target/arm: Do not use gen_mte_checkN in trans_STGP

STGP writes to tag memory, it does not check it.
This happened to work because we wrote tag memory first
so that the check always succeeded.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230901203103.136408-1-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/tcg/translate-a64.c

@@ -3020,37 +3020,17 @@ static bool trans_STGP(DisasContext *s, arg_ldstpair *a)
         tcg_gen_addi_i64(dirty_addr, dirty_addr, offset);
     }
 
-    if (!s->ata) {
-        /*
-         * TODO: We could rely on the stores below, at least for
-         * system mode, if we arrange to add MO_ALIGN_16.
-         */
-        gen_helper_stg_stub(cpu_env, dirty_addr);
-    } else if (tb_cflags(s->base.tb) & CF_PARALLEL) {
-        gen_helper_stg_parallel(cpu_env, dirty_addr, dirty_addr);
-    } else {
-        gen_helper_stg(cpu_env, dirty_addr, dirty_addr);
-    }
-
-    mop = finalize_memop(s, MO_64);
-    clean_addr = gen_mte_checkN(s, dirty_addr, true, false, 2 << MO_64, mop);
-
+    clean_addr = clean_data_tbi(s, dirty_addr);
     tcg_rt = cpu_reg(s, a->rt);
     tcg_rt2 = cpu_reg(s, a->rt2);
 
     /*
-     * STGP is defined as two 8-byte memory operations and one tag operation.
-     * We implement it as one single 16-byte memory operation for convenience.
-     * Rebuild mop as for STP.
-     * TODO: The atomicity with LSE2 is stronger than required.
-     * Need a form of MO_ATOM_WITHIN16_PAIR that never requires
-     * 16-byte atomicity.
+     * STGP is defined as two 8-byte memory operations, aligned to TAG_GRANULE,
+     * and one tag operation.  We implement it as one single aligned 16-byte
+     * memory operation for convenience.  Note that the alignment ensures
+     * MO_ATOM_IFALIGN_PAIR produces 8-byte atomicity for the memory store.
      */
-    mop = MO_128;
-    if (s->align_mem) {
-        mop |= MO_ALIGN_8;
-    }
-    mop = finalize_memop_pair(s, mop);
+    mop = finalize_memop_atom(s, MO_128 | MO_ALIGN, MO_ATOM_IFALIGN_PAIR);
 
     tmp = tcg_temp_new_i128();
     if (s->be_data == MO_LE) {
@@ -3060,6 +3040,15 @@ static bool trans_STGP(DisasContext *s, arg_ldstpair *a)
     }
     tcg_gen_qemu_st_i128(tmp, clean_addr, get_mem_index(s), mop);
 
+    /* Perform the tag store, if tag access enabled. */
+    if (s->ata) {
+        if (tb_cflags(s->base.tb) & CF_PARALLEL) {
+            gen_helper_stg_parallel(cpu_env, dirty_addr, dirty_addr);
+        } else {
+            gen_helper_stg(cpu_env, dirty_addr, dirty_addr);
+        }
+    }
+
     op_addr_ldstpair_post(s, a, dirty_addr, offset);
     return true;
 }