From a0c231e651b249960906f250b8e5eef5ed9888c4 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Fri, 14 Jul 2017 09:05:06 -1000 Subject: [PATCH] target/arm: Use DISAS_NORETURN Fold DISAS_EXC and DISAS_TB_JUMP into DISAS_NORETURN. In both cases all following code is dead. In the first case because we have exited the TB via exception; in the second case because we have exited the TB via goto_tb and its associated machinery. Reviewed-by: Emilio G. Cota Signed-off-by: Richard Henderson --- target/arm/translate-a64.c | 37 ++++++++++++++++++++----------------- target/arm/translate.c | 14 ++++++++------ target/arm/translate.h | 8 ++------ 3 files changed, 30 insertions(+), 29 deletions(-) diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c index cb44632d16..881d3c0cbb 100644 --- a/target/arm/translate-a64.c +++ b/target/arm/translate-a64.c @@ -304,7 +304,7 @@ static void gen_exception_internal_insn(DisasContext *s, int offset, int excp) { gen_a64_set_pc_im(s->pc - offset); gen_exception_internal(excp); - s->is_jmp = DISAS_EXC; + s->is_jmp = DISAS_NORETURN; } static void gen_exception_insn(DisasContext *s, int offset, int excp, @@ -312,7 +312,7 @@ static void gen_exception_insn(DisasContext *s, int offset, int excp, { gen_a64_set_pc_im(s->pc - offset); gen_exception(excp, syndrome, target_el); - s->is_jmp = DISAS_EXC; + s->is_jmp = DISAS_NORETURN; } static void gen_ss_advance(DisasContext *s) @@ -340,7 +340,7 @@ static void gen_step_complete_exception(DisasContext *s) gen_ss_advance(s); gen_exception(EXCP_UDEF, syn_swstep(s->ss_same_el, 1, s->is_ldex), default_exception_el(s)); - s->is_jmp = DISAS_EXC; + s->is_jmp = DISAS_NORETURN; } static inline bool use_goto_tb(DisasContext *s, int n, uint64_t dest) @@ -371,7 +371,7 @@ static inline void gen_goto_tb(DisasContext *s, int n, uint64_t dest) tcg_gen_goto_tb(n); gen_a64_set_pc_im(dest); tcg_gen_exit_tb((intptr_t)tb + n); - s->is_jmp = DISAS_TB_JUMP; + s->is_jmp = DISAS_NORETURN; } else { gen_a64_set_pc_im(dest); if (s->ss_active) { @@ -380,7 +380,7 @@ static inline void gen_goto_tb(DisasContext *s, int n, uint64_t dest) gen_exception_internal(EXCP_DEBUG); } else { tcg_gen_lookup_and_goto_ptr(cpu_pc); - s->is_jmp = DISAS_TB_JUMP; + s->is_jmp = DISAS_NORETURN; } } } @@ -11326,7 +11326,7 @@ void gen_intermediate_code_a64(CPUState *cs, TranslationBlock *tb) assert(num_insns == 1); gen_exception(EXCP_UDEF, syn_swstep(dc->ss_same_el, 0, 0), default_exception_el(dc)); - dc->is_jmp = DISAS_EXC; + dc->is_jmp = DISAS_NORETURN; break; } @@ -11353,21 +11353,25 @@ void gen_intermediate_code_a64(CPUState *cs, TranslationBlock *tb) gen_io_end(); } - if (unlikely(cs->singlestep_enabled || dc->ss_active) - && dc->is_jmp != DISAS_EXC) { + if (unlikely(cs->singlestep_enabled || dc->ss_active)) { /* Note that this means single stepping WFI doesn't halt the CPU. * For conditional branch insns this is harmless unreachable code as * gen_goto_tb() has already handled emitting the debug exception * (and thus a tb-jump is not possible when singlestepping). */ - assert(dc->is_jmp != DISAS_TB_JUMP); - if (dc->is_jmp != DISAS_JUMP) { + switch (dc->is_jmp) { + default: gen_a64_set_pc_im(dc->pc); - } - if (cs->singlestep_enabled) { - gen_exception_internal(EXCP_DEBUG); - } else { - gen_step_complete_exception(dc); + /* fall through */ + case DISAS_JUMP: + if (cs->singlestep_enabled) { + gen_exception_internal(EXCP_DEBUG); + } else { + gen_step_complete_exception(dc); + } + break; + case DISAS_NORETURN: + break; } } else { switch (dc->is_jmp) { @@ -11377,8 +11381,7 @@ void gen_intermediate_code_a64(CPUState *cs, TranslationBlock *tb) case DISAS_JUMP: tcg_gen_lookup_and_goto_ptr(cpu_pc); break; - case DISAS_TB_JUMP: - case DISAS_EXC: + case DISAS_NORETURN: case DISAS_SWI: break; case DISAS_WFE: diff --git a/target/arm/translate.c b/target/arm/translate.c index e52a6d7622..b14329dc27 100644 --- a/target/arm/translate.c +++ b/target/arm/translate.c @@ -297,7 +297,7 @@ static void gen_step_complete_exception(DisasContext *s) gen_ss_advance(s); gen_exception(EXCP_UDEF, syn_swstep(s->ss_same_el, 1, s->is_ldex), default_exception_el(s)); - s->is_jmp = DISAS_EXC; + s->is_jmp = DISAS_NORETURN; } static void gen_singlestep_exception(DisasContext *s) @@ -1184,7 +1184,7 @@ static void gen_exception_internal_insn(DisasContext *s, int offset, int excp) gen_set_condexec(s); gen_set_pc_im(s, s->pc - offset); gen_exception_internal(excp); - s->is_jmp = DISAS_EXC; + s->is_jmp = DISAS_NORETURN; } static void gen_exception_insn(DisasContext *s, int offset, int excp, @@ -1193,7 +1193,7 @@ static void gen_exception_insn(DisasContext *s, int offset, int excp, gen_set_condexec(s); gen_set_pc_im(s, s->pc - offset); gen_exception(excp, syn, target_el); - s->is_jmp = DISAS_EXC; + s->is_jmp = DISAS_NORETURN; } /* Force a TB lookup after an instruction that changes the CPU state. */ @@ -11974,7 +11974,7 @@ void gen_intermediate_code(CPUState *cs, TranslationBlock *tb) /* We always get here via a jump, so know we are not in a conditional execution block. */ gen_exception_internal(EXCP_KERNEL_TRAP); - dc->is_jmp = DISAS_EXC; + dc->is_jmp = DISAS_NORETURN; break; } #endif @@ -12119,6 +12119,9 @@ void gen_intermediate_code(CPUState *cs, TranslationBlock *tb) default: /* FIXME: Single stepping a WFI insn will not halt the CPU. */ gen_singlestep_exception(dc); + break; + case DISAS_NORETURN: + break; } } else { /* While branches must always occur at the end of an IT block, @@ -12143,8 +12146,7 @@ void gen_intermediate_code(CPUState *cs, TranslationBlock *tb) /* indicate that the hash table must be used to find the next TB */ tcg_gen_exit_tb(0); break; - case DISAS_TB_JUMP: - case DISAS_EXC: + case DISAS_NORETURN: /* nothing more to generate */ break; case DISAS_WFI: diff --git a/target/arm/translate.h b/target/arm/translate.h index 2fe144baa9..90f64d9716 100644 --- a/target/arm/translate.h +++ b/target/arm/translate.h @@ -124,12 +124,8 @@ static void disas_set_insn_syndrome(DisasContext *s, uint32_t syn) * defer them until after the conditional execution state has been updated. * WFI also needs special handling when single-stepping. */ -#define DISAS_WFI 4 -#define DISAS_SWI 5 -/* For instructions which unconditionally cause an exception we can skip - * emitting unreachable code at the end of the TB in the A64 decoder - */ -#define DISAS_EXC 6 +#define DISAS_WFI 5 +#define DISAS_SWI 6 /* WFE */ #define DISAS_WFE 7 #define DISAS_HVC 8 -- 2.11.0