gen_except.s

RTEMS (Real-Time Executive for Multiprocessor Systems) is a free open source real-time operating sys

//
//      $Id: gen_except.S,v 1.1 1998/12/14 23:15:21 joel Exp $
//
//	gen_except.sa 3.7 1/16/92
//
//	gen_except --- FPSP routine to detect reportable exceptions
//	
//	This routine compares the exception enable byte of the
//	user_fpcr on the stack with the exception status byte
//	of the user_fpsr. 
//
//	Any routine which may report an exceptions must load
//	the stack frame in memory with the exceptional operand(s).
//
//	Priority for exceptions is:
//
//	Highest:	bsun
//			snan
//			operr
//			ovfl
//			unfl
//			dz
//			inex2
//	Lowest:		inex1
//
//	Note: The IEEE standard specifies that inex2 is to be
//	reported if ovfl occurs and the ovfl enable bit is not
//	set but the inex2 enable bit is.  
//
//
//		Copyright (C) Motorola, Inc. 1990
//			All Rights Reserved
//
//	THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA 
//	The copyright notice above does not evidence any  
//	actual or intended publication of such source code.

GEN_EXCEPT:    //idnt    2,1 | Motorola 040 Floating Point Software Package

	|section 8

#include "fpsp.defs"

	|xref	real_trace
	|xref	fpsp_done
	|xref	fpsp_fmt_error

exc_tbl:
	.long	bsun_exc
	.long	commonE1
	.long	commonE1
	.long	ovfl_unfl
	.long	ovfl_unfl
	.long	commonE1
	.long	commonE3
	.long	commonE3
	.long	no_match

	.global	gen_except
gen_except:
	cmpib	#IDLE_SIZE-4,1(%a7)	//test for idle frame
	beq	do_check		//go handle idle frame
	cmpib	#UNIMP_40_SIZE-4,1(%a7)	//test for orig unimp frame
	beqs	unimp_x			//go handle unimp frame
	cmpib	#UNIMP_41_SIZE-4,1(%a7)	//test for rev unimp frame
	beqs	unimp_x			//go handle unimp frame
	cmpib	#BUSY_SIZE-4,1(%a7)	//if size <> $60, fmt error
	bnel	fpsp_fmt_error
	leal	BUSY_SIZE+LOCAL_SIZE(%a7),%a1 //init a1 so fpsp.h
//					;equates will work
// Fix up the new busy frame with entries from the unimp frame
//
	movel	ETEMP_EX(%a6),ETEMP_EX(%a1) //copy etemp from unimp
	movel	ETEMP_HI(%a6),ETEMP_HI(%a1) //frame to busy frame
	movel	ETEMP_LO(%a6),ETEMP_LO(%a1) 
	movel	CMDREG1B(%a6),CMDREG1B(%a1) //set inst in frame to unimp
	movel	CMDREG1B(%a6),%d0		//fix cmd1b to make it
	andl	#0x03c30000,%d0		//work for cmd3b
	bfextu	CMDREG1B(%a6){#13:#1},%d1	//extract bit 2
	lsll	#5,%d1			
	swap	%d1
	orl	%d1,%d0			//put it in the right place
	bfextu	CMDREG1B(%a6){#10:#3},%d1	//extract bit 3,4,5
	lsll	#2,%d1
	swap	%d1
	orl	%d1,%d0			//put them in the right place
	movel	%d0,CMDREG3B(%a1)		//in the busy frame
//
// Or in the FPSR from the emulation with the USER_FPSR on the stack.
//
	fmovel	%FPSR,%d0		
	orl	%d0,USER_FPSR(%a6)
	movel	USER_FPSR(%a6),FPSR_SHADOW(%a1) //set exc bits
	orl	#sx_mask,E_BYTE(%a1)
	bra	do_clean

