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target-arm: Fix rounding constant addition for Neon shifts 

Handle cases where adding the rounding constant could overflow in Neon
shift instructions: VRSHR, VRSRA, VQRSHRN, VQRSHRUN, VRSHRN.

Signed-off-by: Christophe Lyon <christophe.lyon@st.com>
[peter.maydell@linaro.org: fix handling of large shifts in rshl_s32,
calculate signed saturated value as other functions do.]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
This commit is contained in:
Christophe Lyon 2011-02-15 13:44:41 +00:00 committed by Aurelien Jarno
parent d68a6f3a6d
commit 4bd4ee072c
1 changed files with 127 additions and 12 deletions
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139
target-arm/neon_helper.c
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@ -558,9 +558,28 @@ uint64_t HELPER(neon_shl_s64)(uint64_t valop, uint64_t shiftop)
}} while (0)
NEON_VOP(rshl_s8, neon_s8, 4)
NEON_VOP(rshl_s16, neon_s16, 2)
NEON_VOP(rshl_s32, neon_s32, 1)
#undef NEON_FN
/* The addition of the rounding constant may overflow, so we use an
* intermediate 64 bits accumulator. */
uint32_t HELPER(neon_rshl_s32)(uint32_t valop, uint32_t shiftop)
{
int32_t dest;
int32_t val = (int32_t)valop;
int8_t shift = (int8_t)shiftop;
if ((shift >= 32) || (shift <= -32)) {
dest = 0;
} else if (shift < 0) {
int64_t big_dest = ((int64_t)val + (1 << (-1 - shift)));
dest = big_dest >> -shift;
} else {
dest = val << shift;
}
return dest;
}
/* Handling addition overflow with 64 bits inputs values is more
* tricky than with 32 bits values. */
uint64_t HELPER(neon_rshl_s64)(uint64_t valop, uint64_t shiftop)
{
int8_t shift = (int8_t)shiftop;
@ -574,7 +593,16 @@ uint64_t HELPER(neon_rshl_s64)(uint64_t valop, uint64_t shiftop)
val++;
val >>= 1;
} else if (shift < 0) {
val = (val + ((int64_t)1 << (-1 - shift))) >> -shift;
val >>= (-shift - 1);
if (val == INT64_MAX) {
/* In this case, it means that the rounding constant is 1,
* and the addition would overflow. Return the actual
* result directly. */
val = 0x4000000000000000LL;
} else {
val++;
val >>= 1;
}
} else {
val <<= shift;
}
@ -596,9 +624,29 @@ uint64_t HELPER(neon_rshl_s64)(uint64_t valop, uint64_t shiftop)
}} while (0)
NEON_VOP(rshl_u8, neon_u8, 4)
NEON_VOP(rshl_u16, neon_u16, 2)
NEON_VOP(rshl_u32, neon_u32, 1)
#undef NEON_FN
/* The addition of the rounding constant may overflow, so we use an
* intermediate 64 bits accumulator. */
uint32_t HELPER(neon_rshl_u32)(uint32_t val, uint32_t shiftop)
{
uint32_t dest;
int8_t shift = (int8_t)shiftop;
if (shift >= 32 || shift < -32) {
dest = 0;
} else if (shift == -32) {
dest = val >> 31;
} else if (shift < 0) {
uint64_t big_dest = ((uint64_t)val + (1 << (-1 - shift)));
dest = big_dest >> -shift;
} else {
dest = val << shift;
}
return dest;
}
/* Handling addition overflow with 64 bits inputs values is more
* tricky than with 32 bits values. */
uint64_t HELPER(neon_rshl_u64)(uint64_t val, uint64_t shiftop)
{
int8_t shift = (uint8_t)shiftop;
@ -607,9 +655,17 @@ uint64_t HELPER(neon_rshl_u64)(uint64_t val, uint64_t shiftop)
} else if (shift == -64) {
