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Diffstat (limited to 'arch/m68k/fpsp040/x_unfl.S')
| -rw-r--r-- | arch/m68k/fpsp040/x_unfl.S | 269 |
1 files changed, 269 insertions, 0 deletions
diff --git a/arch/m68k/fpsp040/x_unfl.S b/arch/m68k/fpsp040/x_unfl.S new file mode 100644 index 0000000..077fcc2 --- /dev/null +++ b/arch/m68k/fpsp040/x_unfl.S @@ -0,0 +1,269 @@ +| +| x_unfl.sa 3.4 7/1/91 +| +| fpsp_unfl --- FPSP handler for underflow exception +| +| Trap disabled results +| For 881/2 compatibility, sw must denormalize the intermediate +| result, then store the result. Denormalization is accomplished +| by taking the intermediate result (which is always normalized) and +| shifting the mantissa right while incrementing the exponent until +| it is equal to the denormalized exponent for the destination +| format. After denormalization, the result is rounded to the +| destination format. +| +| Trap enabled results +| All trap disabled code applies. In addition the exceptional +| operand needs to made available to the user with a bias of $6000 +| added to 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 +| + +| Copyright (C) Motorola, Inc. 1990 +| All Rights Reserved +| +| THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA +| The copyright notice above does not evidence any +| actual or intended publication of such source code.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_UNFL: |idnt 2,1 | Motorola 040 Floating Point Software Package + + |section 8 + +#include "fpsp.h" + + |xref denorm + |xref round + |xref store + |xref g_rndpr + |xref g_opcls + |xref g_dfmtou + |xref real_unfl + |xref real_inex + |xref fpsp_done + |xref b1238_fix + + .global fpsp_unfl +fpsp_unfl: + 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) + +| + bsrl unf_res |denormalize, round & store interm op +| +| If underflow exceptions are not enabled, check for inexact +| exception +| + btstb #unfl_bit,FPCR_ENABLE(%a6) + beqs ck_inex + + btstb #E3,E_BYTE(%a6) + beqs no_e3_1 +| +| 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) +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_unfl +| +| It is possible to have either inex2 or inex1 exceptions with the +| unfl. 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 + beqs unfl_done + +| +| Inexact enabled and reported, and we must take an inexact exception +| +take_inex: + btstb #E3,E_BYTE(%a6) + beqs no_e3_2 +| +| 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) +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 + +unfl_done: + bclrb #E3,E_BYTE(%a6) + beqs e1_set |if set then branch +| +| 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 +| +| unf_res --- underflow result calculation +| +unf_res: + bsrl g_rndpr |returns RND_PREC in d0 0=ext, +| ;1=sgl, 2=dbl +| ;we need the RND_PREC in the +| ;upper word for round + movew #0,-(%a7) + movew %d0,-(%a7) |copy RND_PREC to stack +| +| +| If the exception bit set is E3, the exceptional operand from the +| fpu is in WBTEMP; else it is in FPTEMP. +| + btstb #E3,E_BYTE(%a6) + beqs unf_E1 +unf_E3: + lea WBTEMP(%a6),%a0 |a0 now points to operand +| +| Test for fsgldiv and fsglmul. If the inst was one of these, then +| force the precision to extended for the denorm routine. Use +| the user's precision for the round routine. +| + movew CMDREG3B(%a6),%d1 |check for fsgldiv or fsglmul + andiw #0x7f,%d1 + cmpiw #0x30,%d1 |check for sgldiv + beqs unf_sgl + cmpiw #0x33,%d1 |check for sglmul + bnes unf_cont |if not, use fpcr prec in round +unf_sgl: + clrl %d0 + movew #0x1,(%a7) |override g_rndpr precision +| ;force single + bras unf_cont +unf_E1: + lea FPTEMP(%a6),%a0 |a0 now points to operand +unf_cont: + bclrb #sign_bit,LOCAL_EX(%a0) |clear sign bit + sne LOCAL_SGN(%a0) |store sign + + bsrl denorm |returns denorm, a0 points to it +| +| WARNING: +| ;d0 has guard,round sticky bit +| ;make sure that it is not corrupted +| ;before it reaches the round subroutine +| ;also ensure that a0 isn't corrupted + +| +| Set up d1 for round subroutine d1 contains the PREC/MODE +| information respectively on upper/lower register halves. +| + bfextu FPCR_MODE(%a6){#2:#2},%d1 |get mode from FPCR +| ;mode in lower d1 + addl (%a7)+,%d1 |merge PREC/MODE +| +| WARNING: a0 and d0 are assumed to be intact between the denorm and +| round subroutines. All code between these two subroutines +| must not corrupt a0 and d0. +| +| +| Perform Round +| Input: a0 points to input operand +| d0{31:29} has guard, round, sticky +| d1{01:00} has rounding mode +| d1{17:16} has rounding precision +| Output: a0 points to rounded operand +| + + bsrl round |returns rounded denorm at (a0) +| +| Differentiate between store to memory vs. store to register +| +unf_store: + bsrl g_opcls |returns opclass in d0{2:0} + cmpib #0x3,%d0 + bnes not_opc011 +| +| At this point, a store to memory is pending +| +opc011: + bsrl g_dfmtou + tstb %d0 + beqs ext_opc011 |If extended, do not subtract +| ;If destination format is sgl/dbl, + tstb LOCAL_HI(%a0) |If rounded result is normal,don't +| ;subtract + bmis ext_opc011 + subqw #1,LOCAL_EX(%a0) |account for denorm bias vs. +| ;normalized bias +| ; normalized denormalized +| ;single $7f $7e +| ;double $3ff $3fe +| +ext_opc011: + bsrl store |stores to memory + bras unf_done |finish up + +| +| At this point, a store to a float register is pending +| +not_opc011: + bsrl store |stores to float register +| ;a0 is not corrupted on a store to a +| ;float register. +| +| Set the condition codes according to result +| + tstl LOCAL_HI(%a0) |check upper mantissa + bnes ck_sgn + tstl LOCAL_LO(%a0) |check lower mantissa + bnes ck_sgn + bsetb #z_bit,FPSR_CC(%a6) |set condition codes if zero +ck_sgn: + btstb #sign_bit,LOCAL_EX(%a0) |check the sign bit + beqs unf_done + bsetb #neg_bit,FPSR_CC(%a6) + +| +| Finish. +| +unf_done: + btstb #inex2_bit,FPSR_EXCEPT(%a6) + beqs no_aunfl + bsetb #aunfl_bit,FPSR_AEXCEPT(%a6) +no_aunfl: + rts + + |end |