[PATCH for-9.0 v13 4/8] target/riscv: always clear vstart in whole vec move insns

[Daniel Henrique Barboza]

These insns have 2 paths: we'll either have vstart already cleared if
vstart_eq_zero or we'll do a brcond to check if vstart >= maxsz to call
the 'vmvr_v' helper. The helper will clear vstart if it executes until
the end, or if vstart >= vl.

However, if vstart >= maxsz, the helper will be skipped, and vstart
won't be cleared since the helper is being responsible from doing it.

We want to make the helpers responsible to manage vstart, including
these corner cases, precisely to avoid these situations. Move the vstart
>= maxsz cond to the helper, and be sure to clear vstart if that
happens.  This way we're now 100% sure that vstart is being clearer in
the end of the execution, regardless of the path taken.

Fixes: f714361ed7 ("target/riscv: rvv-1.0: implement vstart CSR")
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/insn_trans/trans_rvv.c.inc | 3 ---
 target/riscv/vector_helper.c            | 5 +++++
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/target/riscv/insn_trans/trans_rvv.c.inc 
b/target/riscv/insn_trans/trans_rvv.c.inc
index 8c16a9f5b3..52c26a7834 100644
--- a/target/riscv/insn_trans/trans_rvv.c.inc
+++ b/target/riscv/insn_trans/trans_rvv.c.inc
@@ -3664,12 +3664,9 @@ static bool trans_##NAME(DisasContext *s, arg_##NAME * 
a)               \
                              vreg_ofs(s, a->rs2), maxsz, maxsz);        \
             mark_vs_dirty(s);                                           \
         } else {                                                        \
-            TCGLabel *over = gen_new_label();                           \
-            tcg_gen_brcondi_tl(TCG_COND_GEU, cpu_vstart, maxsz, over);  \
             tcg_gen_gvec_2_ptr(vreg_ofs(s, a->rd), vreg_ofs(s, a->rs2), \
                                tcg_env, maxsz, maxsz, 0, gen_helper_vmvr_v); \
             mark_vs_dirty(s);                                           \
-            gen_set_label(over);                                        \
         }                                                               \
         return true;                                                    \
     }                                                                   \
diff --git a/target/riscv/vector_helper.c b/target/riscv/vector_helper.c
index b4360dbd52..7260a5972b 100644
--- a/target/riscv/vector_helper.c
+++ b/target/riscv/vector_helper.c
@@ -5163,6 +5163,11 @@ void HELPER(vmvr_v)(void *vd, void *vs2, CPURISCVState 
*env, uint32_t desc)
 
     VSTART_CHECK_EARLY_EXIT(env);
 
+    if (env->vstart >= maxsz) {
+        env->vstart = 0;
+        return;
+    }
+
     memcpy((uint8_t *)vd + H1(i),
            (uint8_t *)vs2 + H1(i),
            maxsz - startb);
-- 
2.43.2