bugfix.s

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

//
//      $Id: bugfix.S,v 1.1 1998/12/14 23:15:19 joel Exp $
//
//	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

	|section	8

#include "fpsp.defs"

	|xref	fpsp_fmt_error

	.global	b1238_fix
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.
//
	cmpib	#VER_40,4(%a7)
	bne	fix_done
//
// Test for cu_savepc equal to zero.  If not, this is not a bug
// #1238 case.
//
	moveb	CU_SAVEPC(%a6),%d0
	andib	#0xFE,%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.
//
	movew	CMDREG1B(%a6),%d0
	andiw	#0xE000,%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
	cmpb	%d0,%d1
	beqs	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 
	cmpb	%d0,%d1			//cmp 1st dest with 3rd dest
	beqs	op0			//if equal, continue bugfix
//
// Check for cu and xu register conflict.
//
	bfextu	CMDREG2B(%a6){#6:#3},%d1	//get 2nd dest
	cmpb	%d0,%d1			//cmp 1st dest with 2nd dest
	beqs	op0_xu			//if equal, continue bugfix
	bfextu	CMDREG1B(%a6){#3:#3},%d0	//get 1st src 
	cmpb	%d0,%d1			//cmp 1st src with 2nd dest
	beq	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
	movel	#7,%d1
	subl	%d0,%d1
	clrl	%d0
	bsetl	%d1,%d0
	fmovemx %d0,ETEMP(%a6)		//load source to ETEMP

	moveb	#0x12,%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	setete15
	bclr	#etemp15_bit,STAG(%a6)
	bra	finish
setete15:
	bset	#etemp15_bit,STAG(%a6)
	bra	finish

//
// 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:
	movel	STAG(%a6),L_SCR1(%a6)	
	movel	CMDREG1B(%a6),L_SCR2(%a6)	
	movel	DTAG(%a6),L_SCR3(%a6)
	andil	#0xe0000000,L_SCR3(%a6)
	moveb	#0,CU_SAVEPC(%a6)
	movel	(%a7)+,%d1		//save return address from bsr
	frestore (%a7)+
	fsave	-(%a7)
//
// Check if the instruction which just completed was exceptional.
// 
	cmpw	#0x4060,(%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
	cmpil	#3,%d0
	bgts	op0_xi
	beqs	op0_fp3
	cmpil	#1,%d0
	blts	op0_fp0
	beqs	op0_fp1
op0_fp2:
	fmovemx %fp2-%fp2,USER_FP2(%a6)
	bras	op0_xi
op0_fp1:
	fmovemx %fp1-%fp1,USER_FP1(%a6)
	bras	op0_xi
op0_fp0:
	fmovemx %fp0-%fp0,USER_FP0(%a6)
	bras	op0_xi
op0_fp3:
	fmovemx %fp3-%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:
	movel	#22,%d0		//clear 23 lwords
	clrl	(%a7)
op0_loop:
	clrl	-(%a7)
	dbf	%d0,op0_loop
	movel	#0x40600000,-(%a7)
	movel	L_SCR1(%a6),STAG(%a6)
	movel	L_SCR2(%a6),CMDREG1B(%a6)
	movel	L_SCR3(%a6),DTAG(%a6)
	moveb	#0x6,CU_SAVEPC(%a6)
	movel	%d1,-(%a7)		//return bsr return address
	bfextu	CMDREG1B(%a6){#3:#3},%d0	//get source register no
	movel	#7,%d1
	subl	%d0,%d1
	clrl	%d0
	bsetl	%d1,%d0
	fmovemx %d0,ETEMP(%a6)		//load source to ETEMP

	moveb	#0x12,%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	op0_sete15
	bclr	#etemp15_bit,STAG(%a6)
	bra	finish
op0_sete15:
	bset	#etemp15_bit,STAG(%a6)
	bra	finish

//
// 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:
	movew	CMDREG1B(%a6),%d0
	andiw	#0xFC00,%d0		//strip all but opclass and size
	cmpiw	#0x4400,%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
	cmpb	%d0,%d1			//cmp 1st dest with 3rd dest
	beq	op2_com			//if equal, continue bugfix
	bfextu	CMDREG2B(%a6){#6:#3},%d1	//get 2nd dest 
	cmpb	%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:
	movel	STAG(%a6),L_SCR1(%a6)	
	movel	CMDREG1B(%a6),L_SCR2(%a6)	
	movel	DTAG(%a6),L_SCR3(%a6)	
	andil	#0xe0000000,L_SCR3(%a6)
	moveb	#0,CU_SAVEPC(%a6)
	movel	ETEMP(%a6),FP_SCR2(%a6)
	movel	ETEMP_HI(%a6),FP_SCR2+4(%a6)
	movel	ETEMP_LO(%a6),FP_SCR2+8(%a6)
	movel	(%a7)+,%d1		//save return address from bsr
	frestore (%a7)+
	fsave	-(%a7)
//
// Check if the instruction which just completed was exceptional.
// 
	cmpw	#0x4060,(%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
	cmpil	#3,%d0
	bgts	op2_xi
	beqs	op2_fp3
	cmpil	#1,%d0
	blts	op2_fp0
	beqs	op2_fp1
op2_fp2:
	fmovemx %fp2-%fp2,USER_FP2(%a6)
	bras	op2_xi
op2_fp1:
	fmovemx %fp1-%fp1,USER_FP1(%a6)
	bras	op2_xi
op2_fp0:
	fmovemx %fp0-%fp0,USER_FP0(%a6)
	bras	op2_xi
op2_fp3:
	fmovemx %fp3-%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:
	movel	#22,%d0		//clear 23 lwords
	clrl	(%a7)
op2_loop:
	clrl	-(%a7)
	dbf	%d0,op2_loop
	movel	#0x40600000,-(%a7)
	movel	L_SCR1(%a6),STAG(%a6)
	movel	L_SCR2(%a6),CMDREG1B(%a6)
	movel	L_SCR3(%a6),DTAG(%a6)
	moveb	#0x6,CU_SAVEPC(%a6)
	movel	FP_SCR2(%a6),ETEMP(%a6)
	movel	FP_SCR2+4(%a6),ETEMP_HI(%a6)
	movel	FP_SCR2+8(%a6),ETEMP_LO(%a6)
	movel	%d1,-(%a7)
	bra	op2_com

//
// We have the opclass 2 single source situation.
//
op2_com:
	moveb	#0x15,%d0
	bfins	%d0,CMDREG1B(%a6){#0:#6}	//opclass 2, double

	cmpw	#0x407F,ETEMP_EX(%a6)	//single +max
	bnes	case2
	movew	#0x43FF,ETEMP_EX(%a6)	//to double +max
	bra	finish
case2:	
	cmpw	#0xC07F,ETEMP_EX(%a6)	//single -max
	bnes	case3
	movew	#0xC3FF,ETEMP_EX(%a6)	//to double -max
	bra	finish
case3:	
	cmpw	#0x3F80,ETEMP_EX(%a6)	//single +min
	bnes	case4
	movew	#0x3C00,ETEMP_EX(%a6)	//to double +min
	bra	finish
case4:
	cmpw	#0xBF80,ETEMP_EX(%a6)	//single -min
	bne	fix_done
	movew	#0xBC00,ETEMP_EX(%a6)	//to double -min
	bra	finish
//
// 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.
//
finish:
fix_done:
	rts

	|end