mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-16 01:04:08 +08:00
3927f2e8f9
Here is the current version of the 64 bit divide common code. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
230 lines
7.6 KiB
C
230 lines
7.6 KiB
C
#ifndef __ASM_ARM_DIV64
|
|
#define __ASM_ARM_DIV64
|
|
|
|
#include <asm/system.h>
|
|
#include <linux/types.h>
|
|
|
|
/*
|
|
* The semantics of do_div() are:
|
|
*
|
|
* uint32_t do_div(uint64_t *n, uint32_t base)
|
|
* {
|
|
* uint32_t remainder = *n % base;
|
|
* *n = *n / base;
|
|
* return remainder;
|
|
* }
|
|
*
|
|
* In other words, a 64-bit dividend with a 32-bit divisor producing
|
|
* a 64-bit result and a 32-bit remainder. To accomplish this optimally
|
|
* we call a special __do_div64 helper with completely non standard
|
|
* calling convention for arguments and results (beware).
|
|
*/
|
|
|
|
#ifdef __ARMEB__
|
|
#define __xh "r0"
|
|
#define __xl "r1"
|
|
#else
|
|
#define __xl "r0"
|
|
#define __xh "r1"
|
|
#endif
|
|
|
|
#define __do_div_asm(n, base) \
|
|
({ \
|
|
register unsigned int __base asm("r4") = base; \
|
|
register unsigned long long __n asm("r0") = n; \
|
|
register unsigned long long __res asm("r2"); \
|
|
register unsigned int __rem asm(__xh); \
|
|
asm( __asmeq("%0", __xh) \
|
|
__asmeq("%1", "r2") \
|
|
__asmeq("%2", "r0") \
|
|
__asmeq("%3", "r4") \
|
|
"bl __do_div64" \
|
|
: "=r" (__rem), "=r" (__res) \
|
|
: "r" (__n), "r" (__base) \
|
|
: "ip", "lr", "cc"); \
|
|
n = __res; \
|
|
__rem; \
|
|
})
|
|
|
|
#if __GNUC__ < 4
|
|
|
|
/*
|
|
* gcc versions earlier than 4.0 are simply too problematic for the
|
|
* optimized implementation below. First there is gcc PR 15089 that
|
|
* tend to trig on more complex constructs, spurious .global __udivsi3
|
|
* are inserted even if none of those symbols are referenced in the
|
|
* generated code, and those gcc versions are not able to do constant
|
|
* propagation on long long values anyway.
|
|
*/
|
|
#define do_div(n, base) __do_div_asm(n, base)
|
|
|
|
#elif __GNUC__ >= 4
|
|
|
|
#include <asm/bug.h>
|
|
|
|
/*
|
|
* If the divisor happens to be constant, we determine the appropriate
|
|
* inverse at compile time to turn the division into a few inline
|
|
* multiplications instead which is much faster. And yet only if compiling
|
|
* for ARMv4 or higher (we need umull/umlal) and if the gcc version is
|
|
* sufficiently recent to perform proper long long constant propagation.
|
|
* (It is unfortunate that gcc doesn't perform all this internally.)
|
|
*/
|
|
#define do_div(n, base) \
|
|
({ \
|
|
unsigned int __r, __b = (base); \
|
|
if (!__builtin_constant_p(__b) || __b == 0 || \
|
|
(__LINUX_ARM_ARCH__ < 4 && (__b & (__b - 1)) != 0)) { \
|
|
/* non-constant divisor (or zero): slow path */ \
|
|
__r = __do_div_asm(n, __b); \
|
|
} else if ((__b & (__b - 1)) == 0) { \
|
|
/* Trivial: __b is constant and a power of 2 */ \
|
|
/* gcc does the right thing with this code. */ \
|
|
__r = n; \
|
|
__r &= (__b - 1); \
|
|
n /= __b; \
|
|
} else { \
|
|
/* Multiply by inverse of __b: n/b = n*(p/b)/p */ \
|
|
/* We rely on the fact that most of this code gets */ \
|
|
/* optimized away at compile time due to constant */ \
|
|
/* propagation and only a couple inline assembly */ \
|
|
/* instructions should remain. Better avoid any */ \
|
|
/* code construct that might prevent that. */ \
|
|
unsigned long long __res, __x, __t, __m, __n = n; \
|
|
unsigned int __c, __p, __z = 0; \
|
|
/* preserve low part of n for reminder computation */ \
|
|
__r = __n; \
|
|
/* determine number of bits to represent __b */ \
|
|
__p = 1 << __div64_fls(__b); \
|
|
/* compute __m = ((__p << 64) + __b - 1) / __b */ \
|
|
__m = (~0ULL / __b) * __p; \
|
|
__m += (((~0ULL % __b + 1) * __p) + __b - 1) / __b; \
|
|
/* compute __res = __m*(~0ULL/__b*__b-1)/(__p << 64) */ \
|
|
__x = ~0ULL / __b * __b - 1; \
|
|
__res = (__m & 0xffffffff) * (__x & 0xffffffff); \
|
|
__res >>= 32; \
|
|
__res += (__m & 0xffffffff) * (__x >> 32); \
|
|
