target-arm: Add the THUMB_DSP feature

Create an ARM_FEATURE_THUMB_DSP controlling the Thumb encodings of
the 85 DSP instructions (these are all Thumb2). This is enabled for
all non-M-profile CPUs with Thumb2 support, as the instructions are
mandatory for R and A profiles. On M profile they are optional and
not present in the Cortex-M3 (though they are in the M4).

The effect of this commit is that we will now treat the DSP
encodings as illegal instructions on M3, when previously we
incorrectly implemented them.

Signed-off-by: Aurelio C. Remonda <aurelioremonda@gmail.com>
Message-id: 1434311355-26554-1-git-send-email-aurelioremonda@gmail.com
[PMM: added clz/crc32/crc32c and default case to the early-decode switch;
 minor format/spacing fixups; reworded commit message a bit]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

3 files changed, 107 insertions, 10 deletions

diff --git a/target-arm/cpu.c b/target-arm/cpu.c
index 34990acb82..6fa51f4446 100644
--- a/target-arm/cpu.c
+++ b/target-arm/cpu.c
@@ -545,6 +545,10 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
     if (arm_feature(env, ARM_FEATURE_CBAR_RO)) {
         set_feature(env, ARM_FEATURE_CBAR);
     }
+    if (arm_feature(env, ARM_FEATURE_THUMB2) &&
+        !arm_feature(env, ARM_FEATURE_M)) {
+        set_feature(env, ARM_FEATURE_THUMB_DSP);
+    }
 
     if (cpu->reset_hivecs) {
             cpu->reset_sctlr |= (1 << 13);
diff --git a/target-arm/cpu.h b/target-arm/cpu.h
index 7c1d95c815..c9d2330014 100644
--- a/target-arm/cpu.h
+++ b/target-arm/cpu.h
@@ -889,6 +889,7 @@ enum arm_features {
     ARM_FEATURE_V8_SHA1, /* implements SHA1 part of v8 Crypto Extensions */
     ARM_FEATURE_V8_SHA256, /* implements SHA256 part of v8 Crypto Extensions */
     ARM_FEATURE_V8_PMULL, /* implements PMULL part of v8 Crypto Extensions */
+    ARM_FEATURE_THUMB_DSP, /* DSP insns supported in the Thumb encodings */
 };
 
 static inline int arm_feature(CPUARMState *env, int feature)
diff --git a/target-arm/translate.c b/target-arm/translate.c
index 39692d7a8e..125b6da165 100644
--- a/target-arm/translate.c
+++ b/target-arm/translate.c
@@ -9444,6 +9444,9 @@ static int disas_thumb2_insn(CPUARMState *env, DisasContext *s, uint16_t insn_hw
 
