diff options
Diffstat (limited to 'arch/i386/math-emu/reg_round.S')
| -rw-r--r-- | arch/i386/math-emu/reg_round.S | 708 |
1 files changed, 0 insertions, 708 deletions
diff --git a/arch/i386/math-emu/reg_round.S b/arch/i386/math-emu/reg_round.S deleted file mode 100644 index d1d4e48b4f67..000000000000 --- a/arch/i386/math-emu/reg_round.S +++ /dev/null @@ -1,708 +0,0 @@ - .file "reg_round.S" -/*---------------------------------------------------------------------------+ - | reg_round.S | - | | - | Rounding/truncation/etc for FPU basic arithmetic functions. | - | | - | Copyright (C) 1993,1995,1997 | - | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, | - | Australia. E-mail billm@suburbia.net | - | | - | This code has four possible entry points. | - | The following must be entered by a jmp instruction: | - | fpu_reg_round, fpu_reg_round_sqrt, and fpu_Arith_exit. | - | | - | The FPU_round entry point is intended to be used by C code. | - | From C, call as: | - | int FPU_round(FPU_REG *arg, unsigned int extent, unsigned int control_w) | - | | - | Return value is the tag of the answer, or-ed with FPU_Exception if | - | one was raised, or -1 on internal error. | - | | - | For correct "up" and "down" rounding, the argument must have the correct | - | sign. | - | | - +---------------------------------------------------------------------------*/ - -/*---------------------------------------------------------------------------+ - | Four entry points. | - | | - | Needed by both the fpu_reg_round and fpu_reg_round_sqrt entry points: | - | %eax:%ebx 64 bit significand | - | %edx 32 bit extension of the significand | - | %edi pointer to an FPU_REG for the result to be stored | - | stack calling function must have set up a C stack frame and | - | pushed %esi, %edi, and %ebx | - | | - | Needed just for the fpu_reg_round_sqrt entry point: | - | %cx A control word in the same format as the FPU control word. | - | Otherwise, PARAM4 must give such a value. | - | | - | | - | The significand and its extension are assumed to be exact in the | - | following sense: | - | If the significand by itself is the exact result then the significand | - | extension (%edx) must contain 0, otherwise the significand extension | - | must be non-zero. | - | If the significand extension is non-zero then the significand is | - | smaller than the magnitude of the correct exact result by an amount | - | greater than zero and less than one ls bit of the significand. | - | The significand extension is only required to have three possible | - | non-zero values: | - | less than 0x80000000 <=> the significand is less than 1/2 an ls | - | bit smaller than the magnitude of the | - | true exact result. | - | exactly 0x80000000 <=> the significand is exactly 1/2 an ls bit | - | smaller than the magnitude of the true | - | exact result. | - | greater than 0x80000000 <=> the significand is more than 1/2 an ls | - | bit smaller than the magnitude of the | - | true exact result. | - | | - +---------------------------------------------------------------------------*/ - -/*---------------------------------------------------------------------------+ - | The code in this module has become quite complex, but it should handle | - | all of the FPU flags which are set at this stage of the basic arithmetic | - | computations. | - | There are a few rare