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From: Alistair Francis <alistair.francis@wdc.com>
To: peter.maydell@linaro.org
Subject: [PULL v3 18/42] target/riscv: Fixup saturate subtract function
Date: Tue, 11 May 2021 20:19:27 +1000
Message-Id: <20210511101951.165287-19-alistair.francis@wdc.com>
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Cc: alistair23@gmail.com, Alistair Francis <alistair.francis@wdc.com>,
Richard Henderson <richard.henderson@linaro.org>, qemu-devel@nongnu.org,
LIU Zhiwei <zhiwei_liu@c-sky.com>
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From: LIU Zhiwei <zhiwei_liu@c-sky.com>
The overflow predication ((a - b) ^ a) & (a ^ b) & INT64_MIN is right.
However, when the predication is ture and a is 0, it should return maximum.
Signed-off-by: LIU Zhiwei <zhiwei_liu@c-sky.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20210212150256.885-4-zhiwei_liu@c-sky.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
---
target/riscv/vector_helper.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/target/riscv/vector_helper.c b/target/riscv/vector_helper.c
index a156573d28..356cef8a09 100644
--- a/target/riscv/vector_helper.c
+++ b/target/riscv/vector_helper.c
@@ -2451,7 +2451,7 @@ static inline int8_t ssub8(CPURISCVState *env, int vx=
rm, int8_t a, int8_t b)
{
int8_t res =3D a - b;
if ((res ^ a) & (a ^ b) & INT8_MIN) {
- res =3D a > 0 ? INT8_MAX : INT8_MIN;
+ res =3D a >=3D 0 ? INT8_MAX : INT8_MIN;
env->vxsat =3D 0x1;
}
return res;
@@ -2461,7 +2461,7 @@ static inline int16_t ssub16(CPURISCVState *env, int =
vxrm, int16_t a, int16_t b)
{
int16_t res =3D a - b;
if ((res ^ a) & (a ^ b) & INT16_MIN) {
- res =3D a > 0 ? INT16_MAX : INT16_MIN;
+ res =3D a >=3D 0 ? INT16_MAX : INT16_MIN;
env->vxsat =3D 0x1;
}
return res;
@@ -2471,7 +2471,7 @@ static inline int32_t ssub32(CPURISCVState *env, int =
vxrm, int32_t a, int32_t b)
{
int32_t res =3D a - b;
if ((res ^ a) & (a ^ b) & INT32_MIN) {
- res =3D a > 0 ? INT32_MAX : INT32_MIN;
+ res =3D a >=3D 0 ? INT32_MAX : INT32_MIN;
env->vxsat =3D 0x1;
}
return res;
@@ -2481,7 +2481,7 @@ static inline int64_t ssub64(CPURISCVState *env, int =
vxrm, int64_t a, int64_t b)
{
int64_t res =3D a - b;
if ((res ^ a) & (a ^ b) & INT64_MIN) {
- res =3D a > 0 ? INT64_MAX : INT64_MIN;
+ res =3D a >=3D 0 ? INT64_MAX : INT64_MIN;
env->vxsat =3D 0x1;
}
return res;
--=20
2.31.1