[PATCH 08/13] target/i386: make cc_op handling more explicit for repeated string instructions.

[Paolo Bonzini]

Since the cost of gen_update_cc_op() must be paid anyway, it's easier
to place them manually and not rely on spilling that is buried under
multiple levels of function calls.

And since cc_op will have been spilled at the point of a fault, just
make the whole insn CC_OP_DYNAMIC.  Once repz_opt is reintroduced,
a fault could happen either before or after the first execution of
CMPS/SCAS, and CC_OP_DYNAMIC sidesteps the complicated matter of what
x86_restore_state_to_opc would do.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 target/i386/tcg/translate.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c
index 4ff0ccf71cb..4b53a47000e 100644
--- a/target/i386/tcg/translate.c
+++ b/target/i386/tcg/translate.c
@@ -1345,14 +1345,29 @@ static void do_gen_rep(DisasContext *s, MemOp ot,
      */
     s->flags &= ~HF_RF_MASK;
 
+    /*
+     * For CMPS/SCAS, the CC_OP after a memory fault could come from either
+     * the previous instruction or the string instruction; but because we
+     * arrange to keep CC_OP up to date all the time, just mark the whole
+     * insn as CC_OP_DYNAMIC.
+     *
+     * It's not a problem to do this even for instructions that do not
+     * modify the flags, so do it unconditionally.
+     */
     gen_update_cc_op(s);
+    tcg_set_insn_start_param(s->base.insn_start, 1, CC_OP_DYNAMIC);
+
+    /* Any iteration at all?  */
     gen_op_jz_ecx(s, done);
 
     fn(s, ot);
     gen_op_add_reg_im(s, s->aflag, R_ECX, -1);
+    gen_update_cc_op(s);
+
+    /* Leave if REP condition fails.  */
     if (is_repz_nz) {
         int nz = (s->prefix & PREFIX_REPNZ) ? 1 : 0;
-        gen_jcc(s, (JCC_Z << 1) | (nz ^ 1), done);
+        gen_jcc_noeob(s, (JCC_Z << 1) | (nz ^ 1), done);
     }
 
     /*
-- 
2.47.1