fptan

Partial Tangent

FPTAN

Computes tangent of ST(0) and pushes 1.0.

Pseudocode Operation

temp ← ST(0); ST(0) ← tan(temp); push(1.0); TOS ← TOS + 1

Encoding

Binary Layout

D9

+0

F2

+1

 

Format Legacy

Opcode D9 F2

Extension x87 FPU

Operands

Related

More in x87 FPU

Reference

View in Intel® 64 and IA-32 Architectures SDM ↗ Intel® SDM

Instruction Forms

Opcode	Instruction	Op/En	64/32-bit Mode	CPUID	Description
D9 F2	FPTAN		Valid Valid		Replace ST(0) with its approximate tangent and push 1 onto the FPU stack.

Description

Computes the approximate tangent of the source operand in register ST(0), stores the result in ST(0), and pushes a 1.0 onto the FPU register stack. The source operand must be given in radians and must be less than ±263. The following table shows the unmasked results obtained when computing the partial tangent of various classes of numbers, assuming that underflow does not occur. Table 3-35. FPTAN Results

ST(0) SRC ST(0) DEST

- ∞ *

- F                                               - F to + F
- 0                                                                                            - 0
+ 0                                                 + 0
+ F                                               - F to + F

+ ∞ * NaN NaN

Operation

IF ST(0) < 263
THEN
C2 := 0;
ST(0) := fptan(ST(0)); // approximation of tan
TOP := TOP - 1;
ST(0) := 1.0;
ELSE (* Source operand is out-of-range *)
C2 := 1;
FI;

Exceptions

Protected Mode Exceptions

#NM CR0.EM[bit 2] or CR0.TS[bit 3] = 1. #MF If there is a pending x87 FPU exception. #UD If the LOCK prefix is used.

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. FPTAN-Partial Tangent Vol. 2A 3-371