[PULL 22/57] target/arm: Revise decoding for disas_add_sub_imm

[Peter Maydell]

From: Richard Henderson <richard.henderson@linaro.org>

The current Arm ARM has adjusted the official decode of
"Add/subtract (immediate)" so that the shift field is only bit 22,
and bit 23 is part of the op1 field of the parent category
"Data processing - immediate".

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200626033144.790098-11-richard.henderson@linaro.org
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/translate-a64.c | 23 ++++++++---------------
 1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c
index 30683061f94..03aa0925983 100644
--- a/target/arm/translate-a64.c
+++ b/target/arm/translate-a64.c
@@ -3754,22 +3754,22 @@ static void disas_pc_rel_adr(DisasContext *s, uint32_t 
insn)
 /*
  * Add/subtract (immediate)
  *
- *  31 30 29 28       24 23 22 21         10 9   5 4   0
- * +--+--+--+-----------+-----+-------------+-----+-----+
- * |sf|op| S| 1 0 0 0 1 |shift|    imm12    |  Rn | Rd  |
- * +--+--+--+-----------+-----+-------------+-----+-----+
+ *  31 30 29 28         23 22 21         10 9   5 4   0
+ * +--+--+--+-------------+--+-------------+-----+-----+
+ * |sf|op| S| 1 0 0 0 1 0 |sh|    imm12    |  Rn | Rd  |
+ * +--+--+--+-------------+--+-------------+-----+-----+
  *
  *    sf: 0 -> 32bit, 1 -> 64bit
  *    op: 0 -> add  , 1 -> sub
  *     S: 1 -> set flags
- * shift: 00 -> LSL imm by 0, 01 -> LSL imm by 12
+ *    sh: 1 -> LSL imm by 12
  */
 static void disas_add_sub_imm(DisasContext *s, uint32_t insn)
 {
     int rd = extract32(insn, 0, 5);
     int rn = extract32(insn, 5, 5);
     uint64_t imm = extract32(insn, 10, 12);
-    int shift = extract32(insn, 22, 2);
+    bool shift = extract32(insn, 22, 1);
     bool setflags = extract32(insn, 29, 1);
     bool sub_op = extract32(insn, 30, 1);
     bool is_64bit = extract32(insn, 31, 1);
@@ -3778,15 +3778,8 @@ static void disas_add_sub_imm(DisasContext *s, uint32_t 
insn)
     TCGv_i64 tcg_rd = setflags ? cpu_reg(s, rd) : cpu_reg_sp(s, rd);
     TCGv_i64 tcg_result;
 
-    switch (shift) {
-    case 0x0:
-        break;
-    case 0x1:
+    if (shift) {
         imm <<= 12;
-        break;
-    default:
-        unallocated_encoding(s);
-        return;
     }
 
     tcg_result = tcg_temp_new_i64();
@@ -4174,7 +4167,7 @@ static void disas_data_proc_imm(DisasContext *s, uint32_t 
insn)
     case 0x20: case 0x21: /* PC-rel. addressing */
         disas_pc_rel_adr(s, insn);
         break;
-    case 0x22: case 0x23: /* Add/subtract (immediate) */
+    case 0x22: /* Add/subtract (immediate) */
         disas_add_sub_imm(s, insn);
         break;
     case 0x24: /* Logical (immediate) */
-- 
2.20.1