target/xtensa: don't generate extra EXCP_DEBUG on exception

Commit Message

Max Filippov April 15, 2021, 8:55 p.m. UTC

target/xtensa used to generate an extra EXCP_DEBUG exception before the
first instruction executed after an interrupt or an exception is taken
to allow single-stepping that instruction in the debugger.
This is no longer needed after the following commits:
a7ba744f4082 ("tcg/cpu-exec: precise single-stepping after an exception")
ba3c35d9c402 ("tcg/cpu-exec: precise single-stepping after an interrupt")
Drop exception state tracking/extra EXCP_DEBUG generation code.

Signed-off-by: Max Filippov <[e-mail]>
---
This patch depends on the "target/xtensa: Make sure that tb->size != 0"
patch.

 target/xtensa/cpu.c        | 1 -
 target/xtensa/cpu.h        | 7 -------
 target/xtensa/exc_helper.c | 5 -----
 target/xtensa/translate.c  | 6 ------
 4 files changed, 19 deletions(-)

Comments

Richard Henderson April 15, 2021, 10:29 p.m. UTC | #1

On 4/15/21 1:55 PM, Max Filippov wrote:
> target/xtensa used to generate an extra EXCP_DEBUG exception before the
> first instruction executed after an interrupt or an exception is taken
> to allow single-stepping that instruction in the debugger.
> This is no longer needed after the following commits:
> a7ba744f4082 ("tcg/cpu-exec: precise single-stepping after an exception")
> ba3c35d9c402 ("tcg/cpu-exec: precise single-stepping after an interrupt")
> Drop exception state tracking/extra EXCP_DEBUG generation code.
> 
> Signed-off-by: Max Filippov<[e-mail]>
> ---
> This patch depends on the "target/xtensa: Make sure that tb->size != 0"
> patch.
> 
>   target/xtensa/cpu.c        | 1 -
>   target/xtensa/cpu.h        | 7 -------
>   target/xtensa/exc_helper.c | 5 -----
>   target/xtensa/translate.c  | 6 ------
>   4 files changed, 19 deletions(-)

Reviewed-by: Richard Henderson <[e-mail]>

r~

Patch

diff --git a/target/xtensa/cpu.c b/target/xtensa/cpu.c
index e2b2c7a71c1d..210ef800923b 100644
--- a/target/xtensa/cpu.c
+++ b/target/xtensa/cpu.c
@@ -79,7 +79,6 @@  static void xtensa_cpu_reset(DeviceState *dev)
 
     xcc->parent_reset(dev);
 
-    env->exception_taken = 0;
     env->pc = env->config->exception_vector[EXC_RESET0 + env->static_vectors];
     env->sregs[LITBASE] &= ~1;
 #ifndef CONFIG_USER_ONLY
diff --git a/target/xtensa/cpu.h b/target/xtensa/cpu.h
index 3bd4f691c1a0..2345cb59c790 100644
--- a/target/xtensa/cpu.h
+++ b/target/xtensa/cpu.h
@@ -540,7 +540,6 @@  typedef struct CPUXtensaState {
     uint32_t ccount_base;
 #endif
 
-    int exception_taken;
     int yield_needed;
     unsigned static_vectors;
 
@@ -711,7 +710,6 @@  static inline int cpu_mmu_index(CPUXtensaState *env, bool ifetch)
 #define XTENSA_TBFLAG_ICOUNT 0x20
 #define XTENSA_TBFLAG_CPENABLE_MASK 0x3fc0
 #define XTENSA_TBFLAG_CPENABLE_SHIFT 6
-#define XTENSA_TBFLAG_EXCEPTION 0x4000
 #define XTENSA_TBFLAG_WINDOW_MASK 0x18000
 #define XTENSA_TBFLAG_WINDOW_SHIFT 15
 #define XTENSA_TBFLAG_YIELD 0x20000
@@ -732,8 +730,6 @@  typedef XtensaCPU ArchCPU;
 static inline void cpu_get_tb_cpu_state(CPUXtensaState *env, target_ulong *pc,
         target_ulong *cs_base, uint32_t *flags)
 {
-    CPUState *cs = env_cpu(env);
-
     *pc = env->pc;
     *cs_base = 0;
     *flags = 0;
@@ -782,9 +778,6 @@  static inline void cpu_get_tb_cpu_state(CPUXtensaState *env, target_ulong *pc,
     if (xtensa_option_enabled(env->config, XTENSA_OPTION_COPROCESSOR)) {
         *flags |= env->sregs[CPENABLE] << XTENSA_TBFLAG_CPENABLE_SHIFT;
     }
-    if (cs->singlestep_enabled && env->exception_taken) {
-        *flags |= XTENSA_TBFLAG_EXCEPTION;
-    }
     if (xtensa_option_enabled(env->config, XTENSA_OPTION_WINDOWED_REGISTER) &&
         (env->sregs[PS] & (PS_WOE | PS_EXCM)) == PS_WOE) {
         uint32_t windowstart = xtensa_replicate_windowstart(env) >>
diff --git a/target/xtensa/exc_helper.c b/target/xtensa/exc_helper.c
index 2f032bc05333..10e75ab070d7 100644
--- a/target/xtensa/exc_helper.c
+++ b/target/xtensa/exc_helper.c
@@ -40,9 +40,6 @@  void HELPER(exception)(CPUXtensaState *env, uint32_t excp)
     if (excp == EXCP_YIELD) {
         env->yield_needed = 0;
     }
-    if (excp == EXCP_DEBUG) {
-        env->exception_taken = 0;
-    }
     cpu_loop_exit(cs);
 }
 
@@ -197,7 +194,6 @@  static void handle_interrupt(CPUXtensaState *env)
             }
             env->sregs[PS] |= PS_EXCM;
         }
-        env->exception_taken = 1;
     }
 }
 
@@ -242,7 +238,6 @@  void xtensa_cpu_do_interrupt(CPUState *cs)
 
             vector = env->config->exception_vector[cs->exception_index];
             env->pc = relocated_vector(env, vector);
-            env->exception_taken = 1;
         } else {
             qemu_log_mask(CPU_LOG_INT,
                           "%s(pc = %08x) bad exception_index: %d\n",
diff --git a/target/xtensa/translate.c b/target/xtensa/translate.c
index 73584d9d605b..f93df87ec490 100644
--- a/target/xtensa/translate.c
+++ b/target/xtensa/translate.c
@@ -1279,12 +1279,6 @@  static void xtensa_tr_translate_insn(DisasContextBase *dcbase, CPUState *cpu)
         dc->base.is_jmp = DISAS_NORETURN;
         return;
     }
-    if (dc->base.tb->flags & XTENSA_TBFLAG_EXCEPTION) {
-        gen_exception(dc, EXCP_DEBUG);
-        dc->base.pc_next = dc->pc + 1;
-        dc->base.is_jmp = DISAS_NORETURN;
-        return;
-    }
 
     if (dc->icount) {
         TCGLabel *label = gen_new_label();