target/arm: Convert T16, long branches

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20190904193059.26202-68-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

2 files changed, 43 insertions, 49 deletions

diff --git a/target/arm/t16.decode b/target/arm/t16.decode
index a4c89db..43b9a26 100644
--- a/target/arm/t16.decode
+++ b/target/arm/t16.decode
@@ -272,3 +272,10 @@ LDM_t16         1011 110 ......... \
 %imm11_0x2      0:s11 !function=times_2
 
 B               11100 ...........               &i imm=%imm11_0x2
+
+# thumb_insn_is_16bit() ensures we won't be decoding these as
+# T16 instructions for a Thumb2 CPU, so these patterns must be
+# a Thumb1 split BL/BLX.
+BLX_suffix      11101 imm:11                    &i
+BL_BLX_prefix   11110 imm:s11                   &i
+BL_suffix       11111 imm:11                    &i
diff --git a/target/arm/translate.c b/target/arm/translate.c
index 3238ccb..a99a5c2 100644
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -10147,6 +10147,40 @@ static bool trans_BLX_i(DisasContext *s, arg_BLX_i *a)
     return true;
 }
 
+static bool trans_BL_BLX_prefix(DisasContext *s, arg_BL_BLX_prefix *a)
+{
+    assert(!arm_dc_feature(s, ARM_FEATURE_THUMB2));
+    tcg_gen_movi_i32(cpu_R[14], read_pc(s) + (a->imm << 12));
+    return true;
+}
+
+static bool trans_BL_suffix(DisasContext *s, arg_BL_suffix *a)
+{
+    TCGv_i32 tmp = tcg_temp_new_i32();
+
+    assert(!arm_dc_feature(s, ARM_FEATURE_THUMB2));
+    tcg_gen_addi_i32(tmp, cpu_R[14], (a->imm << 1) | 1);
+    tcg_gen_movi_i32(cpu_R[14], s->base.pc_next | 1);
+    gen_bx(s, tmp);
+    return true;
+}
+
+static bool trans_BLX_suffix(DisasContext *s, arg_BLX_suffix *a)
+{
+    TCGv_i32 tmp;
+
+    assert(!arm_dc_feature(s, ARM_FEATURE_THUMB2));
+    if (!ENABLE_ARCH_5) {
+        return false;
+    }
+    tmp = tcg_temp_new_i32();
+    tcg_gen_addi_i32(tmp, cpu_R[14], a->imm << 1);
+    tcg_gen_andi_i32(tmp, tmp, 0xfffffffc);
+    tcg_gen_movi_i32(cpu_R[14], s->base.pc_next | 1);
+    gen_bx(s, tmp);
+    return true;
+}
+
 static bool op_tbranch(DisasContext *s, arg_tbranch *a, bool half)
 {
     TCGv_i32 addr, tmp;
@@ -10736,10 +10770,6 @@ static void disas_thumb2_insn(DisasContext *s, uint32_t insn)
 
 static void disas_thumb_insn(DisasContext *s, uint32_t insn)
 {
-    int32_t offset;
-    TCGv_i32 tmp;
-    TCGv_i32 tmp2;
-
     if (disas_t16(s, insn)) {
         return;
     }
@@ -10758,53 +10788,10 @@ static void disas_thumb_insn(DisasContext *s, uint32_t insn)
     case 11: /* misc, in decodetree */
     case 12: /* load/store multiple, in decodetree */
     case 13: /* conditional branch or swi, in decodetree */
-        goto illegal_op;
-
     case 14:
-        if (insn & (1 << 11)) {
-            /* thumb_insn_is_16bit() ensures we can't get here for
-             * a Thumb2 CPU, so this must be a thumb1 split BL/BLX:
-             * 0b1110_1xxx_xxxx_xxxx : BLX suffix (or UNDEF)
-             */
-            assert(!arm_dc_feature(s, ARM_FEATURE_THUMB2));
-            ARCH(5);
-            offset = ((insn & 0x7ff) << 1);
-            tmp = load_reg(s, 14);
-            tcg_gen_addi_i32(tmp, tmp, offset);
-            tcg_gen_andi_i32(tmp, tmp, 0xfffffffc);
-
-            tmp2 = tcg_temp_new_i32();
-            tcg_gen_movi_i32(tmp2, s->base.pc_next | 1);
-            store_reg(s, 14, tmp2);
-            gen_bx(s, tmp);
-            break;
-        }
-        /* unconditional branch, in decodetree */
-        goto illegal_op;
-
     case 15:
-        /* thumb_insn_is_16bit() ensures we can't get here for
-         * a Thumb2 CPU, so this must be a thumb1 split BL/BLX.
-         */
-        assert(!arm_dc_feature(s, ARM_FEATURE_THUMB2));
-
-        if (insn & (1 << 11)) {
-            /* 0b1111_1xxx_xxxx_xxxx : BL suffix */
-            offset = ((insn & 0x7ff) << 1) | 1;
-            tmp = load_reg(s, 14);
-            tcg_gen_addi_i32(tmp, tmp, offset);
-
-            tmp2 = tcg_temp_new_i32();
-            tcg_gen_movi_i32(tmp2, s->base.pc_next | 1);
-            store_reg(s, 14, tmp2);
-            gen_bx(s, tmp);
-        } else {
-            /* 0b1111_0xxx_xxxx_xxxx : BL/BLX prefix */
-            uint32_t uoffset = ((int32_t)insn << 21) >> 9;
-
-            tcg_gen_movi_i32(cpu_R[14], read_pc(s) + uoffset);
-        }
-        break;
+        /* branches, in decodetree */
+        goto illegal_op;
     }
     return;
 illegal_op: