FFREE
Free Floating-Point Register
stableVMJITAOTinstruction
Encodings
| Opcode | Instruction | Op/En | 64-bit | Compat/Legacy | Description |
|---|---|---|---|---|---|
DD C0+i | FFREE ST(i) | Valid | Valid | Sets tag for ST(i) to empty. |
Measured cost
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Description
Sets the tag in the FPU tag register associated with register ST(i) to empty (11B). The contents of ST(i) and the FPU stack-top pointer (TOP) are not affected.
This instruction's operation is the same in non-64-bit modes and 64-bit mode.
Operation
TAG(i) := 11B;
FPU Flags Affected
C0, C1, C2, C3 undefined.Floating-Point Exceptions
None
Exceptions
Protected mode
#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
| Same exceptions as in protected mode. |
Virtual-8086 mode
| Same exceptions as in protected mode. |
Compatibility mode
| Same exceptions as in protected mode. |
64-bit mode
| Same exceptions as in protected mode. |