Patchwork [08/57] target-i386: move eflags computation closer to gen_op_set_cc_op

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Submitter Richard Henderson
Date Feb. 19, 2013, 5:39 p.m.
Message ID <1361295631-21316-9-git-send-email-rth@twiddle.net>
Download mbox | patch
Permalink /patch/221761/
State New
Headers show

Comments

Richard Henderson - Feb. 19, 2013, 5:39 p.m.
From: Paolo Bonzini <pbonzini@redhat.com>

This ensures the invariant that cpu_cc_op matches s->cc_op when calling
the helpers.  The next patches need this because gen_compute_eflags and
gen_compute_eflags_c will take care of setting cpu_cc_op.

Always compute EFLAGS first since it is needed whenever the shift is
non-zero, i.e. most of the time.  This makes it possible to remove some
writes of CC_OP_EFLAGS to cpu_cc_op and more importantly removes cases
where s->cc_op becomes CC_OP_DYNAMIC.  These are slow and we want to
avoid them: CC_OP_EFLAGS is quite efficient once we paid the initial
cost of computing the flags.

Finally, always follow gen_compute_eflags(cpu_cc_src) by setting s->cc_op
and discarding cpu_cc_dst.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 target-i386/translate.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

Patch

diff --git a/target-i386/translate.c b/target-i386/translate.c
index ed373c3..0970954 100644
--- a/target-i386/translate.c
+++ b/target-i386/translate.c
@@ -1597,14 +1597,16 @@  static void gen_rot_rm_T1(DisasContext *s, int ot, int op1,
         gen_op_mov_reg_v(ot, op1, t0);
     }
     
-    /* update eflags */
+    /* update eflags.  It is needed anyway most of the time, do it always.  */
     if (s->cc_op != CC_OP_DYNAMIC)
         gen_op_set_cc_op(s->cc_op);
+    gen_compute_eflags(cpu_cc_src);
+    tcg_gen_discard_tl(cpu_cc_dst);
+    s->cc_op = CC_OP_EFLAGS;
 
     label2 = gen_new_label();
     tcg_gen_brcondi_tl(TCG_COND_EQ, t1, 0, label2);
 
-    gen_compute_eflags(cpu_cc_src);
     tcg_gen_andi_tl(cpu_cc_src, cpu_cc_src, ~(CC_O | CC_C));
     tcg_gen_xor_tl(cpu_tmp0, t2, t0);
     tcg_gen_lshift(cpu_tmp0, cpu_tmp0, 11 - (data_bits - 1));
@@ -1615,12 +1617,8 @@  static void gen_rot_rm_T1(DisasContext *s, int ot, int op1,
     }
     tcg_gen_andi_tl(t0, t0, CC_C);
     tcg_gen_or_tl(cpu_cc_src, cpu_cc_src, t0);
-    
-    tcg_gen_discard_tl(cpu_cc_dst);
-    tcg_gen_movi_i32(cpu_cc_op, CC_OP_EFLAGS);
-        
+
     gen_set_label(label2);
-    s->cc_op = CC_OP_DYNAMIC; /* cannot predict flags after */
 
     tcg_temp_free(t0);
     tcg_temp_free(t1);
@@ -1684,6 +1682,9 @@  static void gen_rot_rm_im(DisasContext *s, int ot, int op1, int op2,
             gen_op_set_cc_op(s->cc_op);
 
         gen_compute_eflags(cpu_cc_src);
+        tcg_gen_discard_tl(cpu_cc_dst);
+        s->cc_op = CC_OP_EFLAGS;
+
         tcg_gen_andi_tl(cpu_cc_src, cpu_cc_src, ~(CC_O | CC_C));
         tcg_gen_xor_tl(cpu_tmp0, t1, t0);
         tcg_gen_lshift(cpu_tmp0, cpu_tmp0, 11 - (data_bits - 1));
@@ -1694,10 +1695,6 @@  static void gen_rot_rm_im(DisasContext *s, int ot, int op1, int op2,
         }
         tcg_gen_andi_tl(t0, t0, CC_C);
         tcg_gen_or_tl(cpu_cc_src, cpu_cc_src, t0);
-
-        tcg_gen_discard_tl(cpu_cc_dst);
-        tcg_gen_movi_i32(cpu_cc_op, CC_OP_EFLAGS);
-        s->cc_op = CC_OP_EFLAGS;
     }
 
     tcg_temp_free(t0);