sys7.1-doc-wip/OS/FPUEmulation/BugFix.a

;
;	File:		BugFix.a
;
;	Contains:	Workaround for bug #1238 in the 040 (D43B masks)
;
;	Originally Written by:	Motorola Inc.
;	Adapted to Apple/MPW:	Jon Okada
;
;	Copyright:	© 1991 by Apple Computer, Inc., all rights reserved.
;
;   This file is used in these builds:   Mac32
;
;	Change History (most recent first):
;
;		 <1>	 3/30/91	BG		First checked into TERROR/BBS.
;

;  bugfix.a

;  Based upon Motorola file 'bugfix.sa' (version 3.2, 1/31/91).

;  CHANGE LOG:
;  05 Mar 91	JPO	Renamed label "finish" to "bffinish".  Deleted
;			  a branch to following instruction.

*
*	bugfix.sa 3.2 1/31/91
*
*
*	This file contains workarounds for bugs in the 040
*	relating to the Floating-Point Software Package (FPSP)
*
*	Fixes for bugs: 1238
*
*	Bug: 1238 
*
*
*    /* The following dirty_bit clear should be left in
*     * the handler permanently to improve throughput.
*     * The dirty_bits are located at bits [23:16] in
*     * longword $08 in the busy frame $4x60.  Bit 16
*     * corresponds to FP0, bit 17 corresponds to FP1,
*     * and so on.
*     */
*    if  (E3_exception_just_serviced)   {
*         dirty_bit[cmdreg3b[9:7]] = 0;
*         }
*
*    if  (fsave_format_version != $40)  {goto NOFIX}
*
*    if !(E3_exception_just_serviced)   {goto NOFIX}
*    if  (cupc == 0000000)              {goto NOFIX}
*    if  ((cmdreg1b[15:13] != 000) &&
*         (cmdreg1b[15:10] != 010001))  {goto NOFIX}
*    if (((cmdreg1b[15:13] != 000) || ((cmdreg1b[12:10] != cmdreg2b[9:7]) &&
*				      (cmdreg1b[12:10] != cmdreg3b[9:7]))  ) &&
*	 ((cmdreg1b[ 9: 7] != cmdreg2b[9:7]) &&
*	  (cmdreg1b[ 9: 7] != cmdreg3b[9:7])) )  {goto NOFIX}
*
*    /* Note: for 6d43b or 8d43b, you may want to add the following code
*     * to get better coverage.  (If you do not insert this code, the part
*     * won't lock up; it will simply get the wrong answer.)
*     * Do NOT insert this code for 10d43b or later parts.
*     *
*     *  if (fpiarcu == integer stack return address) {
*     *       cupc = 0000000;
*     *       goto NOFIX;
*     *       }
*     */
*
*    if (cmdreg1b[15:13] != 000)   {goto FIX_OPCLASS2}
*    FIX_OPCLASS0:
*    if (((cmdreg1b[12:10] == cmdreg2b[9:7]) ||
*	 (cmdreg1b[ 9: 7] == cmdreg2b[9:7])) &&
*	(cmdreg1b[12:10] != cmdreg3b[9:7]) &&
*	(cmdreg1b[ 9: 7] != cmdreg3b[9:7]))  {  /* xu conflict only */
*	/* We execute the following code if there is an
*	   xu conflict and NOT an nu conflict */
*
*	/* first save some values on the fsave frame */
*	stag_temp     = STAG[fsave_frame];
*	cmdreg1b_temp = CMDREG1B[fsave_frame];
*	dtag_temp     = DTAG[fsave_frame];
*	ete15_temp    = ETE15[fsave_frame];
*
*	CUPC[fsave_frame] = 0000000;
*	FRESTORE