cases where the results are not set identically to | - | a real FPU. These require a bit more thought because at this stage the | - | results of the code here appear to be more consistent... | - | This may be changed in a future version. | - +---------------------------------------------------------------------------*/ - - -#include "fpu_emu.h" -#include "exception.h" -#include "control_w.h" - -/* Flags for FPU_bits_lost */ -#define LOST_DOWN $1 -#define LOST_UP $2 - -/* Flags for FPU_denormal */ -#define DENORMAL $1 -#define UNMASKED_UNDERFLOW $2 - - -#ifndef NON_REENTRANT_FPU -/* Make the code re-entrant by putting - local storage on the stack: */ -#define FPU_bits_lost (%esp) -#define FPU_denormal 1(%esp) - -#else -/* Not re-entrant, so we can gain speed by putting - local storage in a static area: */ -.data - .align 4,0 -FPU_bits_lost: - .byte 0 -FPU_denormal: - .byte 0 -#endif /* NON_REENTRANT_FPU */ - - -.text -.globl fpu_reg_round -.globl fpu_Arith_exit - -/* Entry point when called from C */ -ENTRY(FPU_round) - pushl %ebp - movl %esp,%ebp - pushl %esi - pushl %edi - pushl %ebx - - movl PARAM1,%edi - movl SIGH(%edi),%eax - movl SIGL(%edi),%ebx - movl PARAM2,%edx - -fpu_reg_round: /* Normal entry point */ - movl PARAM4,%ecx - -#ifndef NON_REENTRANT_FPU - pushl %ebx /* adjust the stack pointer */ -#endif /* NON_REENTRANT_FPU */ - -#ifdef PARANOID -/* Cannot use this here yet */ -/* orl %eax,%eax */ -/* jns L_entry_bugged */ -#endif /* PARANOID */ - - cmpw EXP_UNDER,EXP(%edi) - jle L_Make_denorm /* The number is a de-normal */ - - movb $0,FPU_denormal /* 0 -> not a de-normal */ - -Denorm_done: - movb $0,FPU_bits_lost /* No bits yet lost in rounding */ - - movl %ecx,%esi - andl CW_PC,%ecx - cmpl PR_64_BITS,%ecx - je LRound_To_64 - - cmpl PR_53_BITS,%ecx - je LRound_To_53 - - cmpl PR_24_BITS,%ecx - je LRound_To_24 - -#ifdef PECULIAR_486 -/* With the precision control bits set to 01 "(reserved)", a real 80486 - behaves as if the precision control bits were set to 11 "64 bits" */ - cmpl PR_RESERVED_BITS,%ecx - je LRound_To_64 -#ifdef PARANOID - jmp L_bugged_denorm_486 -#endif /* PARANOID */ -#else -#ifdef PARANOID - jmp L_bugged_denorm /* There is no bug, just a bad control word */ -#endif /* PARANOID */ -#endif /* PECULIAR_486 */ - - -/* Round etc to 24 bit precision */ -LRound_To_24: - movl %esi,%ecx - andl CW_RC,%ecx - cmpl RC_RND,%ecx - je LRound_nearest_24 - - cmpl RC_CHOP,%ecx - je LCheck_truncate_24 - - cmpl RC_UP,%ecx /* Towards +infinity */ - je LUp_24 - - cmpl RC_DOWN,%ecx /* Towards -infinity */ - je LDown_24 - -#ifdef PARANOID - jmp L_bugged_round24 -#endif /* PARANOID */ - -LUp_24: - cmpb SIGN_POS,PARAM5 - jne LCheck_truncate_24 /* If negative then up==truncate */ - - jmp LCheck_24_round_up - -LDown_24: - cmpb SIGN_POS,PARAM5 - je LCheck_truncate_24 /* If positive then down==truncate */ - -LCheck_24_round_up: - movl %eax,%ecx - andl $0x000000ff,%ecx - orl %ebx,%ecx - orl %edx,%ecx - jnz LDo_24_round_up - jmp L_Re_normalise - -LRound_nearest_24: - /* Do rounding of the 24th bit if needed (nearest or even) */ - movl %eax,%ecx - andl $0x000000ff,%ecx - cmpl $0x00000080,%ecx - jc LCheck_truncate_24 /* less than half, no increment needed */ - - jne LGreater_Half_24 /* greater than half, increment needed */ - - /* Possibly half, we need to check the ls bits */ - orl %ebx,%ebx - jnz