target/arm: Implement VSCCLRM insn

Implement the v8.1M VSCCLRM insn, which zeros floating point
registers if there is an active floating point context.
This requires support in write_neon_element32() for the MO_32
element size, so add it.

Because we want to use arm_gen_condlabel(), we need to move
the definition of that function up in translate.c so it is
before the #include of translate-vfp.c.inc.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20201119215617.29887-5-peter.maydell@linaro.org

target/arm/cpu.h

@@ -3555,6 +3555,15 @@ static inline bool isar_feature_aa32_mprofile(const ARMISARegisters *id)
     return FIELD_EX32(id->id_pfr1, ID_PFR1, MPROGMOD) != 0;
 }
 
+static inline bool isar_feature_aa32_m_sec_state(const ARMISARegisters *id)
+{
+    /*
+     * Return true if M-profile state handling insns
+     * (VSCCLRM, CLRM, FPCTX access insns) are implemented
+     */
+    return FIELD_EX32(id->id_pfr1, ID_PFR1, SECURITY) >= 3;
+}
+
 static inline bool isar_feature_aa32_fp16_arith(const ARMISARegisters *id)
 {
     /* Sadly this is encoded differently for A-profile and M-profile */

target/arm/m-nocp.decode

@@ -29,13 +29,17 @@
 # If the coprocessor is not present or disabled then we will generate
 # the NOCP exception; otherwise we let the insn through to the main decode.
 
+%vd_dp  22:1 12:4
+%vd_sp  12:4 22:1
+
 &nocp cp
 
 {
   # Special cases which do not take an early NOCP: VLLDM and VLSTM
   VLLDM_VLSTM  1110 1100 001 l:1 rn:4 0000 1010 0000 0000
-  # TODO: VSCCLRM (new in v8.1M) is similar:
-  #VSCCLRM      1110 1100 1-01 1111 ---- 1011 ---- ---0
+  # VSCCLRM (new in v8.1M) is similar:
+  VSCCLRM      1110 1100 1.01 1111 .... 1011 imm:7 0   vd=%vd_dp size=3
+  VSCCLRM      1110 1100 1.01 1111 .... 1010 imm:8     vd=%vd_sp size=2
 
   NOCP         111- 1110 ---- ---- ---- cp:4 ---- ---- &nocp
   NOCP         111- 110- ---- ---- ---- cp:4 ---- ---- &nocp

target/arm/translate-vfp.c.inc

@@ -3406,6 +3406,90 @@ static bool trans_VLLDM_VLSTM(DisasContext *s, arg_VLLDM_VLSTM *a)
     return true;
 }
 
+static bool trans_VSCCLRM(DisasContext *s, arg_VSCCLRM *a)
+{
+    int btmreg, topreg;
+    TCGv_i64 zero;
+    TCGv_i32 aspen, sfpa;
+
+    if (!dc_isar_feature(aa32_m_sec_state, s)) {
+        /* Before v8.1M, fall through in decode to NOCP check */
+        return false;
+    }
+
+    /* Explicitly UNDEF because this takes precedence over NOCP */
+    if (!arm_dc_feature(s, ARM_FEATURE_M_MAIN) || !s->v8m_secure) {
+        unallocated_encoding(s);
+        return true;
+    }
+
+    if (!dc_isar_feature(aa32_vfp_simd, s)) {
+        /* NOP if we have neither FP nor MVE */
+        return true;
+    }
+
+    /*
+     * If FPCCR.ASPEN != 0 && CONTROL_S.SFPA == 0 then there is no
+     * active floating point context so we must NOP (without doing
+     * any lazy state preservation or the NOCP check).
+     */
+    aspen = load_cpu_field(v7m.fpccr[M_REG_S]);
+    sfpa = load_cpu_field(v7m.control[M_REG_S]);
+    tcg_gen_andi_i32(aspen, aspen, R_V7M_FPCCR_ASPEN_MASK);
+    tcg_gen_xori_i32(aspen, aspen, R_V7M_FPCCR_ASPEN_MASK);
+    tcg_gen_andi_i32(sfpa, sfpa, R_V7M_CONTROL_SFPA_MASK);
+    tcg_gen_or_i32(sfpa, sfpa, aspen);
+    arm_gen_condlabel(s);
+    tcg_gen_brcondi_i32(TCG_COND_EQ, sfpa, 0, s->condlabel);
+
+    if (s->fp_excp_el != 0) {
+        gen_exception_insn(s, s->pc_curr, EXCP_NOCP,
+                           syn_uncategorized(), s->fp_excp_el);
+        return true;
+    }
+
+    topreg = a->vd + a->imm - 1;
+    btmreg = a->vd;
+
+    /* Convert to Sreg numbers if the insn specified in Dregs */
+    if (a->size == 3) {
+        topreg = topreg * 2 + 1;
+        btmreg *= 2;
+    }
+
+    if (topreg > 63 || (topreg > 31 && !(topreg & 1))) {
+        /* UNPREDICTABLE: we choose to undef */
+        unallocated_encoding(s);
+        return true;
+    }
+
+    /* Silently ignore requests to clear D16-D31 if they don't exist */
+    if (topreg > 31 && !dc_isar_feature(aa32_simd_r32, s)) {
+        topreg = 31;
+    }
+
+    if (!vfp_access_check(s)) {
+        return true;
+    }
+
+    /* Zero the Sregs from btmreg to topreg inclusive. */
+    zero = tcg_const_i64(0);
+    if (btmreg & 1) {
+        write_neon_element64(zero, btmreg >> 1, 1, MO_32);
+        btmreg++;
+    }
+    for (; btmreg + 1 <= topreg; btmreg += 2) {
+        write_neon_element64(zero, btmreg >> 1, 0, MO_64);
+    }
+    if (btmreg == topreg) {
+        write_neon_element64(zero, btmreg >> 1, 0, MO_32);
+        btmreg++;
+    }
+    assert(btmreg == topreg + 1);
+    /* TODO: when MVE is implemented, zero VPR here */
+    return true;
+}
+
 static bool trans_NOCP(DisasContext *s, arg_nocp *a)
 {
     /*

target/arm/translate.c

@@ -100,6 +100,15 @@ void arm_translate_init(void)
     a64_translate_init();
 }
 
+/* Generate a label used for skipping this instruction */
+static void arm_gen_condlabel(DisasContext *s)
+{
+    if (!s->condjmp) {
+        s->condlabel = gen_new_label();
+        s->condjmp = 1;
+    }
+}
+
 /* Flags for the disas_set_da_iss info argument:
  * lower bits hold the Rt register number, higher bits are flags.
  */
@@ -1221,6 +1230,9 @@ static void write_neon_element64(TCGv_i64 src, int reg, int ele, MemOp memop)
     long off = neon_element_offset(reg, ele, memop);
 
     switch (memop) {
+    case MO_32:
+        tcg_gen_st32_i64(src, cpu_env, off);
+        break;
     case MO_64:
         tcg_gen_st_i64(src, cpu_env, off);
         break;
@@ -5156,15 +5168,6 @@ static void gen_srs(DisasContext *s,
     s->base.is_jmp = DISAS_UPDATE_EXIT;
 }
 
-/* Generate a label used for skipping this instruction */
-static void arm_gen_condlabel(DisasContext *s)
-{
-    if (!s->condjmp) {
-        s->condlabel = gen_new_label();
-        s->condjmp = 1;
-    }
-}
-
 /* Skip this instruction if the ARM condition is false */
 static void arm_skip_unless(DisasContext *s, uint32_t cond)
 {