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1 files changed, 285 insertions, 0 deletions

diff --git a/ir/optmem.c b/ir/optmem.c
new file mode 100644
index 0000000..1c137b7
--- /dev/null
+++ b/ir/optmem.c
@@ -0,0 +1,285 @@
+#include "ir.h"
+
+static const uchar loadszcls[] = {
+   [Oloads1 - Oloads1] = 1|KI4<<4, [Oloadu1 - Oloads1] = 1|KI4<<4,
+   [Oloads2 - Oloads1] = 2|KI4<<4, [Oloadu2 - Oloads1] = 2|KI4<<4,
+   [Oloads4 - Oloads1] = 4|KI4<<4, [Oloadu4 - Oloads1] = 4|KI4<<4,
+   [Oloadi8 - Oloads1] = 8|KI8<<4,
+   [Oloadf4 - Oloads1] = 4|KF4<<4,
+   [Oloadf8 - Oloads1] = 8|KF8<<4,
+};
+static const uchar load2ext[] = {
+   [Oloads1 - Oloads1] = Oexts1, [Oloadu1 - Oloads1] = Oextu1,
+   [Oloads2 - Oloads1] = Oexts2, [Oloadu2 - Oloads1] = Oextu2,
+   [Oloads4 - Oloads1] = Oexts4, [Oloadu4 - Oloads1] = Oextu4,
+   [Oloadi8 - Oloads1] = Ocopy,
+};
+#define loadsz(o) (loadszcls[(o) - Oloads1] & 0xF)
+#define loadcls(o) (loadszcls[(o) - Oloads1] >> 4)
+#define load2ext(o) (load2ext[(o) - Oloads1])
+#define storesz(o) (1 << ((o) - Ostore1))
+
+/* Implements algorithm in 'Simple and Efficient Construction of Static Single Assignment' (Braun et al) */
+
+struct pendingphi { ushort var, phi; };
+struct ssabuilder {
+   vec_of(struct pendingphi) *pendingphis; /* map of block to list of incomplete phis in block */
+   imap_of(union ref *) curdefs; /* map of var to (map of block to def of var) */
+   struct bitset *sealed;
+   int lastvisit;
+   int nblk;
+};
+
+static union ref readvar(struct ssabuilder *, int var, enum irclass, struct block *);
+
+static union ref
+deltrivialphis(struct ssabuilder *sb, struct block *blk, union ref phiref)
+{
+   union ref **pcurdefs;
+   int var;
+   struct use *use, *uend;
+   union ref *args = phitab.p[instrtab[phiref.i].l.i];
+   union ref same = {0};
+
+   assert(instrtab[phiref.i].op == Ophi);
+
+   for (int i = 0; i < blk->npred; ++i) {
+      if (args[i].bits == same.bits || args[i].bits == phiref.bits) {
+         continue; /* unique value or self-reference */
+      } if (same.bits != 0) {
+         return phiref; /* non-trivial */
+      }
+      same = args[i];
+   }
+
+   if (same.bits == 0)
+      same = UNDREF; /* the phi is unreachable or in the start block */
+
+   /* replace uses */
+   replcuses(phiref, same);
+   imap_each(&sb->curdefs, var, pcurdefs) {
+      (void)var;
+      for (int i = blk->id; i < sb->nblk; ++i) {
+         if ((*pcurdefs)[i].bits == phiref.bits)
+            (*pcurdefs)[i] = same;
+      }
+   }
+
+   /* stops infinite recursion and marks phi for removal */
+   instrtab[phiref.i].op = Onop;
+
+   /* recursively try to remove all phi users as they might have become trivial */
+Redo:
+   for (use = instruse[phiref.i], uend = use + instrnuse[phiref.i]; use < uend; ++use) {
+      if (use->u != USERJUMP && instrtab[use->u].op == Ophi && use->u != phiref.i) {
+         union ref it = mkref(RTMP, use->u);
+         union ref vphi2 = deltrivialphis(sb, use->blk, it);
+         if (vphi2.bits != it.bits) {
+            /* deletion happened so phiref use may have changed */
