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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/i386/math-emu/reg_u_sub.S
downloadlinux-stericsson-2.6.12-rc2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'arch/i386/math-emu/reg_u_sub.S')
-rw-r--r--arch/i386/math-emu/reg_u_sub.S272
1 files changed, 272 insertions, 0 deletions
diff --git a/arch/i386/math-emu/reg_u_sub.S b/arch/i386/math-emu/reg_u_sub.S
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index 000000000000..1b6c24801d22
--- /dev/null
+++ b/arch/i386/math-emu/reg_u_sub.S
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+ .file "reg_u_sub.S"
+/*---------------------------------------------------------------------------+
+ | reg_u_sub.S |
+ | |
+ | Core floating point subtraction routine. |
+ | |
+ | Copyright (C) 1992,1993,1995,1997 |
+ | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
+ | E-mail billm@suburbia.net |
+ | |
+ | Call from C as: |
+ | int FPU_u_sub(FPU_REG *arg1, FPU_REG *arg2, FPU_REG *answ, |
+ | 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. |
+ | |
+ +---------------------------------------------------------------------------*/
+
+/*
+ | Kernel subtraction routine FPU_u_sub(reg *arg1, reg *arg2, reg *answ).
+ | Takes two valid reg f.p. numbers (TAG_Valid), which are
+ | treated as unsigned numbers,
+ | and returns their difference as a TAG_Valid or TAG_Zero f.p.
+ | number.
+ | The first number (arg1) must be the larger.
+ | The returned number is normalized.
+ | Basic checks are performed if PARANOID is defined.
+ */
+
+#include "exception.h"
+#include "fpu_emu.h"
+#include "control_w.h"
+
+.text
+ENTRY(FPU_u_sub)
+ pushl %ebp
+ movl %esp,%ebp
+ pushl %esi
+ pushl %edi
+ pushl %ebx
+
+ movl PARAM1,%esi /* source 1 */
+ movl PARAM2,%edi /* source 2 */
+
+ movl PARAM6,%ecx
+ subl PARAM7,%ecx /* exp1 - exp2 */
+
+#ifdef PARANOID
+ /* source 2 is always smaller than source 1 */
+ js L_bugged_1
+
+ testl $0x80000000,SIGH(%edi) /* The args are assumed to be be normalized */
+ je L_bugged_2
+
+ testl $0x80000000,SIGH(%esi)
+ je L_bugged_2
+#endif /* PARANOID */
+
+/*--------------------------------------+
+ | Form a register holding the |
+ | smaller number |
+ +--------------------------------------*/
+ movl SIGH(%edi),%eax /* register ms word */
+ movl SIGL(%edi),%ebx /* register ls word */
+
+ movl PARAM3,%edi /* destination */
+ movl PARAM6,%edx
+ movw %dx,EXP(%edi) /* Copy exponent to destination */
+
+ xorl %edx,%edx /* register extension */
+
+/*--------------------------------------+
+ | Shift the temporary register |
+ | right the required number of |
+ | places. |
+ +--------------------------------------*/
+
+ cmpw $32,%cx /* shrd only works for 0..31 bits */
+ jnc L_more_than_31
+
+/* less than 32 bits */
+ shrd %cl,%ebx,%edx
+ shrd %cl,%eax,%ebx
+ shr %cl,%eax
+ jmp L_shift_done
+
+L_more_than_31:
+ cmpw $64,%cx
+ jnc L_more_than_63
+
+ subb $32,%cl
+ jz L_exactly_32
+
+ shrd %cl,%eax,%edx
+ shr %cl,%eax
+ orl %ebx,%ebx
+ jz L_more_31_no_low /* none of the lowest bits is set */
