| Opcode*/Instruction | Op/En | 64/32 bit Mode Support | CPUID Feature Flag | Description |
|---|---|---|---|---|
| F3 0F 53 /r RCPSS xmm1, xmm2/m32 | RM | V/V | SSE | Computes the approximate reciprocal of the scalar single-precision floating-point value in xmm2/m32 and stores the result in xmm1. |
| VEX.LIG.F3.0F.WIG 53 /r VRCPSS xmm1, xmm2, xmm3/m32 | RVM | V/V | AVX | Computes the approximate reciprocal of the scalar single-precision floating-point value in xmm3/m32 and stores the result in xmm1. Also, upper single precision floating-point values (bits[127:32]) from xmm2 are copied to xmm1[127:32]. |
| Op/En | Operand 1 | Operand 2 | Operand 3 | Operand 4 |
| RM | ModRM:reg (w) | ModRM:r/m (r) | NA | NA |
| RVM | ModRM:reg (w) | VEX.vvvv (r) | ModRM:r/m (r) | NA |
Computes of an approximate reciprocal of the low single-precision floating-point value in the source operand (second operand) and stores the single-precision floating-point result in the destination operand. The source operand can be an XMM register or a 32-bit memory location. The destination operand is an XMM register. The three high-order doublewords of the destination operand remain unchanged. See Figure 10-6 in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1, for an illustration of a scalar single-precision floating-point operation.
The relative error for this approximation is:
|Relative Error| ≤ 1.5 ∗ 2−12
The RCPSS instruction is not affected by the rounding control bits in the MXCSR register. When a source value is a 0.0, an ∞ of the sign of the source value is returned. A denormal source value is treated as a 0.0 (of the same sign). Tiny results (see Section 4.9.1.5, “Numeric Underflow Exception (#U)” in Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1) are always flushed to 0.0, with the sign of the operand. (Input values greater than or equal to |1.11111111110100000000000B∗2125| are guaranteed to not produce tiny results; input values less than or equal to |1.00000000000110000000001B*2126| are guaranteed to produce tiny results, which are in turn flushed to 0.0; and input values in between this range may or may not produce tiny results, depending on the implementation.) When a source value is an SNaN or QNaN, the SNaN is converted to a QNaN or the source QNaN is returned.
In 64-bit mode, using a REX prefix in the form of REX.R permits this instruction to access additional registers (XMM8-XMM15).
128-bit Legacy SSE version: The first source operand and the destination operand are the same. Bits (MAXVL-1:32) of the corresponding YMM destination register remain unchanged.
VEX.128 encoded version: Bits (MAXVL-1:128) of the destination YMM register are zeroed.
DEST[31:0] ← APPROXIMATE(1/SRC[31:0]) DEST[MAXVL-1:32] (Unmodified)
DEST[31:0] ← APPROXIMATE(1/SRC2[31:0]) DEST[127:32] ← SRC1[127:32] DEST[MAXVL-1:128] ← 0
RCPSS: __m128 _mm_rcp_ss(__m128 a)
None.
See Exceptions Type 5.