RSQRTPS

Compute Reciprocals of Square Roots of Packed Single Precision Floating

Opcode*/Instruction	Op/En	64/32 bit Mode Support	CPUID Feature Flag	Description
NP 0F 52 /r RSQRTPS xmm1, xmm2/m128	RM	V/V	SSE	Computes the approximate reciprocals of the square roots of the packed single precision floating-point values in xmm2/m128 and stores the results in xmm1.
VEX.128.0F.WIG 52 /r VRSQRTPS xmm1, xmm2/m128	RM	V/V	AVX	Computes the approximate reciprocals of the square roots of packed single precision values in xmm2/mem and stores the results in xmm1.
VEX.256.0F.WIG 52 /r VRSQRTPS ymm1, ymm2/m256	RM	V/V	AVX	Computes the approximate reciprocals of the square roots of packed single precision values in ymm2/mem and stores the results in ymm1.

Instruction Operand Encoding

Op/En	Operand 1	Operand 2	Operand 3	Operand 4
RM	ModRM:reg (w)	ModRM:r/m (r)	N/A	N/A

Description

Performs a SIMD computation of the approximate reciprocals of the square roots of the four packed single precision floating-point values in the source operand (second operand) and stores the packed single precision floating-point results in the destination operand. The source operand can be an XMM register or a 128-bit memory location. The destination operand is an XMM register. See Figure 10-5 in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1, for an illustration of a SIMD single precision floating-point operation.

The relative error for this approximation is:

|Relative Error| ≤ 1.5 ∗ 2−12

The RSQRTPS 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). When a source value is a negative value (other than −0.0), a floating-point indefinite is returned. 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 second source can be an XMM register or an 128-bit memory location. The destination is not distinct from the first source XMM register and the upper bits (MAXVL-1:128) of the corresponding YMM register destination are unmodified.

VEX.128 encoded version: the first source operand is an XMM register or 128-bit memory location. The destination operand is an XMM register. The upper bits (MAXVL-1:128) of the corresponding YMM register destination are zeroed.

VEX.256 encoded version: The first source operand is a YMM register. The second source operand can be a YMM register or a 256-bit memory location. The destination operand is a YMM register.

Note: In VEX-encoded versions, VEX.vvvv is reserved and must be 1111b, otherwise instructions will #​​​UD.

Operation

RSQRTPS (128-bit Legacy SSE Version)

DEST[31:0] := APPROXIMATE(1/SQRT(SRC[31:0]))
DEST[63:32] := APPROXIMATE(1/SQRT(SRC1[63:32]))
DEST[95:64] := APPROXIMATE(1/SQRT(SRC1[95:64]))
DEST[127:96] := APPROXIMATE(1/SQRT(SRC2[127:96]))
DEST[MAXVL-1:128] (Unmodified)

VRSQRTPS (VEX.128 Encoded Version)

DEST[31:0] := APPROXIMATE(1/SQRT(SRC[31:0]))
DEST[63:32] := APPROXIMATE(1/SQRT(SRC1[63:32]))
DEST[95:64] := APPROXIMATE(1/SQRT(SRC1[95:64]))
DEST[127:96] := APPROXIMATE(1/SQRT(SRC2[127:96]))
DEST[MAXVL-1:128] := 0

VRSQRTPS (VEX.256 Encoded Version)

DEST[31:0] := APPROXIMATE(1/SQRT(SRC[31:0]))
DEST[63:32] := APPROXIMATE(1/SQRT(SRC1[63:32]))
DEST[95:64] := APPROXIMATE(1/SQRT(SRC1[95:64]))
DEST[127:96] := APPROXIMATE(1/SQRT(SRC2[127:96]))
DEST[159:128] := APPROXIMATE(1/SQRT(SRC2[159:128]))
DEST[191:160] := APPROXIMATE(1/SQRT(SRC2[191:160]))
DEST[223:192] := APPROXIMATE(1/SQRT(SRC2[223:192]))
DEST[255:224] := APPROXIMATE(1/SQRT(SRC2[255:224]))

Intel C/C++ Compiler Intrinsic Equivalent

RSQRTPS __m128 _mm_rsqrt_ps(__m128 a)

RSQRTPS __m256 _mm256_rsqrt_ps (__m256 a);

SIMD Floating-Point Exceptions

None.

Other Exceptions

See Table 2-21, “Type 4 Class Exception Conditions,” additionally:

#​​​UD	If VEX.vvvv ≠ 1111B.

This UNOFFICIAL, mechanically-separated, non-verified reference is provided for convenience, but it may be incomplete or broken in various obvious or non-obvious ways. Refer to Intel® 64 and IA-32 Architectures Software Developer’s Manual for anything serious.