target/arm: Implement MVE VPST

Implement the MVE VPST insn, which sets the predicate mask
fields in the VPR to the immediate value encoded in the insn.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210617121628.20116-27-peter.maydell@linaro.org

2 files changed, 63 insertions, 0 deletions

diff --git a/target/arm/mve.decode b/target/arm/mve.decode
index a3dbdb72a5..e189e2de64 100644
--- a/target/arm/mve.decode
+++ b/target/arm/mve.decode
@@ -168,3 +168,7 @@ VHADD_U_scalar   1111 1110 0 . .. ... 0 ... 0 1111 . 100 .... @2scalar
 VHSUB_S_scalar   1110 1110 0 . .. ... 0 ... 1 1111 . 100 .... @2scalar
 VHSUB_U_scalar   1111 1110 0 . .. ... 0 ... 1 1111 . 100 .... @2scalar
 VBRSR            1111 1110 0 . .. ... 1 ... 1 1110 . 110 .... @2scalar
+
+# Predicate operations
+%mask_22_13      22:1 13:3
+VPST             1111 1110 0 . 11 000 1 ... 0 1111 0100 1101 mask=%mask_22_13
diff --git a/target/arm/translate-mve.c b/target/arm/translate-mve.c
index 6320064a08..7c4c06e434 100644
--- a/target/arm/translate-mve.c
+++ b/target/arm/translate-mve.c
@@ -90,6 +90,19 @@ static void mve_update_eci(DisasContext *s)
     }
 }
 
+static void mve_update_and_store_eci(DisasContext *s)
+{
+    /*
+     * For insns which don't call a helper function that will call
+     * mve_advance_vpt(), this version updates s->eci and also stores
+     * it out to the CPUState field.
+     */
+    if (s->eci) {
+        mve_update_eci(s);
+        store_cpu_field(tcg_constant_i32(s->eci << 4), condexec_bits);
+    }
+}
+
 static bool mve_skip_first_beat(DisasContext *s)
 {
     /* Return true if PSR.ECI says we must skip the first beat of this insn */
@@ -548,3 +561,49 @@ static bool trans_VRMLSLDAVH(DisasContext *s, arg_vmlaldav *a)
     };
     return do_long_dual_acc(s, a, fns[a->x]);
 }
+
+static bool trans_VPST(DisasContext *s, arg_VPST *a)
+{
+    TCGv_i32 vpr;
+
+    /* mask == 0 is a "related encoding" */
+    if (!dc_isar_feature(aa32_mve, s) || !a->mask) {
+        return false;
+    }
+    if (!mve_eci_check(s) || !vfp_access_check(s)) {
+        return true;
+    }
+    /*
+     * Set the VPR mask fields. We take advantage of MASK01 and MASK23
+     * being adjacent fields in the register.
+     *
+     * This insn is not predicated, but it is subject to beat-wise
+     * execution, and the mask is updated on the odd-numbered beats.
+     * So if PSR.ECI says we should skip beat 1, we mustn't update the
+     * 01 mask field.
+     */
+    vpr = load_cpu_field(v7m.vpr);
+    switch (s->eci) {
+    case ECI_NONE:
+    case ECI_A0:
+        /* Update both 01 and 23 fields */
+        tcg_gen_deposit_i32(vpr, vpr,
+                            tcg_constant_i32(a->mask | (a->mask << 4)),
+                            R_V7M_VPR_MASK01_SHIFT,
+                            R_V7M_VPR_MASK01_LENGTH + R_V7M_VPR_MASK23_LENGTH);
+        break;
+    case ECI_A0A1:
+    case ECI_A0A1A2:
+    case ECI_A0A1A2B0:
+        /* Update only the 23 mask field */
+        tcg_gen_deposit_i32(vpr, vpr,
+                            tcg_constant_i32(a->mask),
+                            R_V7M_VPR_MASK23_SHIFT, R_V7M_VPR_MASK23_LENGTH);
+        break;
+    default:
+        g_assert_not_reached();
+    }
+    store_cpu_field(vpr, v7m.vpr);
+    mve_update_and_store_eci(s);
+    return true;
+}