[PATCH v1 01/15] util: Add RISC-V vector extension probe in cpuinfo

[LIU Zhiwei <zhiwei_liu@linux.alibaba.com>]

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 |  1 +
 util/cpuinfo-riscv.c              | 20 ++++++++++++++++++--
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/host/include/riscv/host/cpuinfo.h b/host/include/riscv/host/cpuinfo.h
index 2b00660e36..bf6ae51f72 100644
--- a/host/include/riscv/host/cpuinfo.h
+++ b/host/include/riscv/host/cpuinfo.h
@@ -10,6 +10,7 @@
 #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;
diff --git a/util/cpuinfo-riscv.c b/util/cpuinfo-riscv.c
index 497ce12680..551821edef 100644
--- a/util/cpuinfo-riscv.c
+++ b/util/cpuinfo-riscv.c
@@ -33,7 +33,7 @@ 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 +49,9 @@ 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 +67,8 @@ 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;
@@ -108,6 +112,18 @@ unsigned __attribute__((constructor)) cpuinfo_init(void)
             left &= ~CPUINFO_ZICOND;
         }
 
+        if (left & CPUINFO_ZVE64X) {
+            /* Probe for Vector: vsetivli t0,1,e64,m1,ta,ma */
+            unsigned vl;
+            got_sigill = 0;
+
+            asm volatile(
+                "vsetivli %0, 1, e64, m1, ta, ma\n\t"
+                : "=r"(vl) : : "vl"
+            );
+            info |= (got_sigill || vl != 1) ? 0 : CPUINFO_ZVE64X;
+        }
+
         sigaction(SIGILL, &sa_old, NULL);
         assert(left == 0);
     }
-- 
2.43.0