diff options
Diffstat (limited to 'kernel/arch/m68k/fpsp040/scale.S')
| -rw-r--r-- | kernel/arch/m68k/fpsp040/scale.S | 370 |
1 files changed, 370 insertions, 0 deletions
diff --git a/kernel/arch/m68k/fpsp040/scale.S b/kernel/arch/m68k/fpsp040/scale.S new file mode 100644 index 000000000..04829dd4f --- /dev/null +++ b/kernel/arch/m68k/fpsp040/scale.S @@ -0,0 +1,370 @@ +| +| scale.sa 3.3 7/30/91 +| +| The entry point sSCALE computes the destination operand +| scaled by the source operand. If the absolute value of +| the source operand is (>= 2^14) an overflow or underflow +| is returned. +| +| The entry point sscale is called from do_func to emulate +| the fscale unimplemented instruction. +| +| Input: Double-extended destination operand in FPTEMP, +| double-extended source operand in ETEMP. +| +| Output: The function returns scale(X,Y) to fp0. +| +| Modifies: fp0. +| +| Algorithm: +| +| 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. + +|SCALE idnt 2,1 | Motorola 040 Floating Point Software Package + + |section 8 + +#include "fpsp.h" + + |xref t_ovfl2 + |xref t_unfl + |xref round + |xref t_resdnrm + +SRC_BNDS: .short 0x3fff,0x400c + +| +| This entry point is used by the unimplemented instruction exception +| handler. +| +| +| +| FSCALE +| + .global sscale +sscale: + fmovel #0,%fpcr |clr user enabled exc + clrl %d1 + movew FPTEMP(%a6),%d1 |get dest exponent + smi L_SCR1(%a6) |use L_SCR1 to hold sign + andil #0x7fff,%d1 |strip sign + movew ETEMP(%a6),%d0 |check src bounds + andiw #0x7fff,%d0 |clr sign bit + cmp2w SRC_BNDS,%d0 + bccs src_in + cmpiw #0x400c,%d0 |test for too large + bge src_out +| +| The source input is below 1, so we check for denormalized numbers +| and set unfl. +| +src_small: + moveb DTAG(%a6),%d0 + andib #0xe0,%d0 + tstb %d0 + beqs no_denorm + st STORE_FLG(%a6) |dest already contains result + orl #unfl_mask,USER_FPSR(%a6) |set UNFL +den_done: + leal FPTEMP(%a6),%a0 + bra t_resdnrm +no_denorm: + fmovel USER_FPCR(%a6),%FPCR + fmovex FPTEMP(%a6),%fp0 |simply return dest + rts + + +| +| Source is within 2^14 range. To perform the int operation, +| move it to d0. +| +src_in: + fmovex ETEMP(%a6),%fp0 |move in src for int + fmovel #rz_mode,%fpcr |force rz for src conversion + fmovel %fp0,%d0 |int src to d0 + fmovel #0,%FPSR |clr status from above + tstw ETEMP(%a6) |check src sign + blt src_neg +| +| Source is positive. Add the src to the dest exponent. +| The result can be denormalized, if src = 0, or overflow, +| if the result of the add sets a bit in the upper word. +| +src_pos: + tstw %d1 |check for denorm + beq dst_dnrm + addl %d0,%d1 |add src to dest exp + beqs denorm |if zero, result is denorm + cmpil #0x7fff,%d1 |test for overflow + bges ovfl + tstb L_SCR1(%a6) + beqs spos_pos + orw #0x8000,%d1 +spos_pos: + movew %d1,FPTEMP(%a6) |result in FPTEMP + fmovel USER_FPCR(%a6),%FPCR + fmovex FPTEMP(%a6),%fp0 |write result to fp0 + rts +ovfl: + tstb L_SCR1(%a6) + beqs sovl_pos + orw #0x8000,%d1 +sovl_pos: + movew FPTEMP(%a6),ETEMP(%a6) |result in ETEMP + movel FPTEMP_HI(%a6),ETEMP_HI(%a6) + movel FPTEMP_LO(%a6),ETEMP_LO(%a6) + bra