xref: /openbmc/linux/arch/x86/math-emu/poly.h (revision b2441318)
1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*---------------------------------------------------------------------------+
3  |  poly.h                                                                   |
4  |                                                                           |
5  |  Header file for the FPU-emu poly*.c source files.                        |
6  |                                                                           |
7  | Copyright (C) 1994,1999                                                   |
8  |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
9  |                       Australia.  E-mail   billm@melbpc.org.au            |
10  |                                                                           |
11  | Declarations and definitions for functions operating on Xsig (12-byte     |
12  | extended-significand) quantities.                                         |
13  |                                                                           |
14  +---------------------------------------------------------------------------*/
15 
16 #ifndef _POLY_H
17 #define _POLY_H
18 
19 /* This 12-byte structure is used to improve the accuracy of computation
20    of transcendental functions.
21    Intended to be used to get results better than 8-byte computation
22    allows. 9-byte would probably be sufficient.
23    */
24 typedef struct {
25 	unsigned long lsw;
26 	unsigned long midw;
27 	unsigned long msw;
28 } Xsig;
29 
30 asmlinkage void mul64(unsigned long long const *a, unsigned long long const *b,
31 		      unsigned long long *result);
32 asmlinkage void polynomial_Xsig(Xsig *, const unsigned long long *x,
33 				const unsigned long long terms[], const int n);
34 
35 asmlinkage void mul32_Xsig(Xsig *, const unsigned long mult);
36 asmlinkage void mul64_Xsig(Xsig *, const unsigned long long *mult);
37 asmlinkage void mul_Xsig_Xsig(Xsig *dest, const Xsig *mult);
38 
39 asmlinkage void shr_Xsig(Xsig *, const int n);
40 asmlinkage int round_Xsig(Xsig *);
41 asmlinkage int norm_Xsig(Xsig *);
42 asmlinkage void div_Xsig(Xsig *x1, const Xsig *x2, const Xsig *dest);
43 
44 /* Macro to extract the most significant 32 bits from a long long */
45 #define LL_MSW(x)     (((unsigned long *)&x)[1])
46 
47 /* Macro to initialize an Xsig struct */
48 #define MK_XSIG(a,b,c)     { c, b, a }
49 
50 /* Macro to access the 8 ms bytes of an Xsig as a long long */
51 #define XSIG_LL(x)         (*(unsigned long long *)&x.midw)
52 
53 /*
54    Need to run gcc with optimizations on to get these to
55    actually be in-line.
56    */
57 
58 /* Multiply two fixed-point 32 bit numbers, producing a 32 bit result.
59    The answer is the ms word of the product. */
60 /* Some versions of gcc make it difficult to stop eax from being clobbered.
61    Merely specifying that it is used doesn't work...
62  */
mul_32_32(const unsigned long arg1,const unsigned long arg2)63 static inline unsigned long mul_32_32(const unsigned long arg1,
64 				      const unsigned long arg2)
65 {
66 	int retval;
67 	asm volatile ("mull %2; movl %%edx,%%eax":"=a" (retval)
68 		      :"0"(arg1), "g"(arg2)
69 		      :"dx");
70 	return retval;
71 }
72 
73 /* Add the 12 byte Xsig x2 to Xsig dest, with no checks for overflow. */
add_Xsig_Xsig(Xsig * dest,const Xsig * x2)74 static inline void add_Xsig_Xsig(Xsig *dest, const Xsig *x2)
75 {
76 	asm volatile ("movl %1,%%edi; movl %2,%%esi;\n"
77 		      "movl (%%esi),%%eax; addl %%eax,(%%edi);\n"
78 		      "movl 4(%%esi),%%eax; adcl %%eax,4(%%edi);\n"
79 		      "movl 8(%%esi),%%eax; adcl %%eax,8(%%edi);\n":"=g"
80 		      (*dest):"g"(dest), "g"(x2)
81 		      :"ax", "si", "di");
82 }
83 
84 /* Add the 12 byte Xsig x2 to Xsig dest, adjust exp if overflow occurs. */
85 /* Note: the constraints in the asm statement didn't always work properly
86    with gcc 2.5.8.  Changing from using edi to using ecx got around the
87    problem, but keep fingers crossed! */
add_two_Xsig(Xsig * dest,const Xsig * x2,long int * exp)88 static inline void add_two_Xsig(Xsig *dest, const Xsig *x2, long int *exp)
89 {
90 	asm volatile ("movl %2,%%ecx; movl %3,%%esi;\n"
91 		      "movl (%%esi),%%eax; addl %%eax,(%%ecx);\n"
92 		      "movl 4(%%esi),%%eax; adcl %%eax,4(%%ecx);\n"
93 		      "movl 8(%%esi),%%eax; adcl %%eax,8(%%ecx);\n"
94 		      "jnc 0f;\n"
95 		      "rcrl 8(%%ecx); rcrl 4(%%ecx); rcrl (%%ecx)\n"
96 		      "movl %4,%%ecx; incl (%%ecx)\n"
97 		      "movl $1,%%eax; jmp 1f;\n"
98 		      "0: xorl %%eax,%%eax;\n" "1:\n":"=g" (*exp), "=g"(*dest)
99 		      :"g"(dest), "g"(x2), "g"(exp)
100 		      :"cx", "si", "ax");
101 }
102 
103 /* Negate (subtract from 1.0) the 12 byte Xsig */
104 /* This is faster in a loop on my 386 than using the "neg" instruction. */
negate_Xsig(Xsig * x)105 static inline void negate_Xsig(Xsig *x)
106 {
107 	asm volatile ("movl %1,%%esi;\n"
108 		      "xorl %%ecx,%%ecx;\n"
109 		      "movl %%ecx,%%eax; subl (%%esi),%%eax; movl %%eax,(%%esi);\n"
110 		      "movl %%ecx,%%eax; sbbl 4(%%esi),%%eax; movl %%eax,4(%%esi);\n"
111 		      "movl %%ecx,%%eax; sbbl 8(%%esi),%%eax; movl %%eax,8(%%esi);\n":"=g"
112 		      (*x):"g"(x):"si", "ax", "cx");
113 }
114 
115 #endif /* _POLY_H */
116