ref: 12e226ac6798412271020d42645f69138715c519
dir: /utils/8c/mul.c/
#include "gc.h" typedef struct Malg Malg; typedef struct Mparam Mparam; struct Malg { char vals[10]; }; struct Mparam { ulong value; char alg; char neg; char shift; char arg; char off; }; static Mparam multab[32]; static int mulptr; static Malg malgs[] = { {0, 100}, {-1, 1, 100}, {-9, -5, -3, 3, 5, 9, 100}, {6, 10, 12, 18, 20, 24, 36, 40, 72, 100}, {-8, -4, -2, 2, 4, 8, 100}, }; /* * return position of lowest 1 */ int lowbit(ulong v) { int s, i; ulong m; s = 0; m = 0xFFFFFFFFUL; for(i = 16; i > 0; i >>= 1) { m >>= i; if((v & m) == 0) { v >>= i; s += i; } } return s; } void genmuladd(Node *d, Node *s, int m, Node *a) { Node nod; nod.op = OINDEX; nod.left = a; nod.right = s; nod.scale = m; nod.type = types[TIND]; nod.xoffset = 0; xcom(&nod); gopcode(OADDR, d->type, &nod, d); } void mulparam(ulong m, Mparam *mp) { int c, i, j, n, o, q, s; int bc, bi, bn, bo, bq, bs, bt; char *p; long u; ulong t; bc = bq = 10; bi = bn = bo = bs = bt = 0; for(i = 0; i < nelem(malgs); i++) { for(p = malgs[i].vals, j = 0; (o = p[j]) < 100; j++) for(s = 0; s < 2; s++) { c = 10; q = 10; u = m - o; if(u == 0) continue; if(s) { o = -o; if(o > 0) continue; u = -u; } n = lowbit(u); t = (ulong)u >> n; switch(i) { case 0: if(t == 1) { c = s + 1; q = 0; break; } switch(t) { case 3: case 5: case 9: c = s + 1; if(n) c++; q = 0; break; } if(s) break; switch(t) { case 15: case 25: case 27: case 45: case 81: c = 2; if(n) c++; q = 1; break; } break; case 1: if(t == 1) { c = 3; q = 3; break; } switch(t) { case 3: case 5: case 9: c = 3; q = 2; break; } break; case 2: if(t == 1) { c = 3; q = 2; break; } break; case 3: if(s) break; if(t == 1) { c = 3; q = 1; break; } break; case 4: if(t == 1) { c = 3; q = 0; break; } break; } if(c < bc || (c == bc && q > bq)) { bc = c; bi = i; bn = n; bo = o; bq = q; bs = s; bt = t; } } } mp->value = m; if(bc <= 3) { mp->alg = bi; mp->shift = bn; mp->off = bo; mp->neg = bs; mp->arg = bt; } else mp->alg = -1; } int m0(int a) { switch(a) { case -2: case 2: return 2; case -3: case 3: return 2; case -4: case 4: return 4; case -5: case 5: return 4; case 6: return 2; case -8: case 8: return 8; case -9: case 9: return 8; case 10: return 4; case 12: return 2; case 15: return 2; case 18: return 8; case 20: return 4; case 24: return 2; case 25: return 4; case 27: return 2; case 36: return 8; case 40: return 4; case 45: return 4; case 72: return 8; case 81: return 8; } diag(Z, "bad m0"); return 0; } int m1(int a) { switch(a) { case 15: return 4; case 25: return 4; case 27: return 8; case 45: return 8; case 81: return 8; } diag(Z, "bad m1"); return 0; } int m2(int a) { switch(a) { case 6: return 2; case 10: return 2; case 12: return 4; case 18: return 2; case 20: return 4; case 24: return 8; case 36: return 4; case 40: return 8; case 72: return 8; } diag(Z, "bad m2"); return 0; } void shiftit(Type *t, Node *s, Node *d) { long c; c = (long)s->vconst & 31; switch(c) { case 0: break; case 1: gopcode(OADD, t, d, d); break; default: gopcode(OASHL, t, s, d); } } static int mulgen1(ulong v, Node *n) { int i, o; Mparam *p; Node nod, nods; for(i = 0; i < nelem(multab); i++) { p = &multab[i]; if(p->value == v) goto found; } p = &multab[mulptr]; if(++mulptr == nelem(multab)) mulptr = 0; mulparam(v, p); found: // print("v=%.lx a=%d n=%d s=%d g=%d o=%d \n", p->value, p->alg, p->neg, p->shift, p->arg, p->off); if(p->alg < 0) return 0; nods = *nodconst(p->shift); o = OADD; if(p->alg > 0) { regalloc(&nod, n, Z); if(p->off < 0) o = OSUB; } switch(p->alg) { case 0: switch(p->arg) { case 1: shiftit(n->type, &nods, n); break; case 15: case 25: case 27: case 45: case 81: genmuladd(n, n, m1(p->arg), n); /* fall thru */ case 3: case 5: case 9: genmuladd(n, n, m0(p->arg), n); shiftit(n->type, &nods, n); break; default: goto bad; } if(p->neg == 1) gins(ANEGL, Z, n); break; case 1: switch(p->arg) { case 1: gmove(n, &nod); shiftit(n->type, &nods, &nod); break; case 3: case 5: case 9: genmuladd(&nod, n, m0(p->arg), n); shiftit(n->type, &nods, &nod); break; default: goto bad; } if(p->neg) gopcode(o, n->type, &nod, n); else { gopcode(o, n->type, n, &nod); gmove(&nod, n); } break; case 2: genmuladd(&nod, n, m0(p->off), n); shiftit(n->type, &nods, n); goto comop; case 3: genmuladd(&nod, n, m0(p->off), n); shiftit(n->type, &nods, n); genmuladd(n, &nod, m2(p->off), n); break; case 4: genmuladd(&nod, n, m0(p->off), nodconst(0)); shiftit(n->type, &nods, n); goto comop; default: diag(Z, "bad mul alg"); break; comop: if(p->neg) { gopcode(o, n->type, n, &nod); gmove(&nod, n); } else gopcode(o, n->type, &nod, n); } if(p->alg > 0) regfree(&nod); return 1; bad: diag(Z, "mulgen botch"); return 1; } void mulgen(Type *t, Node *r, Node *n) { if(!mulgen1(r->vconst, n)) gopcode(OMUL, t, r, n); }