//
// Frame is an unimp frame possible resulting from an fmove <ea>,fp0
// that caused an exception
//
// a1 is modified to point into the new frame allowing fpsp equates
// to be valid.
//
unimp_x:
	cmpib	#UNIMP_40_SIZE-4,1(%a7)	//test for orig unimp frame
	bnes	test_rev
	leal	UNIMP_40_SIZE+LOCAL_SIZE(%a7),%a1
	bras	unimp_con
test_rev:
	cmpib	#UNIMP_41_SIZE-4,1(%a7)	//test for rev unimp frame
	bnel	fpsp_fmt_error		//if not $28 or $30
	leal	UNIMP_41_SIZE+LOCAL_SIZE(%a7),%a1
	
unimp_con:
//
// Fix up the new unimp frame with entries from the old unimp frame
//
	movel	CMDREG1B(%a6),CMDREG1B(%a1) //set inst in frame to unimp
//
// Or in the FPSR from the emulation with the USER_FPSR on the stack.
//
	fmovel	%FPSR,%d0		
	orl	%d0,USER_FPSR(%a6)
	bra	do_clean

//
// Frame is idle, so check for exceptions reported through
// USER_FPSR and set the unimp frame accordingly.  
// A7 must be incremented to the point before the
// idle fsave vector to the unimp vector.
//
	
do_check:
	addl	#4,%a7			//point A7 back to unimp frame
//
// Or in the FPSR from the emulation with the USER_FPSR on the stack.
//
	fmovel	%FPSR,%d0		
	orl	%d0,USER_FPSR(%a6)
//
// On a busy frame, we must clear the nmnexc bits.
//
	cmpib	#BUSY_SIZE-4,1(%a7)	//check frame type
	bnes	check_fr		//if busy, clr nmnexc
	clrw	NMNEXC(%a6)		//clr nmnexc & nmcexc
	btstb	#5,CMDREG1B(%a6)		//test for fmove out
	bnes	frame_com
	movel	USER_FPSR(%a6),FPSR_SHADOW(%a6) //set exc bits
	orl	#sx_mask,E_BYTE(%a6)
	bras	frame_com
check_fr:
	cmpb	#UNIMP_40_SIZE-4,1(%a7)
	beqs	frame_com
	clrw	NMNEXC(%a6)
frame_com:
	moveb	FPCR_ENABLE(%a6),%d0	//get fpcr enable byte
	andb	FPSR_EXCEPT(%a6),%d0	//and in the fpsr exc byte
	bfffo	%d0{#24:#8},%d1		//test for first set bit
	leal	exc_tbl,%a0		//load jmp table address
	subib	#24,%d1			//normalize bit offset to 0-8
	movel	(%a0,%d1.w*4),%a0		//load routine address based
//					;based on first enabled exc
	jmp	(%a0)			//jump to routine
//
// Bsun is not possible in unimp or unsupp
//
bsun_exc:
	bra	do_clean
//
// The typical work to be done to the unimp frame to report an 
// exception is to set the E1/E3 byte and clr the U flag.
// commonE1 does this for E1 exceptions, which are snan, 
// operr, and dz.  commonE3 does this for E3 exceptions, which 
// are inex2 and inex1, and also clears the E1 exception bit
// left over from the unimp exception.
//
commonE1:
	bsetb	#E1,E_BYTE(%a6)		//set E1 flag
	bra	commonE			//go clean and exit

commonE3:
	tstb	UFLG_TMP(%a6)		//test flag for unsup/unimp state
	bnes	unsE3
uniE3:
	bsetb	#E3,E_BYTE(%a6)		//set E3 flag
	bclrb	#E1,E_BYTE(%a6)		//clr E1 from unimp
	bra	commonE

