Intel 64 and IA-32 Architectures Software Developers Manual Volume 2A, Instruction Set Reference, A-M

Vol. 2 3-431

INSTRUCTION SET REFERENCE, A-M

equation is used to calculate the scale factor for a particular logarithm base, where n

is the logarithm base desired for the result of the FYL2XP1 instruction:

scale factor ← log

This instruction’s operation is the same in non-64-bit modes and 64-bit mode.

Operation

ST(1) ← ST(1) ∗ log

(ST(0) + 1.0);

PopRegisterStack;

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.

#IA Either operand is an SNaN value or unsupported format.

#D Source operand is a denormal value.

#U Result is too small for destination format.

#O Result is too large for destination format.

#P Value cannot be represented exactly in destination format.

Protected Mode Exceptions

#NM CR0.EM[bit 2] or CR0.TS[bit 3] = 1.

#MF If there is a pending x87 FPU exception.

Real-Address Mode Exceptions

Same exceptions as in Protected Mode.

Virtual-8086 Mode Exceptions

Same exceptions as in Protected Mode.

Compatibility Mode Exceptions

Same exceptions as in Protected Mode.

64-Bit Mode Exceptions

Same exceptions as in Protected Mode.