# VFMSUB132SS/VFMSUB213SS/VFMSUB231SS (Fused Multiply-Subtract of Scalar Single-Precision Floating-Point Values)

## Opcodes

Opcode/Instruction | Op/En | 64/32 -bit Mode | CPUID Feature Flag | Description |
---|---|---|---|---|

VEX.DDS.LIG.128.66.0F38.W0 9B /r
VFMSUB132SS xmm0, xmm1, xmm2/m32 |
A | V/V | FMA | Multiply scalar single-precision floating-point value from xmm0 and xmm2/mem, subtract xmm1 and put result in xmm0. |

VEX.DDS.LIG.128.66.0F38.W0 AB /r
VFMSUB213SS xmm0, xmm1, xmm2/m32 |
A | V/V | FMA | Multiply scalar single-precision floating-point value from xmm0 and xmm1, subtract xmm2/mem and put result in xmm0. |

VEX.DDS.LIG.128.66.0F38.W0 BB /r
VFMSUB231SS xmm0, xmm1, xmm2/m32 |
A | V/V | FMA | Multiply scalar single-precision floating-point value from xmm1 and xmm2/mem, subtract xmm0 and put result in xmm0. |

## Instruction Operand Encoding

Op/En | Operand 1 | Operand 2 | Operand 3 | Operand 4 |
---|---|---|---|---|

A | ModRM:reg (r, w) | VEX.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-add result in the destination operand. The destination operand is also the first source operand. The second operand must be a SIMD register. The third source operand can be a SIMD register or a 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 interme-diate 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 interme-diate 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 encoded version: The destination operand (also first source operand) is a XMM register and encoded in reg_field. The second source operand is a XMM register and encoded in VEX.vvvv. The third source operand is a XMM register or a 32-bit memory location and encoded in rm_field. The upper bits ([VLMAX-1:128]) of the YMM destination register are zeroed.

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. See also Section 14.5.1, “FMA Instruction Operand Order and Arithmetic Behavior” in the *Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1*.

## Operation

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

**VFMSUB132SS DEST, SRC2, SRC3**

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

**VFMSUB213SS DEST, SRC2, SRC3**

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

**VFMSUB231SS DEST, SRC2, SRC3**

DEST[31:0] ← RoundFPControl_MXCSR(SRC2[31:0]*SRC3[63:0] - DEST[31:0]) DEST[127:32] ← DEST[127:32] DEST[VLMAX-1:128] ← 0

## Intel C/C++ Compiler Intrinsic Equivalent

VFMSUB132SS: __m128 _mm_fmsub_ss (__m128 a, __m128 b, __m128 c);

VFMSUB213SS: __m128 _mm_fmsub_ss (__m128 a, __m128 b, __m128 c);

VFMSUB231SS: __m128 _mm_fmsub_ss (__m128 a, __m128 b, __m128 c);

## SIMD Floating-Point Exceptions

Overflow, Underflow, Invalid, Precision, Denormal

## Other Exceptions

See Exceptions Type 3