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Re: [Qemu-arm] [PATCH v2 08/13] target/arm: optimize cross-page block ch


From: Richard Henderson
Subject: Re: [Qemu-arm] [PATCH v2 08/13] target/arm: optimize cross-page block chaining in softmmu
Date: Tue, 25 Apr 2017 13:11:59 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.0

On 04/25/2017 09:53 AM, Emilio G. Cota wrote:
Instead of unconditionally exiting to the exec loop, use the
lookup_tb_ptr helper to jump to the target if it is valid.
As long as the hit rate in tb_jmp_cache remains high, this
will improve performance.

Perf impact: see the next commit's log.

Signed-off-by: Emilio G. Cota <address@hidden>
---
  target/arm/translate.c | 6 +++++-
  1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/target/arm/translate.c b/target/arm/translate.c
index e32e38c..574cf70 100644
--- a/target/arm/translate.c
+++ b/target/arm/translate.c
@@ -4085,8 +4085,12 @@ static inline void gen_goto_tb(DisasContext *s, int n, 
target_ulong dest)
          gen_set_pc_im(s, dest);
          tcg_gen_exit_tb((uintptr_t)s->tb + n);
      } else {
+        TCGv_ptr ptr = tcg_temp_new_ptr();
+
          gen_set_pc_im(s, dest);
-        tcg_gen_exit_tb(0);
+        gen_helper_lookup_tb_ptr(ptr, cpu_env, cpu_R[15]);
+        tcg_gen_goto_ptr(ptr);
+        tcg_temp_free_ptr(ptr);
      }

This does not compile for aarch64.  You need to tcg_gen_extu_i32_tl first.


r~



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