~(CPUINFO_ZBA | CPUINFO_ZBB);
+            info |= pair.value & RISCV_HWPROBE_IMA_V ? CPUINFO_ZVE64X : 0;
+            left &= ~(CPUINFO_ZBA | CPUINFO_ZBB | CPUINFO_ZVE64X);
 #ifdef RISCV_HWPROBE_EXT_ZICOND
             info |= pair.value & RISCV_HWPROBE_EXT_ZICOND ? CPUINFO_ZICOND : 0;
             left &= ~CPUINFO_ZICOND;
@@ -112,6 +117,23 @@ unsigned __attribute__((constructor)) cpuinfo_init(void)
         assert(left == 0);
     }
 
+    if (info & CPUINFO_ZVE64X) {
+        /*
+         * Get vlenb for Vector: vsetvli rd, x0, e64.
+         * VLMAX = LMUL * VLEN / SEW.
+         * The "vsetvli rd, x0, e64" means "LMUL = 1, SEW = 64, rd = VLMAX",
+         * so "vlenb = VLMAX * 64 / 8".
+         */
+        unsigned long vlmax = 0;
+        asm volatile(".insn i 0x57, 7, %0, zero, (3 << 3)" : "=r"(vlmax));
+        if (vlmax) {
+            riscv_vlenb = vlmax * 8;
+            assert(riscv_vlen >= 64 && !(riscv_vlen & (riscv_vlen - 1)));
+        } else {
+            info &= ~CPUINFO_ZVE64X;
+        }
+    }
+
     info |= CPUINFO_ALWAYS;
     cpuinfo = info;
     return info;
-- 
2.43.0