LGreater_Half_24 /* greater than half, increment needed */ - - orl %edx,%edx - jnz LGreater_Half_24 /* greater than half, increment needed */ - - /* Exactly half, increment only if 24th bit is 1 (round to even) */ - testl $0x00000100,%eax - jz LDo_truncate_24 - -LGreater_Half_24: /* Rounding: increment at the 24th bit */ -LDo_24_round_up: - andl $0xffffff00,%eax /* Truncate to 24 bits */ - xorl %ebx,%ebx - movb LOST_UP,FPU_bits_lost - addl $0x00000100,%eax - jmp LCheck_Round_Overflow - -LCheck_truncate_24: - movl %eax,%ecx - andl $0x000000ff,%ecx - orl %ebx,%ecx - orl %edx,%ecx - jz L_Re_normalise /* No truncation needed */ - -LDo_truncate_24: - andl $0xffffff00,%eax /* Truncate to 24 bits */ - xorl %ebx,%ebx - movb LOST_DOWN,FPU_bits_lost - jmp L_Re_normalise - - -/* Round etc to 53 bit precision */ -LRound_To_53: - movl %esi,%ecx - andl CW_RC,%ecx - cmpl RC_RND,%ecx - je LRound_nearest_53 - - cmpl RC_CHOP,%ecx - je LCheck_truncate_53 - - cmpl RC_UP,%ecx /* Towards +infinity */ - je LUp_53 - - cmpl RC_DOWN,%ecx /* Towards -infinity */ - je LDown_53 - -#ifdef PARANOID - jmp L_bugged_round53 -#endif /* PARANOID */ - -LUp_53: - cmpb SIGN_POS,PARAM5 - jne LCheck_truncate_53 /* If negative then up==truncate */ - - jmp LCheck_53_round_up - -LDown_53: - cmpb SIGN_POS,PARAM5 - je LCheck_truncate_53 /* If positive then down==truncate */ - -LCheck_53_round_up: - movl %ebx,%ecx - andl $0x000007ff,%ecx - orl %edx,%ecx - jnz LDo_53_round_up - jmp L_Re_normalise - -LRound_nearest_53: - /* Do rounding of the 53rd bit if needed (nearest or even) */ - movl %ebx,%ecx - andl $0x000007ff,%ecx - cmpl $0x00000400,%ecx - jc LCheck_truncate_53 /* less than half, no increment needed */ - - jnz LGreater_Half_53 /* greater than half, increment needed */ - - /* Possibly half, we need to check the ls bits */ - orl %edx,%edx - jnz LGreater_Half_53 /* greater than half, increment needed */ - - /* Exactly half, increment only if 53rd bit is 1 (round to even) */ - testl $0x00000800,%ebx - jz LTruncate_53 - -LGreater_Half_53: /* Rounding: increment at the 53rd bit */ -LDo_53_round_up: - movb LOST_UP,FPU_bits_lost - andl $0xfffff800,%ebx /* Truncate to 53 bits */ - addl $0x00000800,%ebx - adcl $0,%eax - jmp LCheck_Round_Overflow - -LCheck_truncate_53: - movl %ebx,%ecx - andl $0x000007ff,%ecx - orl %edx,%ecx - jz L_Re_normalise - -LTruncate_53: - movb LOST_DOWN,FPU_bits_lost - andl $0xfffff800,%ebx /* Truncate to 53 bits */ - jmp L_Re_normalise - - -/* Round etc to 64 bit precision */ -LRound_To_64: - movl %esi,%ecx - andl CW_RC,%ecx - cmpl RC_RND,%ecx - je LRound_nearest_64 - - cmpl RC_CHOP,%ecx - je LCheck_truncate_64 - - cmpl RC_UP,%ecx /* Towards +infinity */ - je LUp_64 - - cmpl RC_DOWN,%ecx /* Towards -infinity */ - je LDown_64 - -#ifdef PARANOID - jmp L_bugged_round64 -#endif /* PARANOID */ - -LUp_64: - cmpb SIGN_POS,PARAM5 - jne LCheck_truncate_64 /* If negative then up==truncate */ - - orl %edx,%edx - jnz LDo_64_round_up - jmp L_Re_normalise - -LDown_64: - cmpb SIGN_POS,PARAM5 - je LCheck_truncate_64 /* If positive then down==truncate */ - - orl %edx,%edx - jnz LDo_64_round_up - jmp L_Re_normalise - -LRound_nearest_64: - cmpl $0x80000000,%edx - jc LCheck_truncate_64 - - jne LDo_64_round_up - - /* Now test for round-to-even */ - testb $1,%bl - jz LCheck_truncate_64 - -LDo_64_round_up: - movb LOST_UP,FPU_bits_lost - addl $1,%ebx - adcl $0,%eax - -LCheck_Round_Overflow: - jnc L_Re_normalise - - /* Overflow, adjust the result (significand to 1.0) */ - rcrl $1,%eax - rcrl $1,%ebx - incw EXP(%edi) - jmp L_Re_normalise - -LCheck_truncate_64: - orl %edx,%edx - jz L_Re_normalise - -LTruncate_64: - movb LOST_DOWN,FPU_bits_lost - -L_Re_normalise: - testb $0xff,FPU_denormal - jnz Normalise_result - -L_Normalised: - movl TAG_Valid,%edx - -L_deNormalised: - cmpb LOST_UP,FPU_bits_lost - je L_precision_lost_up - - cmpb LOST_DOWN,FPU_bits_lost - je L_precision_lost_down - -L_no_precision_loss: - /* store the result */ - -L_Store_significand: - movl %eax,SIGH(%edi) - movl %ebx,SIGL(%edi) - - cmpw EXP_OVER,EXP(%edi) - jge L_overflow - - movl %edx,%eax - - /* Convert the exponent to 80x87 form. */ - addw EXTENDED_Ebias,EXP(%edi) - andw $0x7fff,EXP(%edi) - -fpu_reg_round_signed_special_exit: - - cmpb SIGN_POS,PARAM5 - je fpu_reg_round_special_exit - - orw $0x8000,EXP(%edi) /* Negative sign for the result. */ - -fpu_reg_round_special_exit: - -#ifndef NON_REENTRANT_FPU - popl %ebx /* adjust the stack pointer */ -#endif /* NON_REENTRANT_FPU */ - -fpu_Arith_exit: - popl %ebx - popl %edi - popl %esi - leave - ret - - -/* - * Set the FPU status flags to represent precision loss due to - * round-up. - */ -L_precision_lost_up: - push %edx - push %eax - call set_precision_flag_up - popl %eax - popl %edx - jmp L_no_precision_loss - -/* - * Set the FPU status flags to represent precision loss due to - * truncation. - */ -L_precision_lost_down: - push %edx - push %eax - call set_precision_flag_down - popl %eax - popl %edx - jmp L_no_precision_loss - - -/* - * The number is a denormal (which might get rounded up to a normal) - * Shift the number right the required number of bits, which will - * have to be undone later... - */ -L_Make_denorm: - /* The action to be taken depends upon whether the underflow - exception is masked */ - testb CW_Underflow,%cl /* Underflow mask. */ - jz Unmasked_underflow /* Do not make a denormal. */ - - movb DENORMAL,FPU_denormal - - pushl %ecx /* Save */ - movw EXP_UNDER+1,%cx - subw EXP(%edi),%cx - - cmpw $64,%cx /* shrd only works for 0..31 bits */ - jnc Denorm_shift_more_than_63 - - cmpw $32,%cx /* shrd only works for 0..31 bits */ - jnc Denorm_shift_more_than_32 - -/* - * We got here without jumps by assuming that the most common requirement - * is for a small de-normalising shift. - * Shift by [1..31] bits - */ - addw %cx,EXP(%edi) - orl %edx,%edx /* extension */ - setne %ch /* Save whether %edx is non-zero */ - xorl %edx,%edx - shrd %cl,%ebx,%edx - shrd %cl,%eax,%ebx - shr %cl,%eax - orb %ch,%dl - popl %ecx - jmp Denorm_done - -/* Shift by [32..63] bits */ -Denorm_shift_more_than_32: - addw %cx,EXP(%edi) - subb $32,%cl - orl %edx,%edx - setne %ch - orb %ch,%bl - xorl %edx,%edx - shrd %cl,%ebx,%edx - shrd %cl,%eax,%ebx - shr %cl,%eax - orl %edx,%edx /* test these 32 bits */ - setne %cl - orb %ch,%bl - orb %cl,%bl - movl %ebx,%edx - movl %eax,%ebx - xorl %eax,%eax - popl %ecx - jmp Denorm_done - -/* Shift by [64..) bits */ -Denorm_shift_more_than_63: - cmpw $64,%cx - jne Denorm_shift_more_than_64 - -/* Exactly 64 bit shift */ - addw %cx,EXP(%edi) - xorl %ecx,%ecx - orl %edx,%edx - setne %cl - orl %ebx,%ebx - setne %ch - orb %ch,%cl - orb %cl,%al - movl %eax,%edx - xorl %eax,%eax - xorl %ebx,%ebx - popl %ecx - jmp