target/arm: Make disas_thumb2_insn() generate its own UNDEF exceptions

Refactor disas_thumb2_insn() so that it generates the code for raising
an UNDEF exception for invalid insns, rather than returning a flag
which the caller must check to see if it needs to generate the UNDEF
code. This brings the function in to line with the behaviour of
disas_thumb_insn() and disas_arm_insn().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 1513080506-17703-1-git-send-email-peter.maydell@linaro.org

target/arm/translate.c

@@ -9775,9 +9775,8 @@ gen_thumb2_data_op(DisasContext *s, int op, int conds, uint32_t shifter_out,
     return 0;
 }
 
-/* Translate a 32-bit thumb instruction.  Returns nonzero if the instruction
-   is not legal.  */
-static int disas_thumb2_insn(DisasContext *s, uint32_t insn)
+/* Translate a 32-bit thumb instruction. */
+static void disas_thumb2_insn(DisasContext *s, uint32_t insn)
 {
     uint32_t imm, shift, offset;
     uint32_t rd, rn, rm, rs;
@@ -11016,16 +11015,16 @@ static int disas_thumb2_insn(DisasContext *s, uint32_t insn)
                     /* UNPREDICTABLE, unallocated hint or
                      * PLD/PLDW/PLI (literal)
                      */
-                    return 0;
+                    return;
                 }
                 if (op1 & 1) {
-                    return 0; /* PLD/PLDW/PLI or unallocated hint */
+                    return; /* PLD/PLDW/PLI or unallocated hint */
                 }
                 if ((op2 == 0) || ((op2 & 0x3c) == 0x30)) {
-                    return 0; /* PLD/PLDW/PLI or unallocated hint */
+                    return; /* PLD/PLDW/PLI or unallocated hint */
                 }
                 /* UNDEF space, or an UNPREDICTABLE */
-                return 1;
+                goto illegal_op;
             }
         }
         memidx = get_mem_index(s);
@@ -11151,9 +11150,10 @@ static int disas_thumb2_insn(DisasContext *s, uint32_t insn)
     default:
         goto illegal_op;
     }
-    return 0;
+    return;
 illegal_op:
-    return 1;
+    gen_exception_insn(s, 4, EXCP_UDEF, syn_uncategorized(),
+                       default_exception_el(s));
 }
 
 static void disas_thumb_insn(DisasContext *s, uint32_t insn)
@@ -12275,10 +12275,7 @@ static void thumb_tr_translate_insn(DisasContextBase *dcbase, CPUState *cpu)
     if (is_16bit) {
         disas_thumb_insn(dc, insn);
     } else {
-        if (disas_thumb2_insn(dc, insn)) {
-            gen_exception_insn(dc, 4, EXCP_UDEF, syn_uncategorized(),
-                               default_exception_el(dc));
-        }
+        disas_thumb2_insn(dc, insn);
     }
 
     /* Advance the Thumb condexec condition.  */