         op = (insn >> 21) & 0xf;
         if (op == 6) {
+            if (!arm_dc_feature(s, ARM_FEATURE_THUMB_DSP)) {
+                goto illegal_op;
+            }
             /* Halfword pack.  */
             tmp = load_reg(s, rn);
             tmp2 = load_reg(s, rm);
@@ -9508,6 +9511,27 @@ static int disas_thumb2_insn(CPUARMState *env, DisasContext *s, uint16_t insn_hw
             store_reg_bx(s, rd, tmp);
             break;
         case 1: /* Sign/zero extend.  */
+            op = (insn >> 20) & 7;
+            switch (op) {
+            case 0: /* SXTAH, SXTH */
+            case 1: /* UXTAH, UXTH */
+            case 4: /* SXTAB, SXTB */
+            case 5: /* UXTAB, UXTB */
+                break;
+            case 2: /* SXTAB16, SXTB16 */
+            case 3: /* UXTAB16, UXTB16 */
+                if (!arm_dc_feature(s, ARM_FEATURE_THUMB_DSP)) {
+                    goto illegal_op;
+                }
+                break;
+            default:
+                goto illegal_op;
+            }
+            if (rn != 15) {
+                if (!arm_dc_feature(s, ARM_FEATURE_THUMB_DSP)) {
+                    goto illegal_op;
+                }
+            }
             tmp = load_reg(s, rm);
             shift = (insn >> 4) & 3;
             /* ??? In many cases it's not necessary to do a
@@ -9522,7 +9546,8 @@ static int disas_thumb2_insn(CPUARMState *env, DisasContext *s, uint16_t insn_hw
             case 3: gen_uxtb16(tmp); break;
             case 4: gen_sxtb(tmp);   break;
             case 5: gen_uxtb(tmp);   break;
-            default: goto illegal_op;
+            default:
+                g_assert_not_reached();
             }
             if (rn != 15) {
                 tmp2 = load_reg(s, rn);
@@ -9536,6 +9561,9 @@ static int disas_thumb2_insn(CPUARMState *env, DisasContext *s, uint16_t insn_hw
             store_reg(s, rd, tmp);
             break;
         case 2: /* SIMD add/subtract.  */
+            if (!arm_dc_feature(s, ARM_FEATURE_THUMB_DSP)) {
+                goto illegal_op;
+            }
             op = (insn >> 20) & 7;
             shift = (insn >> 4) & 7;
             if ((op & 3) == 3 || (shift & 3) == 3)
@@ -9550,6 +9578,9 @@ static int disas_thumb2_insn(CPUARMState *env, DisasContext *s, uint16_t insn_hw
             op = ((insn >> 17) & 0x38) | ((insn >> 4) & 7);
             if (op < 4) {
                 /* Saturating add/subtract.  */
+                if (!arm_dc_feature(s, ARM_FEATURE_THUMB_DSP)) {
+                    goto illegal_op;
+                }
                 tmp = load_reg(s, rn);
                 tmp2 = load_reg(s, rm);
                 if (op & 1)
@@ -9560,6 +9591,31 @@ static int disas_thumb2_insn(CPUARMState *env, DisasContext *s, uint16_t insn_hw
                     gen_helper_add_saturate(tmp, cpu_env, tmp, tmp2);
                 tcg_temp_free_i32(tmp2);
             } else {
+                switch (op) {
+                case 0x0a: /* rbit */
+                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 0x20: /* crc32/crc32c */
+                case 0x21:
+                case 0x22:
+                case 0x28:
+                case 0x29:
+                case 0x2a:
+                    if (!arm_dc_feature(s, ARM_FEATURE_CRC)) {
+                        goto illegal_op;
+                    }
+                    break;
+                default:
+                    goto illegal_op;
+                }
                 tmp = load_reg(s, rn);
                 switch (op) {
                 case 0x0a: /* rbit */
@@ -9596,10 +9652,6 @@ static int disas_thumb2_insn(CPUARMState *env, DisasContext *s, uint16_t insn_hw
                     uint32_t sz = op & 0x3;
                     uint32_t c = op & 0x8;
 