*	FSAVE
*
*	/* If the xu instruction is exceptional, we punt.
*	 * Otherwise, we would have to include OVFL/UNFL handler
*	 * code here to get the correct answer.
*	 */
*	if (fsave_frame_format == $4060) {goto KILL_PROCESS}
*
*	fsave_frame = /* build a long frame of all zeros */
*	fsave_frame_format = $4060;  /* label it as long frame */
*
*	/* load it with the temps we saved */
*	STAG[fsave_frame]     =  stag_temp;
*	CMDREG1B[fsave_frame] =  cmdreg1b_temp;
*	DTAG[fsave_frame]     =  dtag_temp;
*	ETE15[fsave_frame]    =  ete15_temp;
*
*	/* Make sure that the cmdreg3b dest reg is not going to
*	 * be destroyed by a FMOVEM at the end of all this code.
*	 * If it is, you should move the current value of the reg
*	 * onto the stack so that the reg will loaded with that value.
*	 */
*
*	/* All done.  Proceed with the code below */
*    }
*
*    etemp  = FP_reg_[cmdreg1b[12:10]];
*    ete15  = ~ete14;
*    cmdreg1b[15:10] = 010010;
*    clear(bug_flag_procIDxxxx);
*    FRESTORE and return;
*
*
*    FIX_OPCLASS2:
*    if ((cmdreg1b[9:7] == cmdreg2b[9:7]) &&
*	(cmdreg1b[9:7] != cmdreg3b[9:7]))  {  /* xu conflict only */
*	/* We execute the following code if there is an
*	   xu conflict and NOT an nu conflict */
*
*	/* first save some values on the fsave frame */
*	stag_temp     = STAG[fsave_frame];
*	cmdreg1b_temp = CMDREG1B[fsave_frame];
*	dtag_temp     = DTAG[fsave_frame];
*	ete15_temp    = ETE15[fsave_frame];
*	etemp_temp    = ETEMP[fsave_frame];
*
*	CUPC[fsave_frame] = 0000000;
*	FRESTORE
*	FSAVE
*
*
*	/* If the xu instruction is exceptional, we punt.
*	 * Otherwise, we would have to include OVFL/UNFL handler
*	 * code here to get the correct answer.
*	 */
*	if (fsave_frame_format == $4060) {goto KILL_PROCESS}
*
*	fsave_frame = /* build a long frame of all zeros */
*	fsave_frame_format = $4060;  /* label it as long frame */
*
*	/* load it with the temps we saved */
*	STAG[fsave_frame]     =  stag_temp;
*	CMDREG1B[fsave_frame] =  cmdreg1b_temp;
*	DTAG[fsave_frame]     =  dtag_temp;
*	ETE15[fsave_frame]    =  ete15_temp;
*	ETEMP[fsave_frame]    =  etemp_temp;
*
*	/* Make sure that the cmdreg3b dest reg is not going to
*	 * be destroyed by a FMOVEM at the end of all this code.
*	 * If it is, you should move the current value of the reg
*	 * onto the stack so that the reg will loaded with that value.
*	 */
*
*	/* All done.  Proceed with the code below */
*    }
*
*    if (etemp_exponent == min_sgl)   etemp_exponent = min_dbl;
*    if (etemp_exponent == max_sgl)   etemp_exponent = max_dbl;
*    cmdreg1b[15:10] = 010101;
*    clear(bug_flag_procIDxxxx);
*    FRESTORE and return;
*
*
*    NOFIX:
*    clear(bug_flag_procIDxxxx);
*    FRESTORE and return;
*


