VFMSUB132SS/VFMSUB213SS/VFMSUB231SS — Fused Multiply-Subtract of Scalar Single- Precision Floating-Point Values

Opcode/Instruction Op / En 64/32 bit Mode Support CPUID Feature Flag Description
VEX.LIG.66.0F38.W0 9B /r VFMSUB132SS xmm1, xmm2, xmm3/m32 A V/V FMA Multiply scalar single-precision floating-point value from xmm1 and xmm3/m32, subtract xmm2 and put result in xmm1.
VEX.LIG.66.0F38.W0 AB /r VFMSUB213SS xmm1, xmm2, xmm3/m32 A V/V FMA Multiply scalar single-precision floating-point value from xmm1 and xmm2, subtract xmm3/m32 and put result in xmm1.
VEX.LIG.66.0F38.W0 BB /r VFMSUB231SS xmm1, xmm2, xmm3/m32 A V/V FMA Multiply scalar single-precision floating-point value from xmm2 and xmm3/m32, subtract xmm1 and put result in xmm1.
EVEX.LIG.66.0F38.W0 9B /r VFMSUB132SS xmm1 {k1}{z}, xmm2, xmm3/m32{er} B V/V AVX512F Multiply scalar single-precision floating-point value from xmm1 and xmm3/m32, subtract xmm2 and put result in xmm1.
EVEX.LIG.66.0F38.W0 AB /r VFMSUB213SS xmm1 {k1}{z}, xmm2, xmm3/m32{er} B V/V AVX512F Multiply scalar single-precision floating-point value from xmm1 and xmm2, subtract xmm3/m32 and put result in xmm1.
EVEX.LIG.66.0F38.W0 BB /r VFMSUB231SS xmm1 {k1}{z}, xmm2, xmm3/m32{er} B V/V AVX512F Multiply scalar single-precision floating-point value from xmm2 and xmm3/m32, subtract xmm1 and put result in xmm1.

Instruction Operand Encoding

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

Description

Performs a SIMD multiply-subtract computation on the low packed single-precision floating-point values using three source operands and writes the multiply-subtract result in the destination operand. The destination operand is also the first source operand. The second operand must be a XMM register. The third source operand can be a XMM register or a 32-bit memory location.

VFMSUB132SS: Multiplies the low packed single-precision floating-point value from the first source operand to the low packed single-precision floating-point value in the third source operand. From the infinite precision intermediate result, subtracts the low packed single-precision floating-point values in the second source operand, performs rounding and stores the resulting packed single-precision floating-point value to the destination operand (first source operand).

VFMSUB213SS: Multiplies the low packed single-precision floating-point value from the second source operand to the low packed single-precision floating-point value in the first source operand. From the infinite precision intermediate result, subtracts the low packed single-precision floating-point value in the third source operand, performs rounding and stores the resulting packed single-precision floating-point value to the destination operand (first source operand).

VFMSUB231SS: Multiplies the low packed single-precision floating-point value from the second source to the low packed single-precision floating-point value in the third source operand. From the infinite precision intermediate result, subtracts the low packed single-precision floating-point value in the first source operand, performs rounding and stores the resulting packed single-precision floating-point value to the destination operand (first source operand).

VEX.128 and EVEX encoded version: The destination operand (also first source operand) is encoded in reg_field. The second source operand is encoded in VEX.vvvv/EVEX.vvvv. The third source operand is encoded in rm_field. Bits 127:32 of the destination are unchanged. Bits MAXVL-1:128 of the destination register are zeroed.

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

Compiler tools may optionally support a complementary mnemonic for each instruction mnemonic listed in the opcode/instruction column of the summary table. The behavior of the complementary mnemonic in situations involving NANs are governed by the definition of the instruction mnemonic defined in the opcode/instruction column.

Operation

In the operations below, “*” and “-” symbols represent multiplication and subtraction with infinite precision inputs and outputs (no
rounding).

