1 /*******************************************************************************
3 * Module Name: utmath - Integer math support routines
5 ******************************************************************************/
8 * Copyright (C) 2000 - 2005, R. Byron Moore
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12 * modification, are permitted provided that the following conditions
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23 * of any contributors may be used to endorse or promote products derived
24 * from this software without specific prior written permission.
26 * Alternatively, this software may be distributed under the terms of the
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44 #include <acpi/acpi.h>
46 #define _COMPONENT ACPI_UTILITIES
47 ACPI_MODULE_NAME("utmath")
50 * Support for double-precision integer divide. This code is included here
51 * in order to support kernel environments where the double-precision math
52 * library is not available.
54 #ifndef ACPI_USE_NATIVE_DIVIDE
55 /*******************************************************************************
57 * FUNCTION: acpi_ut_short_divide
59 * PARAMETERS: Dividend - 64-bit dividend
60 * Divisor - 32-bit divisor
61 * out_quotient - Pointer to where the quotient is returned
62 * out_remainder - Pointer to where the remainder is returned
64 * RETURN: Status (Checks for divide-by-zero)
66 * DESCRIPTION: Perform a short (maximum 64 bits divided by 32 bits)
67 * divide and modulo. The result is a 64-bit quotient and a
70 ******************************************************************************/
72 acpi_ut_short_divide(acpi_integer dividend,
74 acpi_integer * out_quotient, u32 * out_remainder)
76 union uint64_overlay dividend_ovl;
77 union uint64_overlay quotient;
80 ACPI_FUNCTION_TRACE("ut_short_divide");
82 /* Always check for a zero divisor */
85 ACPI_REPORT_ERROR(("acpi_ut_short_divide: Divide by zero\n"));
86 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
89 dividend_ovl.full = dividend;
92 * The quotient is 64 bits, the remainder is always 32 bits,
93 * and is generated by the second divide.
95 ACPI_DIV_64_BY_32(0, dividend_ovl.part.hi, divisor,
96 quotient.part.hi, remainder32);
97 ACPI_DIV_64_BY_32(remainder32, dividend_ovl.part.lo, divisor,
98 quotient.part.lo, remainder32);
100 /* Return only what was requested */
103 *out_quotient = quotient.full;
106 *out_remainder = remainder32;
109 return_ACPI_STATUS(AE_OK);
112 /*******************************************************************************
114 * FUNCTION: acpi_ut_divide
116 * PARAMETERS: in_dividend - Dividend
117 * in_divisor - Divisor
118 * out_quotient - Pointer to where the quotient is returned
119 * out_remainder - Pointer to where the remainder is returned
121 * RETURN: Status (Checks for divide-by-zero)
123 * DESCRIPTION: Perform a divide and modulo.
125 ******************************************************************************/
128 acpi_ut_divide(acpi_integer in_dividend,
129 acpi_integer in_divisor,
130 acpi_integer * out_quotient, acpi_integer * out_remainder)
132 union uint64_overlay dividend;
133 union uint64_overlay divisor;
134 union uint64_overlay quotient;
135 union uint64_overlay remainder;
136 union uint64_overlay normalized_dividend;
137 union uint64_overlay normalized_divisor;
139 union uint64_overlay partial2;
140 union uint64_overlay partial3;
142 ACPI_FUNCTION_TRACE("ut_divide");
144 /* Always check for a zero divisor */
146 if (in_divisor == 0) {
147 ACPI_REPORT_ERROR(("acpi_ut_divide: Divide by zero\n"));
148 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
151 divisor.full = in_divisor;
152 dividend.full = in_dividend;
153 if (divisor.part.hi == 0) {
155 * 1) Simplest case is where the divisor is 32 bits, we can
156 * just do two divides
158 remainder.part.hi = 0;
161 * The quotient is 64 bits, the remainder is always 32 bits,
162 * and is generated by the second divide.
164 ACPI_DIV_64_BY_32(0, dividend.part.hi, divisor.part.lo,
165 quotient.part.hi, partial1);
166 ACPI_DIV_64_BY_32(partial1, dividend.part.lo, divisor.part.lo,
167 quotient.part.lo, remainder.part.lo);
172 * 2) The general case where the divisor is a full 64 bits
175 quotient.part.hi = 0;
176 normalized_dividend = dividend;
177 normalized_divisor = divisor;
179 /* Normalize the operands (shift until the divisor is < 32 bits) */
182 ACPI_SHIFT_RIGHT_64(normalized_divisor.part.hi,
183 normalized_divisor.part.lo);
184 ACPI_SHIFT_RIGHT_64(normalized_dividend.part.hi,
185 normalized_dividend.part.lo);
187 } while (normalized_divisor.part.hi != 0);
191 ACPI_DIV_64_BY_32(normalized_dividend.part.hi,
192 normalized_dividend.part.lo,
193 normalized_divisor.part.lo,
194 quotient.part.lo, partial1);
197 * The quotient is always 32 bits, and simply requires adjustment.
198 * The 64-bit remainder must be generated.
200 partial1 = quotient.part.lo * divisor.part.hi;
202 (acpi_integer) quotient.part.lo * divisor.part.lo;
203 partial3.full = (acpi_integer) partial2.part.hi + partial1;
205 remainder.part.hi = partial3.part.lo;
206 remainder.part.lo = partial2.part.lo;
208 if (partial3.part.hi == 0) {
209 if (partial3.part.lo >= dividend.part.hi) {
210 if (partial3.part.lo == dividend.part.hi) {
211 if (partial2.part.lo > dividend.part.lo) {
213 remainder.full -= divisor.full;
217 remainder.full -= divisor.full;
221 remainder.full = remainder.full - dividend.full;
222 remainder.part.hi = (u32) - ((s32) remainder.part.hi);
223 remainder.part.lo = (u32) - ((s32) remainder.part.lo);
225 if (remainder.part.lo) {
231 /* Return only what was requested */
234 *out_quotient = quotient.full;
237 *out_remainder = remainder.full;
240 return_ACPI_STATUS(AE_OK);
244 /*******************************************************************************
246 * FUNCTION: acpi_ut_short_divide, acpi_ut_divide
248 * PARAMETERS: See function headers above
250 * DESCRIPTION: Native versions of the ut_divide functions. Use these if either
251 * 1) The target is a 64-bit platform and therefore 64-bit
252 * integer math is supported directly by the machine.
253 * 2) The target is a 32-bit or 16-bit platform, and the
254 * double-precision integer math library is available to
255 * perform the divide.
257 ******************************************************************************/
259 acpi_ut_short_divide(acpi_integer in_dividend,
261 acpi_integer * out_quotient, u32 * out_remainder)
264 ACPI_FUNCTION_TRACE("ut_short_divide");
266 /* Always check for a zero divisor */
269 ACPI_REPORT_ERROR(("acpi_ut_short_divide: Divide by zero\n"));
270 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
273 /* Return only what was requested */
276 *out_quotient = in_dividend / divisor;
279 *out_remainder = (u32) in_dividend % divisor;
282 return_ACPI_STATUS(AE_OK);
286 acpi_ut_divide(acpi_integer in_dividend,
287 acpi_integer in_divisor,
288 acpi_integer * out_quotient, acpi_integer * out_remainder)
290 ACPI_FUNCTION_TRACE("ut_divide");
292 /* Always check for a zero divisor */
294 if (in_divisor == 0) {
295 ACPI_REPORT_ERROR(("acpi_ut_divide: Divide by zero\n"));
296 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
299 /* Return only what was requested */
302 *out_quotient = in_dividend / in_divisor;
305 *out_remainder = in_dividend % in_divisor;
308 return_ACPI_STATUS(AE_OK);