While ~T0+T1+CF = T1-T0+CF-1 is true for the low 32-bits,
it does not produce the correct carry-out to bit 33. Do
exactly what the manual says.
Cc: Alexander Graf <ag...@suse.de>
Signed-off-by: Richard Henderson <r...@twiddle.net>
---
target-ppc/translate.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/target-ppc/translate.c b/target-ppc/translate.c
index f886441..b3d509f 100644
--- a/target-ppc/translate.c
+++ b/target-ppc/translate.c
@@ -1120,14 +1120,15 @@ static inline void gen_op_arith_subf(DisasContext *ctx,
TCGv ret, TCGv arg1,
}
if (add_ca) {
- /* dest = ~arg1 + arg2 + ca = arg2 - arg1 + ca - 1. */
+ /* dest = ~arg1 + arg2 + ca. */
if (compute_ca) {
- TCGv zero;
- tcg_gen_subi_tl(cpu_ca, cpu_ca, 1);
+ TCGv zero, inv1 = tcg_temp_new();
+ tcg_gen_not_tl(inv1, arg1);
zero = tcg_const_tl(0);
tcg_gen_add2_tl(t0, cpu_ca, arg2, zero, cpu_ca, zero);
- tcg_gen_sub2_tl(t0, cpu_ca, t0, cpu_ca, arg1, zero);
+ tcg_gen_sub2_tl(t0, cpu_ca, t0, cpu_ca, inv1, zero);
tcg_temp_free(zero);
+ tcg_temp_free(inv1);
} else {
tcg_gen_sub_tl(t0, arg2, arg1);
tcg_gen_add_tl(t0, t0, cpu_ca);
--
1.8.1.2
