target/riscv/vector_helpers: do early exit when vstart >= vl

We're going to make changes that will required each helper to be
responsible for the 'vstart' management, i.e. we will relieve the
'vstart < vl' assumption that helpers have today.

Helpers are usually able to deal with vstart >= vl, i.e. doing nothing
aside from setting vstart = 0 at the end, but the tail update functions
will update the tail regardless of vstart being valid or not. Unifying
the tail update process in a single function that would handle the
vstart >= vl case isn't trivial (see [1] for more info).

This patch takes a blunt approach: do an early exit in every single
vector helper if vstart >= vl, unless the helper is guarded with
vstart_eq_zero in the translation. For those cases the helper is ready
to deal with cases where vl might be zero, i.e. throwing exceptions
based on it like vcpop_m() and first_m().

Helpers that weren't changed:

- vcpop_m(), vfirst_m(), vmsetm(), GEN_VEXT_VIOTA_M(): these are guarded
  directly with vstart_eq_zero;

- GEN_VEXT_VCOMPRESS_VM(): guarded with vcompress_vm_check() that checks
  vstart_eq_zero;

- GEN_VEXT_RED(): guarded with either reduction_check() or
  reduction_widen_check(), both check vstart_eq_zero;

- GEN_VEXT_FRED(): guarded with either freduction_check() or
  freduction_widen_check(), both check vstart_eq_zero.

Another exception is vext_ldst_whole(), who operates on effective vector
length regardless of the current settings in vtype and vl.

[1] https://lore.kernel.org/qemu-riscv/1590234b-0291-432a-a0fa-c5a6876097bc@linux.alibaba.com/

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20240314175704.478276-7-dbarboza@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