unsE3:
	tstb	RES_FLG(%a6)
	bnes	unsE3_0	
unsE3_1:
	bsetb	#E3,E_BYTE(%a6)		//set E3 flag
unsE3_0:
	bclrb	#E1,E_BYTE(%a6)		//clr E1 flag
	movel	CMDREG1B(%a6),%d0
	andl	#0x03c30000,%d0		//work for cmd3b
	bfextu	CMDREG1B(%a6){#13:#1},%d1	//extract bit 2
	lsll	#5,%d1			
	swap	%d1
	orl	%d1,%d0			//put it in the right place
	bfextu	CMDREG1B(%a6){#10:#3},%d1	//extract bit 3,4,5
	lsll	#2,%d1
	swap	%d1
	orl	%d1,%d0			//put them in the right place
	movel	%d0,CMDREG3B(%a6)		//in the busy frame

commonE:
	bclrb	#UFLAG,T_BYTE(%a6)	//clr U flag from unimp
	bra	do_clean		//go clean and exit
//
// No bits in the enable byte match existing exceptions.  Check for
// the case of the ovfl exc without the ovfl enabled, but with
// inex2 enabled.
//
no_match:
	btstb	#inex2_bit,FPCR_ENABLE(%a6) //check for ovfl/inex2 case
	beqs	no_exc			//if clear, exit
	btstb	#ovfl_bit,FPSR_EXCEPT(%a6) //now check ovfl
	beqs	no_exc			//if clear, exit
	bras	ovfl_unfl		//go to unfl_ovfl to determine if
//					;it is an unsupp or unimp exc
	
// No exceptions are to be reported.  If the instruction was 
// unimplemented, no FPU restore is necessary.  If it was
// unsupported, we must perform the restore.
no_exc:
	tstb	UFLG_TMP(%a6)	//test flag for unsupp/unimp state
	beqs	uni_no_exc
uns_no_exc:
	tstb	RES_FLG(%a6)	//check if frestore is needed
	bne	do_clean 	//if clear, no frestore needed
uni_no_exc:
	moveml	USER_DA(%a6),%d0-%d1/%a0-%a1
	fmovemx USER_FP0(%a6),%fp0-%fp3
	fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar
	unlk	%a6
	bra	finish_up
//
// Unsupported Data Type Handler:
// Ovfl:
//   An fmoveout that results in an overflow is reported this way.
// Unfl:
//   An fmoveout that results in an underflow is reported this way.
//
// Unimplemented Instruction Handler:
// Ovfl:
//   Only scosh, setox, ssinh, stwotox, and scale can set overflow in 
//   this manner.
// Unfl:
//   Stwotox, setox, and scale can set underflow in this manner.
//   Any of the other Library Routines such that f(x)=x in which
//   x is an extended denorm can report an underflow exception. 
//   It is the responsibility of the exception-causing exception 
//   to make sure that WBTEMP is correct.
//
//   The exceptional operand is in FP_SCR1.
//
ovfl_unfl:
	tstb	UFLG_TMP(%a6)	//test flag for unsupp/unimp state
	beqs	ofuf_con
//
// The caller was from an unsupported data type trap.  Test if the
// caller set CU_ONLY.  If so, the exceptional operand is expected in
// FPTEMP, rather than WBTEMP.
//
	tstb	CU_ONLY(%a6)		//test if inst is cu-only
	beq	unsE3
//	move.w	#$fe,CU_SAVEPC(%a6)
	clrb	CU_SAVEPC(%a6)
	bsetb	#E1,E_BYTE(%a6)		//set E1 exception flag
	movew	ETEMP_EX(%a6),FPTEMP_EX(%a6)
	movel	ETEMP_HI(%a6),FPTEMP_HI(%a6)
	movel	ETEMP_LO(%a6),FPTEMP_LO(%a6)
	bsetb	#fptemp15_bit,DTAG(%a6)	//set fpte15
	bclrb	#UFLAG,T_BYTE(%a6)	//clr U flag from unimp
	bra	do_clean		//go clean and exit

