| #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 |
| |
| #endif |
