target/arm: Simplify disas_thumb2_insn

Fold away all of the cases that now just goto illegal_op,
because all of their internal bits are now in decodetree.

Backports commit f843e77144c9334e244a422848177f2fbef5eb05 from qemu

qemu/target/arm/translate.c

@@ -10905,10 +10905,6 @@ static bool thumb_insn_is_16bit(DisasContext *s, uint32_t pc, uint32_t insn)
 /* Translate a 32-bit thumb instruction. */
 static void disas_thumb2_insn(DisasContext *s, uint32_t insn)
 {
-    TCGContext *tcg_ctx = s->uc->tcg_ctx;
-    uint32_t rn;
-    int op;
-
     /*
      * ARMv6-M supports a limited subset of Thumb2 instructions.
      * Other Thumb1 architectures allow only 32-bit
@@ -10949,35 +10945,10 @@ static void disas_thumb2_insn(DisasContext *s, uint32_t insn)
     }
     /* fall back to legacy decoder */
 
-    rn = (insn >> 16) & 0xf;
     switch ((insn >> 25) & 0xf) {
     case 0: case 1: case 2: case 3:
         /* 16-bit instructions.  Should never happen.  */
         abort();
-    case 4:
-        /* All in decodetree */
-        goto illegal_op;
-    case 5:
-        /* All in decodetree */
-        goto illegal_op;
-    case 13: /* Misc data processing.  */
-        op = ((insn >> 22) & 6) | ((insn >> 7) & 1);
-        if (op < 4 && (insn & 0xf000) != 0xf000)
-            goto illegal_op;
-        switch (op) {
-        case 0: /* Register controlled shift, in decodetree */
-            goto illegal_op;
-        case 1: /* Sign/zero extend, in decodetree */
-        case 2: /* SIMD add/subtract, in decodetree */
-        case 3: /* Other data processing, in decodetree */
-            goto illegal_op;
-        case 4: case 5:
-            /* 32-bit multiply.  Sum of absolute differences, in decodetree */
-            goto illegal_op;
-        case 6: case 7: /* 64-bit multiply, Divide, in decodetree */
-            goto illegal_op;
-        }
-        break;
     case 6: case 7: case 14: case 15:
         /* Coprocessor.  */
         if (arm_dc_feature(s, ARM_FEATURE_M)) {
@@ -11006,6 +10977,8 @@ static void disas_thumb2_insn(DisasContext *s, uint32_t insn)
                 }
 
                 if (arm_dc_feature(s, ARM_FEATURE_VFP)) {
+                    TCGContext *tcg_ctx = s->uc->tcg_ctx;
+                    uint32_t rn = (insn >> 16) & 0xf;
                     TCGv_i32 fptr = load_reg(s, rn);
 
                     if (extract32(insn, 20, 1)) {
@@ -11064,50 +11037,6 @@ static void disas_thumb2_insn(DisasContext *s, uint32_t insn)
             }
         }
         break;
-    case 8: case 9: case 10: case 11:
-        if (insn & (1 << 15)) {
-            /* Branches, misc control.  */
-            if (insn & 0x5000) {
-                /* Unconditional branch, in decodetree */
-                goto illegal_op;
-            } else if (((insn >> 23) & 7) == 7) {
-                /* Misc control */
-                if (insn & (1 << 13))
-                    goto illegal_op;
-
-                if (insn & (1 << 26)) {
-                    /* hvc, smc, in decodetree */
-                    goto illegal_op;
-                } else {
-                    op = (insn >> 20) & 7;
-                    switch (op) {
-                    case 0: /* msr cpsr, in decodetree  */
-                    case 1: /* msr spsr, in decodetree  */
-                        goto illegal_op;
-                    case 2: /* cps, nop-hint, in decodetree */
-                        goto illegal_op;
-                    case 3: /* Special control operations, in decodetree */
-                    case 4: /* bxj, in decodetree */
-                        goto illegal_op;
-                    case 5: /* Exception return.  */
-                    case 6: /* MRS, in decodetree */
-                    case 7: /* MSR, in decodetree */
-                        goto illegal_op;
-                    }
-                }
-            } else {
-                /* Conditional branch, in decodetree */
-                goto illegal_op;
-            }
-        } else {
-            /*
-             * 0b1111_0xxx_xxxx_0xxx_xxxx_xxxx
-             *  - Data-processing (modified immediate, plain binary immediate)
-             * All in decodetree.
-             */
-            goto illegal_op;
-        }
-        break;
     case 12:
         if ((insn & 0x01100000) == 0x01000000) {
             if (disas_neon_ls_insn(s, insn)) {
@@ -11115,15 +11044,13 @@ static void disas_thumb2_insn(DisasContext *s, uint32_t insn)
             }
             break;
         }
-        /* Load/store single data item, in decodetree */
         goto illegal_op;
     default:
         goto illegal_op;
-    }
-    return;
     illegal_op:
         unallocated_encoding(s);
     }
+}
 
 static void disas_thumb_insn(DisasContext *s, uint32_t insn)
 {