target/arm: Note that we handle VMOVL as a special case of VSHLL

Although the architecture doesn't define it as an alias, VMOVL
(vector move long) is encoded as a VSHLL with a zero shift.
Add a comment in the decode file noting that we handle VMOVL
as part of VSHLL.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/target/arm/mve.decode b/target/arm/mve.decode
index 595d97568e..fa9d921f93 100644
--- a/target/arm/mve.decode
+++ b/target/arm/mve.decode
@@ -364,6 +364,8 @@ VRSHRI_U          111 1 1111 1 . ... ... ... 0 0010 0 1 . 1 ... 0 @2_shr_h
 VRSHRI_U          111 1 1111 1 . ... ... ... 0 0010 0 1 . 1 ... 0 @2_shr_w
 
 # VSHLL T1 encoding; the T2 VSHLL encoding is elsewhere in this file
+# Note that VMOVL is encoded as "VSHLL with a zero shift count"; we
+# implement it that way rather than special-casing it in the decode.
 VSHLL_BS          111 0 1110 1 . 1 .. ... ... 0 1111 0 1 . 0 ... 0 @2_shll_b
 VSHLL_BS          111 0 1110 1 . 1 .. ... ... 0 1111 0 1 . 0 ... 0 @2_shll_h