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|
|
| x_ovfl.sa 3.5 7/1/91
|
| fpsp_ovfl --- FPSP handler for overflow exception
|
| Overflow occurs when a floating-point intermediate result is
| too large to be represented in a floating-point data register,
| or when storing to memory, the contents of a floating-point
| data register are too large to be represented in the
| destination format.
|
| Trap disabled results
|
| If the instruction is move_out, then garbage is stored in the
| destination. If the instruction is not move_out, then the
| destination is not affected. For 68881 compatibility, the
| following values should be stored at the destination, based
| on the current rounding mode:
|
| RN Infinity with the sign of the intermediate result.
| RZ Largest magnitude number, with the sign of the
| intermediate result.
| RM For pos overflow, the largest pos number. For neg overflow,
| -infinity
| RP For pos overflow, +infinity. For neg overflow, the largest
| neg number
|
| Trap enabled results
| All trap disabled code applies. In addition the exceptional
| operand needs to be made available to the users exception handler
| with a bias of $6000 subtracted from the exponent.
|
|
| 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| THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA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.
X_OVFL: |idnt 2,1 | Motorola 040 Floating Point Software Package
|section 8
.include "fpsp.h"
|xref ovf_r_x2
|xref ovf_r_x3
|xref store
|xref real_ovfl
|xref real_inex
|xref fpsp_done
|xref g_opcls
|xref b1238_fix
.global fpsp_ovfl
fpsp_ovfl:
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)
|
| The 040 doesn't set the AINEX bit in the FPSR, the following
| line temporarily rectifies this error.
|
bsetb #ainex_bit,FPSR_AEXCEPT(%a6)
|
bsrl ovf_adj |denormalize, round & store interm op
|
| if overflow traps not enabled check for inexact exception
|
btstb #ovfl_bit,FPCR_ENABLE(%a6)
beqs ck_inex
|
btstb #E3,E_BYTE(%a6)
beqs no_e3_1
bfextu CMDREG3B(%a6){#6:#3},%d0 |get dest reg no
bclrb %d0,FPR_DIRTY_BITS(%a6) |clr dest dirty bit
bsrl b1238_fix
movel USER_FPSR(%a6),FPSR_SHADOW(%a6)
orl #sx_mask,E_BYTE(%a6)
no_e3_1:
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_ovfl
|
| It is possible to have either inex2 or inex1 exceptions with the
| ovfl. 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:
| move.b FPCR_ENABLE(%a6),%d0
| and.b FPSR_EXCEPT(%a6),%d0
| andi.b #$3,%d0
btstb #inex2_bit,FPCR_ENABLE(%a6)
beqs ovfl_exit
|
| Inexact enabled and reported, and we must take an inexact exception.
|
take_inex:
btstb #E3,E_BYTE(%a6)
beqs no_e3_2
bfextu CMDREG3B(%a6){#6:#3},%d0 |get dest reg no
bclrb %d0,FPR_DIRTY_BITS(%a6) |clr dest dirty bit
bsrl b1238_fix
movel USER_FPSR(%a6),FPSR_SHADOW(%a6)
orl #sx_mask,E_BYTE(%a6)
no_e3_2:
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
ovfl_exit:
bclrb #E3,E_BYTE(%a6) |test and clear E3 bit
beqs e1_set
|
| Clear dirty bit on dest resister in the frame before branching
| to b1238_fix.
|
bfextu CMDREG3B(%a6){#6:#3},%d0 |get dest reg no
bclrb %d0,FPR_DIRTY_BITS(%a6) |clr dest dirty bit
bsrl b1238_fix |test for bug1238 case
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
e1_set:
moveml USER_DA(%a6),%d0-%d1/%a0-%a1
fmovemx USER_FP0(%a6),%fp0-%fp3
fmoveml USER_FPCR(%a6),%fpcr/%fpsr/%fpiar
unlk %a6
bral fpsp_done
|
| ovf_adj
|
ovf_adj:
|
| Have a0 point to the correct operand.
|
btstb #E3,E_BYTE(%a6) |test E3 bit
beqs ovf_e1
lea WBTEMP(%a6),%a0
bras ovf_com
ovf_e1:
lea ETEMP(%a6),%a0
ovf_com:
bclrb #sign_bit,LOCAL_EX(%a0)
sne LOCAL_SGN(%a0)
bsrl g_opcls |returns opclass in d0
cmpiw #3,%d0 |check for opclass3
bnes not_opc011
|
| FPSR_CC is saved and restored because ovf_r_x3 affects it. The
| CCs are defined to be 'not affected' for the opclass3 instruction.
|
moveb FPSR_CC(%a6),L_SCR1(%a6)
bsrl ovf_r_x3 |returns a0 pointing to result
moveb L_SCR1(%a6),FPSR_CC(%a6)
bral store |stores to memory or register
not_opc011:
bsrl ovf_r_x2 |returns a0 pointing to result
bral store |stores to memory or register
|end
|
