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- From cf90aa93ab52ea954d20734e7d8df906433636e5 Mon Sep 17 00:00:00 2001
- From: LIU Zhiwei <zhiwei_liu@c-sky.com>
- Date: Fri, 12 Feb 2021 23:02:21 +0800
- Subject: [PATCH 007/107] target/riscv: Fixup saturate subtract function
- 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
- Message-Id: <20210212150256.885-4-zhiwei_liu@c-sky.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 vxrm, int8_t a, int8_t b)
- {
- int8_t res = a - b;
- if ((res ^ a) & (a ^ b) & INT8_MIN) {
- - res = a > 0 ? INT8_MAX : INT8_MIN;
- + res = a >= 0 ? INT8_MAX : INT8_MIN;
- env->vxsat = 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 = a - b;
- if ((res ^ a) & (a ^ b) & INT16_MIN) {
- - res = a > 0 ? INT16_MAX : INT16_MIN;
- + res = a >= 0 ? INT16_MAX : INT16_MIN;
- env->vxsat = 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 = a - b;
- if ((res ^ a) & (a ^ b) & INT32_MIN) {
- - res = a > 0 ? INT32_MAX : INT32_MIN;
- + res = a >= 0 ? INT32_MAX : INT32_MIN;
- env->vxsat = 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 = a - b;
- if ((res ^ a) & (a ^ b) & INT64_MIN) {
- - res = a > 0 ? INT64_MAX : INT64_MIN;
- + res = a >= 0 ? INT64_MAX : INT64_MIN;
- env->vxsat = 0x1;
- }
- return res;
- --
- 2.33.1
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