4 files changed, 111 insertions, 0 deletions

diff --git a/target/riscv/vcrypto_helper.c b/target/riscv/vcrypto_helper.c
index e2d719b13b..f7423df226 100644
--- a/target/riscv/vcrypto_helper.c
+++ b/target/riscv/vcrypto_helper.c
@@ -222,6 +222,8 @@ static inline void xor_round_key(AESState *round_state, AESState *round_key)
         uint32_t total_elems = vext_get_total_elems(env, desc, 4);        \
         uint32_t vta = vext_vta(desc);                                    \
                                                                           \
+        VSTART_CHECK_EARLY_EXIT(env);                                     \
+                                                                          \
         for (uint32_t i = env->vstart / 4; i < env->vl / 4; i++) {        \
             AESState round_key;                                           \
             round_key.d[0] = *((uint64_t *)vs2 + H8(i * 2 + 0));          \
@@ -246,6 +248,8 @@ static inline void xor_round_key(AESState *round_state, AESState *round_key)
         uint32_t total_elems = vext_get_total_elems(env, desc, 4);        \
         uint32_t vta = vext_vta(desc);                                    \
                                                                           \
+        VSTART_CHECK_EARLY_EXIT(env);                                     \
+                                                                          \
         for (uint32_t i = env->vstart / 4; i < env->vl / 4; i++) {        \
             AESState round_key;                                           \
             round_key.d[0] = *((uint64_t *)vs2 + H8(0));                  \
@@ -305,6 +309,8 @@ void HELPER(vaeskf1_vi)(void *vd_vptr, void *vs2_vptr, uint32_t uimm,
     uint32_t total_elems = vext_get_total_elems(env, desc, 4);
     uint32_t vta = vext_vta(desc);
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     uimm &= 0b1111;
     if (uimm > 10 || uimm == 0) {
         uimm ^= 0b1000;
@@ -351,6 +357,8 @@ void HELPER(vaeskf2_vi)(void *vd_vptr, void *vs2_vptr, uint32_t uimm,
     uint32_t total_elems = vext_get_total_elems(env, desc, 4);
     uint32_t vta = vext_vta(desc);
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     uimm &= 0b1111;
     if (uimm > 14 || uimm < 2) {
         uimm ^= 0b1000;
@@ -457,6 +465,8 @@ void HELPER(vsha2ms_vv)(void *vd, void *vs1, void *vs2, CPURISCVState *env,
     uint32_t total_elems;
     uint32_t vta = vext_vta(desc);
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (uint32_t i = env->vstart / 4; i < env->vl / 4; i++) {
         if (sew == MO_32) {
             vsha2ms_e32(((uint32_t *)vd) + i * 4, ((uint32_t *)vs1) + i * 4,
@@ -572,6 +582,8 @@ void HELPER(vsha2ch32_vv)(void *vd, void *vs1, void *vs2, CPURISCVState *env,
     uint32_t total_elems;
     uint32_t vta = vext_vta(desc);
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (uint32_t i = env->vstart / 4; i < env->vl / 4; i++) {
         vsha2c_32(((uint32_t *)vs2) + 4 * i, ((uint32_t *)vd) + 4 * i,
                   ((uint32_t *)vs1) + 4 * i + 2);
@@ -590,6 +602,8 @@ void HELPER(vsha2ch64_vv)(void *vd, void *vs1, void *vs2, CPURISCVState *env,
     uint32_t total_elems;
     uint32_t vta = vext_vta(desc);
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (uint32_t i = env->vstart / 4; i < env->vl / 4; i++) {
         vsha2c_64(((uint64_t *)vs2) + 4 * i, ((uint64_t *)vd) + 4 * i,
                   ((uint64_t *)vs1) + 4 * i + 2);
@@ -608,6 +622,8 @@ void HELPER(vsha2cl32_vv)(void *vd, void *vs1, void *vs2, CPURISCVState *env,
     uint32_t total_elems;
     uint32_t vta = vext_vta(desc);
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (uint32_t i = env->vstart / 4; i < env->vl / 4; i++) {
         vsha2c_32(((uint32_t *)vs2) + 4 * i, ((uint32_t *)vd) + 4 * i,
                   (((uint32_t *)vs1) + 4 * i));
@@ -626,6 +642,8 @@ void HELPER(vsha2cl64_vv)(void *vd, void *vs1, void *vs2, CPURISCVState *env,
     uint32_t total_elems;
     uint32_t vta = vext_vta(desc);
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (uint32_t i = env->vstart / 4; i < env->vl / 4; i++) {
         vsha2c_64(((uint64_t *)vs2) + 4 * i, ((uint64_t *)vd) + 4 * i,
                   (((uint64_t *)vs1) + 4 * i));
@@ -658,6 +676,8 @@ void HELPER(vsm3me_vv)(void *vd_vptr, void *vs1_vptr, void *vs2_vptr,
     uint32_t *vs1 = vs1_vptr;
     uint32_t *vs2 = vs2_vptr;
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (int i = env->vstart / 8; i < env->vl / 8; i++) {
         uint32_t w[24];
         for (int j = 0; j < 8; j++) {
@@ -757,6 +777,8 @@ void HELPER(vsm3c_vi)(void *vd_vptr, void *vs2_vptr, uint32_t uimm,
     uint32_t *vs2 = vs2_vptr;
     uint32_t v1[8], v2[8], v3[8];
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (int i = env->vstart / 8; i < env->vl / 8; i++) {
         for (int k = 0; k < 8; k++) {
             v2[k] = bswap32(vd[H4(i * 8 + k)]);
@@ -780,6 +802,8 @@ void HELPER(vghsh_vv)(void *vd_vptr, void *vs1_vptr, void *vs2_vptr,
     uint32_t vta = vext_vta(desc);
     uint32_t total_elems = vext_get_total_elems(env, desc, 4);
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (uint32_t i = env->vstart / 4; i < env->vl / 4; i++) {
         uint64_t Y[2] = {vd[i * 2 + 0], vd[i * 2 + 1]};
         uint64_t H[2] = {brev8(vs2[i * 2 + 0]), brev8(vs2[i * 2 + 1])};
@@ -817,6 +841,8 @@ void HELPER(vgmul_vv)(void *vd_vptr, void *vs2_vptr, CPURISCVState *env,
     uint32_t vta = vext_vta(desc);
