diff mbox series

[PULL,10/26] target/ppc: bcdsub fix sign when result is zero

Message ID 20180821043343.7514-11-david@gibson.dropbear.id.au (mailing list archive)
State New, archived
Headers show
Series [PULL,01/26] spapr_cpu_core: vmstate_[un]register per-CPU data from (un)realizefn | expand

Commit Message

David Gibson Aug. 21, 2018, 4:33 a.m. UTC 
From: Yasmin Beatriz <yasmins@linux.ibm.com>

When the result of bcdsub is equal to zero, the result sign may be
set to negative in some cases, and this does not follow the Power ISA
specifications as to decimal integer arithmetic instructions.

Signed-off-by: Yasmin Beatriz <yasmins@linux.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 target/ppc/int_helper.c | 3 +++
 1 file changed, 3 insertions(+)
diff mbox series

Patch

diff --git a/target/ppc/int_helper.c b/target/ppc/int_helper.c
index d52338ed71..ac7f92d7ae 100644
--- a/target/ppc/int_helper.c
+++ b/target/ppc/int_helper.c
@@ -2747,6 +2747,9 @@  uint32_t helper_bcdadd(ppc_avr_t *r,  ppc_avr_t *a, ppc_avr_t *b, uint32_t ps)
             result.u8[BCD_DIG_BYTE(0)] = bcd_preferred_sgn(sgna, ps);
             zero = bcd_sub_mag(&result, a, b, &invalid, &overflow);
             cr = (sgna > 0) ? CRF_GT : CRF_LT;
+        } else if (bcd_cmp_mag(a, b) == 0) {
+            result.u8[BCD_DIG_BYTE(0)] = bcd_preferred_sgn(0, ps);
+            zero = bcd_sub_mag(&result, b, a, &invalid, &overflow);
         } else {
             result.u8[BCD_DIG_BYTE(0)] = bcd_preferred_sgn(sgnb, ps);
             zero = bcd_sub_mag(&result, b, a, &invalid, &overflow);