ofuf_con:
	moveb	(%a7),VER_TMP(%a6)	//save version number
	cmpib	#BUSY_SIZE-4,1(%a7)	//check for busy frame
	beqs	busy_fr			//if unimp, grow to busy
	cmpib	#VER_40,(%a7)		//test for orig unimp frame
	bnes	try_41			//if not, test for rev frame
	moveql	#13,%d0			//need to zero 14 lwords
	bras	ofuf_fin
try_41:
	cmpib	#VER_41,(%a7)		//test for rev unimp frame
	bnel	fpsp_fmt_error		//if neither, exit with error
	moveql	#11,%d0			//need to zero 12 lwords

ofuf_fin:
	clrl	(%a7)
loop1:
	clrl	-(%a7)			//clear and dec a7
	dbra	%d0,loop1
	moveb	VER_TMP(%a6),(%a7)
	moveb	#BUSY_SIZE-4,1(%a7)		//write busy fmt word.
busy_fr:
	movel	FP_SCR1(%a6),WBTEMP_EX(%a6)	//write
	movel	FP_SCR1+4(%a6),WBTEMP_HI(%a6)	//exceptional op to
	movel	FP_SCR1+8(%a6),WBTEMP_LO(%a6)	//wbtemp
	bsetb	#E3,E_BYTE(%a6)			//set E3 flag
	bclrb	#E1,E_BYTE(%a6)			//make sure E1 is clear
	bclrb	#UFLAG,T_BYTE(%a6)		//clr U flag
	movel	USER_FPSR(%a6),FPSR_SHADOW(%a6)
	orl	#sx_mask,E_BYTE(%a6)
	movel	CMDREG1B(%a6),%d0		//fix cmd1b to make it
	andl	#0x03c30000,%d0		//work for cmd3b
	bfextu	CMDREG1B(%a6){#13:#1},%d1	//extract bit 2
	lsll	#5,%d1			
	swap	%d1
	orl	%d1,%d0			//put it in the right place
	bfextu	CMDREG1B(%a6){#10:#3},%d1	//extract bit 3,4,5
	lsll	#2,%d1
	swap	%d1
	orl	%d1,%d0			//put them in the right place
	movel	%d0,CMDREG3B(%a6)		//in the busy frame

//
// Check if the frame to be restored is busy or unimp.
//** NOTE *** Bug fix for errata (0d43b #3)
// If the frame is unimp, we must create a busy frame to 
// fix the bug with the nmnexc bits in cases in which they
// are set by a previous instruction and not cleared by
// the save. The frame will be unimp only if the final 
// instruction in an emulation routine caused the exception
// by doing an fmove <ea>,fp0.  The exception operand, in
// internal format, is in fptemp.
//
do_clean:
	cmpib	#UNIMP_40_SIZE-4,1(%a7)
	bnes	do_con
	moveql	#13,%d0			//in orig, need to zero 14 lwords
	bras	do_build
do_con:
	cmpib	#UNIMP_41_SIZE-4,1(%a7)
	bnes	do_restore		//frame must be busy
	moveql	#11,%d0			//in rev, need to zero 12 lwords

do_build:
	moveb	(%a7),VER_TMP(%a6)
	clrl	(%a7)
loop2:
	clrl	-(%a7)			//clear and dec a7
	dbra	%d0,loop2
//
// Use a1 as pointer into new frame.  a6 is not correct if an unimp or
// busy frame was created as the result of an exception on the final
// instruction of an emulation routine.
//
// We need to set the nmcexc bits if the exception is E1. Otherwise,
// the exc taken will be inex2.
//
	leal	BUSY_SIZE+LOCAL_SIZE(%a7),%a1	//init a1 for new frame
	moveb	VER_TMP(%a6),(%a7)	//write busy fmt word
	moveb	#BUSY_SIZE-4,1(%a7)
	movel	FP_SCR1(%a6),WBTEMP_EX(%a1) 	//write
	movel	FP_SCR1+4(%a6),WBTEMP_HI(%a1)	//exceptional op to
	movel	FP_SCR1+8(%a6),WBTEMP_LO(%a1)	//wbtemp
//	btst.b	#E1,E_BYTE(%a1)
//	beq.b	do_restore
	bfextu	USER_FPSR(%a6){#17:#4},%d0	//get snan/operr/ovfl/unfl bits
	bfins	%d0,NMCEXC(%a1){#4:#4}	//and insert them in nmcexc
	movel	USER_FPSR(%a6),FPSR_SHADOW(%a1) //set exc bits
	orl	#sx_mask,E_BYTE(%a1)
	
