Zack Buhman
ab809791cd
I'd like to include bits of libgcc piecemeal--I don't want to "accidentally" start depending on libgcc bits that I'm not aware of. Reworked division so that it uses the on-chip division register.
121 lines
2.2 KiB
C++
121 lines
2.2 KiB
C++
#pragma once
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#include <stdint.h>
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#ifndef USE_SH2_DVSR
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inline constexpr uint32_t
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__udiv32(uint32_t n, uint32_t d)
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{
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uint32_t q = 0;
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uint32_t r = 0;
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for (int i = 31; i >= 0; --i) {
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q = q << 1;
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r = r << 1;
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r |= (n >> 31) & 1;
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n = n << 1;
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if (d <= r) {
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r = r - d;
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q = q | 1;
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}
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}
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return q;
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}
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inline constexpr uint32_t
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__udiv64_32(uint64_t n, uint32_t base)
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{
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uint64_t rem = n;
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uint64_t b = base;
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uint64_t res = 0, d = 1;
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uint32_t high = rem >> 32;
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if (high >= base) {
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high = __udiv32(high, base);
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res = (uint64_t)high << 32;
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rem -= (uint64_t)(high*base) << 32;
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}
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while ((int64_t)b > 0 && b < rem) {
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b = b+b;
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d = d+d;
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}
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do {
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if (rem >= b) {
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rem -= b;
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res += d;
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}
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b >>= 1;
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d >>= 1;
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} while (d);
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return res;
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}
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#else
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#include "sh2.h"
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inline uint32_t
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__udiv64_32(uint64_t n, uint32_t d)
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{
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sh2.reg.DVSR = d;
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sh2.reg.DVDNTH = (uint32_t)(n >> 32);
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sh2.reg.DVDNTL = (uint32_t)(n);
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// 39 cycles
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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asm volatile ("nop");
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return sh2.reg.DVDNTL;
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}
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#endif
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inline int32_t
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__div64_32(int64_t n, int32_t d)
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{
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uint64_t n_abs = n >= 0 ? (uint64_t)n : -(uint64_t)n;
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uint32_t d_abs = d >= 0 ? (uint32_t)d : -(uint32_t)d;
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uint32_t q_abs = __udiv64_32(n_abs, d_abs);
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return (n < 0) == (d < 0) ? (int32_t)q_abs : -(int32_t)q_abs;
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}
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