E-18
GUIDELINES FOR WRITING FPU EXCEPTIONS HANDLERS
;
; APPLICATION-DEPENDENT EXCEPTION HANDLING CODE GOES HERE
;
; CLEAR EXCEPTION FLAGS IN STATUS WORD (WHICH IS IN MEMORY)
; RESTORE MODIFIED STATE IMAGE
MOVBYTE PTR [EBP-104], 0H
FRSTOR[EBP-108]
; DE-ALLOCATE STACK SPACE, RESTORE REGISTERS
MOVESP, EBP
.
.
POPEBP
;
; RETURN TO INTERRUPTED CALCULATION
IRETD
SAVE_ALLENDP
Example E-4. Reduced-Latency Exception Handler
SAVE_ENVIRONMENTPROC
;
; SAVE REGISTERS, ALLOCATE STACK SPACE FOR FPU ENVIRONMENT
PUSHEBP
.
.
MOV EBP, ESP
SUB ESP, 28 ; ALLOCATES 28 BYTES (32-bit PROTECTED MODE SIZE)
;SAVE ENVIRONMENT, RESTORE INTERRUPT ENABLE FLAG (IF)
FNSTENV[EBP-28]
PUSH [EBP + OFFSET_TO_EFLAGS] ; COPY OLD EFLAGS TO STACK TOP
POPFD; RESTORE IF TO VALUE BEFORE FPU EXCEPTION
;
; APPLICATION-DEPENDENT EXCEPTION HANDLING CODE GOES HERE
;
; CLEAR EXCEPTION FLAGS IN STATUS WORD (WHICH IS IN MEMORY)
; RESTORE MODIFIED ENVIRONMENT IMAGE
MOV BYTE PTR [EBP-24], 0H
FLDENV[EBP-28]
; DE-ALLOCATE STACK SPACE, RESTORE REGISTERS
MOV ESP, EBP
.
.
POP EBP
;
; RETURN TO INTERRUPTED CALCULATION
IRETD
