FBLD - Load Binary Coded Decimal

Opcode

Instruction

64-Bit Mode

Compat/ Leg Mode

Description

DF /4

FBLD m80bcd

Valid

Valid

Convert BCD value to floating-point and push onto the FPU stack.

Description

Converts the BCD source operand into double extended-precision floating-point format and pushes the value onto the FPU stack. The source operand is loaded without rounding errors. The sign of the source operand is preserved,

including that of - 0.

The packed BCD digits are assumed to be in the range 0 through 9; the instruction does not check for invalid digits (AH through FH). Attempting to load an invalid encoding produces an undefined result.

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

Operation 

TOP := TOP  -  1;
ST(0) := ConvertToDoubleExtendedPrecisionFP(SRC);

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

#GP(0)

If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit. If the DS, ES, FS, or GS register contains a NULL segment selector.

#SS(0)

If a memory operand effective address is outside the SS segment limit.

#NM

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

#PF(fault-code)

If a page fault occurs.

#AC(0)

If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3.

#UD

If the LOCK prefix is used.

Real-Address Mode Exceptions

#GP

If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.

#SS

If a memory operand effective address is outside the SS segment limit.

#NM

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

#UD

If the LOCK prefix is used.

Virtual-8086 Mode Exceptions

#GP(0)

If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.

#SS(0)

If a memory operand effective address is outside the SS segment limit.

#NM

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

#PF(fault-code)

If a page fault occurs.

#AC(0)

If alignment checking is enabled and an unaligned memory reference is made.

#UD

If the LOCK prefix is used.

Compatibility Mode Exceptions

Same exceptions as in protected mode.

64-Bit Mode Exceptions

#SS(0)

If a memory address referencing the SS segment is in a non-canonical form.

#GP(0)

If the memory address is in a non-canonical form.

#NM

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

#MF

If there is a pending x87 FPU exception.

#PF(fault-code)

If a page fault occurs.

#AC(0)

If alignment checking is enabled and an unaligned memory reference is made while the current privilege level is 3.

#UD

If the LOCK prefix is used.