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[PATCH] target/riscv/vector_helper.c: Avoid shifting negative in fractio


From: Max Chou
Subject: [PATCH] target/riscv/vector_helper.c: Avoid shifting negative in fractional LMUL checking
Date: Thu, 7 Mar 2024 00:10:22 +0800

When vlmul is larger than 5, the original fractional LMUL checking may
gets unexpected result.

Signed-off-by: Max Chou <max.chou@sifive.com>
---
 target/riscv/vector_helper.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/target/riscv/vector_helper.c b/target/riscv/vector_helper.c
index 84cec73eb20..adceec378fd 100644
--- a/target/riscv/vector_helper.c
+++ b/target/riscv/vector_helper.c
@@ -53,10 +53,9 @@ target_ulong HELPER(vsetvl)(CPURISCVState *env, target_ulong 
s1,
          * VLEN * LMUL >= SEW
          * VLEN >> (8 - lmul) >= sew
          * (vlenb << 3) >> (8 - lmul) >= sew
-         * vlenb >> (8 - 3 - lmul) >= sew
          */
         if (vlmul == 4 ||
-            cpu->cfg.vlenb >> (8 - 3 - vlmul) < sew) {
+            ((cpu->cfg.vlenb << 3) >> (8 - vlmul)) < sew) {
             vill = true;
         }
     }
-- 
2.34.1




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