ADDSS

Add Scalar Single Precision Floating

Opcode/Instruction	Op / En	64/32 bit Mode Support	CPUID Feature Flag	Description
F3 0F 58 /r ADDSS xmm1, xmm2/m32	A	V/V	SSE	Add the low single precision floating-point value from xmm2/mem to xmm1 and store the result in xmm1.
VEX.LIG.F3.0F.WIG 58 /r VADDSS xmm1,xmm2, xmm3/m32	B	V/V	AVX	Add the low single precision floating-point value from xmm3/mem to xmm2 and store the result in xmm1.
EVEX.LLIG.F3.0F.W0 58 /r VADDSS xmm1{k1}{z}, xmm2, xmm3/m32{er}	C	V/V	AVX512F	Add the low single precision floating-point value from xmm3/m32 to xmm2 and store the result in xmm1with writemask k1.

Instruction Operand Encoding

Op/En	Tuple Type	Operand 1	Operand 2	Operand 3	Operand 4
A	N/A	ModRM:reg (r, w)	ModRM:r/m (r)	N/A	N/A
B	N/A	ModRM:reg (w)	VEX.vvvv (r)	ModRM:r/m (r)	N/A
C	Tuple1 Scalar	ModRM:reg (w)	EVEX.vvvv (r)	ModRM:r/m (r)	N/A

Description

Adds the low single precision floating-point values from the second source operand and the first source operand, and stores the double precision floating-point result in the destination operand.

The second source operand can be an XMM register or a 64-bit memory location. The first source and destination operands are XMM registers.

128-bit Legacy SSE version: The first source and destination operands are the same. Bits (MAXVL-1:32) of the corresponding the destination register remain unchanged.

EVEX and VEX.128 encoded version: The first source operand is encoded by EVEX.vvvv/VEX.vvvv. Bits (127:32) of the XMM register destination are copied from corresponding bits in the first source operand. Bits (MAXVL-1:128) of the destination register are zeroed.

EVEX version: The low doubleword element of the destination is updated according to the writemask.

Software should ensure VADDSS is encoded with VEX.L=0. Encoding VADDSS with VEX.L=1 may encounter unpredictable behavior across different processor generations.

Operation

VADDSS (EVEX Encoded Versions)

IF (EVEX.b = 1) AND SRC2 *is a register*
    THEN
        SET_ROUNDING_MODE_FOR_THIS_INSTRUCTION(EVEX.RC);
    ELSE
        SET_ROUNDING_MODE_FOR_THIS_INSTRUCTION(MXCSR.RC);
FI;
IF k1[0] or *no writemask*
    THEN DEST[31:0] := SRC1[31:0] + SRC2[31:0]
    ELSE
        IF *merging-masking* ; merging-masking
            THEN *DEST[31:0] remains unchanged*
            ELSE ; zeroing-masking
                THEN DEST[31:0] := 0
        FI;
FI;
DEST[127:32] := SRC1[127:32]
DEST[MAXVL-1:128] := 0

VADDSS DEST, SRC1, SRC2 (VEX.128 Encoded Version)

DEST[31:0] := SRC1[31:0] + SRC2[31:0]
DEST[127:32] := SRC1[127:32]
DEST[MAXVL-1:128] := 0

ADDSS DEST, SRC (128-bit Legacy SSE Version)

DEST[31:0] := DEST[31:0] + SRC[31:0]
DEST[MAXVL-1:32] (Unmodified)

Intel C/C++ Compiler Intrinsic Equivalent

VADDSS __m128 _mm_mask_add_ss (__m128 s, __mmask8 k, __m128 a, __m128 b);

VADDSS __m128 _mm_maskz_add_ss (__mmask8 k, __m128 a, __m128 b);

VADDSS __m128 _mm_add_round_ss (__m128 a, __m128 b, int);

VADDSS __m128 _mm_mask_add_round_ss (__m128 s, __mmask8 k, __m128 a, __m128 b, int);

VADDSS __m128 _mm_maskz_add_round_ss (__mmask8 k, __m128 a, __m128 b, int);

ADDSS __m128 _mm_add_ss (__m128 a, __m128 b);

SIMD Floating-Point Exceptions

Overflow, Underflow, Invalid, Precision, Denormal.

Other Exceptions

VEX-encoded instruction, see Table 2-20, “Type 3 Class Exception Conditions.”

EVEX-encoded instruction, see Table 2-47, “Type E3 Class Exception Conditions.”

This UNOFFICIAL, mechanically-separated, non-verified reference is provided for convenience, but it may be incomplete or broken in various obvious or non-obvious ways. Refer to Intel® 64 and IA-32 Architectures Software Developer’s Manual for anything serious.