x86doc › 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.LLIG.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.LLIG.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.LLIG.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. |

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

A | N/A | ModRM:reg (r, w) | VEX.vvvv (r) | ModRM:r/m (r) | N/A |

B | Tuple1 Scalar | ModRM:reg (r, w) | EVEX.vvvv (r) | ModRM:r/m (r) | N/A |

**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 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 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_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] := 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_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] := 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_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] := 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 Table 2-20, “Type 3 Class Exception Conditions.” |

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