     uint32_t total_elems = vext_get_total_elems(env, desc, 4);
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (uint32_t i = env->vstart / 4; i < env->vl / 4; i++) {
         uint64_t Y[2] = {brev8(vd[i * 2 + 0]), brev8(vd[i * 2 + 1])};
         uint64_t H[2] = {brev8(vs2[i * 2 + 0]), brev8(vs2[i * 2 + 1])};
@@ -853,6 +879,8 @@ void HELPER(vsm4k_vi)(void *vd, void *vs2, uint32_t uimm5, CPURISCVState *env,
     uint32_t esz = sizeof(uint32_t);
     uint32_t total_elems = vext_get_total_elems(env, desc, esz);
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (uint32_t i = group_start; i < group_end; ++i) {
         uint32_t vstart = i * egs;
         uint32_t vend = (i + 1) * egs;
@@ -909,6 +937,8 @@ void HELPER(vsm4r_vv)(void *vd, void *vs2, CPURISCVState *env, uint32_t desc)
     uint32_t esz = sizeof(uint32_t);
     uint32_t total_elems = vext_get_total_elems(env, desc, esz);
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (uint32_t i = group_start; i < group_end; ++i) {
         uint32_t vstart = i * egs;
         uint32_t vend = (i + 1) * egs;
@@ -943,6 +973,8 @@ void HELPER(vsm4r_vs)(void *vd, void *vs2, CPURISCVState *env, uint32_t desc)
     uint32_t esz = sizeof(uint32_t);
     uint32_t total_elems = vext_get_total_elems(env, desc, esz);
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (uint32_t i = group_start; i < group_end; ++i) {
         uint32_t vstart = i * egs;
         uint32_t vend = (i + 1) * egs;
diff --git a/target/riscv/vector_helper.c b/target/riscv/vector_helper.c
index 1f4c276b21..63a1083f03 100644
--- a/target/riscv/vector_helper.c
+++ b/target/riscv/vector_helper.c
@@ -207,6 +207,8 @@ vext_ldst_stride(void *vd, void *v0, target_ulong base,
     uint32_t esz = 1 << log2_esz;
     uint32_t vma = vext_vma(desc);
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (i = env->vstart; i < env->vl; i++, env->vstart++) {
         k = 0;
         while (k < nf) {
@@ -272,6 +274,8 @@ vext_ldst_us(void *vd, target_ulong base, CPURISCVState *env, uint32_t desc,
     uint32_t max_elems = vext_max_elems(desc, log2_esz);
     uint32_t esz = 1 << log2_esz;
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     /* load bytes from guest memory */
     for (i = env->vstart; i < evl; i++, env->vstart++) {
         k = 0;
@@ -386,6 +390,8 @@ vext_ldst_index(void *vd, void *v0, target_ulong base,
     uint32_t esz = 1 << log2_esz;
     uint32_t vma = vext_vma(desc);
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     /* load bytes from guest memory */
     for (i = env->vstart; i < env->vl; i++, env->vstart++) {
         k = 0;
@@ -477,6 +483,8 @@ vext_ldff(void *vd, void *v0, target_ulong base,
     target_ulong addr, offset, remain;
     int mmu_index = riscv_env_mmu_index(env, false);
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     /* probe every access */
     for (i = env->vstart; i < env->vl; i++) {
         if (!vm && !vext_elem_mask(v0, i)) {
@@ -882,6 +890,8 @@ void HELPER(NAME)(void *vd, void *v0, void *vs1, void *vs2,   \
     uint32_t vta = vext_vta(desc);                            \
     uint32_t i;                                               \
                                                               \
+    VSTART_CHECK_EARLY_EXIT(env);                             \
+                                                              \
     for (i = env->vstart; i < vl; i++) {                      \
         ETYPE s1 = *((ETYPE *)vs1 + H(i));                    \
         ETYPE s2 = *((ETYPE *)vs2 + H(i));                    \
@@ -914,6 +924,8 @@ void HELPER(NAME)(void *vd, void *v0, target_ulong s1, void *vs2,        \
     uint32_t vta = vext_vta(desc);                                       \
     uint32_t i;                                                          \
                                                                          \
+    VSTART_CHECK_EARLY_EXIT(env);                                        \
+                                                                         \
     for (i = env->vstart; i < vl; i++) {                                 \
         ETYPE s2 = *((ETYPE *)vs2 + H(i));                               \
         ETYPE carry = vext_elem_mask(v0, i);                             \
@@ -949,6 +961,8 @@ void HELPER(NAME)(void *vd, void *v0, void *vs1, void *vs2,   \
     uint32_t vta_all_1s = vext_vta_all_1s(desc);              \
     uint32_t i;                                               \
                                                               \
+    VSTART_CHECK_EARLY_EXIT(env);                             \
+                                                              \
     for (i = env->vstart; i < vl; i++) {                      \
         ETYPE s1 = *((ETYPE *)vs1 + H(i));                    \
         ETYPE s2 = *((ETYPE *)vs2 + H(i));                    \
@@ -987,6 +1001,8 @@ void HELPER(NAME)(void *vd, void *v0, target_ulong s1,          \
     uint32_t vta_all_1s = vext_vta_all_1s(desc);                \
     uint32_t i;                                                 \
                                                                 \
+    VSTART_CHECK_EARLY_EXIT(env);                               \
+                                                                \
     for (i = env->vstart; i < vl; i++) {                        \
         ETYPE s2 = *((ETYPE *)vs2 + H(i));                      \
         ETYPE carry = !vm && vext_elem_mask(v0, i);             \
