|
  |	x_snan.sa 3.3 7/1/91
  |
  | fpsp_snan --- FPSP handler for signalling NAN exception
  |
  | SNAN for float -> integer conversions (integer conversion of
  | an SNAN) is a non-maskable run-time exception.
  |
  | For trap disabled the 040 does the following:
  | If the dest data format is s, d, or x, then the SNAN bit in the NAN
  | is set to one and the resulting non-signaling NAN (truncated if
  | necessary) is transferred to the dest.  If the dest format is b, w,
  | or l, then garbage is written to the dest (actually the upper 32 bits
  | of the mantissa are sent to the integer unit).
  |
  | For trap enabled the 040 does the following:
  | If the inst is move_out, then the results are the same as for trap
  | disabled with the exception posted.  If the instruction is not move_
  | out, the dest. is not modified, and the exception is posted.
  |
  
  |		Copyright (C) Motorola, Inc. 1990
  |			All Rights Reserved
  |

  |       For details on the license for this file, please see the
  |       file, README, in this same directory.

  
  X_SNAN:	|idnt    2,1 | Motorola 040 Floating Point Software Package
  
  	|section	8
  
  #include "fpsp.h"
  
  	|xref	get_fline
  	|xref	mem_write
  	|xref	real_snan
  	|xref	real_inex
  	|xref	fpsp_done
  	|xref	reg_dest
  
  	.global	fpsp_snan
  fpsp_snan:
  	link		%a6,#-LOCAL_SIZE
  	fsave		-(%a7)
  	moveml		%d0-%d1/%a0-%a1,USER_DA(%a6)
  	fmovemx	%fp0-%fp3,USER_FP0(%a6)
  	fmoveml	%fpcr/%fpsr/%fpiar,USER_FPCR(%a6)
  
  |
  | Check if trap enabled
  |
  	btstb		#snan_bit,FPCR_ENABLE(%a6)
  	bnes		ena		|If enabled, then branch
  
  	bsrl		move_out	|else SNAN disabled
  |
  | It is possible to have an inex1 exception with the
  | snan.  If the inex enable bit is set in the FPCR, and either
  | inex2 or inex1 occurred, we must clean up and branch to the
  | real inex handler.
  |
  ck_inex:
  	moveb	FPCR_ENABLE(%a6),%d0
  	andb	FPSR_EXCEPT(%a6),%d0
  	andib	#0x3,%d0
  	beq	end_snan
  |
  | Inexact enabled and reported, and we must take an inexact exception.
  |
  take_inex:
  	moveb		#INEX_VEC,EXC_VEC+1(%a6)
  	moveml		USER_DA(%a6),%d0-%d1/%a0-%a1
  	fmovemx	USER_FP0(%a6),%fp0-%fp3
  	fmoveml	USER_FPCR(%a6),%fpcr/%fpsr/%fpiar
  	frestore	(%a7)+
  	unlk		%a6
  	bral		real_inex
  |
  | SNAN is enabled.  Check if inst is move_out.
  | Make any corrections to the 040 output as necessary.
  |
  ena:
  	btstb		#5,CMDREG1B(%a6) |if set, inst is move out
  	beq		not_out
  
  	bsrl		move_out
  
  report_snan:
  	moveb		(%a7),VER_TMP(%a6)
  	cmpib		#VER_40,(%a7)	|test for orig unimp frame
  	bnes		ck_rev
  	moveql		#13,%d0		|need to zero 14 lwords
  	bras		rep_con
  ck_rev:
  	moveql		#11,%d0		|need to zero 12 lwords
  rep_con:
  	clrl		(%a7)
  loop1:
  	clrl		-(%a7)		|clear and dec a7
  	dbra		%d0,loop1
  	moveb		VER_TMP(%a6),(%a7) |format a busy frame
  	moveb		#BUSY_SIZE-4,1(%a7)
  	movel		USER_FPSR(%a6),FPSR_SHADOW(%a6)
  	orl		#sx_mask,E_BYTE(%a6)
  	moveml		USER_DA(%a6),%d0-%d1/%a0-%a1
  	fmovemx	USER_FP0(%a6),%fp0-%fp3
  	fmoveml	USER_FPCR(%a6),%fpcr/%fpsr/%fpiar
  	frestore	(%a7)+
  	unlk		%a6
  	bral		real_snan
  |
  | Exit snan handler by expanding the unimp frame into a busy frame
  |
  end_snan:
  	bclrb		#E1,E_BYTE(%a6)
  
  	moveb		(%a7),VER_TMP(%a6)
  	cmpib		#VER_40,(%a7)	|test for orig unimp frame
  	bnes		ck_rev2
  	moveql		#13,%d0		|need to zero 14 lwords
  	bras		rep_con2
  ck_rev2:
  	moveql		#11,%d0		|need to zero 12 lwords
  rep_con2:
  	clrl		(%a7)
  loop2:
  	clrl		-(%a7)		|clear and dec a7
  	dbra		%d0,loop2
  	moveb		VER_TMP(%a6),(%a7) |format a busy frame
  	moveb		#BUSY_SIZE-4,1(%a7) |write busy size
  	movel		USER_FPSR(%a6),FPSR_SHADOW(%a6)
  	orl		#sx_mask,E_BYTE(%a6)
  	moveml		USER_DA(%a6),%d0-%d1/%a0-%a1
  	fmovemx	USER_FP0(%a6),%fp0-%fp3
  	fmoveml	USER_FPCR(%a6),%fpcr/%fpsr/%fpiar
  	frestore	(%a7)+
  	unlk		%a6
  	bral		fpsp_done
  
