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

Instruction Operand Encoding

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 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 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