@@ -1083,6 +1099,8 @@ void HELPER(NAME)(void *vd, void *v0, void *vs1,                          \
     uint32_t vma = vext_vma(desc);                                        \
     uint32_t i;                                                           \
                                                                           \
+    VSTART_CHECK_EARLY_EXIT(env);                                         \
+                                                                          \
     for (i = env->vstart; i < vl; i++) {                                  \
         if (!vm && !vext_elem_mask(v0, i)) {                              \
             /* set masked-off elements to 1s */                           \
@@ -1130,6 +1148,8 @@ void HELPER(NAME)(void *vd, void *v0, target_ulong s1,      \
     uint32_t vma = vext_vma(desc);                          \
     uint32_t i;                                             \
                                                             \
+    VSTART_CHECK_EARLY_EXIT(env);                           \
+                                                            \
     for (i = env->vstart; i < vl; i++) {                    \
         if (!vm && !vext_elem_mask(v0, i)) {                \
             /* set masked-off elements to 1s */             \
@@ -1192,6 +1212,8 @@ void HELPER(NAME)(void *vd, void *v0, void *vs1, void *vs2,   \
     uint32_t vma = vext_vma(desc);                            \
     uint32_t i;                                               \
                                                               \
+    VSTART_CHECK_EARLY_EXIT(env);                             \
+                                                              \
     for (i = env->vstart; i < vl; i++) {                      \
         ETYPE s1 = *((ETYPE *)vs1 + H(i));                    \
         ETYPE s2 = *((ETYPE *)vs2 + H(i));                    \
@@ -1257,6 +1279,8 @@ void HELPER(NAME)(void *vd, void *v0, target_ulong s1, void *vs2,   \
     uint32_t vma = vext_vma(desc);                                  \
     uint32_t i;                                                     \
                                                                     \
+    VSTART_CHECK_EARLY_EXIT(env);                                   \
+                                                                    \
     for (i = env->vstart; i < vl; i++) {                            \
         ETYPE s2 = *((ETYPE *)vs2 + H(i));                          \
         if (!vm && !vext_elem_mask(v0, i)) {                        \
@@ -1804,6 +1828,8 @@ void HELPER(NAME)(void *vd, void *vs1, CPURISCVState *env,           \
     uint32_t vta = vext_vta(desc);                                   \
     uint32_t i;                                                      \
                                                                      \
+    VSTART_CHECK_EARLY_EXIT(env);                                    \
+                                                                     \
     for (i = env->vstart; i < vl; i++) {                             \
         ETYPE s1 = *((ETYPE *)vs1 + H(i));                           \
         *((ETYPE *)vd + H(i)) = s1;                                  \
@@ -1828,6 +1854,8 @@ void HELPER(NAME)(void *vd, uint64_t s1, CPURISCVState *env,         \
     uint32_t vta = vext_vta(desc);                                   \
     uint32_t i;                                                      \
                                                                      \
+    VSTART_CHECK_EARLY_EXIT(env);                                    \
+                                                                     \
     for (i = env->vstart; i < vl; i++) {                             \
         *((ETYPE *)vd + H(i)) = (ETYPE)s1;                           \
     }                                                                \
@@ -1851,6 +1879,8 @@ void HELPER(NAME)(void *vd, void *v0, void *vs1, void *vs2,          \
     uint32_t vta = vext_vta(desc);                                   \
     uint32_t i;                                                      \
                                                                      \
+    VSTART_CHECK_EARLY_EXIT(env);                                    \
+                                                                     \
     for (i = env->vstart; i < vl; i++) {                             \
         ETYPE *vt = (!vext_elem_mask(v0, i) ? vs2 : vs1);            \
         *((ETYPE *)vd + H(i)) = *(vt + H(i));                        \
@@ -1875,6 +1905,8 @@ void HELPER(NAME)(void *vd, void *v0, target_ulong s1,               \
     uint32_t vta = vext_vta(desc);                                   \
     uint32_t i;                                                      \
                                                                      \
+    VSTART_CHECK_EARLY_EXIT(env);                                    \
+                                                                     \
     for (i = env->vstart; i < vl; i++) {                             \
         ETYPE s2 = *((ETYPE *)vs2 + H(i));                           \
         ETYPE d = (!vext_elem_mask(v0, i) ? s2 :                     \
@@ -1920,6 +1952,8 @@ vext_vv_rm_1(void *vd, void *v0, void *vs1, void *vs2,
              uint32_t vl, uint32_t vm, int vxrm,
              opivv2_rm_fn *fn, uint32_t vma, uint32_t esz)
 {
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (uint32_t i = env->vstart; i < vl; i++) {
