RCPSS

Compute Reciprocal of Scalar Single-Precision Floating-Point Values

Opcodes

Hex Mnemonic Encoding Long Mode Legacy Mode Description
F3 0F 53 /r RCPSS xmm1, xmm2/m32 A Valid Valid Computes the approximate reciprocal of the scalar single-precision floating-point value in xmm2/m32 and stores the result in xmm1.

Instruction Operand Encoding

Op/En Operand 0 Operand 1 Operand 2 Operand 3
A NA NA ModRM:r/m (r) ModRM:reg (w)

Description

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'sManual, Volume 1, for an illustration of a scalar single-precision floating-point operation.

The relative error for this approximation is:

|Relative Error| &le 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 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).

Pseudo Code

DEST[31:0] = APPROX (1.0/(SRC[31:0])); (* DEST[127:32] unchanged *)

Exceptions

SIMD Floating-Point Exceptions

None.

64-Bit Mode Exceptions

Exception Description
#AC(0) If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3.
#UD If CR0.EM[bit 2] = 1. If CR4.OSFXSR[bit 9] = 0. If CPUID.01H:EDX.SSE[bit 25] = 0. If the LOCK prefix is used.
#NM If CR0.TS[bit 3] = 1.
#PF(fault-code) For a page fault.
#GP(0) If the memory address is in a non-canonical form.
#SS(0) If a memory address referencing the SS segment is in a non- canonical form.

Compatibility Mode Exceptions

Same exceptions as in protected mode.

Virtual-8086 Mode Exceptions

Exception Description
#AC(0) For unaligned memory reference.
#PF(fault-code) For a page fault.
Same exceptions as in real address mode.

Real-Address Mode Exceptions

Exception Description
#UD If CR0.EM[bit 2] = 1. If CR4.OSFXSR[bit 9] = 0. If CPUID.01H:EDX.SSE[bit 25] = 0. If the LOCK prefix is used.
#NM If CR0.TS[bit 3] = 1.
#GP If any part of the operand lies outside the effective address space from 0 to FFFFH.

Protected Mode Exceptions

Exception Description
#AC(0) If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3.
#UD If CR0.EM[bit 2] = 1. If CR4.OSFXSR[bit 9] = 0. If CPUID.01H:EDX.SSE[bit 25] = 0. If the LOCK prefix is used.
#NM If CR0.TS[bit 3] = 1.
#PF(fault-code) For a page fault.
#SS(0) For an illegal address in the SS segment.
#GP(0) For an illegal memory operand effective address in the CS, DS, ES, FS or GS segments.