?? multiply.c
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#include "emul.h"// Perform long multiplication of x by y.extern MIPS_State * mstate;void multiply_UInt64(UInt64 u, UInt64 v){ UInt64 u0 = bits(u, 31, 0); UInt64 u1 = bits(u, 63, 32); UInt64 v0 = bits(v, 31, 0); UInt64 v1 = bits(v, 63, 32); UInt64 w0 = 0; UInt64 w1 = 0; UInt64 w2; UInt64 w3; UInt64 t, k; k = 0; // i == 0, j == 0 t = u0 * v0 + w0 + k; w0 = bits(t, 31, 0); k = bits(t, 63, 32); // i == 1, j == 0 t = u1 * v0 + w1 + k; w1 = bits(t, 31, 0); k = bits(t, 63, 32); w2 = k; k = 0; // i == 0, j == 1 t = u0 * v1 + w1 + k; w1 = bits(t, 31, 0); k = bits(t, 63, 32); // j == 1, i == 1 t = u1 * v1 + w2 + k; w2 = bits(t, 31, 0); k = bits(t, 63, 32); w3 = k; // Glue the bits back into full words. mstate->lo = w0 | (w1 << 32); mstate->hi = w2 | (w3 << 32);}void multiply_Int64(Int64 u, Int64 v){ // Compute the sign of the result; int neg; if (u < 0) { if (v < 0) { neg =0; v = -v; } else { neg = 1; } u = -u; } else { if (v < 0) { neg = 1; v = -v; } else { neg =0; } } multiply_UInt64((UInt64)u, (UInt64)v); if (neg) { mstate->lo = ~mstate->lo; mstate->hi = ~mstate->hi; if (++mstate->lo == 0) { ++mstate->hi; } }}?? 快捷鍵說明
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