FINCSTP
Increment Stack-Top Pointer
stableVMJITAOTinstruction
Encodings
| Opcode | Instruction | Op/En | 64-bit | Compat/Legacy | Description |
|---|---|---|---|---|---|
D9 F7 | FINCSTP | Valid | Valid | Increment the TOP field in the FPU status register. |
Measured cost
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Description
Adds one to the TOP field of the FPU status word (increments the top-of-stack pointer). If the TOP field contains a 7, it is set to 0. The effect of this instruction is to rotate the stack by one position. The contents of the FPU data registers and tag register are not affected. This operation is not equivalent to popping the stack, because the tag for the previous top-of-stack register is not marked empty.
This instruction's operation is the same in non-64-bit modes and 64-bit mode.
Operation
IF TOP = 7
THEN TOP := 0;
ELSE TOP := TOP + 1;
FI;
FPU Flags Affected
The C1 flag is set to 0. The C0, C2, and C3 flags are 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. |