From c38e5b1b2c9b12fde377e3c183c2d496d17ba1d9 Mon Sep 17 00:00:00 2001
From: Nicolas Williams <nico@cryptonector.com>
Date: Sun, 13 Jul 2014 18:36:27 -0500
Subject: [PATCH] Lib defs don't bind to each other; fix #479 again

---
 compile.c | 49 +++++++++++++++++++++++++++++++++++++++++--------
 parser.y  |  2 +-
 2 files changed, 42 insertions(+), 9 deletions(-)

diff --git a/compile.c b/compile.c
index 64ff41d0..b0ff054c 100644
--- a/compile.c
+++ b/compile.c
@@ -243,6 +243,20 @@ static int block_count_actuals(block b) {
   return args;
 }
 
+static int block_count_refs(block binder, block body) {
+  int nrefs = 0;
+  for (inst* i = body.first; i; i = i->next) {
+    if (i != binder.first && i->bound_by == binder.first) {
+      nrefs++;
+    }
+    // counting recurses into closures
+    nrefs += block_count_refs(binder, i->subfn);
+    // counting recurses into argument list
+    nrefs += block_count_refs(binder, i->arglist);
+  }
+  return nrefs;
+}
+
 static int block_bind_subblock(block binder, block body, int bindflags) {
   assert(block_is_single(binder));
   assert((opcode_describe(binder.first->op)->flags & bindflags) == bindflags);
@@ -274,12 +288,14 @@ static int block_bind_subblock(block binder, block body, int bindflags) {
   return nrefs;
 }
 
-static void block_bind_each(block binder, block body, int bindflags) {
+static int block_bind_each(block binder, block body, int bindflags) {
   assert(block_has_only_binders(binder, bindflags));
   bindflags |= OP_HAS_BINDING;
+  int nrefs = 0;
   for (inst* curr = binder.first; curr; curr = curr->next) {
-    block_bind_subblock(inst_block(curr), body, bindflags);
+    nrefs += block_bind_subblock(inst_block(curr), body, bindflags);
   }
+  return nrefs;
 }
 
 block block_bind(block binder, block body, int bindflags) {
@@ -287,18 +303,35 @@ block block_bind(block binder, block body, int bindflags) {
   return block_join(binder, body);
 }
 
+// Bind binder to body and throw away any defs in binder not referenced
+// (directly or indirectly) from body.
 block block_bind_referenced(block binder, block body, int bindflags) {
   assert(block_has_only_binders(binder, bindflags));
   bindflags |= OP_HAS_BINDING;
   block refd = gen_noop();
-  for (inst* curr; (curr = block_take(&binder));) {
-    block b = inst_block(curr);
-    if (block_bind_subblock(b, body, bindflags)) {
-      refd = BLOCK(refd, b);
-    } else {
-      block_free(b);
+  block unrefd = gen_noop();
+  int nrefs;
+  for (int last_kept = 0, kept = 0; ; ) {
+    for (inst* curr; (curr = block_take(&binder));) {
+      block b = inst_block(curr);
+      nrefs = block_bind_each(b, body, bindflags);
+      // Check if this binder is referenced from any of the ones we
+      // already know are referenced by body.
+      nrefs += block_count_refs(b, refd);
+      if (nrefs) {
+        refd = BLOCK(refd, b);
+        kept++;
+      } else {
+        unrefd = BLOCK(unrefd, b);
+      }
     }
+    if (kept == last_kept)
+      break;
+    last_kept = kept;
+    binder = unrefd;
+    unrefd = gen_noop();
   }
+  block_free(unrefd);
   return block_join(refd, body);
 }
 
diff --git a/parser.y b/parser.y
index 55a01fa0..79483713 100644
--- a/parser.y
+++ b/parser.y
@@ -217,7 +217,7 @@ FuncDefs:
   $$ = gen_noop();
 } |
 FuncDef FuncDefs {
-  $$ = block_join($1, $2);
+  $$ = block_bind($1, $2, OP_IS_CALL_PSEUDO);
 }
 
 Exp: