x86 Instruction Set Reference

FINCSTP

Increment Stack-Top Pointer

Opcode	Mnemonic	Description
`D9 F7`	`FINCSTP`	Increment the TOP field in the FPU status register.

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.

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.

Operation
if(Top == 7) Top = 0; else Top = Top + 1;

FPU flags affected
The C1 flag is set to 0. The C0, C2, and C3 flags are undefined.

Floating-Point Exceptions
None.

Protected Mode Exceptions

#NM EM or TS in CR0 is set.

Real-Address Mode Exceptions

#NM EM or TS in CR0 is set.

Virtual-8086 Mode Exceptions

#NM EM or TS in CR0 is set.