+
+ orl $1,%edx /* record the fact in the extension */
+
+L_more_31_no_low:
+ movl %eax,%ebx
+ xorl %eax,%eax
+ jmp L_shift_done
+
+L_exactly_32:
+ movl %ebx,%edx
+ movl %eax,%ebx
+ xorl %eax,%eax
+ jmp L_shift_done
+
+L_more_than_63:
+ cmpw $65,%cx
+ jnc L_more_than_64
+
+ /* Shift right by 64 bits */
+ movl %eax,%edx
+ orl %ebx,%ebx
+ jz L_more_63_no_low
+
+ orl $1,%edx
+ jmp L_more_63_no_low
+
+L_more_than_64:
+ jne L_more_than_65
+
+ /* Shift right by 65 bits */
+ /* Carry is clear if we get here */
+ movl %eax,%edx
+ rcrl %edx
+ jnc L_shift_65_nc
+
+ orl $1,%edx
+ jmp L_more_63_no_low
+
+L_shift_65_nc:
+ orl %ebx,%ebx
+ jz L_more_63_no_low
+
+ orl $1,%edx
+ jmp L_more_63_no_low
+
+L_more_than_65:
+ movl $1,%edx /* The shifted nr always at least one '1' */
+
+L_more_63_no_low:
+ xorl %ebx,%ebx
+ xorl %eax,%eax
+
+L_shift_done:
+L_subtr:
+/*------------------------------+
+ | Do the subtraction |
+ +------------------------------*/
+ xorl %ecx,%ecx
+ subl %edx,%ecx
+ movl %ecx,%edx
+ movl SIGL(%esi),%ecx
+ sbbl %ebx,%ecx
+ movl %ecx,%ebx
+ movl SIGH(%esi),%ecx
+ sbbl %eax,%ecx
+ movl %ecx,%eax
+
+#ifdef PARANOID
+ /* We can never get a borrow */
+ jc L_bugged
+#endif /* PARANOID */
+
+/*--------------------------------------+
+ | Normalize the result |
+ +--------------------------------------*/
+ testl $0x80000000,%eax
+ jnz L_round /* no shifting needed */
+
+ orl %eax,%eax
+ jnz L_shift_1 /* shift left 1 - 31 bits */
+
+ orl %ebx,%ebx
+ jnz L_shift_32 /* shift left 32 - 63 bits */
+
+/*
+ * A rare case, the only one which is non-zero if we got here
+ * is: 1000000 .... 0000
+ * -0111111 .... 1111 1
+ * --------------------
+ * 0000000 .... 0000 1
+ */
+
+ cmpl $0x80000000,%edx
+ jnz L_must_be_zero
+
+ /* Shift left 64 bits */
+ subw $64,EXP(%edi)
+ xchg %edx,%eax
+ jmp fpu_reg_round
+
+L_must_be_zero:
+#ifdef PARANOID
+ orl %edx,%edx
+ jnz L_bugged_3
+#endif /* PARANOID */
+
+ /* The result is zero */
+ movw $0,EXP(%edi) /* exponent */
+ movl $0,SIGL(%edi)
+ movl $0,SIGH(%edi)
+ movl TAG_Zero,%eax
+ jmp L_exit
+
+L_shift_32:
+ movl %ebx,%eax
+ movl %edx,%ebx
+ movl $0,%edx
+ subw $32,EXP(%edi) /* Can get underflow here */
+
+/* We need to shift left by 1 - 31 bits */
+L_shift_1:
+ bsrl %eax,%ecx /* get the required shift in %ecx */
+ subl $31,%ecx
+ negl %ecx
+ shld %cl,%ebx,%eax
+ shld %cl,%edx,%ebx
+ shl %cl,%edx
+ subw %cx,EXP(%edi) /* Can get underflow here */
+
+L_round:
+ jmp fpu_reg_round /* Round the result */
+
+
+#ifdef PARANOID
+L_bugged_1:
+ pushl EX_INTERNAL|0x206
+ call EXCEPTION
+ pop %ebx
+ jmp L_error_exit
+
+L_bugged_2:
+ pushl EX_INTERNAL|0x209
+ call EXCEPTION
+ pop %ebx
+ jmp L_error_exit
+
+L_bugged_3:
+ pushl EX_INTERNAL|0x210
+ call EXCEPTION
+ pop %ebx
+ jmp L_error_exit
+
+L_bugged_4:
+ pushl EX_INTERNAL|0x211
+ call EXCEPTION
+ pop %ebx
+ jmp L_error_exit
+
+L_bugged:
+ pushl EX_INTERNAL|0x212
+ call EXCEPTION
+ pop %ebx
+ jmp L_error_exit
+
+L_error_exit:
+ movl $-1,%eax
+
+#endif /* PARANOID */
+
+L_exit:
+ popl %ebx
+ popl %edi
+ popl %esi
+ leave
+ ret