psignb

Packed Sign Byte

PSIGNB xmm1, xmm2/m128

Negates/Zeroes bytes in dest based on sign of src.

Details

Negates or zeros bytes in the destination operand based on the sign of corresponding bytes in the source operand. If the source byte is negative, the destination byte is negated; if zero, the destination byte is zeroed; if positive, the destination byte is unchanged. No CPU flags are affected by this instruction.

Pseudocode Operation

for i ← 0 to 15 do
  if src[i*8:i*8+7] < 0 then
    dest[i*8:i*8+7] ← -dest[i*8:i*8+7]
  else if src[i*8:i*8+7] == 0 then
    dest[i*8:i*8+7] ← 0
  else
    dest[i*8:i*8+7] ← dest[i*8:i*8+7]
  end if
end for

Example

PSIGNB xmm1, xmm2/m128

Encoding

Binary Layout
66
+0
0F
+1
38
+2
08
+3
 
Format SSSE3
Opcode 66 0F 38 08
Extension SSSE3

Operands

  • dest
    128-bit XMM SIMD register
  • src
    128-bit XMM SIMD register or Memory operand

Reference (Intel® SDM)

Instruction Forms

Opcode Instruction Op/En 64/32-bit Mode CPUID Description
NP 0F 38 08 /r1 PSIGNB mm1, mm2/m64 RM V/V SSSE3 Negate/zero/preserve packed byte integers in mm1 depending on the corresponding sign in mm2/m64.
66 0F 38 08 /r PSIGNB xmm1, xmm2/m128 RM V/V SSSE3 Negate/zero/preserve packed byte integers in xmm1 depending on the corresponding sign in xmm2/m128.
NP 0F 38 09 /r1 PSIGNW mm1, mm2/m64 RM V/V SSSE3 Negate/zero/preserve packed word integers in mm1 depending on the corresponding sign in mm2/m128.
66 0F 38 09 /r PSIGNW xmm1, xmm2/m128 RM V/V SSSE3 Negate/zero/preserve packed word integers in xmm1 depending on the corresponding sign in xmm2/m128.
NP 0F 38 0A /r1 PSIGND mm1, mm2/m64 RM V/V SSSE3 Negate/zero/preserve packed doubleword integers in mm1 depending on the corresponding sign in mm2/m128.
66 0F 38 0A /r PSIGND xmm1, xmm2/m128 RM V/V SSSE3 Negate/zero/preserve packed doubleword integers in xmm1 depending on the corresponding sign in xmm2/m128.
VEX.128.66.0F38.WIG 08 /r VPSIGNB xmm1, xmm2, xmm3/m128 AVX RVM V/V Negate/zero/preserve packed byte integers in xmm2 depending on the corresponding sign in xmm3/m128.
VEX.128.66.0F38.WIG 09 /r VPSIGNW xmm1, xmm2, xmm3/m128 AVX RVM V/V Negate/zero/preserve packed word integers in xmm2 depending on the corresponding sign in xmm3/m128.
VEX.128.66.0F38.WIG 0A /r VPSIGND xmm1, xmm2, xmm3/m128 AVX RVM V/V Negate/zero/preserve packed doubleword integers in xmm2 depending on the corresponding sign in xmm3/m128.
VEX.256.66.0F38.WIG 08 /r VPSIGNB ymm1, ymm2, ymm3/m256 AVX2 RVM V/V Negate packed byte integers in ymm2 if the corresponding sign in ymm3/m256 is less than zero.
VEX.256.66.0F38.WIG 09 /r VPSIGNW ymm1, ymm2, ymm3/m256 AVX2 RVM V/V Negate packed 16-bit integers in ymm2 if the corresponding sign in ymm3/m256 is less than zero.
VEX.256.66.0F38.WIG 0A /r VPSIGND ymm1, ymm2, ymm3/m256 AVX2 RVM V/V Negate packed doubleword integers in ymm2 if the corresponding sign in ymm3/m256 is less than zero.

