accel/tcg: Avoid load of icount_decr if unused

With CF_NOIRQ and without !CF_USE_ICOUNT, the load isn't used.
Avoid emitting it.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

accel/tcg/translator.c

@@ -49,12 +49,15 @@ bool translator_io_start(DisasContextBase *db)
 
 static TCGOp *gen_tb_start(uint32_t cflags)
 {
-    TCGv_i32 count = tcg_temp_new_i32();
+    TCGv_i32 count = NULL;
     TCGOp *icount_start_insn = NULL;
 
-    tcg_gen_ld_i32(count, cpu_env,
-                   offsetof(ArchCPU, neg.icount_decr.u32) -
-                   offsetof(ArchCPU, env));
+    if ((cflags & CF_USE_ICOUNT) || !(cflags & CF_NOIRQ)) {
+        count = tcg_temp_new_i32();
+        tcg_gen_ld_i32(count, cpu_env,
+                       offsetof(ArchCPU, neg.icount_decr.u32) -
+                       offsetof(ArchCPU, env));
+    }
 
     if (cflags & CF_USE_ICOUNT) {
         /*