target/i386: prepare for implementation of STOS/SCAS in new decoder

Do not use gen_op, and pull the load from the accumulator into
disas_insn.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

target/i386/tcg/translate.c

@@ -1264,7 +1264,6 @@ static TCGLabel *gen_jz_ecx_string(DisasContext *s)
 
 static void gen_stos(DisasContext *s, MemOp ot)
 {
-    gen_op_mov_v_reg(s, MO_32, s->T0, R_EAX);
     gen_string_movl_A0_EDI(s);
     gen_op_st_v(s, ot, s->T0, s->A0);
     gen_op_add_reg(s, s->aflag, R_EDI, gen_compute_Dshift(s, ot));
@@ -1282,7 +1281,11 @@ static void gen_scas(DisasContext *s, MemOp ot)
 {
     gen_string_movl_A0_EDI(s);
     gen_op_ld_v(s, ot, s->T1, s->A0);
-    gen_op(s, OP_CMPL, ot, R_EAX);
+    tcg_gen_mov_tl(cpu_cc_src, s->T1);
+    tcg_gen_mov_tl(s->cc_srcT, s->T0);
+    tcg_gen_sub_tl(cpu_cc_dst, s->T0, s->T1);
+    set_cc_op(s, CC_OP_SUBB + ot);
+
     gen_op_add_reg(s, s->aflag, R_EDI, gen_compute_Dshift(s, ot));
 }
 
@@ -4952,6 +4955,7 @@ static bool disas_insn(DisasContext *s, CPUState *cpu)
     case 0xaa: /* stosS */
     case 0xab:
         ot = mo_b_d(b, dflag);
+        gen_op_mov_v_reg(s, MO_32, s->T0, R_EAX);
         if (prefixes & (PREFIX_REPZ | PREFIX_REPNZ)) {
             gen_repz_stos(s, ot);
         } else {
@@ -4970,6 +4974,7 @@ static bool disas_insn(DisasContext *s, CPUState *cpu)
     case 0xae: /* scasS */
     case 0xaf:
         ot = mo_b_d(b, dflag);
+        gen_op_mov_v_reg(s, MO_32, s->T0, R_EAX);
         if (prefixes & PREFIX_REPNZ) {
             gen_repz_scas(s, ot, 1);
         } else if (prefixes & PREFIX_REPZ) {