         if (!vm && !vext_elem_mask(v0, i)) {
             /* set masked-off elements to 1s */
@@ -2045,6 +2079,8 @@ vext_vx_rm_1(void *vd, void *v0, target_long s1, void *vs2,
              uint32_t vl, uint32_t vm, int vxrm,
              opivx2_rm_fn *fn, uint32_t vma, uint32_t esz)
 {
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (uint32_t i = env->vstart; i < vl; i++) {
         if (!vm && !vext_elem_mask(v0, i)) {
             /* set masked-off elements to 1s */
@@ -2842,6 +2878,8 @@ void HELPER(NAME)(void *vd, void *v0, void *vs1,          \
     uint32_t vma = vext_vma(desc);                        \
     uint32_t i;                                           \
                                                           \
+    VSTART_CHECK_EARLY_EXIT(env);                         \
+                                                          \
     for (i = env->vstart; i < vl; i++) {                  \
         if (!vm && !vext_elem_mask(v0, i)) {              \
             /* set masked-off elements to 1s */           \
@@ -2885,6 +2923,8 @@ void HELPER(NAME)(void *vd, void *v0, uint64_t s1,        \
     uint32_t vma = vext_vma(desc);                        \
     uint32_t i;                                           \
                                                           \
+    VSTART_CHECK_EARLY_EXIT(env);                         \
+                                                          \
     for (i = env->vstart; i < vl; i++) {                  \
         if (!vm && !vext_elem_mask(v0, i)) {              \
             /* set masked-off elements to 1s */           \
@@ -3471,6 +3511,8 @@ void HELPER(NAME)(void *vd, void *v0, void *vs2,       \
     uint32_t vma = vext_vma(desc);                     \
     uint32_t i;                                        \
                                                        \
+    VSTART_CHECK_EARLY_EXIT(env);                      \
+                                                       \
     if (vl == 0) {                                     \
         return;                                        \
     }                                                  \
@@ -3992,6 +4034,8 @@ void HELPER(NAME)(void *vd, void *v0, void *vs1, void *vs2,   \
     uint32_t vma = vext_vma(desc);                            \
     uint32_t i;                                               \
                                                               \
+    VSTART_CHECK_EARLY_EXIT(env);                             \
+                                                              \
     for (i = env->vstart; i < vl; i++) {                      \
         ETYPE s1 = *((ETYPE *)vs1 + H(i));                    \
         ETYPE s2 = *((ETYPE *)vs2 + H(i));                    \
@@ -4032,6 +4076,8 @@ void HELPER(NAME)(void *vd, void *v0, uint64_t s1, void *vs2,       \
     uint32_t vma = vext_vma(desc);                                  \
     uint32_t i;                                                     \
                                                                     \
+    VSTART_CHECK_EARLY_EXIT(env);                                   \
+                                                                    \
     for (i = env->vstart; i < vl; i++) {                            \
         ETYPE s2 = *((ETYPE *)vs2 + H(i));                          \
         if (!vm && !vext_elem_mask(v0, i)) {                        \
@@ -4225,6 +4271,8 @@ void HELPER(NAME)(void *vd, void *v0, uint64_t s1, void *vs2, \
     uint32_t vta = vext_vta(desc);                            \
     uint32_t i;                                               \
                                                               \
+    VSTART_CHECK_EARLY_EXIT(env);                             \
+                                                              \
     for (i = env->vstart; i < vl; i++) {                      \
         ETYPE s2 = *((ETYPE *)vs2 + H(i));                    \
         *((ETYPE *)vd + H(i)) =                               \
@@ -4549,6 +4597,8 @@ void HELPER(NAME)(void *vd, void *v0, void *vs1,          \
     uint32_t i;                                           \
     int a, b;                                             \
                                                           \
+    VSTART_CHECK_EARLY_EXIT(env);                         \
+                                                          \
     for (i = env->vstart; i < vl; i++) {                  \
         a = vext_elem_mask(vs1, i);                       \
         b = vext_elem_mask(vs2, i);                       \
@@ -4742,6 +4792,8 @@ void HELPER(NAME)(void *vd, void *v0, CPURISCVState *env, uint32_t desc)  \
     uint32_t vma = vext_vma(desc);                                        \
     int i;                                                                \
                                                                           \
+    VSTART_CHECK_EARLY_EXIT(env);                                         \
+                                                                          \
     for (i = env->vstart; i < vl; i++) {                                  \
         if (!vm && !vext_elem_mask(v0, i)) {                              \
             /* set masked-off elements to 1s */                           \
@@ -4777,6 +4829,8 @@ void HELPER(NAME)(void *vd, void *v0, target_ulong s1, void *vs2,         \