+            if (same.bits == it.bits) same.bits = vphi2.bits;
+            goto Redo;
+         }
+      }
+   }
+   deluses(phiref.i);
+
+   return same;
+}
+
+static union ref
+addphiargs(struct ssabuilder *sb, int var, enum irclass cls, struct block *blk, union ref phiref)
+{
+   union ref *args = phitab.p[instrtab[phiref.i].l.i];
+   for (int i = 0; i < blk->npred; ++i) {
+      struct block *pred = blkpred(blk, i);
+      args[i] = readvar(sb, var, cls, pred);
+      adduse(blk, phiref.i, args[i]);
+   }
+   return deltrivialphis(sb, blk, phiref);
+}
+
+static void
+writevar(struct ssabuilder *sb, int var, struct block *blk, union ref val)
+{
+   union ref **pcurdefs;
+   if (!(pcurdefs = imap_get(&sb->curdefs, var))) {
+      pcurdefs = imap_set(&sb->curdefs, var, xcalloc(sb->nblk * sizeof(union ref)));
+   }
+   if (val.t == RTMP) assert(instrtab[val.i].op != Onop);
+   (*pcurdefs)[blk->id] = val;
+}
+
+static union ref
+readvarrec(struct ssabuilder *sb, int var, enum irclass cls, struct block *blk)
+{
+   union ref val;
+   assert(blk->npred > 0);
+   if (!bstest(sb->sealed, blk->id)) { /* unsealed block */
+      val = insertphi(blk, cls);
+      vpush(&sb->pendingphis[blk->id], ((struct pendingphi) { var, val.i }));
+   } else if (blk->npred == 1) {
+      val = readvar(sb, var, cls, blkpred(blk, 0));
+   } else {
+      val = insertphi(blk, cls);
+      writevar(sb, var, blk, val);
+      val = addphiargs(sb, var, cls, blk, val);
+   }
+   writevar(sb, var, blk, val);
+   return val;
+}
+
+static union ref
+readvar(struct ssabuilder *sb, int var, enum irclass cls, struct block *blk)
+{
+   union ref **pcurdefs;
+   if ((pcurdefs = imap_get(&sb->curdefs, var)) && (*pcurdefs)[blk->id].bits)
+      return (*pcurdefs)[blk->id];
+   if (blk->npred == 0) /* entry block, var is read before being written to */
+      return UNDREF;
+   return readvarrec(sb, var, cls, blk);
+}
+
+static bool
+trysealrec(struct ssabuilder *sb, struct block *blk)
+{
+   vec_of(struct pendingphi) *pending;
+
+Recur:
+   if (bstest(sb->sealed, blk->id)) return 1;
+   if (blk->id > sb->lastvisit) return 0;
+   markvisited(blk);
+   for (int i = 0; i < blk->npred; ++i) {
+      struct block *p = blkpred(blk, i);
+      if (wasvisited(p)) continue;
+      if (!trysealrec(sb, p)) return 0;
+   }
+
+   bsset(sb->sealed, blk->id);
+   pending = (void *) &sb->pendingphis[blk->id];
+   for (int i = 0; i < pending->n; ++i) {
+      addphiargs(sb, pending->p[i].var, instrtab[pending->p[i].phi].cls, blk,
+                 mkref(RTMP, pending->p[i].phi));
+   }
+   vfree(pending);
+   if (blk->s1 && !blk->s2) {
+      blk = blk->s1;
+      goto Recur;
+   } else if (blk->s1 && blk->s2) {
+      trysealrec(sb, blk->s1);
+      blk = blk->s2;
+      goto Recur;
+   }
+   return 1;
+}
+
+static void
+tryseal(struct ssabuilder *sb, struct block *blk)
+{
+   startbbvisit();
+   trysealrec(sb, blk);
+}
+
+/* require use, blkid; keeps use */
+void
+mem2reg(struct function *fn)
+{
+   static struct bitset ssealed[4];
+   struct ssabuilder sb = { .nblk = fn->nblk };
+   struct block *blk;
+