Description

(V)PSIGNB/(V)PSIGNW/(V)PSIGND negates each data element of the destination operand (the first operand) if the signed integer value of the corresponding data element in the source operand (the second operand) is less than zero. If the signed integer value of a data element in the source operand is positive, the corresponding data element in the destination operand is unchanged. If a data element in the source operand is zero, the corresponding data element in the destination operand is set to zero. (V)PSIGNB operates on signed bytes. (V)PSIGNW operates on 16-bit signed words. (V)PSIGND operates on signed 32-bit integers. Legacy SSE instructions: Both operands can be MMX registers. In 64-bit mode, use the REX prefix to access additional registers. 128-bit Legacy SSE version: The first source and destination operands are XMM registers. The second source operand is an XMM register or a 128-bit memory location. Bits (MAXVL-1:128) of the corresponding YMM destination register remain unchanged. VEX.128 encoded version: The first source and destination operands are XMM registers. The second source operand is an XMM register or a 128-bit memory location. Bits (MAXVL-1:128) of the destination YMM register are zeroed. VEX.L must be 0, otherwise instructions will #UD. VEX.256 encoded version: The first source and destination operands are YMM registers. The second source operand is an YMM register or a 256-bit memory location.

Operation

def byte_sign(control, input_val):
if control<0:
return negate(input_val)
elif control==0:
return 0
return input_val

def word_sign(control, input_val):
if control<0:
return negate(input_val)
elif control==0:
return 0
return input_val

def dword_sign(control, input_val):
if control<0:
return negate(input_val)
elif control==0:
return 0
return input_val

PSIGNB srcdest, src  // MMX 64-bit Operands
VL=64
KL := VL/8
for i in 0...KL-1:
srcdest.byte[i] := byte_sign(src.byte[i], srcdest.byte[i])

PSIGNW srcdest, src  // MMX 64-bit Operands
VL=64
KL := VL/16
FOR i in 0...KL-1:
srcdest.word[i] := word_sign(src.word[i], srcdest.word[i])



PSIGNB/PSIGNW/PSIGND—Packed SIGN                                                                                                          Vol. 2B 4-438
PSIGND srcdest, src  // MMX 64-bit Operands
VL=64
KL := VL/32
FOR i in 0...KL-1:
srcdest.dword[i] := dword_sign(src.dword[i], srcdest.dword[i])

PSIGNB srcdest, src  // SSE 128-bit Operands
VL=128
KL := VL/8
FOR i in 0...KL-1:
srcdest.byte[i] := byte_sign(src.byte[i], srcdest.byte[i])

PSIGNW srcdest, src  // SSE 128-bit Operands
VL=128
KL := VL/16
FOR i in 0...KL-1:
srcdest.word[i] := word_sign(src.word[i], srcdest.word[i])

PSIGND srcdest, src  // SSE 128-bit Operands
VL=128
KL := VL/32
FOR i in 0...KL-1:
srcdest.dword[i] := dword_sign(src.dword[i], srcdest.dword[i])

VPSIGNB dest, src1, src2  // AVX 128-bit or 256-bit Operands
VL=(128,256)
KL := VL/8
FOR i in 0...KL-1:
dest.byte[i] := byte_sign(src2.byte[i], src1.byte[i])
DEST[MAXVL-1:VL] := 0

VPSIGNW dest, src1, src2  // AVX 128-bit or 256-bit Operands
VL=(128,256)
KL := VL/16
FOR i in 0...KL-1:
dest.word[i] := word_sign(src2.word[i], src1.word[i])
DEST[MAXVL-1:VL] := 0

VPSIGND dest, src1, src2   // AVX 128-bit or 256-bit Operands
VL=(128,256)
KL := VL/32
FOR i in 0...KL-1:
dest.dword[i] := dword_sign(src2.dword[i], src1.dword[i])
DEST[MAXVL-1:VL] := 0





PSIGNB/PSIGNW/PSIGND—Packed SIGN                                                                                                          Vol. 2B 4-439

Intel C/C++ Compiler Intrinsic Equivalent

PSIGNB __m64 _mm_sign_pi8 (__m64 a, __m64 b)
(V)PSIGNB __m128i _mm_sign_epi8 (__m128i a, __m128i b)
VPSIGNB __m256i _mm256_sign_epi8 (__m256i a, __m256i b)
PSIGNW __m64 _mm_sign_pi16 (__m64 a, __m64 b)
(V)PSIGNW __m128i _mm_sign_epi16 (__m128i a, __m128i b)
VPSIGNW __m256i _mm256_sign_epi16 (__m256i a, __m256i b)
PSIGND __m64 _mm_sign_pi32 (__m64 a, __m64 b)
(V)PSIGND __m128i _mm_sign_epi32 (__m128i a, __m128i b)
VPSIGND __m256i _mm256_sign_epi32 (__m256i a, __m256i b)

Exceptions

SIMD Floating-Point Exceptions

None.

Other Exceptions

See Table 2-21, “Type 4 Class Exception Conditions,” additionally: #UD If VEX.L = 1. PSIGNB/PSIGNW/PSIGND—Packed SIGN Vol. 2B 4-440