Denorm_done - -Denorm_shift_more_than_64: - movw EXP_UNDER+1,EXP(%edi) -/* This is easy, %eax must be non-zero, so.. */ - movl $1,%edx - xorl %eax,%eax - xorl %ebx,%ebx - popl %ecx - jmp Denorm_done - - -Unmasked_underflow: - movb UNMASKED_UNDERFLOW,FPU_denormal - jmp Denorm_done - - -/* Undo the de-normalisation. */ -Normalise_result: - cmpb UNMASKED_UNDERFLOW,FPU_denormal - je Signal_underflow - -/* The number must be a denormal if we got here. */ -#ifdef PARANOID - /* But check it... just in case. */ - cmpw EXP_UNDER+1,EXP(%edi) - jne L_norm_bugged -#endif /* PARANOID */ - -#ifdef PECULIAR_486 - /* - * This implements a special feature of 80486 behaviour. - * Underflow will be signalled even if the number is - * not a denormal after rounding. - * This difference occurs only for masked underflow, and not - * in the unmasked case. - * Actual 80486 behaviour differs from this in some circumstances. - */ - orl %eax,%eax /* ms bits */ - js LPseudoDenormal /* Will be masked underflow */ -#else - orl %eax,%eax /* ms bits */ - js L_Normalised /* No longer a denormal */ -#endif /* PECULIAR_486 */ - - jnz LDenormal_adj_exponent - - orl %ebx,%ebx - jz L_underflow_to_zero /* The contents are zero */ - -LDenormal_adj_exponent: - decw EXP(%edi) - -LPseudoDenormal: - testb $0xff,FPU_bits_lost /* bits lost == underflow */ - movl TAG_Special,%edx - jz L_deNormalised - - /* There must be a masked underflow */ - push %eax - pushl EX_Underflow - call EXCEPTION - popl %eax - popl %eax - movl TAG_Special,%edx - jmp L_deNormalised - - -/* - * The operations resulted in a number too small to represent. - * Masked response. - */ -L_underflow_to_zero: - push %eax - call set_precision_flag_down - popl %eax - - push %eax - pushl EX_Underflow - call EXCEPTION - popl %eax - popl %eax - -/* Reduce the exponent to EXP_UNDER */ - movw EXP_UNDER,EXP(%edi) - movl TAG_Zero,%edx - jmp L_Store_significand - - -/* The operations resulted in a number too large to represent. */ -L_overflow: - addw EXTENDED_Ebias,EXP(%edi) /* Set for unmasked response. */ - push %edi - call arith_overflow - pop %edi - jmp fpu_reg_round_signed_special_exit - - -Signal_underflow: - /* The number may have been changed to a non-denormal */ - /* by the rounding operations. */ - cmpw EXP_UNDER,EXP(%edi) - jle Do_unmasked_underflow - - jmp L_Normalised - -Do_unmasked_underflow: - /* Increase the exponent by the magic number */ - addw $(3*(1<<13)),EXP(%edi) - push %eax - pushl EX_Underflow - call EXCEPTION - popl %eax - popl %eax - jmp L_Normalised - - -#ifdef PARANOID -#ifdef PECULIAR_486 -L_bugged_denorm_486: - pushl EX_INTERNAL|0x236 - call EXCEPTION - popl %ebx - jmp L_exception_exit -#else -L_bugged_denorm: - pushl EX_INTERNAL|0x230 - call EXCEPTION - popl %ebx - jmp L_exception_exit -#endif /* PECULIAR_486 */ - -L_bugged_round24: - pushl EX_INTERNAL|0x231 - call EXCEPTION - popl %ebx - jmp L_exception_exit - -L_bugged_round53: - pushl EX_INTERNAL|0x232 - call EXCEPTION - popl %ebx - jmp L_exception_exit - -L_bugged_round64: - pushl EX_INTERNAL|0x233 - call EXCEPTION - popl %ebx - jmp L_exception_exit - -L_norm_bugged: - pushl EX_INTERNAL|0x234 - call EXCEPTION - popl %ebx - jmp L_exception_exit - -L_entry_bugged: - pushl EX_INTERNAL|0x235 - call EXCEPTION - popl %ebx -L_exception_exit: - mov $-1,%eax - jmp fpu_reg_round_special_exit -#endif /* PARANOID */ |