*		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.

* BUGFIX    IDNT    2,1 Motorola 040 Floating Point Software Package

b1238_fix:
*
* This code is entered only on completion of the handling of an 
* nu-generated ovfl, unfl, or inex exception.  If the version 
* number of the fsave is not $40, this handler is not necessary.
* Simply branch to fix_done and exit normally.
*
	cmpi.b	#VER_40,4(a7)
	bne.w	fix_done
*
* Test for cu_savepc equal to zero.  If not, this is not a bug
* #1238 case.
*
	move.b	CU_SAVEPC(a6),d0
	andi.b	#$FE,d0
	beq 	fix_done	;if zero, this is not bug #1238

*
* Test the register conflict aspect.  If opclass0, check for
* cu src equal to xu dest or equal to nu dest.  If so, go to 
* op0.  Else, or if opclass2, check for cu dest equal to
* xu dest or equal to nu dest.  If so, go to tst_opcl.  Else,
* exit, it is not the bug case.
*
* Check for opclass 0.  If not, go and check for opclass 2 and sgl.
*
	move.w	CMDREG1B(a6),d0
	andi.w	#$E000,d0		;strip all but opclass
	bne	op2sgl			;not opclass 0, check op2
*
* Check for cu and nu register conflict.  If one exists, this takes
* priority over a cu and xu conflict. 
*
	bfextu	CMDREG1B(a6){3:3},d0	;get 1st src 
	bfextu	CMDREG3B(a6){6:3},d1	;get 3rd dest
	cmp.b	d0,d1
	beq.b	op0			;if equal, continue bugfix
*
* Check for cu dest equal to nu dest.  If so, go and fix the 
* bug condition.  Otherwise, exit.
*
	bfextu	CMDREG1B(a6){6:3},d0	;get 1st dest 
	cmp.b	d0,d1			;cmp 1st dest with 3rd dest
	beq.b	op0			;if equal, continue bugfix
*
* Check for cu and xu register conflict.
*
	bfextu	CMDREG2B(a6){6:3},d1	;get 2nd dest
	cmp.b	d0,d1			;cmp 1st dest with 2nd dest
	beq.b	op0_xu			;if equal, continue bugfix
	bfextu	CMDREG1B(a6){3:3},d0	;get 1st src 
	cmp.b	d0,d1			;cmp 1st src with 2nd dest
	beq.b	op0_xu
	bne	fix_done		;if the reg checks fail, exit
*
* We have the opclass 0 situation.
*
op0:
	bfextu	CMDREG1B(a6){3:3},d0	;get source register no
	move.l	#7,d1
	sub.l	d0,d1
	clr.l	d0
	bset.l	d1,d0
	fmovem.x d0,ETEMP(a6)		;load source to ETEMP

	move.b	#$12,d0
	bfins	d0,CMDREG1B(a6){0:6}	;opclass 2, extended
*
*	Set ETEMP exponent bit 15 as the opposite of ete14
*
	btst	#6,ETEMP_EX(a6)		;check etemp exponent bit 14
	beq.b	setete15
	bclr	#etemp15_bit,STAG(a6)
	bra	bffinish		; label RENAMED <3/5/91, JPO>
setete15:
	bset	#etemp15_bit,STAG(a6)
	bra	bffinish		; label RENAMED <3/5/91, JPO>

*
* We have the case in which a conflict exists between the cu src or
* dest and the dest of the xu.  We must clear the instruction in 
* the cu and restore the state, allowing the instruction in the
* xu to complete.  Remember, the instruction in the nu
* was exceptional, and was completed by the appropriate handler.
* If the result of the xu instruction is not exceptional, we can
* restore the instruction from the cu to the frame and continue
* processing the original exception.  If the result is also
* exceptional, we choose to kill the process.
*
*	Items saved from the stack:
*	
*		$3c stag     - L_SCR1
*		$40 cmdreg1b - L_SCR2
*		$44 dtag     - L_SCR3
*
* The cu savepc is set to zero, and the frame is restored to the
* fpu.
*
op0_xu:
	move.l	STAG(a6),L_SCR1(a6)	
	move.l	CMDREG1B(a6),L_SCR2(a6)	
	move.l	DTAG(a6),L_SCR3(a6)
	andi.l	#$e0000000,L_SCR3(a6)
	move.b	#0,CU_SAVEPC(a6)
	move.l	(a7)+,d1		;save return address from bsr
	frestore (a7)+
	fsave	-(a7)
*
* Check if the instruction which just completed was exceptional.
* 
	cmp.w	#$4060,(a7)
	beq	op0_xb
* 
* It is necessary to isolate the result of the instruction in the
* xu if it is to fp0 - fp3 and write that value to the USER_FPn
* locations on the stack.  The correct destination register is in 
* cmdreg2b.
*
	bfextu	CMDREG2B(a6){6:3},d0	;get dest register no
	cmpi.l	#3,d0
	bgt.b	op0_xi
	beq.b	op0_fp3
	cmpi.l	#1,d0
	blt.b	op0_fp0
	beq.b	op0_fp1
op0_fp2:
	fmovem.x fp2,USER_FP2(a6)
	bra.b	op0_xi
op0_fp1:
	fmovem.x fp1,USER_FP1(a6)
	bra.b	op0_xi
op0_fp0:
	fmovem.x fp0,USER_FP0(a6)
	bra.b	op0_xi
op0_fp3:
	fmovem.x fp3,USER_FP3(a6)
*
* The frame returned is idle.  We must build a busy frame to hold
* the cu state information and setup etemp.
*
op0_xi:
	move.l	#22,d0		;clear 23 lwords
	clr.l	(a7)
op0_loop:
	clr.l	-(a7)
	dbf	d0,op0_loop
	move.l	#$40600000,-(a7)
	move.l	L_SCR1(a6),STAG(a6)
	move.l	L_SCR2(a6),CMDREG1B(a6)
	move.l	L_SCR3(a6),DTAG(a6)
	move.b	#$6,CU_SAVEPC(a6)
	move.l	d1,-(a7)		;return bsr return address
	bfextu	CMDREG1B(a6){3:3},d0	;get source register no
	move.l	#7,d1
	sub.l	d0,d1
	clr.l	d0
	bset.l	d1,d0
	fmovem.x d0,ETEMP(a6)		;load source to ETEMP