t_ovfl2 + +denorm: + tstb L_SCR1(%a6) + beqs den_pos + orw #0x8000,%d1 +den_pos: + tstl FPTEMP_HI(%a6) |check j bit + blts nden_exit |if set, not denorm + movew %d1,ETEMP(%a6) |input expected in ETEMP + movel FPTEMP_HI(%a6),ETEMP_HI(%a6) + movel FPTEMP_LO(%a6),ETEMP_LO(%a6) + orl #unfl_bit,USER_FPSR(%a6) |set unfl + leal ETEMP(%a6),%a0 + bra t_resdnrm +nden_exit: + movew %d1,FPTEMP(%a6) |result in FPTEMP + fmovel USER_FPCR(%a6),%FPCR + fmovex FPTEMP(%a6),%fp0 |write result to fp0 + rts + +| +| Source is negative. Add the src to the dest exponent. +| (The result exponent will be reduced). The result can be +| denormalized. +| +src_neg: + addl %d0,%d1 |add src to dest + beqs denorm |if zero, result is denorm + blts fix_dnrm |if negative, result is +| ;needing denormalization + tstb L_SCR1(%a6) + beqs sneg_pos + orw #0x8000,%d1 +sneg_pos: + movew %d1,FPTEMP(%a6) |result in FPTEMP + fmovel USER_FPCR(%a6),%FPCR + fmovex FPTEMP(%a6),%fp0 |write result to fp0 + rts + + +| +| The result exponent is below denorm value. Test for catastrophic +| underflow and force zero if true. If not, try to shift the +| mantissa right until a zero exponent exists. +| +fix_dnrm: + cmpiw #0xffc0,%d1 |lower bound for normalization + blt fix_unfl |if lower, catastrophic unfl + movew %d1,%d0 |use d0 for exp + movel %d2,-(%a7) |free d2 for norm + movel FPTEMP_HI(%a6),%d1 + movel FPTEMP_LO(%a6),%d2 + clrl L_SCR2(%a6) +fix_loop: + addw #1,%d0 |drive d0 to 0 + lsrl #1,%d1 |while shifting the + roxrl #1,%d2 |mantissa to the right + bccs no_carry + st L_SCR2(%a6) |use L_SCR2 to capture inex +no_carry: + tstw %d0 |it is finished when + blts fix_loop |d0 is zero or the mantissa + tstb L_SCR2(%a6) + beqs tst_zero + orl #unfl_inx_mask,USER_FPSR(%a6) +| ;set unfl, aunfl, ainex +| +| Test for zero. If zero, simply use fmove to return +/- zero +| to the fpu. +| +tst_zero: + clrw FPTEMP_EX(%a6) + tstb L_SCR1(%a6) |test for sign + beqs tst_con + orw #0x8000,FPTEMP_EX(%a6) |set sign bit +tst_con: + movel %d1,FPTEMP_HI(%a6) + movel %d2,FPTEMP_LO(%a6) + movel (%a7)+,%d2 + tstl %d1 + bnes not_zero + tstl FPTEMP_LO(%a6) + bnes not_zero +| +| Result is zero. Check for rounding mode to set lsb. If the +| mode is rp, and the zero is positive, return smallest denorm. +| If the mode is rm, and the zero is negative, return smallest +| negative denorm. +| + btstb #5,FPCR_MODE(%a6) |test if rm or rp + beqs no_dir + btstb #4,FPCR_MODE(%a6) |check which one + beqs zer_rm +zer_rp: + tstb L_SCR1(%a6) |check sign + bnes no_dir |if set, neg op, no inc + movel #1,FPTEMP_LO(%a6) |set lsb + bras sm_dnrm +zer_rm: + tstb L_SCR1(%a6) |check sign + beqs no_dir |if clr, neg op, no inc + movel #1,FPTEMP_LO(%a6) |set lsb + orl #neg_mask,USER_FPSR(%a6) |set N + bras sm_dnrm +no_dir: + fmovel USER_FPCR(%a6),%FPCR + fmovex FPTEMP(%a6),%fp0 |use fmove to set cc's + rts + +| +| The rounding mode changed the zero to a smallest denorm. Call +| t_resdnrm with exceptional operand in ETEMP. +| +sm_dnrm: + movel FPTEMP_EX(%a6),ETEMP_EX(%a6) + movel FPTEMP_HI(%a6),ETEMP_HI(%a6) + movel FPTEMP_LO(%a6),ETEMP_LO(%a6) + leal