     uint32_t vma = vext_vma(desc);                                        \
     target_ulong offset = s1, i_min, i;                                   \
                                                                           \
+    VSTART_CHECK_EARLY_EXIT(env);                                         \
+                                                                          \
     i_min = MAX(env->vstart, offset);                                     \
     for (i = i_min; i < vl; i++) {                                        \
         if (!vm && !vext_elem_mask(v0, i)) {                              \
@@ -4810,6 +4864,8 @@ void HELPER(NAME)(void *vd, void *v0, target_ulong s1, void *vs2,         \
     uint32_t vma = vext_vma(desc);                                        \
     target_ulong i_max, i_min, i;                                         \
                                                                           \
+    VSTART_CHECK_EARLY_EXIT(env);                                         \
+                                                                          \
     i_min = MIN(s1 < vlmax ? vlmax - s1 : 0, vl);                         \
     i_max = MAX(i_min, env->vstart);                                      \
     for (i = env->vstart; i < i_max; ++i) {                               \
@@ -4852,6 +4908,8 @@ static void vslide1up_##BITWIDTH(void *vd, void *v0, uint64_t s1,           \
     uint32_t vma = vext_vma(desc);                                          \
     uint32_t i;                                                             \
                                                                             \
+    VSTART_CHECK_EARLY_EXIT(env);                                           \
+                                                                            \
     for (i = env->vstart; i < vl; i++) {                                    \
         if (!vm && !vext_elem_mask(v0, i)) {                                \
             /* set masked-off elements to 1s */                             \
@@ -4901,6 +4959,8 @@ static void vslide1down_##BITWIDTH(void *vd, void *v0, uint64_t s1,           \
     uint32_t vma = vext_vma(desc);                                            \
     uint32_t i;                                                               \
                                                                               \
+    VSTART_CHECK_EARLY_EXIT(env);                                             \
+                                                                              \
     for (i = env->vstart; i < vl; i++) {                                      \
         if (!vm && !vext_elem_mask(v0, i)) {                                  \
             /* set masked-off elements to 1s */                               \
@@ -4976,6 +5036,8 @@ void HELPER(NAME)(void *vd, void *v0, void *vs1, void *vs2,               \
     uint64_t index;                                                       \
     uint32_t i;                                                           \
                                                                           \
+    VSTART_CHECK_EARLY_EXIT(env);                                         \
+                                                                          \
     for (i = env->vstart; i < vl; i++) {                                  \
         if (!vm && !vext_elem_mask(v0, i)) {                              \
             /* set masked-off elements to 1s */                           \
@@ -5019,6 +5081,8 @@ void HELPER(NAME)(void *vd, void *v0, target_ulong s1, void *vs2,         \
     uint64_t index = s1;                                                  \
     uint32_t i;                                                           \
                                                                           \
+    VSTART_CHECK_EARLY_EXIT(env);                                         \
+                                                                          \
     for (i = env->vstart; i < vl; i++) {                                  \
         if (!vm && !vext_elem_mask(v0, i)) {                              \
             /* set masked-off elements to 1s */                           \
@@ -5113,6 +5177,8 @@ void HELPER(NAME)(void *vd, void *v0, void *vs2,                 \
     uint32_t vma = vext_vma(desc);                               \
     uint32_t i;                                                  \
                                                                  \
+    VSTART_CHECK_EARLY_EXIT(env);                                \
+                                                                 \
     for (i = env->vstart; i < vl; i++) {                         \
         if (!vm && !vext_elem_mask(v0, i)) {                     \
             /* set masked-off elements to 1s */                  \
diff --git a/target/riscv/vector_internals.c b/target/riscv/vector_internals.c
index 12f5964fbb..996c21eb31 100644
--- a/target/riscv/vector_internals.c
+++ b/target/riscv/vector_internals.c
@@ -44,6 +44,8 @@ void do_vext_vv(void *vd, void *v0, void *vs1, void *vs2,
     uint32_t vma = vext_vma(desc);
     uint32_t i;
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (i = env->vstart; i < vl; i++) {
         if (!vm && !vext_elem_mask(v0, i)) {
             /* set masked-off elements to 1s */
@@ -68,6 +70,8 @@ void do_vext_vx(void *vd, void *v0, target_long s1, void *vs2,
     uint32_t vma = vext_vma(desc);
     uint32_t i;
 
