accel/tcg: Always require can_do_io

Require i/o as the last insn of a TranslationBlock always,
not only with icount.  This is required for i/o that alters
the address space, such as a pci config space write.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1866
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

accel/tcg/translator.c

@@ -28,12 +28,6 @@ static void set_can_do_io(DisasContextBase *db, bool val)
 
 bool translator_io_start(DisasContextBase *db)
 {
-    uint32_t cflags = tb_cflags(db->tb);
-
-    if (!(cflags & CF_USE_ICOUNT)) {
-        return false;
-    }
-
     set_can_do_io(db, true);
 
     /*
@@ -86,15 +80,15 @@ static TCGOp *gen_tb_start(DisasContextBase *db, uint32_t cflags)
         tcg_gen_st16_i32(count, cpu_env,
                          offsetof(ArchCPU, neg.icount_decr.u16.low) -
                          offsetof(ArchCPU, env));
-        /*
-         * cpu->can_do_io is set automatically here at the beginning of
-         * each translation block.  The cost is minimal and only paid for
-         * -icount, plus it would be very easy to forget doing it in the
-         * translator.
-         */
-        set_can_do_io(db, db->max_insns == 1 && (cflags & CF_LAST_IO));
     }
 
+    /*
+     * cpu->can_do_io is set automatically here at the beginning of
+     * each translation block.  The cost is minimal, plus it would be
+     * very easy to forget doing it in the translator.
+     */
+    set_can_do_io(db, db->max_insns == 1 && (cflags & CF_LAST_IO));
+
     return icount_start_insn;
 }
 

target/mips/tcg/translate.c

@@ -11212,7 +11212,6 @@ static void gen_branch(DisasContext *ctx, int insn_bytes)
         /* Branches completion */
         clear_branch_hflags(ctx);
         ctx->base.is_jmp = DISAS_NORETURN;
-        /* FIXME: Need to clear can_do_io.  */
         switch (proc_hflags & MIPS_HFLAG_BMASK_BASE) {
         case MIPS_HFLAG_FBNSLOT:
             gen_goto_tb(ctx, 0, ctx->base.pc_next + insn_bytes);