	move.b	#$12,d0
	bfins	d0,CMDREG1B(a6){0:6}	;opclass 2, extended
*
*	Set ETEMP exponent bit 15 as the opposite of ete14
*
	btst	#6,ETEMP_EX(a6)		;check etemp exponent bit 14
	beq.b	op0_sete15
	bclr	#etemp15_bit,STAG(a6)
	bra	bffinish		; label RENAMED <3/5/91, JPO>
op0_sete15:
	bset	#etemp15_bit,STAG(a6)
	bra	bffinish		; label RENAMED <3/5/91, JPO>

*
* The frame returned is busy.  It is not possible to reconstruct
* the code sequence to allow completion.  We will jump to 
* fpsp_fmt_error and allow the kernel to kill the process.
*
op0_xb:
	jmp	fpsp_fmt_error

*
* Check for opclass 2 and single size.  If not both, exit.
*
op2sgl:
	move.w	CMDREG1B(a6),d0
	andi.w	#$FC00,d0		;strip all but opclass and size
	cmpi.w	#$4400,d0		;test for opclass 2 and size=sgl
	bne	fix_done		;if not, it is not bug 1238
*
* Check for cu dest equal to nu dest or equal to xu dest, with 
* a cu and nu conflict taking priority an nu conflict.  If either,
* go and fix the bug condition.  Otherwise, exit.
*
	bfextu	CMDREG1B(a6){6:3},d0	;get 1st dest 
	bfextu	CMDREG3B(a6){6:3},d1	;get 3rd dest
	cmp.b	d0,d1			;cmp 1st dest with 3rd dest
	beq	op2_com			;if equal, continue bugfix
	bfextu	CMDREG2B(a6){6:3},d1	;get 2nd dest 
	cmp.b	d0,d1			;cmp 1st dest with 2nd dest
	bne	fix_done		;if the reg checks fail, exit
*
* We have the case in which a conflict exists between the cu src or
* dest and the dest of the xu.  We must clear the instruction in 
* the cu and restore the state, allowing the instruction in the
* xu to complete.  Remember, the instruction in the nu
* was exceptional, and was completed by the appropriate handler.
* If the result of the xu instruction is not exceptional, we can
* restore the instruction from the cu to the frame and continue
* processing the original exception.  If the result is also
* exceptional, we choose to kill the process.
*
*	Items saved from the stack:
*	
*		$3c stag     - L_SCR1
*		$40 cmdreg1b - L_SCR2
*		$44 dtag     - L_SCR3
*		etemp        - FP_SCR2
*
* The cu savepc is set to zero, and the frame is restored to the
* fpu.
*
op2_xu:
	move.l	STAG(a6),L_SCR1(a6)	
	move.l	CMDREG1B(a6),L_SCR2(a6)	
	move.l	DTAG(a6),L_SCR3(a6)	
	andi.l	#$e0000000,L_SCR3(a6)
	move.b	#0,CU_SAVEPC(a6)
	move.l	ETEMP(a6),FP_SCR2(a6)
	move.l	ETEMP_HI(a6),FP_SCR2+4(a6)
	move.l	ETEMP_LO(a6),FP_SCR2+8(a6)
	move.l	(a7)+,d1		;save return address from bsr
	frestore (a7)+