ETEMP(%a6),%a0 + bra t_resdnrm + +| +| Result is still denormalized. +| +not_zero: + orl #unfl_mask,USER_FPSR(%a6) |set unfl + tstb L_SCR1(%a6) |check for sign + beqs fix_exit + orl #neg_mask,USER_FPSR(%a6) |set N +fix_exit: + bras sm_dnrm + + +| +| The result has underflowed to zero. Return zero and set +| unfl, aunfl, and ainex. +| +fix_unfl: + orl #unfl_inx_mask,USER_FPSR(%a6) + btstb #5,FPCR_MODE(%a6) |test if rm or rp + beqs no_dir2 + btstb #4,FPCR_MODE(%a6) |check which one + beqs zer_rm2 +zer_rp2: + tstb L_SCR1(%a6) |check sign + bnes no_dir2 |if set, neg op, no inc + clrl FPTEMP_EX(%a6) + clrl FPTEMP_HI(%a6) + movel #1,FPTEMP_LO(%a6) |set lsb + bras sm_dnrm |return smallest denorm +zer_rm2: + tstb L_SCR1(%a6) |check sign + beqs no_dir2 |if clr, neg op, no inc + movew #0x8000,FPTEMP_EX(%a6) + clrl FPTEMP_HI(%a6) + movel #1,FPTEMP_LO(%a6) |set lsb + orl #neg_mask,USER_FPSR(%a6) |set N + bra sm_dnrm |return smallest denorm + +no_dir2: + tstb L_SCR1(%a6) + bges pos_zero +neg_zero: + clrl FP_SCR1(%a6) |clear the exceptional operand + clrl FP_SCR1+4(%a6) |for gen_except. + clrl FP_SCR1+8(%a6) + fmoves #0x80000000,%fp0 + rts +pos_zero: + clrl FP_SCR1(%a6) |clear the exceptional operand + clrl FP_SCR1+4(%a6) |for gen_except. + clrl FP_SCR1+8(%a6) + fmoves #0x00000000,%fp0 + rts + +| +| The destination is a denormalized number. It must be handled +| by first shifting the bits in the mantissa until it is normalized, +| then adding the remainder of the source to the exponent. +| +dst_dnrm: + moveml %d2/%d3,-(%a7) + movew FPTEMP_EX(%a6),%d1 + movel FPTEMP_HI(%a6),%d2 + movel FPTEMP_LO(%a6),%d3 +dst_loop: + tstl %d2 |test for normalized result + blts dst_norm |exit loop if so + tstl %d0 |otherwise, test shift count + beqs dst_fin |if zero, shifting is done + subil #1,%d0 |dec src + lsll #1,%d3 + roxll #1,%d2 + bras dst_loop +| +| Destination became normalized. Simply add the remaining +| portion of the src to the exponent. +| +dst_norm: + addw %d0,%d1 |dst is normalized; add src + tstb L_SCR1(%a6) + beqs dnrm_pos + orl #0x8000,%d1 +dnrm_pos: + movemw %d1,FPTEMP_EX(%a6) + moveml %d2,FPTEMP_HI(%a6) + moveml %d3,FPTEMP_LO(%a6) + fmovel USER_FPCR(%a6),%FPCR + fmovex FPTEMP(%a6),%fp0 + moveml (%a7)+,%d2/%d3 + rts + +| +| Destination remained denormalized. Call t_excdnrm with +| exceptional operand in ETEMP. +| +dst_fin: + tstb L_SCR1(%a6) |check for sign + beqs dst_exit + orl #neg_mask,USER_FPSR(%a6) |set N + orl #0x8000,%d1 +dst_exit: + movemw %d1,ETEMP_EX(%a6) + moveml %d2,ETEMP_HI(%a6) + moveml %d3,ETEMP_LO(%a6) + orl #unfl_mask,USER_FPSR(%a6) |set unfl + moveml (%a7)+,%d2/%d3 + leal ETEMP(%a6),%a0 + bra t_resdnrm + +| +| Source is outside of 2^14 range. Test the sign and branch +| to the appropriate exception handler. +| +src_out: + tstb L_SCR1(%a6) + beqs scro_pos + orl #0x8000,%d1 +scro_pos: + movel FPTEMP_HI(%a6),ETEMP_HI(%a6) + movel FPTEMP_LO(%a6),ETEMP_LO(%a6) + tstw ETEMP(%a6) + blts res_neg +res_pos: + movew %d1,ETEMP(%a6) |result in ETEMP + bra t_ovfl2 +res_neg: + movew %d1,ETEMP(%a6) |result in ETEMP + leal ETEMP(%a6),%a0 + bra t_unfl + |end |