[PATCH] tcg/i386: Bound shift count expanding sari_vec

[Richard Henderson]

A given RISU testcase for SVE can produce

tcg-op-vec.c:511: do_shifti: Assertion `i >= 0 && i < (8 << vece)' failed.

because expand_vec_sari gave a shift count of 32 to a MO_32
vector shift.

In 44f1441dbe1, we changed from direct expansion of vector opcodes
to re-use of the tcg expanders.  So while the comment correctly notes
that the hw will handle such a shift count, we now have to take our
own sanity checks into account.  Which is easy in this particular case.

Fixes: 44f1441dbe1
Signed-off-by: Richard Henderson <address@hidden>
---
 tcg/i386/tcg-target.inc.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/tcg/i386/tcg-target.inc.c b/tcg/i386/tcg-target.inc.c
index cdedcb2b25..223dba9c8c 100644
--- a/tcg/i386/tcg-target.inc.c
+++ b/tcg/i386/tcg-target.inc.c
@@ -3391,12 +3391,15 @@ static void expand_vec_sari(TCGType type, unsigned vece,
 
     case MO_64:
         if (imm <= 32) {
-            /* We can emulate a small sign extend by performing an arithmetic
+            /*
+             * We can emulate a small sign extend by performing an arithmetic
              * 32-bit shift and overwriting the high half of a 64-bit logical
-             * shift (note that the ISA says shift of 32 is valid).
+             * shift.  Note that the ISA says shift of 32 is valid, but TCG
+             * does not, so we have to bound the smaller shift -- we get the
+             * same result in the high half either way.
              */
             t1 = tcg_temp_new_vec(type);
-            tcg_gen_sari_vec(MO_32, t1, v1, imm);
+            tcg_gen_sari_vec(MO_32, t1, v1, MIN(imm, 31));
             tcg_gen_shri_vec(MO_64, v0, v1, imm);
             vec_gen_4(INDEX_op_x86_blend_vec, type, MO_32,
                       tcgv_vec_arg(v0), tcgv_vec_arg(v0),
-- 
2.17.1