cpu-exec: allow temporary disabling icount

This patch is required for deterministic replay to generate an exception
by trying executing an instruction without changing icount.
It adds new flag to TB for disabling icount while translating it.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NPavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20150917162359.8676.77011.stgit@PASHA-ISP.def.inno>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

cpu-exec.c

@@ -184,7 +184,7 @@ static inline tcg_target_ulong cpu_tb_exec(CPUState *cpu, uint8_t *tb_ptr)
 /* Execute the code without caching the generated code. An interpreter
    could be used if available. */
 static void cpu_exec_nocache(CPUState *cpu, int max_cycles,
-                             TranslationBlock *orig_tb)
+                             TranslationBlock *orig_tb, bool ignore_icount)
 {
     TranslationBlock *tb;
 
@@ -194,7 +194,8 @@ static void cpu_exec_nocache(CPUState *cpu, int max_cycles,
         max_cycles = CF_COUNT_MASK;
 
     tb = tb_gen_code(cpu, orig_tb->pc, orig_tb->cs_base, orig_tb->flags,
-                     max_cycles | CF_NOCACHE);
+                     max_cycles | CF_NOCACHE
+                         | (ignore_icount ? CF_IGNORE_ICOUNT : 0));
     tb->orig_tb = tcg_ctx.tb_ctx.tb_invalidated_flag ? NULL : orig_tb;
     cpu->current_tb = tb;
     /* execute the generated code */
@@ -519,7 +520,7 @@ int cpu_exec(CPUState *cpu)
                             if (insns_left > 0) {
                                 /* Execute remaining instructions.  */
                                 tb = (TranslationBlock *)(next_tb & ~TB_EXIT_MASK);
-                                cpu_exec_nocache(cpu, insns_left, tb);
+                                cpu_exec_nocache(cpu, insns_left, tb, false);
                                 align_clocks(&sc, cpu);
                             }
                             cpu->exception_index = EXCP_INTERRUPT;

include/exec/exec-all.h

@@ -190,6 +190,7 @@ struct TranslationBlock {
 #define CF_LAST_IO     0x8000 /* Last insn may be an IO access.  */
 #define CF_NOCACHE     0x10000 /* To be freed after execution */
 #define CF_USE_ICOUNT  0x20000
+#define CF_IGNORE_ICOUNT 0x40000 /* Do not generate icount code */
 
     void *tc_ptr;    /* pointer to the translated code */
     uint8_t *tc_search;  /* pointer to search data */

translate-all.c

@@ -1069,7 +1069,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
 #endif
 
     phys_pc = get_page_addr_code(env, pc);
-    if (use_icount) {
+    if (use_icount && !(cflags & CF_IGNORE_ICOUNT)) {
         cflags |= CF_USE_ICOUNT;
     }