target-arm: Implement YIELD insn to yield in ARM and Thumb translators

Implement the YIELD instruction in the ARM and Thumb translators to
actually yield control back to the top level loop rather than being
a simple no-op. (We already do this for A64.)
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NPeter Crosthwaite <peter.crosthwaite@xilinx.com>
Message-id: 1435672316-3311-3-git-send-email-peter.maydell@linaro.org

target-arm/translate.c

@@ -4080,6 +4080,10 @@ static void gen_rfe(DisasContext *s, TCGv_i32 pc, TCGv_i32 cpsr)
 static void gen_nop_hint(DisasContext *s, int val)
 {
     switch (val) {
+    case 1: /* yield */
+        gen_set_pc_im(s, s->pc);
+        s->is_jmp = DISAS_YIELD;
+        break;
     case 3: /* wfi */
         gen_set_pc_im(s, s->pc);
         s->is_jmp = DISAS_WFI;
@@ -11459,6 +11463,9 @@ static inline void gen_intermediate_code_internal(ARMCPU *cpu,
         case DISAS_WFE:
             gen_helper_wfe(cpu_env);
             break;
+        case DISAS_YIELD:
+            gen_helper_yield(cpu_env);
+            break;
         case DISAS_SWI:
             gen_exception(EXCP_SWI, syn_aa32_svc(dc->svc_imm, dc->thumb),
                           default_exception_el(dc));