target/arm: Split out thumb_tr_translate_insn

We need not check for ARM vs Thumb state in order to dispatch
disassembly of every instruction.

Tested-by: Emilio G. Cota <cota@braap.org>
Reviewed-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>

target/arm/translate.c

@@ -11981,11 +11981,8 @@ static bool arm_tr_breakpoint_check(DisasContextBase *dcbase, CPUState *cpu,
     return true;
 }
 
-static void arm_tr_translate_insn(DisasContextBase *dcbase, CPUState *cpu)
+static bool arm_pre_translate_insn(DisasContext *dc)
 {
-    DisasContext *dc = container_of(dcbase, DisasContext, base);
-    CPUARMState *env = cpu->env_ptr;
-
 #ifdef CONFIG_USER_ONLY
     /* Intercept jump to the magic kernel page.  */
     if (dc->pc >= 0xffff0000) {
@@ -11993,7 +11990,7 @@ static void arm_tr_translate_insn(DisasContextBase *dcbase, CPUState *cpu)
            conditional execution block.  */
         gen_exception_internal(EXCP_KERNEL_TRAP);
         dc->base.is_jmp = DISAS_NORETURN;
-        return;
+        return true;
     }
 #endif
 
@@ -12012,56 +12009,85 @@ static void arm_tr_translate_insn(DisasContextBase *dcbase, CPUState *cpu)
         gen_exception(EXCP_UDEF, syn_swstep(dc->ss_same_el, 0, 0),
                       default_exception_el(dc));
         dc->base.is_jmp = DISAS_NORETURN;
-        return;
+        return true;
     }
 
-    if (dc->thumb) {
+    return false;
-        disas_thumb_insn(env, dc);
+}
-        if (dc->condexec_mask) {
-            dc->condexec_cond = (dc->condexec_cond & 0xe)
-                | ((dc->condexec_mask >> 4) & 1);
-            dc->condexec_mask = (dc->condexec_mask << 1) & 0x1f;
-            if (dc->condexec_mask == 0) {
-                dc->condexec_cond = 0;
-            }
-        }
-    } else {
-        unsigned int insn = arm_ldl_code(env, dc->pc, dc->sctlr_b);
-        dc->pc += 4;
-        disas_arm_insn(dc, insn);
-    }
 
+static void arm_post_translate_insn(CPUARMState *env, DisasContext *dc)
+{
     if (dc->condjmp && !dc->base.is_jmp) {
         gen_set_label(dc->condlabel);
         dc->condjmp = 0;
     }
 
-    if (dc->base.is_jmp == DISAS_NEXT) {
+    /* Translation stops when a conditional branch is encountered.
-        /* Translation stops when a conditional branch is encountered.
+     * Otherwise the subsequent code could get translated several times.
-         * Otherwise the subsequent code could get translated several times.
+     * Also stop translation when a page boundary is reached.  This
-         * Also stop translation when a page boundary is reached.  This
+     * ensures prefetch aborts occur at the right place.
-         * ensures prefetch aborts occur at the right place.  */
+     *
-
+     * We want to stop the TB if the next insn starts in a new page,
-        if (dc->pc >= dc->next_page_start ||
+     * or if it spans between this page and the next. This means that
-            (dc->pc >= dc->next_page_start - 3 &&
+     * if we're looking at the last halfword in the page we need to
-             insn_crosses_page(env, dc))) {
+     * see if it's a 16-bit Thumb insn (which will fit in this TB)
-            /* We want to stop the TB if the next insn starts in a new page,
+     * or a 32-bit Thumb insn (which won't).
-             * or if it spans between this page and the next. This means that
+     * This is to avoid generating a silly TB with a single 16-bit insn
-             * if we're looking at the last halfword in the page we need to
+     * in it at the end of this page (which would execute correctly
-             * see if it's a 16-bit Thumb insn (which will fit in this TB)
+     * but isn't very efficient).
-             * or a 32-bit Thumb insn (which won't).
+     */
-             * This is to avoid generating a silly TB with a single 16-bit insn
+    if (dc->base.is_jmp == DISAS_NEXT
-             * in it at the end of this page (which would execute correctly
+        && (dc->pc >= dc->next_page_start
-             * but isn't very efficient).
+            || (dc->pc >= dc->next_page_start - 3
-             */
+                && insn_crosses_page(env, dc)))) {
-            dc->base.is_jmp = DISAS_TOO_MANY;
+        dc->base.is_jmp = DISAS_TOO_MANY;
-        }
     }
 
     dc->base.pc_next = dc->pc;
     translator_loop_temp_check(&dc->base);
 }
 
+static void arm_tr_translate_insn(DisasContextBase *dcbase, CPUState *cpu)
+{
+    DisasContext *dc = container_of(dcbase, DisasContext, base);
+    CPUARMState *env = cpu->env_ptr;
+    unsigned int insn;
+
+    if (arm_pre_translate_insn(dc)) {
+        return;
+    }
+
+    insn = arm_ldl_code(env, dc->pc, dc->sctlr_b);
+    dc->pc += 4;
+    disas_arm_insn(dc, insn);
+
+    arm_post_translate_insn(env, dc);
+}
+
+static void thumb_tr_translate_insn(DisasContextBase *dcbase, CPUState *cpu)
+{
+    DisasContext *dc = container_of(dcbase, DisasContext, base);
+    CPUARMState *env = cpu->env_ptr;
+
+    if (arm_pre_translate_insn(dc)) {
+        return;
+    }
+
+    disas_thumb_insn(env, dc);
+
+    /* Advance the Thumb condexec condition.  */
+    if (dc->condexec_mask) {
+        dc->condexec_cond = ((dc->condexec_cond & 0xe) |
+                             ((dc->condexec_mask >> 4) & 1));
+        dc->condexec_mask = (dc->condexec_mask << 1) & 0x1f;
+        if (dc->condexec_mask == 0) {
+            dc->condexec_cond = 0;
+        }
+    }
+
+    arm_post_translate_insn(env, dc);
+}
+
 static void arm_tr_tb_stop(DisasContextBase *dcbase, CPUState *cpu)
 {
     DisasContext *dc = container_of(dcbase, DisasContext, base);
@@ -12198,12 +12224,25 @@ static const TranslatorOps arm_translator_ops = {
     .disas_log          = arm_tr_disas_log,
 };
 
+static const TranslatorOps thumb_translator_ops = {
+    .init_disas_context = arm_tr_init_disas_context,
+    .tb_start           = arm_tr_tb_start,
+    .insn_start         = arm_tr_insn_start,
+    .breakpoint_check   = arm_tr_breakpoint_check,
+    .translate_insn     = thumb_tr_translate_insn,
+    .tb_stop            = arm_tr_tb_stop,
+    .disas_log          = arm_tr_disas_log,
+};
+
 /* generate intermediate code for basic block 'tb'.  */
 void gen_intermediate_code(CPUState *cpu, TranslationBlock *tb)
 {
     DisasContext dc;
     const TranslatorOps *ops = &arm_translator_ops;
 
+    if (ARM_TBFLAG_THUMB(tb->flags)) {
+        ops = &thumb_translator_ops;
+    }
 #ifdef TARGET_AARCH64
     if (ARM_TBFLAG_AARCH64_STATE(tb->flags)) {
         ops = &aarch64_translator_ops;