  |
  | Move_out
  |
  move_out:
  	movel		EXC_EA(%a6),%a0	|get <ea> from exc frame
  
  	bfextu		CMDREG1B(%a6){#3:#3},%d0 |move rx field to d0{2:0}
  	cmpil		#0,%d0		|check for long
  	beqs		sto_long	|branch if move_out long
  
  	cmpil		#4,%d0		|check for word
  	beqs		sto_word	|branch if move_out word
  
  	cmpil		#6,%d0		|check for byte
  	beqs		sto_byte	|branch if move_out byte
  
  |
  | Not byte, word or long
  |
  	rts
  |
  | Get the 32 most significant bits of etemp mantissa
  |
  sto_long:
  	movel		ETEMP_HI(%a6),%d1
  	movel		#4,%d0		|load byte count
  |
  | Set signalling nan bit
  |
  	bsetl		#30,%d1
  |
  | Store to the users destination address
  |
  	tstl		%a0		|check if <ea> is 0
  	beqs		wrt_dn		|destination is a data register
  
  	movel		%d1,-(%a7)	|move the snan onto the stack
  	movel		%a0,%a1		|load dest addr into a1
  	movel		%a7,%a0		|load src addr of snan into a0
  	bsrl		mem_write	|write snan to user memory
  	movel		(%a7)+,%d1	|clear off stack
  	rts
  |
  | Get the 16 most significant bits of etemp mantissa
  |
  sto_word:
  	movel		ETEMP_HI(%a6),%d1
  	movel		#2,%d0		|load byte count
  |
  | Set signalling nan bit
  |
  	bsetl		#30,%d1
  |
  | Store to the users destination address
  |
  	tstl		%a0		|check if <ea> is 0
  	beqs		wrt_dn		|destination is a data register
  
  	movel		%d1,-(%a7)	|move the snan onto the stack
  	movel		%a0,%a1		|load dest addr into a1
  	movel		%a7,%a0		|point to low word
  	bsrl		mem_write	|write snan to user memory
  	movel		(%a7)+,%d1	|clear off stack
  	rts
  |
  | Get the 8 most significant bits of etemp mantissa
  |
  sto_byte:
  	movel		ETEMP_HI(%a6),%d1
  	movel		#1,%d0		|load byte count
  |
  | Set signalling nan bit
  |
  	bsetl		#30,%d1
  |
  | Store to the users destination address
  |
  	tstl		%a0		|check if <ea> is 0
  	beqs		wrt_dn		|destination is a data register
  	movel		%d1,-(%a7)	|move the snan onto the stack
  	movel		%a0,%a1		|load dest addr into a1
  	movel		%a7,%a0		|point to source byte
  	bsrl		mem_write	|write snan to user memory
  	movel		(%a7)+,%d1	|clear off stack
  	rts
  
  |
  |	wrt_dn --- write to a data register
  |
  |	We get here with D1 containing the data to write and D0 the
  |	number of bytes to write: 1=byte,2=word,4=long.
  |
  wrt_dn:
  	movel		%d1,L_SCR1(%a6)	|data
  	movel		%d0,-(%a7)	|size
  	bsrl		get_fline	|returns fline word in d0
  	movel		%d0,%d1
  	andil		#0x7,%d1		|d1 now holds register number
  	movel		(%sp)+,%d0	|get original size
  	cmpil		#4,%d0
  	beqs		wrt_long
  	cmpil		#2,%d0
  	bnes		wrt_byte
  wrt_word:
  	orl		#0x8,%d1
  	bral		reg_dest
  wrt_long:
  	orl		#0x10,%d1
  	bral		reg_dest
  wrt_byte:
  	bral		reg_dest
  |
  | Check if it is a src nan or dst nan
  |
  not_out:
  	movel		DTAG(%a6),%d0
  	bfextu		%d0{#0:#3},%d0	|isolate dtag in lsbs
  
  	cmpib		#3,%d0		|check for nan in destination
  	bnes		issrc		|destination nan has priority
  dst_nan:
  	btstb		#6,FPTEMP_HI(%a6) |check if dest nan is an snan
  	bnes		issrc		|no, so check source for snan
  	movew		FPTEMP_EX(%a6),%d0
  	bras		cont
  issrc:
  	movew		ETEMP_EX(%a6),%d0
  cont:
  	btstl		#15,%d0		|test for sign of snan
  	beqs		clr_neg
  	bsetb		#neg_bit,FPSR_CC(%a6)
  	bra		report_snan
  clr_neg:
  	bclrb		#neg_bit,FPSR_CC(%a6)
  	bra		report_snan
  
  	|end