+    VSTART_CHECK_EARLY_EXIT(env);
+
     for (i = env->vstart; i < vl; i++) {
         if (!vm && !vext_elem_mask(v0, i)) {
             /* set masked-off elements to 1s */
diff --git a/target/riscv/vector_internals.h b/target/riscv/vector_internals.h
index 842765f6c1..9e1e15b575 100644
--- a/target/riscv/vector_internals.h
+++ b/target/riscv/vector_internals.h
@@ -24,6 +24,13 @@
 #include "tcg/tcg-gvec-desc.h"
 #include "internals.h"
 
+#define VSTART_CHECK_EARLY_EXIT(env) do { \
+    if (env->vstart >= env->vl) {         \
+        env->vstart = 0;                  \
+        return;                           \
+    }                                     \
+} while (0)
+
 static inline uint32_t vext_nf(uint32_t desc)
 {
     return FIELD_EX32(simd_data(desc), VDATA, NF);
@@ -151,6 +158,8 @@ void HELPER(NAME)(void *vd, void *v0, void *vs2,       \
     uint32_t vma = vext_vma(desc);                     \
     uint32_t i;                                        \
                                                        \
+    VSTART_CHECK_EARLY_EXIT(env);                      \
+                                                       \
     for (i = env->vstart; i < vl; i++) {               \
         if (!vm && !vext_elem_mask(v0, i)) {           \
             /* set masked-off elements to 1s */        \