x86 Instruction Set Reference

FSQRT

Square Root

Opcode	Mnemonic	Description
`D9 FA`	`FSQRT`	Computes square root of ST(0) and stores the result in ST(0).

Description

Computes the square root of the source value in the ST(0) register and stores the result in ST(0).

The following table shows the results obtained when taking the square root of various classes of numbers, assuming that neither overflow nor underflow occurs.

FSQRT Results
Source (ST(0))	Destination (ST(0))
-inf	*
-F	*
-0	-0
+0	+0
+F	+F
+inf	+inf
NaN	NaN
F Means finite floating-point value.
* Indicates floating-point invalid-arithmetic-operand (#IA) exception.

Operation
ST(0) = SquareRoot(ST(0));

FPU flags affected
C1 Set to 0 if stack underflow occurred. Set if result was rounded up; cleared otherwise. C0, C2, C3 Undefined.

Floating-Point Exceptions

`#IS`	Stack underflow occurred.
`#IS`	Stack underflow occurred.
`#IA`	Source operand is an SNaN value or unsupported format. Source operand is a negative value (except for -0).
`#D`	Source operand is a denormal value.

Protected Mode Exceptions

#NM EM or TS in CR0 is set.

Real-Address Mode Exceptions

#NM EM or TS in CR0 is set.

Virtual-8086 Mode Exceptions

#NM EM or TS in CR0 is set.

Instruction	Latency	Throughput	Execution Unit
`CPUID`	0F3n/0F2n	0F3n/0F2n	0F2n
`FSQRT SP`	30/23	30/23	FP_DIV
`FSQRT DP`	40/38	40/38	FP_DIV
`FSQRT EP`	44/43	44/43	FP_DIV