	fsave	-(a7)
*
* Check if the instruction which just completed was exceptional.
* 
	cmp.w	#$4060,(a7)
	beq	op2_xb
* 
* It is necessary to isolate the result of the instruction in the
* xu if it is to fp0 - fp3 and write that value to the USER_FPn
* locations on the stack.  The correct destination register is in 
* cmdreg2b.
*
	bfextu	CMDREG2B(a6){6:3},d0	;get dest register no
	cmpi.l	#3,d0
	bgt.b	op2_xi
	beq.b	op2_fp3
	cmpi.l	#1,d0
	blt.b	op2_fp0
	beq.b	op2_fp1
op2_fp2:
	fmovem.x fp2,USER_FP2(a6)
	bra.b	op2_xi
op2_fp1:
	fmovem.x fp1,USER_FP1(a6)
	bra.b	op2_xi
op2_fp0:
	fmovem.x fp0,USER_FP0(a6)
	bra.b	op2_xi
op2_fp3:
	fmovem.x fp3,USER_FP3(a6)
*
* The frame returned is idle.  We must build a busy frame to hold
* the cu state information and fix up etemp.
*
op2_xi:
	move.l	#22,d0		;clear 23 lwords
	clr.l	(a7)
op2_loop:
	clr.l	-(a7)
	dbf	d0,op2_loop
	move.l	#$40600000,-(a7)
	move.l	L_SCR1(a6),STAG(a6)
	move.l	L_SCR2(a6),CMDREG1B(a6)
	move.l	L_SCR3(a6),DTAG(a6)
	move.b	#$6,CU_SAVEPC(a6)
	move.l	FP_SCR2(a6),ETEMP(a6)
	move.l	FP_SCR2+4(a6),ETEMP_HI(a6)
	move.l	FP_SCR2+8(a6),ETEMP_LO(a6)
	move.l	d1,-(a7)
;	bra	op2_com			; DELETED <3/5/91, JPO>

*
* We have the opclass 2 single source situation.
*
op2_com:
	move.b	#$15,d0
	bfins	d0,CMDREG1B(a6){0:6}	;opclass 2, double

	cmp.w	#$407F,ETEMP_EX(a6)	;single +max
	bne.b	case2
	move.w	#$43FF,ETEMP_EX(a6)	;to double +max
	bra.b	bffinish		; label RENAMED <3/5/91, JPO>
case2:	
	cmp.w	#$C07F,ETEMP_EX(a6)	;single -max
	bne.b	case3
	move.w	#$C3FF,ETEMP_EX(a6)	;to double -max
	bra.b	bffinish		; label RENAMED <3/5/91, JPO>
case3:	
	cmp.w	#$3F80,ETEMP_EX(a6)	;single +min
	bne.b	case4
	move.w	#$3C00,ETEMP_EX(a6)	;to double +min
	bra.b	bffinish		; label RENAMED <3/5/91, JPO>
case4:
	cmp.w	#$BF80,ETEMP_EX(a6)	;single -min
	bne.b	fix_done
	move.w	#$BC00,ETEMP_EX(a6)	;to double -min
	bra.b	bffinish		; label RENAMED <3/5/91, JPO>
*
* The frame returned is busy.  It is not possible to reconstruct
* the code sequence to allow completion.  fpsp_fmt_error causes
* an fline illegal instruction to be executed.
*
* You should replace the jump to fpsp_fmt_error with a jump
* to the entry point used to kill a process. 
*
op2_xb:
	jmp	fpsp_fmt_error

*
* Enter here if the case is not of the situations affected by
* bug #1238, or if the fix is completed, and exit.
*
bffinish:				; label RENAMED <3/5/91, JPO>
fix_done:
	rts