code review 63650044: cmd/gc: handle variable initialization by block move in...

src/cmd/6g/cgen.c

 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 #include <u.h>
 #include <libc.h>
 #include "gg.h"
 
 /*
  * generate:
@@ skipping 1319 matching lines @@
 
 /*
  * block copy:
  *      memmove(&ns, &n, w);
  */
 void
 sgen(Node *n, Node *ns, int64 w)
 {
         Node nodl, nodr, nodsi, noddi, cx, oldcx, tmp;
         vlong c, q, odst, osrc;
+        NodeList *l;
 
         if(debug['g']) {
                 print("\nsgen w=%lld\n", w);
                 dump("r", n);
                 dump("res", ns);
         }
 
         if(n->ullman >= UINF && ns->ullman >= UINF)
                 fatal("sgen UINF");
 
         if(w < 0)
                 fatal("sgen copy %lld", w);
+········
+        // Record site of definition of ns for liveness analysis.
+        if(ns->op == ONAME && ns->class != PEXTERN)
+                gvardef(ns);
+········
+        // If copying .args, that's all the results, so record definition sites
+        // for them for the liveness analysis.
+        if(ns->op == ONAME && strcmp(ns->sym->name, ".args") == 0)
+                for(l = curfn->dcl; l != nil; l = l->next)
+                        if(l->n->class == PPARAMOUT)
+                                gvardef(l->n);
 
         // Avoid taking the address for simple enough types.
         if(componentgen(n, ns))
                 return;
 ········
         if(w == 0) {
                 // evaluate side effects only
                 regalloc(&nodr, types[tptr], N);
                 agen(ns, &nodr);
                 agen(n, &nodr);
@@ skipping 324 matching lines @@
                 regfree(&nodl);
         return 0;
 
 yes:
         if(freer)
                 regfree(&nodr);
         if(freel)
                 regfree(&nodl);
         return 1;
 }