diff options
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm/include/asm/div64.h | 283 |
1 files changed, 93 insertions, 190 deletions
diff --git a/arch/arm/include/asm/div64.h b/arch/arm/include/asm/div64.h index 662c7bd06108..e1f07764b0d6 100644 --- a/arch/arm/include/asm/div64.h +++ b/arch/arm/include/asm/div64.h @@ -5,9 +5,9 @@ #include <asm/compiler.h> /* - * The semantics of do_div() are: + * The semantics of __div64_32() are: * - * uint32_t do_div(uint64_t *n, uint32_t base) + * uint32_t __div64_32(uint64_t *n, uint32_t base) * { * uint32_t remainder = *n % base; * *n = *n / base; @@ -16,8 +16,9 @@ * * 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). + * we override the generic version in lib/div64.c to call our __do_div64 + * assembly implementation with completely non standard calling convention + * for arguments and results (beware). */ #ifdef __ARMEB__ @@ -28,199 +29,101 @@ #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 || !defined(CONFIG_AEABI) +static inline uint32_t __div64_32(uint64_t *n, uint32_t 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; + return __rem; +} +#define __div64_32 __div64_32 + +#if !defined(CONFIG_AEABI) /* - * 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. + * In OABI configurations, some uses of the do_div function + * cause gcc to run out of registers. To work around that, + * we can force the use of the out-of-line version for + * configurations that build a OABI kernel. */ -#define do_div(n, base) __do_div_asm(n, base) - -#elif __GNUC__ >= 4 +#define do_div(n, base) __div64_32(&(n), base) -#include <asm/bug.h> +#else /* - * 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.) + * gcc versions earlier than 4.0 are simply too problematic for the + * __div64_const32() code in asm-generic/div64.h. 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) \ -({ \ - 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, %Q1, %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; \ -}) + +#define __div64_const32_is_OK (__GNUC__ >= 4) + +static inline uint64_t __arch_xprod_64(uint64_t m, uint64_t n, bool bias) +{ + unsigned long long res; + unsigned int tmp = 0; + + if (!bias) { + asm ( "umull %Q0, %R0, %Q1, %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" (tmp) + : "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" (tmp) + : "r" (m), "r" (n) + : "cc"); + } + + return res; +} +#define __arch_xprod_64 __arch_xprod_64 + +#include <asm-generic/div64.h> #endif |