-                    if (!arm_dc_feature(s, ARM_FEATURE_CRC)) {
-                        goto illegal_op;
-                    }
-
                     tmp2 = load_reg(s, rm);
                     if (sz == 0) {
                         tcg_gen_andi_i32(tmp2, tmp2, 0xff);
@@ -9617,12 +9669,26 @@ static int disas_thumb2_insn(CPUARMState *env, DisasContext *s, uint16_t insn_hw
                     break;
                 }
                 default:
-                    goto illegal_op;
+                    g_assert_not_reached();
                 }
             }
             store_reg(s, rd, tmp);
             break;
         case 4: case 5: /* 32-bit multiply.  Sum of absolute differences.  */
+            switch ((insn >> 20) & 7) {
+            case 0: /* 32 x 32 -> 32 */
+            case 7: /* Unsigned sum of absolute differences.  */
+                break;
+            case 1: /* 16 x 16 -> 32 */
+            case 2: /* Dual multiply add.  */
+            case 3: /* 32 * 16 -> 32msb */
+            case 4: /* Dual multiply subtract.  */
+            case 5: case 6: /* 32 * 32 -> 32msb (SMMUL, SMMLA, SMMLS) */
+                if (!arm_dc_feature(s, ARM_FEATURE_THUMB_DSP)) {
+                    goto illegal_op;
+                }
+                break;
+            }
             op = (insn >> 4) & 0xf;
             tmp = load_reg(s, rn);
             tmp2 = load_reg(s, rm);
@@ -9735,6 +9801,11 @@ static int disas_thumb2_insn(CPUARMState *env, DisasContext *s, uint16_t insn_hw
                 store_reg(s, rd, tmp);
             } else if ((op & 0xe) == 0xc) {
                 /* Dual multiply accumulate long.  */
+                if (!arm_dc_feature(s, ARM_FEATURE_THUMB_DSP)) {
+                    tcg_temp_free_i32(tmp);
+                    tcg_temp_free_i32(tmp2);
+                    goto illegal_op;
+                }
                 if (op & 1)
                     gen_swap_half(tmp2);
                 gen_smul_dual(tmp, tmp2);
@@ -9758,6 +9829,11 @@ static int disas_thumb2_insn(CPUARMState *env, DisasContext *s, uint16_t insn_hw
                 } else {
                     if (op & 8) {
                         /* smlalxy */
+                        if (!arm_dc_feature(s, ARM_FEATURE_THUMB_DSP)) {
+                            tcg_temp_free_i32(tmp2);
+                            tcg_temp_free_i32(tmp);
+                            goto illegal_op;
+                        }
                         gen_mulxy(tmp, tmp2, op & 2, op & 1);
                         tcg_temp_free_i32(tmp2);
                         tmp64 = tcg_temp_new_i64();
@@ -9770,6 +9846,10 @@ static int disas_thumb2_insn(CPUARMState *env, DisasContext *s, uint16_t insn_hw
                 }
                 if (op & 4) {
                     /* umaal */
+                    if (!arm_dc_feature(s, ARM_FEATURE_THUMB_DSP)) {
+                        tcg_temp_free_i64(tmp64);
+                        goto illegal_op;
+                    }
                     gen_addq_lo(s, tmp64, rs);
                     gen_addq_lo(s, tmp64, rd);
                 } else if (op & 0x40) {
@@ -10034,16 +10114,28 @@ static int disas_thumb2_insn(CPUARMState *env, DisasContext *s, uint16_t insn_hw
                         tmp2 = tcg_const_i32(imm);
                         if (op & 4) {
                             /* Unsigned.  */
-                            if ((op & 1) && shift == 0)
+                            if ((op & 1) && shift == 0) {
+                                if (!arm_dc_feature(s, ARM_FEATURE_THUMB_DSP)) {
+                                    tcg_temp_free_i32(tmp);
+                                    tcg_temp_free_i32(tmp2);
+                                    goto illegal_op;
+                                }
                                 gen_helper_usat16(tmp, cpu_env, tmp, tmp2);
-                            else
+                            } else {
                                 gen_helper_usat(tmp, cpu_env, tmp, tmp2);
+                            }
                         } else {
                             /* Signed.  */
-                            if ((op & 1) && shift == 0)
+                            if ((op & 1) && shift == 0) {
+                                if (!arm_dc_feature(s, ARM_FEATURE_THUMB_DSP)) {
+                                    tcg_temp_free_i32(tmp);
+                                    tcg_temp_free_i32(tmp2);
+                                    goto illegal_op;
+                                }
                                 gen_helper_ssat16(tmp, cpu_env, tmp, tmp2);
-                            else
+                            } else {
                                 gen_helper_ssat(tmp, cpu_env, tmp, tmp2);
+                            }
                         }
                         tcg_temp_free_i32(tmp2);
                         break;