VFMSUB132SS DEST, SRC2, SRC3 (EVEX encoded version)

IF (EVEX.b = 1) and SRC3 *is a register*
    THEN
        SET_RM(EVEX.RC);
    ELSE
        SET_RM(MXCSR.RM);
FI;
IF k1[0] or *no writemask*
    THEN DEST[31:0]←RoundFPControl(DEST[31:0]*SRC3[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] ← DEST[127:32]
DEST[MAXVL-1:128] ← 0

VFMSUB213SS DEST, SRC2, SRC3 (EVEX encoded version)

IF (EVEX.b = 1) and SRC3 *is a register*
    THEN
        SET_RM(EVEX.RC);
    ELSE
        SET_RM(MXCSR.RM);
FI;
IF k1[0] or *no writemask*
    THEN DEST[31:0]←RoundFPControl(SRC2[31:0]*DEST[31:0] - SRC3[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] ← DEST[127:32]
DEST[MAXVL-1:128] ← 0

VFMSUB231SS DEST, SRC2, SRC3 (EVEX encoded version)

IF (EVEX.b = 1) and SRC3 *is a register*
    THEN
        SET_RM(EVEX.RC);
    ELSE
        SET_RM(MXCSR.RM);
FI;
IF k1[0] or *no writemask*
    THEN DEST[31:0]←RoundFPControl(SRC2[31:0]*SRC3[63:0] - DEST[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] ← DEST[127:32]
DEST[MAXVL-1:128] ← 0

VFMSUB132SS DEST, SRC2, SRC3 (VEX encoded version)

DEST[31:0]←RoundFPControl_MXCSR(DEST[31:0]*SRC3[31:0] - SRC2[31:0])
DEST[127:32] ←DEST[127:32]
DEST[MAXVL-1:128] ←0

VFMSUB213SS DEST, SRC2, SRC3 (VEX encoded version)

DEST[31:0]←RoundFPControl_MXCSR(SRC2[31:0]*DEST[31:0] - SRC3[31:0])
DEST[127:32] ←DEST[127:32]
DEST[MAXVL-1:128] ←0

VFMSUB231SS DEST, SRC2, SRC3 (VEX encoded version)

DEST[31:0]←RoundFPControl_MXCSR(SRC2[31:0]*SRC3[31:0] - DEST[31:0])
DEST[127:32] ←DEST[127:32]
DEST[MAXVL-1:128] ←0

Intel C/C++ Compiler Intrinsic Equivalent

VFMSUBxxxSS __m128 _mm_fmsub_round_ss(__m128 a, __m128 b, __m128 c, int r);
VFMSUBxxxSS __m128 _mm_mask_fmsub_ss(__m128 a, __mmask8 k, __m128 b, __m128 c);
VFMSUBxxxSS __m128 _mm_maskz_fmsub_ss(__mmask8 k, __m128 a, __m128 b, __m128 c);
VFMSUBxxxSS __m128 _mm_mask3_fmsub_ss(__m128 a, __m128 b, __m128 c, __mmask8 k);
VFMSUBxxxSS __m128 _mm_mask_fmsub_round_ss(__m128 a, __mmask8 k, __m128 b, __m128 c, int r);
VFMSUBxxxSS __m128 _mm_maskz_fmsub_round_ss(__mmask8 k, __m128 a, __m128 b, __m128 c, int r);
VFMSUBxxxSS __m128 _mm_mask3_fmsub_round_ss(__m128 a, __m128 b, __m128 c, __mmask8 k, int r);
VFMSUBxxxSS __m128 _mm_fmsub_ss (__m128 a, __m128 b, __m128 c);

SIMD Floating-Point Exceptions

Overflow, Underflow, Invalid, Precision, Denormal

Other Exceptions

VEX-encoded instructions, see Exceptions Type 3.

EVEX-encoded instructions, see Exceptions Type E3.