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[PATCH 03/38] target/riscv: Fixup saturate subtract function
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From: |
LIU Zhiwei |
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Subject: |
[PATCH 03/38] target/riscv: Fixup saturate subtract function |
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Date: |
Fri, 12 Feb 2021 23:02:21 +0800 |
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>
---
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 9371d70f6b..9786f630b4 100644
--- a/target/riscv/vector_helper.c
+++ b/target/riscv/vector_helper.c
@@ -2425,7 +2425,7 @@ 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;
@@ -2435,7 +2435,7 @@ 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;
@@ -2445,7 +2445,7 @@ 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;
@@ -2455,7 +2455,7 @@ 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;
--
2.17.1
[PATCH 05/38] target/riscv: 8-bit Addition & Subtraction Instruction, LIU Zhiwei, 2021/02/12
[PATCH 06/38] target/riscv: SIMD 16-bit Shift Instructions, LIU Zhiwei, 2021/02/12