target/arm: Convert CLZ

Document our choice about the T32 CONSTRAINED UNPREDICTABLE behaviour.
This matches the undocumented choice made by the legacy decoder.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20190904193059.26202-17-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

3 files changed, 24 insertions, 16 deletions

diff --git a/target/arm/a32.decode b/target/arm/a32.decode
index 6cb9c16e2f..182f2b6725 100644
--- a/target/arm/a32.decode
+++ b/target/arm/a32.decode
@@ -29,6 +29,7 @@
 &s_rrrr          s rd rn rm ra
 &rrrr            rd rn rm ra
 &rrr             rd rn rm
+&rr              rd rm
 &r               rm
 &msr_reg         rn r mask
 &mrs_reg         rd r
@@ -197,6 +198,7 @@ CRC32CW          .... 0001 0100 .... .... 0010 0100 ....      @rndm
 %sysm            8:1 16:4
 
 @rm              ---- .... .... .... .... .... .... rm:4      &r
+@rdm             ---- .... .... .... rd:4 .... .... rm:4      &rr
 
 MRS_bank         ---- 0001 0 r:1 00 .... rd:4 001. 0000 0000  &mrs_bank %sysm
 MSR_bank         ---- 0001 0 r:1 10 .... 1111 001. 0000 rn:4  &msr_bank %sysm
@@ -207,3 +209,5 @@ MSR_reg          ---- 0001 0 r:1 10 mask:4 1111 0000 0000 rn:4  &msr_reg
 BX               .... 0001 0010 1111 1111 1111 0001 ....      @rm
 BXJ              .... 0001 0010 1111 1111 1111 0010 ....      @rm
 BLX_r            .... 0001 0010 1111 1111 1111 0011 ....      @rm
+
+CLZ              .... 0001 0110 1111 .... 1111 0001 ....      @rdm
diff --git a/target/arm/t32.decode b/target/arm/t32.decode
index 337706ebbe..67724efe4b 100644
--- a/target/arm/t32.decode
+++ b/target/arm/t32.decode
@@ -26,6 +26,7 @@
 &s_rrrr          !extern s rd rn rm ra
 &rrrr            !extern rd rn rm ra
 &rrr             !extern rd rn rm
+&rr              !extern rd rm
 &r               !extern rm
 &msr_reg         !extern rn r mask
 &mrs_reg         !extern rd r
@@ -126,6 +127,7 @@ RSB_rri          1111 0.0 1110 . .... 0 ... .... ........     @s_rri_rot
 @rnadm           .... .... .... rn:4 ra:4 rd:4 .... rm:4      &rrrr
 @rn0dm           .... .... .... rn:4 .... rd:4 .... rm:4      &rrrr ra=0
 @rndm            .... .... .... rn:4 .... rd:4 .... rm:4      &rrr
+@rdm             .... .... .... .... .... rd:4 .... rm:4      &rr
 
 {
   MUL            1111 1011 0000 .... 1111 .... 0000 ....      @s0_rn0dm
@@ -180,6 +182,9 @@ CRC32CB          1111 1010 1101 .... 1111 .... 1000 ....      @rndm
 CRC32CH          1111 1010 1101 .... 1111 .... 1001 ....      @rndm
 CRC32CW          1111 1010 1101 .... 1111 .... 1010 ....      @rndm
 
+# Note rn != rm is CONSTRAINED UNPREDICTABLE; we choose to ignore rn.
+CLZ              1111 1010 1011 ---- 1111 .... 1000 ....      @rdm
+
 # Branches and miscellaneous control
 
 %msr_sysm        4:1 8:4
diff --git a/target/arm/translate.c b/target/arm/translate.c
index 386a460bf5..7de6949db3 100644
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -8490,6 +8490,19 @@ static bool trans_BLX_r(DisasContext *s, arg_BLX_r *a)
     return true;
 }
 
+static bool trans_CLZ(DisasContext *s, arg_CLZ *a)
+{
+    TCGv_i32 tmp;
+
+    if (!ENABLE_ARCH_5) {
+        return false;
+    }
+    tmp = load_reg(s, a->rm);
+    tcg_gen_clzi_i32(tmp, tmp, 32);
+    store_reg(s, a->rd, tmp);
+    return true;
+}
+
 /*
  * Legacy decoder.
  */
@@ -8778,18 +8791,7 @@ static void disas_arm_insn(DisasContext *s, unsigned int insn)
             /* MSR/MRS (banked/register) */
             /* All done in decodetree.  Illegal ops already signalled.  */
             g_assert_not_reached();
-        case 0x1:
-            if (op1 == 3) {
-                /* clz */
-                ARCH(5);
-                rd = (insn >> 12) & 0xf;
-                tmp = load_reg(s, rm);
-                tcg_gen_clzi_i32(tmp, tmp, 32);
-                store_reg(s, rd, tmp);
-            } else {
-                goto illegal_op;
-            }
-            break;
+        case 0x1: /* bx, clz */
         case 0x2: /* bxj */
         case 0x3: /* blx */
         case 0x4: /* crc32 */
@@ -10236,13 +10238,13 @@ static void disas_thumb2_insn(DisasContext *s, uint32_t insn)
                 case 0x08: /* rev */
                 case 0x09: /* rev16 */
                 case 0x0b: /* revsh */
-                case 0x18: /* clz */
                     break;
                 case 0x10: /* sel */
                     if (!arm_dc_feature(s, ARM_FEATURE_THUMB_DSP)) {
                         goto illegal_op;
                     }
                     break;
+                case 0x18: /* clz, in decodetree */
                 case 0x20: /* crc32/crc32c, in decodetree */
                 case 0x21:
                 case 0x22:
@@ -10275,9 +10277,6 @@ static void disas_thumb2_insn(DisasContext *s, uint32_t insn)
                     tcg_temp_free_i32(tmp3);
                     tcg_temp_free_i32(tmp2);
                     break;
-                case 0x18: /* clz */
-                    tcg_gen_clzi_i32(tmp, tmp, 32);
-                    break;
                 default:
                     g_assert_not_reached();
                 }