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Do slightly better code gen.

    Remove some spurious spills.

--- a/6/ra.c

+++ b/6/ra.c

@@ -609,6 +609,8 @@

     ni = nodemoves(s, n, &il);

     for (i = 0; i < ni; i++) {

+        if (!bshas(s->mactiveset, il[i]->uid))

+            continue;

         for (j = 0; j < s->nmactive; j++) {

             if (il[i] == s->mactive[j]) {

                 ldel(&s->mactive, &s->nmactive, j);

@@ -1137,6 +1139,15 @@

     return useidx > 0 || defidx > 0;

 }

+static int nopmov(Insn *insn)

+{

+    if (insn->op != Imov && insn->op != Imovs)

+        return 0;

+    if (insn->args[0]->type != Locreg || insn->args[1]->type != Locreg)

+        return 0;

+    return insn->args[0]->reg.id == insn->args[1]->reg.id;

+}

+

 /*

  * Rewrite instructions using spilled registers, inserting

  * appropriate loads and stores into the BB

@@ -1155,6 +1166,8 @@

     if (!bb)

         return;

     for (j = 0; j < bb->ni; j++) {

+        if (nopmov(bb->il[j]))

+            continue;

         /* if there is a remapping, insert the loads and stores as needed */

         if (remap(s, bb->il[j], use, &nuse, def, &ndef)) {

             for (i = 0; i < nuse; i++) {

@@ -1208,6 +1221,34 @@

     htput(s->spillslots, itop(l->reg.id), itop(s->stksz->lit));

 }

+void replacealias(Isel *s, Asmbb *bb, Loc **map)

+{

+    size_t i, j;

+    Insn *insn;

+    Loc **alias;

+    Loc *l;

+

+    if (!map || !bb)

+        return;

+    alias = s->aliasmap;

+    s->aliasmap = alias;

+    for (i = 0; i < bb->ni; i++) {

+        insn = bb->il[i];

+        for (j = 0; j < insn->nargs; j++) {

+            l = insn->args[j];

+            if (l->type == Locreg) {

+                insn->args[j] = locmap[getalias(s, l->reg.id)];

+            } else if (l->type == Locmem || l->type == Locmeml) {

+                if (l->mem.base)

+                    l->mem.base = locmap[getalias(s, l->mem.base->reg.id)];

+                if (l->mem.idx)

+                    l->mem.idx = locmap[getalias(s, l->mem.idx->reg.id)];

+            }

+        }

+    }

+    s->aliasmap = alias;

+}

+

 /* 

  * Rewrites the function code so that it no longer contains

  * references to spilled registers. Every use of spilled regs

@@ -1220,7 +1261,7 @@

  *      insn %rZ,%rW

  *      mov %rW,234(%rsp)

  */

-static void rewrite(Isel *s)

+static void rewrite(Isel *s, Loc **aliasmap)

 {

     size_t i;

@@ -1231,6 +1272,8 @@

     /* rewrite instructions using them */

     for (i = 0; i < s->nbb; i++)

+        replacealias(s, s->bb[i], aliasmap);

+    for (i = 0; i < s->nbb; i++)

         rewritebb(s, s->bb[i]);

     htfree(s->spillslots);

     bsclear(s->spilled);

@@ -1276,6 +1319,7 @@

 {

     int spilled;

     size_t i;

+    Loc **aliasmap;

     /* Initialize the list of prepainted registers */

     s->prepainted = mkbs();

@@ -1289,6 +1333,7 @@

     for (i = 0; i < s->nsaved; i++)

         bsput(s->shouldspill, s->calleesave[i]->reg.id);

     do {

+        aliasmap = NULL;

         setup(s);

         liveness(s);

         build(s);

@@ -1302,12 +1347,15 @@

                 coalesce(s);

             else if (s->nwlfreeze)

                 freeze(s);

-            else if (s->nwlspill)

+            else if (s->nwlspill) {

+                if (!aliasmap)

+                    aliasmap = memdup(s->aliasmap, s->nreg * sizeof(Loc*));

                 selspill(s);

+            }

         } while (s->nwlsimp || s->nwlmove || s->nwlfreeze || s->nwlspill);

         spilled = paint(s);

         if (spilled)

-            rewrite(s);

+            rewrite(s, aliasmap);

     } while (spilled);

     delnops(s);

     bsfree(s->prepainted);

--- a/parse/infer.c

+++ b/parse/infer.c

@@ -524,6 +524,7 @@

 {

     Type *t;

+    t = NULL;

     if (!n->lit.type) {

         switch (n->lit.littype) {

             case Lchr:      t = mktype(n->loc, Tychar);                         break;