target/arm: Implement SME ZERO

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220708151540.18136-19-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/helper-sme.h

@@ -19,3 +19,5 @@
 
 DEF_HELPER_FLAGS_2(set_pstate_sm, TCG_CALL_NO_RWG, void, env, i32)
 DEF_HELPER_FLAGS_2(set_pstate_za, TCG_CALL_NO_RWG, void, env, i32)
+
+DEF_HELPER_FLAGS_3(sme_zero, TCG_CALL_NO_RWG, void, env, i32, i32)

target/arm/sme.decode

@@ -18,3 +18,7 @@
 #
 # This file is processed by scripts/decodetree.py
 #
+
+### SME Misc
+
+ZERO            11000000 00 001 00000000000 imm:8

target/arm/sme_helper.c

@@ -59,3 +59,28 @@ void helper_set_pstate_za(CPUARMState *env, uint32_t i)
         memset(env->zarray, 0, sizeof(env->zarray));
     }
 }
+
+void helper_sme_zero(CPUARMState *env, uint32_t imm, uint32_t svl)
+{
+    uint32_t i;
+
+    /*
+     * Special case clearing the entire ZA space.
+     * This falls into the CONSTRAINED UNPREDICTABLE zeroing of any
+     * parts of the ZA storage outside of SVL.
+     */
+    if (imm == 0xff) {
+        memset(env->zarray, 0, sizeof(env->zarray));
+        return;
+    }
+
+    /*
+     * Recall that ZAnH.D[m] is spread across ZA[n+8*m],
+     * so each row is discontiguous within ZA[].
+     */
+    for (i = 0; i < svl; i++) {
+        if (imm & (1 << (i % 8))) {
+            memset(&env->zarray[i], 0, svl);
+        }
+    }
+}

target/arm/translate-sme.c

@@ -33,3 +33,16 @@
  */
 
 #include "decode-sme.c.inc"
+
+
+static bool trans_ZERO(DisasContext *s, arg_ZERO *a)
+{
+    if (!dc_isar_feature(aa64_sme, s)) {
+        return false;
+    }
+    if (sme_za_enabled_check(s)) {
+        gen_helper_sme_zero(cpu_env, tcg_constant_i32(a->imm),
+                            tcg_constant_i32(streaming_vec_reg_size(s)));
+    }
+    return true;
+}