__t = __res; \
|
|
__res += (__x & 0xffffffff) * (__m >> 32); \
|
|
__t = (__res < __t) ? (1ULL << 32) : 0; \
|
|
__res = (__res >> 32) + __t; \
|
|
__res += (__m >> 32) * (__x >> 32); \
|
|
__res /= __p; \
|
|
/* Now sanitize and optimize what we've got. */ \
|
|
if (~0ULL % (__b / (__b & -__b)) == 0) { \
|
|
/* those cases can be simplified with: */ \
|
|
__n /= (__b & -__b); \
|
|
__m = ~0ULL / (__b / (__b & -__b)); \
|
|
__p = 1; \
|
|
__c = 1; \
|
|
} else if (__res != __x / __b) { \
|
|
/* We can't get away without a correction */ \
|
|
/* to compensate for bit truncation errors. */ \
|
|
/* To avoid it we'd need an additional bit */ \
|
|
/* to represent __m which would overflow it. */ \
|
|
/* Instead we do m=p/b and n/b=(n*m+m)/p. */ \
|
|
__c = 1; \
|
|
/* Compute __m = (__p << 64) / __b */ \
|
|
__m = (~0ULL / __b) * __p; \
|
|
__m += ((~0ULL % __b + 1) * __p) / __b; \
|
|
} else { \
|
|
/* Reduce __m/__p, and try to clear bit 31 */ \
|
|
/* of __m when possible otherwise that'll */ \
|
|
/* need extra overflow handling later. */ \
|
|
unsigned int __bits = -(__m & -__m); \
|
|
__bits |= __m >> 32; \
|
|
__bits = (~__bits) << 1; \
|
|
/* If __bits == 0 then setting bit 31 is */ \
|
|
/* unavoidable. Simply apply the maximum */ \
|
|
/* possible reduction in that case. */ \
|
|
/* Otherwise the MSB of __bits indicates the */ \
|
|
/* best reduction we should apply. */ \
|
|
if (!__bits) { \
|
|
__p /= (__m & -__m); \
|
|
__m /= (__m & -__m); \
|
|
} else { \
|
|
__p >>= __div64_fls(__bits); \
|
|
__m >>= __div64_fls(__bits); \
|
|
} \
|
|
/* No correction needed. */ \
|
|
__c = 0; \
|
|
} \
|
|
/* Now we have a combination of 2 conditions: */ \
|
|
/* 1) whether or not we need a correction (__c), and */ \
|
|
/* 2) whether or not there might be an overflow in */ \
|
|
/* the cross product (__m & ((1<<63) | (1<<31))) */ \
|
|
/* Select the best insn combination to perform the */ \
|
|
/* actual __m * __n / (__p << 64) operation. */ \
|
|
if (!__c) { \
|
|
asm ( "umull %Q0, %R0, %1, %Q2\n\t" \
|
|
"mov %Q0, #0" \
|
|
: "=&r" (__res) \
|
|
: "r" (__m), "r" (__n) \
|
|
: "cc" ); \
|
|
} else if (!(__m & ((1ULL << 63) | (1ULL << 31)))) { \
|
|
__res = __m; \
|
|
asm ( "umlal %Q0, %R0, %Q1, %Q2\n\t" \
|
|
"mov %Q0, #0" \
|
|
: "+r" (__res) \
|
|
: "r" (__m), "r" (__n) \
|
|
: "cc" ); \
|
|
} else { \
|
|
asm ( "umull %Q0, %R0, %Q1, %Q2\n\t" \
|
|
"cmn %Q0, %Q1\n\t" \
|
|
"adcs %R0, %R0, %R1\n\t" \
|
|
"adc %Q0, %3, #0" \
|
|
: "=&r" (__res) \
|
|
: "r" (__m), "r" (__n), "r" (__z) \
|
|
: "cc" ); \
|
|
} \
|
|
if (!(__m & ((1ULL << 63) | (1ULL << 31)))) { \
|
|
asm ( "umlal %R0, %Q0, %R1, %Q2\n\t" \
|
|
"umlal %R0, %Q0, %Q1, %R2\n\t" \
|
|
"mov %R0, #0\n\t" \
|
|
"umlal %Q0, %R0, %R1, %R2" \
|
|
: "+r" (__res) \
|
|
: "r" (__m), "r" (__n) \
|
|
: "cc" ); \
|
|
} else { \
|
|
asm ( "umlal %R0, %Q0, %R2, %Q3\n\t" \
|
|
"umlal %R0, %1, %Q2, %R3\n\t" \
|
|
"mov %R0, #0\n\t" \
|
|
"adds %Q0, %1, %Q0\n\t" \
|
|
"adc %R0, %R0, #0\n\t" \
|
|
"umlal %Q0, %R0, %R2, %R3" \
|
|
: "+r" (__res), "+r" (__z) \
|
|
: "r" (__m), "r" (__n) \
|
|
: "cc" ); \
|
|
} \
|
|
__res /= __p; \
|
|
/* The reminder can be computed with 32-bit regs */ \
|
|
/* only, and gcc is good at that. */ \
|
|
{ \
|
|
unsigned int __res0 = __res; \
|
|
unsigned int __b0 = __b; \
|
|
__r -= __res0 * __b0; \
|
|
} \
|
|
/* BUG_ON(__r >= __b || __res * __b + __r != n); */ \
|
|
n = __res; \
|
|
} \
|
|
__r; \
|
|
})
|
|
|
|
/* our own fls implementation to make sure constant propagation is fine */
|
|
#define __div64_fls(bits) \
|
|
({ \
|
|
unsigned int __left = (bits), __nr = 0; \
|
|
if (__left & 0xffff0000) __nr += 16, __left >>= 16; \
|
|
if (__left & 0x0000ff00) __nr += 8, __left >>= 8; \
|
|
if (__left & 0x000000f0) __nr += 4, __left >>= 4; \
|
|
if (__left & 0x0000000c) __nr += 2, __left >>= 2; \
|
|
if (__left & 0x00000002) __nr += 1; \
|
|
__nr; \
|
|
})
|
|
|
|
#endif
|
|
|
|
extern uint64_t div64_64(uint64_t dividend, uint64_t divisor);
|
|
|
|
#endif
|