target-i386: convert gen_compute_eflags_c to TCG

Do the switch at translation time, converting the helper templates to
TCG opcodes.  In some cases CF can be computed with a single setcond,
though others it may require a little more work.

In the CC_OP_DYNAMIC case, compute the whole EFLAGS, same as for ZF/SF/PF.

Reviewed-by: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>

target-i386/translate.c

@@ -869,17 +869,6 @@ static void gen_op_update_neg_cc(void)
     tcg_gen_mov_tl(cpu_cc_dst, cpu_T[0]);
 }
 
-/* compute eflags.C to reg */
-static void gen_compute_eflags_c(DisasContext *s, TCGv reg, bool inv)
-{
-    gen_update_cc_op(s);
-    gen_helper_cc_compute_c(cpu_tmp2_i32, cpu_env, cpu_cc_op);
-    tcg_gen_extu_i32_tl(reg, cpu_tmp2_i32);
-    if (inv) {
-        tcg_gen_xori_tl(reg, reg, 1);
-    }
-}
-
 /* compute all eflags to cc_src */
 static void gen_compute_eflags(DisasContext *s)
 {
@@ -892,6 +881,104 @@ static void gen_compute_eflags(DisasContext *s)
     tcg_gen_extu_i32_tl(cpu_cc_src, cpu_tmp2_i32);
 }
 
+/* compute eflags.C to reg */
+static void gen_compute_eflags_c(DisasContext *s, TCGv reg, bool inv)
+{
+    TCGv t0, t1;
+    int size;
+
+    switch (s->cc_op) {
+    case CC_OP_SUBB ... CC_OP_SUBQ:
+        /* (DATA_TYPE)(CC_DST + CC_SRC) < (DATA_TYPE)CC_SRC */
+        size = s->cc_op - CC_OP_SUBB;
+        t1 = gen_ext_tl(cpu_tmp0, cpu_cc_src, size, false);
+        /* If no temporary was used, be careful not to alias t1 and t0.  */
+        t0 = TCGV_EQUAL(t1, cpu_cc_src) ? cpu_tmp0 : reg;
+        tcg_gen_add_tl(t0, cpu_cc_dst, cpu_cc_src);
+        gen_extu(size, t0);
+        goto add_sub;
+
+    case CC_OP_ADDB ... CC_OP_ADDQ:
+        /* (DATA_TYPE)CC_DST < (DATA_TYPE)CC_SRC */
+        size = s->cc_op - CC_OP_ADDB;
+        t1 = gen_ext_tl(cpu_tmp0, cpu_cc_src, size, false);
+        t0 = gen_ext_tl(reg, cpu_cc_dst, size, false);
+    add_sub:
+        tcg_gen_setcond_tl(inv ? TCG_COND_GEU : TCG_COND_LTU, reg, t0, t1);
+        inv = false;
+        break;
+
+    case CC_OP_SBBB ... CC_OP_SBBQ:
+        /* (DATA_TYPE)(CC_DST + CC_SRC + 1) <= (DATA_TYPE)CC_SRC */
+        size = s->cc_op - CC_OP_SBBB;
+        t1 = gen_ext_tl(cpu_tmp0, cpu_cc_src, size, false);
+        if (TCGV_EQUAL(t1, reg) && TCGV_EQUAL(reg, cpu_cc_src)) {
+            tcg_gen_mov_tl(cpu_tmp0, cpu_cc_src);
+            t1 = cpu_tmp0;
+        }
+
+        tcg_gen_add_tl(reg, cpu_cc_dst, cpu_cc_src);
+        tcg_gen_addi_tl(reg, reg, 1);
+        gen_extu(size, reg);
+        t0 = reg;
+        goto adc_sbb;
+
+    case CC_OP_ADCB ... CC_OP_ADCQ:
+        /* (DATA_TYPE)CC_DST <= (DATA_TYPE)CC_SRC */
+        size = s->cc_op - CC_OP_ADCB;
+        t1 = gen_ext_tl(cpu_tmp0, cpu_cc_src, size, false);
+        t0 = gen_ext_tl(reg, cpu_cc_dst, size, false);
+    adc_sbb:
+        tcg_gen_setcond_tl(inv ? TCG_COND_GTU : TCG_COND_LEU, reg, t0, t1);
+        inv = false;
+        break;
+
+    case CC_OP_LOGICB ... CC_OP_LOGICQ:
+        tcg_gen_movi_tl(reg, 0);
+        break;
+
+    case CC_OP_INCB ... CC_OP_INCQ:
+    case CC_OP_DECB ... CC_OP_DECQ:
+        if (inv) {
+            tcg_gen_xori_tl(reg, cpu_cc_src, 1);
+        } else {
+            tcg_gen_mov_tl(reg, cpu_cc_src);
+        }
+        inv = false;
+        break;
+
+    case CC_OP_SHLB ... CC_OP_SHLQ:
+        /* (CC_SRC >> (DATA_BITS - 1)) & 1 */
+        size = s->cc_op - CC_OP_SHLB;
+        tcg_gen_shri_tl(reg, cpu_cc_src, (8 << size) - 1);
+        tcg_gen_andi_tl(reg, reg, 1);
+        break;
+
+    case CC_OP_MULB ... CC_OP_MULQ:
+        tcg_gen_setcondi_tl(inv ? TCG_COND_EQ : TCG_COND_NE,
+                            reg, cpu_cc_src, 0);
+        inv = false;
+        break;
+
+    case CC_OP_EFLAGS:
+    case CC_OP_SARB ... CC_OP_SARQ:
+        /* CC_SRC & 1 */
+        tcg_gen_andi_tl(reg, cpu_cc_src, 1);
+        break;
+
+    default:
+       /* The need to compute only C from CC_OP_DYNAMIC is important
+          in efficiently implementing e.g. INC at the start of a TB.  */
+       gen_update_cc_op(s);
+       gen_helper_cc_compute_c(cpu_tmp2_i32, cpu_env, cpu_cc_op);
+       tcg_gen_extu_i32_tl(reg, cpu_tmp2_i32);
+       break;
+    }
+    if (inv) {
+        tcg_gen_xori_tl(reg, reg, 1);
+    }
+}
+
 /* compute eflags.P to reg */
 static void gen_compute_eflags_p(DisasContext *s, TCGv reg)
 {