target-arm: A64: add support for 1-src RBIT insn

This adds support for the C5.6.147 RBIT instruction.
Signed-off-by: NAlexander Graf <agraf@suse.de>
[claudio: adapted to new decoder, use bswap64,
          make RBIT part standalone from the rest of the patch,
	  splitting REV into a separate patch]
Signed-off-by: NClaudio Fontana <claudio.fontana@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NRichard Henderson <rth@twiddle.net>

target-arm/helper-a64.c

@@ -49,3 +49,21 @@ uint64_t HELPER(clz64)(uint64_t x)
 {
     return clz64(x);
 }
+
+uint64_t HELPER(rbit64)(uint64_t x)
+{
+    /* assign the correct byte position */
+    x = bswap64(x);
+
+    /* assign the correct nibble position */
+    x = ((x & 0xf0f0f0f0f0f0f0f0ULL) >> 4)
+        | ((x & 0x0f0f0f0f0f0f0f0fULL) << 4);
+
+    /* assign the correct bit position */
+    x = ((x & 0x8888888888888888ULL) >> 3)
+        | ((x & 0x4444444444444444ULL) >> 1)
+        | ((x & 0x2222222222222222ULL) << 1)
+        | ((x & 0x1111111111111111ULL) << 3);
+
+    return x;
+}

target-arm/helper-a64.h

@@ -19,3 +19,4 @@
 DEF_HELPER_FLAGS_2(udiv64, TCG_CALL_NO_RWG_SE, i64, i64, i64)
 DEF_HELPER_FLAGS_2(sdiv64, TCG_CALL_NO_RWG_SE, s64, s64, s64)
 DEF_HELPER_FLAGS_1(clz64, TCG_CALL_NO_RWG_SE, i64, i64)
+DEF_HELPER_FLAGS_1(rbit64, TCG_CALL_NO_RWG_SE, i64, i64)

target-arm/translate-a64.c

@@ -1062,6 +1062,24 @@ static void handle_clz(DisasContext *s, unsigned int sf,
     }
 }
 
+static void handle_rbit(DisasContext *s, unsigned int sf,
+                        unsigned int rn, unsigned int rd)
+{
+    TCGv_i64 tcg_rd, tcg_rn;
+    tcg_rd = cpu_reg(s, rd);
+    tcg_rn = cpu_reg(s, rn);
+
+    if (sf) {
+        gen_helper_rbit64(tcg_rd, tcg_rn);
+    } else {
+        TCGv_i32 tcg_tmp32 = tcg_temp_new_i32();
+        tcg_gen_trunc_i64_i32(tcg_tmp32, tcg_rn);
+        gen_helper_rbit(tcg_tmp32, tcg_tmp32);
+        tcg_gen_extu_i32_i64(tcg_rd, tcg_tmp32);
+        tcg_temp_free_i32(tcg_tmp32);
+    }
+}
+
 /* C3.5.7 Data-processing (1 source)
  *   31  30  29  28             21 20     16 15    10 9    5 4    0
  * +----+---+---+-----------------+---------+--------+------+------+
@@ -1084,6 +1102,8 @@ static void disas_data_proc_1src(DisasContext *s, uint32_t insn)
 
     switch (opcode) {
     case 0: /* RBIT */
+        handle_rbit(s, sf, rn, rd);
+        break;
     case 1: /* REV16 */
     case 2: /* REV32 */
     case 3: /* REV64 */