target/arm: Convert BRAA, BRAB, BLRAA, BLRAB to decodetree

Convert the last four BR-with-pointer-auth insns to decodetree.
The remaining cases in the outer switch in disas_uncond_b_reg()
all return early rather than leaving the case statement, so we
can delete the now-unused code at the end of that function.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230512144106.3608981-20-peter.maydell@linaro.org

target/arm/tcg/a64.decode

@@ -138,3 +138,7 @@ BLRAZ           1101011 0001 11111 00001 m:1 rn:5 11111 &braz   # BLRAAZ, BLRABZ
 
 &reta       m
 RETA            1101011 0010 11111 00001 m:1 11111 11111 &reta  # RETAA, RETAB
+
+&bra        rn rm m
+BRA             1101011 1000 11111 00001 m:1 rn:5 rm:5 &bra # BRAA, BRAB
+BLRA            1101011 1001 11111 00001 m:1 rn:5 rm:5 &bra # BLRAA, BLRAB

target/arm/tcg/translate-a64.c

@@ -1504,6 +1504,41 @@ static bool trans_RETA(DisasContext *s, arg_reta *a)
     return true;
 }
 
+static bool trans_BRA(DisasContext *s, arg_bra *a)
+{
+    TCGv_i64 dst;
+
+    if (!dc_isar_feature(aa64_pauth, s)) {
+        return false;
+    }
+    dst = auth_branch_target(s, cpu_reg(s,a->rn), cpu_reg_sp(s, a->rm), !a->m);
+    gen_a64_set_pc(s, dst);
+    set_btype_for_br(s, a->rn);
+    s->base.is_jmp = DISAS_JUMP;
+    return true;
+}
+
+static bool trans_BLRA(DisasContext *s, arg_bra *a)
+{
+    TCGv_i64 dst, lr;
+
+    if (!dc_isar_feature(aa64_pauth, s)) {
+        return false;
+    }
+    dst = auth_branch_target(s, cpu_reg(s, a->rn), cpu_reg_sp(s, a->rm), !a->m);
+    lr = cpu_reg(s, 30);
+    if (dst == lr) {
+        TCGv_i64 tmp = tcg_temp_new_i64();
+        tcg_gen_mov_i64(tmp, dst);
+        dst = tmp;
+    }
+    gen_pc_plus_diff(s, lr, curr_insn_len(s));
+    gen_a64_set_pc(s, dst);
+    set_btype_for_blr(s);
+    s->base.is_jmp = DISAS_JUMP;
+    return true;
+}
+
 /* HINT instruction group, including various allocated HINTs */
 static void handle_hint(DisasContext *s, uint32_t insn,
                         unsigned int op1, unsigned int op2, unsigned int crm)
@@ -2281,7 +2316,6 @@ static void disas_exc(DisasContext *s, uint32_t insn)
 static void disas_uncond_b_reg(DisasContext *s, uint32_t insn)
 {
     unsigned int opc, op2, op3, rn, op4;
-    unsigned btype_mod = 2;   /* 0: BR, 1: BLR, 2: other */
     TCGv_i64 dst;
     TCGv_i64 modifier;
 
@@ -2299,45 +2333,14 @@ static void disas_uncond_b_reg(DisasContext *s, uint32_t insn)
     case 0:
     case 1:
     case 2:
+    case 8:
+    case 9:
         /*
-         * BR, BLR, RET, RETAA, RETAB, BRAAZ, BRABZ, BLRAAZ, BLRABZ:
+         * BR, BLR, RET, RETAA, RETAB, BRAAZ, BRABZ, BLRAAZ, BLRABZ,
-         * handled in decodetree
+         * BRAA, BLRAA: handled in decodetree
          */
         goto do_unallocated;
 
-    case 8: /* BRAA */
-    case 9: /* BLRAA */
-        if (!dc_isar_feature(aa64_pauth, s)) {
-            goto do_unallocated;
-        }
-        if ((op3 & ~1) != 2) {
-            goto do_unallocated;
-        }
-        btype_mod = opc & 1;
-        if (s->pauth_active) {
-            dst = tcg_temp_new_i64();
-            modifier = cpu_reg_sp(s, op4);
-            if (op3 == 2) {
-                gen_helper_autia(dst, cpu_env, cpu_reg(s, rn), modifier);
-            } else {
-                gen_helper_autib(dst, cpu_env, cpu_reg(s, rn), modifier);
-            }
-        } else {
-            dst = cpu_reg(s, rn);
-        }
-        /* BLRAA also needs to load return address */
-        if (opc == 9) {
-            TCGv_i64 lr = cpu_reg(s, 30);
-            if (dst == lr) {
-                TCGv_i64 tmp = tcg_temp_new_i64();
-                tcg_gen_mov_i64(tmp, dst);
-                dst = tmp;
-            }
-            gen_pc_plus_diff(s, lr, curr_insn_len(s));
-        }
-        gen_a64_set_pc(s, dst);
-        break;
-
     case 4: /* ERET */
         if (s->current_el == 0) {
             goto do_unallocated;
@@ -2407,28 +2410,6 @@ static void disas_uncond_b_reg(DisasContext *s, uint32_t insn)
         unallocated_encoding(s);
         return;
     }
-
-    switch (btype_mod) {
-    case 0: /* BR */
-        if (dc_isar_feature(aa64_bti, s)) {
-            /* BR to {x16,x17} or !guard -> 1, else 3.  */
-            set_btype(s, rn == 16 || rn == 17 || !s->guarded_page ? 1 : 3);
-        }
-        break;
-
-    case 1: /* BLR */
-        if (dc_isar_feature(aa64_bti, s)) {
-            /* BLR sets BTYPE to 2, regardless of source guarded page.  */
-            set_btype(s, 2);
-        }
-        break;
-
-    default: /* RET or none of the above.  */
-        /* BTYPE will be set to 0 by normal end-of-insn processing.  */
-        break;
-    }
-
-    s->base.is_jmp = DISAS_JUMP;
 }
 
 /* Branches, exception generating and system instructions */