do_restore:
	moveml	USER_DA(%a6),%d0-%d1/%a0-%a1
	fmovemx USER_FP0(%a6),%fp0-%fp3
	fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar
	frestore (%a7)+
	tstb	RES_FLG(%a6)	//RES_FLG indicates a "continuation" frame
	beq	cont
	bsr	bug1384
cont:
	unlk	%a6
//
// If trace mode enabled, then go to trace handler.  This handler 
// cannot have any fp instructions.  If there are fp inst's and an 
// exception has been restored into the machine then the exception 
// will occur upon execution of the fp inst.  This is not desirable 
// in the kernel (supervisor mode).  See MC68040 manual Section 9.3.8.
//
finish_up:
	btstb	#7,(%a7)		//test T1 in SR
	bnes	g_trace
	btstb	#6,(%a7)		//test T0 in SR
	bnes	g_trace
	bral	fpsp_done
//
// Change integer stack to look like trace stack
// The address of the instruction that caused the
// exception is already in the integer stack (is
// the same as the saved friar)
//
// If the current frame is already a 6-word stack then all
// that needs to be done is to change the vector# to TRACE.
// If the frame is only a 4-word stack (meaning we got here
// on an Unsupported data type exception), then we need to grow
// the stack an extra 2 words and get the FPIAR from the FPU.
//
g_trace:
	bftst	EXC_VEC-4(%sp){#0:#4}
	bne	g_easy

	subw	#4,%sp		// make room
	movel	4(%sp),(%sp)
	movel	8(%sp),4(%sp)
	subw	#BUSY_SIZE,%sp
	fsave	(%sp)
	fmovel	%fpiar,BUSY_SIZE+EXC_EA-4(%sp)
	frestore (%sp)
	addw	#BUSY_SIZE,%sp

g_easy:
	movew	#TRACE_VEC,EXC_VEC-4(%a7)
	bral	real_trace
//
//  This is a work-around for hardware bug 1384.
//
bug1384:
	link	%a5,#0
	fsave	-(%sp)
	cmpib	#0x41,(%sp)	// check for correct frame
	beq	frame_41
	bgt	nofix		// if more advanced mask, do nada

frame_40:
	tstb	1(%sp)		// check to see if idle
	bne	notidle
idle40:
	clrl	(%sp)		// get rid of old fsave frame
        movel  %d1,USER_D1(%a6)  // save d1
	movew	#8,%d1		// place unimp frame instead
loop40:	clrl	-(%sp)
	dbra	%d1,loop40
        movel  USER_D1(%a6),%d1  // restore d1
	movel	#0x40280000,-(%sp)
	frestore (%sp)+
	unlk  	%a5	
	rts

frame_41:
	tstb	1(%sp)		// check to see if idle
	bne	notidle	
idle41:
	clrl	(%sp)		// get rid of old fsave frame
        movel  %d1,USER_D1(%a6)  // save d1
	movew	#10,%d1		// place unimp frame instead
loop41:	clrl	-(%sp)
	dbra	%d1,loop41
        movel  USER_D1(%a6),%d1  // restore d1
	movel	#0x41300000,-(%sp)
	frestore (%sp)+
	unlk	%a5	
	rts

notidle:
	bclrb	#etemp15_bit,-40(%a5) 
	frestore (%sp)+
	unlk	%a5	
	rts

nofix:
	frestore (%sp)+
	unlk	%a5	
	rts

	|end