SUBSS—Subtract Scalar Single-Precision Floating-Point Value

Opcode/Instruction Op /En 64/32 bit Mode Support CPUID Feature Flag Description
F3 0F 5C /r SUBSS xmm1, xmm2/m32 A V/V SSE Subtract the low single-precision floating-point value in xmm2/m32 from xmm1 and store the result in xmm1.
VEX.LIG.F3.0F.WIG 5C /r VSUBSS xmm1,xmm2, xmm3/m32 B V/V AVX Subtract the low single-precision floating-point value in xmm3/m32 from xmm2 and store the result in xmm1.
EVEX.LLIG.F3.0F.W0 5C /r VSUBSS xmm1 {k1}{z}, xmm2, xmm3/m32{er} C V/V AVX512F Subtract the low single-precision floating-point value in xmm3/m32 from xmm2 and store the result in xmm1 under writemask k1.

Instruction Operand Encoding

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

Description

Subtract the low single-precision floating-point value from the second source operand and the first source operand and store the double-precision floating-point result in the low doubleword of the destination operand.

The second source operand can be an XMM register or a 32-bit memory location. The first source and destination operands are XMM registers.

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

VEX.128 and EVEX encoded versions: 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 encoded version: The low doubleword element of the destination operand is updated according to the writemask.

Software should ensure VSUBSS is encoded with VEX.L=0. Encoding VSUBSD with VEX.L=1 may encounter unpre-dictable behavior across different processor generations.

Operation

VSUBSS (EVEX encoded version)

IF (SRC2 *is register*) AND (EVEX.b = 1)

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

VSUBSS (VEX.128 encoded version)

DEST[31:0] := SRC1[31:0] - SRC2[31:0]

DEST[127:32] := SRC1[127:32]

DEST[MAXVL-1:128] := 0

SUBSS (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

VSUBSS __m128 _mm_mask_sub_ss (__m128 s, __mmask8 k, __m128 a, __m128 b);

VSUBSS __m128 _mm_maskz_sub_ss (__mmask8 k, __m128 a, __m128 b);

VSUBSS __m128 _mm_sub_round_ss (__m128 a, __m128 b, int);

VSUBSS __m128 _mm_mask_sub_round_ss (__m128 s, __mmask8 k, __m128 a, __m128 b, int);

VSUBSS __m128 _mm_maskz_sub_round_ss (__mmask8 k, __m128 a, __m128 b, int);

SUBSS __m128 _mm_sub_ss (__m128 a, __m128 b);

SIMD Floating-Point Exceptions

Overflow, Underflow, Invalid, Precision, Denormal

Other Exceptions

VEX-encoded instructions, see Table 2-20, “Type 3 Class Exception Conditions”.
EVEX-encoded instructions, see Table 2-47, “Type E3 Class Exception Conditions”.