target/arm: Trap non-streaming usage when Streaming SVE is active

This new behaviour is in the ARM pseudocode function
AArch64.CheckFPAdvSIMDEnabled, which applies to AArch32
via AArch32.CheckAdvSIMDOrFPEnabled when the EL to which
the trap would be delivered is in AArch64 mode.

Given that ARMv9 drops support for AArch32 outside EL0, the trap EL
detection ought to be trivially true, but the pseudocode still contains
a number of conditions, and QEMU has not yet committed to dropping A32
support for EL[12] when v9 features are present.

Since the computation of SME_TRAP_NONSTREAMING is necessarily different
for the two modes, we might as well preserve bits within TBFLAG_ANY and
allocate separate bits within TBFLAG_A32 and TBFLAG_A64 instead.

Note that DDI0616A.a has typos for bits [22:21] of LD1RO in the table
of instructions illegal in streaming mode.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220708151540.18136-4-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/translate-vfp.c

@@ -234,6 +234,18 @@ static bool vfp_access_check_a(DisasContext *s, bool ignore_vfp_enabled)
         return false;
     }
 
+    /*
+     * Note that rebuild_hflags_a32 has already accounted for being in EL0
+     * and the higher EL in A64 mode, etc.  Unlike A64 mode, there do not
+     * appear to be any insns which touch VFP which are allowed.
+     */
+    if (s->sme_trap_nonstreaming) {
+        gen_exception_insn(s, s->pc_curr, EXCP_UDEF,
+                           syn_smetrap(SME_ET_Streaming,
+                                       s->base.pc_next - s->pc_curr == 2));
+        return false;
+    }
+
     if (!s->vfp_enabled && !ignore_vfp_enabled) {
         assert(!arm_dc_feature(s, ARM_FEATURE_M));
         unallocated_encoding(s);