FLD1/FLDL2T/FLDL2E/FLDPI/FLDLG2/FLDLN2/FLDZ (Load Constant)

Opcodes

Opcode* Instruction 64-Bit Mode Compat/Leg Mode Description
D9 E8 FLD1 Valid Valid Push +1.0 onto the FPU register stack.
D9 E9 FLDL2T Valid Valid Push log10 onto the FPU register stack.
D9 EA FLDL2E Valid Valid Push loge onto the FPU register stack.
D9 EB FLDPI Valid Valid Push π onto the FPU register stack.
D9 EC FLDLG2 Valid Valid Push log2 onto the FPU register stack.
D9 ED FLDLN2 Valid Valid Push log2 onto the FPU register stack.
D9 EE FLDZ Valid Valid Push +0.0 onto the FPU register stack.

NOTES:

*

See IA-32 Architecture Compatibility section below.

Description

Push one of seven commonly used constants (in double extended-precision floating-point format) onto the FPU register stack. The constants that can be loaded with these instructions include +1.0, +0.0, log10, loge, π, log2, and log2. For each constant, an internal 66-bit constant is rounded (as specified by the RC field in the FPU control word) to double extended-precision floating-point format. The inexact-result exception (#P) is not generated as a result of the rounding, nor is the C1 flag set in the x87 FPU status word if the value is rounded up.

See the section titled “Pi” in Chapter 8 of the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1, for a description of the π constant.

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

IA-32 Architecture Compatibility

When the RC field is set to round-to-nearest, the FPU produces the same constants that is produced by the Intel 8087 and Intel 287 math coprocessors.

Operation

TOP ← TOP − 1;
ST(0) ← CONSTANT;

FPU Flags Affected

C1 Set to 1 if stack overflow occurred; otherwise, set to 0.
C0, C2, C3 Undefined.

Floating-Point Exceptions

#IS Stack overflow occurred.

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.

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.