+   sb.pendingphis = xcalloc(fn->nblk * sizeof *sb.pendingphis);
+   if (fn->nblk <= 64 * arraylength(ssealed)) {
+      sb.sealed = ssealed;
+      memset(ssealed, 0, BSSIZE(fn->nblk) * sizeof *ssealed);
+   } else {
+      sb.sealed = xcalloc(BSSIZE(fn->nblk) * sizeof *sb.sealed);
+   }
+
+   sortrpo(fn);
+   blk = fn->entry;
+
+   do {
+      for (int i = 0; i < blk->ins.n; ++i) {
+         struct use *use, *uend;
+         enum irclass k = 0;
+         int sz = 0, ndef = 0;
+         enum op ext = Ocopy;
+         int var = blk->ins.p[i];
+         struct instr *ins = &instrtab[var];
+         
+         if (!oisalloca(ins->op)) continue;
+         uend = instruse[var] + instrnuse[var];
+         for (use = instruse[var]; use < uend; ++use) {
+            struct instr *m;
+            
+            if (use->u == USERJUMP) goto Next;
+            m = &instrtab[use->u];
+            if (oisload(m->op) && (!sz || sz == loadsz(m->op))) {
+               sz = loadsz(m->op);
+               k = loadcls(m->op);
+               if (sz < 4) ext = load2ext(m->op);
+               continue;
+            }
+            if (oisstore(m->op) && m->l.bits == mkref(RTMP, var).bits
+            && (!sz || sz == storesz(m->op))) {
+               sz = storesz(m->op);
+               ++ndef;
+               continue;
+            }
+            goto Next;
+         }
+         if (!ndef) /* slot is read from but never written to */
+            goto Next;
+         
+         for (use = instruse[var]; use < uend; ++use) {
+            struct instr *m = &instrtab[use->u];
+
+            if (oisstore(m->op)) {
+               writevar(&sb, var, use->blk, m->r);
+               *m = mkinstr(Onop,0,);
+            } else if (oisload(m->op)) {
+               union ref val = readvar(&sb, var, k = m->cls, use->blk);
+               if (!val.bits) { /* var is used uninitialized */
+                  /* TODO emit diagnostic */
+                  /* load some garbage */
+                  *m = mkinstr(kisflt(k) ? Oloadf4 + (k==KF8) : Oloads1+ilog2(sz)*2,
+                               k, mkref(RREG, mctarg->bpr));
+               } else {
+                  adduse(use->blk, use->u, val);
+                  *m = mkinstr(ext, k, val);
+               }
+            }
+         }
+         /* remove alloca */
+         delinstr(blk, i--);
+         
+      Next:;
+      }
+
+      assert(sb.lastvisit == blk->id);
+      ++sb.lastvisit;
+      tryseal(&sb, blk);
+   } while ((blk = blk->lnext) != fn->entry);
+
+   do {
+      /* remove phis marked for deletion */
+      for (int i = 0; i < blk->phi.n; ++i)
+         if (instrtab[blk->phi.p[i]].op == Onop)
+            delphi(blk, i--);
+   } while ((blk = blk->lnext) != fn->entry);
+
+   if (sb.sealed != ssealed) free(sb.sealed);
+   free(sb.pendingphis);
+
+   for (int i = 0; i < sb.curdefs.mb.N; ++i)
+      if (bstest(sb.curdefs.mb.bs, i))
+         free(sb.curdefs.v[i]);
+   imap_free(&sb.curdefs);
+   if (ccopt.dbg.m) {
+      efmt("<< After mem2reg >>\n");
+      irdump(fn);
+   }
+}
+
+
+/* vim:set ts=3 sw=3 expandtab: */