/* Rounding a 1-bit result just preserves that bit. */
val >>= 63;
} if (shift < 0) {
val = (val + ((uint64_t)1 << (-1 - shift))) >> -shift;
val >>= -shift;
} else if (shift < 0) {
val >>= (-shift - 1);
if (val == UINT64_MAX) {
/* In this case, it means that the rounding constant is 1,
* and the addition would overflow. Return the actual
* result directly. */
val = 0x8000000000000000ULL;
} else {
val++;
val >>= 1;
}
} else {
val <<= shift;
}
@ -784,14 +840,43 @@ uint64_t HELPER(neon_qshlu_s64)(CPUState *env, uint64_t valop, uint64_t shiftop)
}} while (0)
NEON_VOP_ENV(qrshl_u8, neon_u8, 4)
NEON_VOP_ENV(qrshl_u16, neon_u16, 2)
NEON_VOP_ENV(qrshl_u32, neon_u32, 1)
#undef NEON_FN
/* The addition of the rounding constant may overflow, so we use an
* intermediate 64 bits accumulator. */
uint32_t HELPER(neon_qrshl_u32)(CPUState *env, uint32_t val, uint32_t shiftop)
{
uint32_t dest;
int8_t shift = (int8_t)shiftop;
if (shift < 0) {
uint64_t big_dest = ((uint64_t)val + (1 << (-1 - shift)));
dest = big_dest >> -shift;
} else {
dest = val << shift;
if ((dest >> shift) != val) {
SET_QC();
dest = ~0;
}
}
return dest;
}
/* Handling addition overflow with 64 bits inputs values is more
* tricky than with 32 bits values. */
uint64_t HELPER(neon_qrshl_u64)(CPUState *env, uint64_t val, uint64_t shiftop)
{
int8_t shift = (int8_t)shiftop;
if (shift < 0) {
val = (val + (1 << (-1 - shift))) >> -shift;
val >>= (-shift - 1);
if (val == UINT64_MAX) {
/* In this case, it means that the rounding constant is 1,
* and the addition would overflow. Return the actual
* result directly. */
val = 0x8000000000000000ULL;
} else {
val++;
val >>= 1;
}
} else { \
uint64_t tmp = val;
val <<= shift;
@ -817,22 +902,52 @@ uint64_t HELPER(neon_qrshl_u64)(CPUState *env, uint64_t val, uint64_t shiftop)
}} while (0)
NEON_VOP_ENV(qrshl_s8, neon_s8, 4)
NEON_VOP_ENV(qrshl_s16, neon_s16, 2)
NEON_VOP_ENV(qrshl_s32, neon_s32, 1)
#undef NEON_FN
/* The addition of the rounding constant may overflow, so we use an
* intermediate 64 bits accumulator. */
uint32_t HELPER(neon_qrshl_s32)(CPUState *env, uint32_t valop, uint32_t shiftop)
{
int32_t dest;
int32_t val = (int32_t)valop;
int8_t shift = (int8_t)shiftop;
if (shift < 0) {
int64_t big_dest = ((int64_t)val + (1 << (-1 - shift)));
dest = big_dest >> -shift;
} else {
dest = val << shift;
if ((dest >> shift) != val) {
SET_QC();
dest = (val >> 31) ^ ~SIGNBIT;
}
}
return dest;
}
/* Handling addition overflow with 64 bits inputs values is more
* tricky than with 32 bits values. */
uint64_t HELPER(neon_qrshl_s64)(CPUState *env, uint64_t valop, uint64_t shiftop)
{
int8_t shift = (uint8_t)shiftop;
int64_t val = valop;
if (shift < 0) {
val = (val + (1 << (-1 - shift))) >> -shift;
val >>= (-shift - 1);
if (val == INT64_MAX) {
/* In this case, it means that the rounding constant is 1,
* and the addition would overflow. Return the actual
* result directly. */
val = 0x4000000000000000ULL;
} else {
val++;
val >>= 1;
}
} else {
int64_t tmp = val;;
int64_t tmp = val;
val <<= shift;
if ((val >> shift) != tmp) {
SET_QC();
val = tmp >> 31;
val = (tmp >> 63) ^ ~SIGNBIT64;
}
}
return val;