Changeset 04570c7 for src

Timestamp:

Apr 13, 2018, 4:39:28 PM (6 years ago)

Author:

Aaron Moss <a3moss@…>

Branches:

new-env, with_gc

Children:

6f81db3

Parents:

3205495

git-author:

Aaron Moss <a3moss@…> (04/13/18 16:27:11)

git-committer:

Aaron Moss <a3moss@…> (04/13/18 16:39:28)

Message:

First draft of arbitrarily-generational GC

Location:

src/Common

Files:

• GC.cc (modified) (6 diffs)
• GC.h (modified) (3 diffs)

src/Common/GC.cc

@@ -28 +28 @@
 }
 
-GC::GC() : mark(false), using_young(false), old(), young(), static_roots() {
-        old.reserve(70000);
+GC::GC() : gens(1), static_roots(), mark(false), g(0) {
+        gens[0].reserve(70000);
 }
 
 GC::~GC() {
-        for ( GC_Object* o : young ) {
-                delete o;
-        }
-
-        for ( GC_Object* o : old ) {
-                delete o;
+        for ( unsigned i = 0; i <= g; ++i ) {
+                for ( GC_Object* o : gens[i] ) {
+                        delete o;
+                }
         }
 }
@@ -54 +52 @@
 
 void GC::register_object(GC_Object* obj) {
-        (using_young ? young : old).push_back(obj);
+        gens[g].push_back(obj);
         obj->mark = !this->mark;  // initialize as un-marked
 }
@@ -63 +61 @@
 
 void GC::new_generation() {
-        assert(!using_young && "Cannot start new generation when young generation already in use");
-        
-        using_young = true;  // mark young generation as in-use
-        mark = !mark;        // switch mark so aged young objects will still be unmarked in old
+        if ( ++g == gens.size() ) { gens.emplace_back(); }  // ensure new generation available
+        mark = !mark;  // switch mark so aged young objects will still be unmarked in old
 }
 
@@ -77 +73 @@
 
 void GC::collect_young() {
+        // get generations and decrement generation
+        assert(g > 0 && "Cannot collect_young without young generation");
+        Generation& young = gens[g];
+        Generation& old = gens[--g];
+
         // collect young gen
         for ( GC_Object*& obj : young ) {
@@ -89 +90 @@
         old.insert( old.end(), young.begin(), end_live );
         
-        // clear young gen
-        using_young = false;
+        // clear young gen and reset mark to return to old generation mark
         young.clear();
-
-        // reset mark to return to old generation mark
         mark = !mark;
 }
@@ -99 +97 @@
 void GC::collect() {
         // ensure not called when young gen is active
-        assert(!using_young && "Cannot do old collection when young generation is active");
+        assert(g == 0 && "Cannot do old collection when young generation is active");
+        Generation& old = gens[0];
 
         // collect old gen

src/Common/GC.h

@@ -38 +38 @@
         void register_static_root(BaseSyntaxNode*);
 
-        /// Use young generation for subsequent new objects
+        /// Start new generation for subsequent new objects
         void new_generation();
 
@@ -44 +44 @@
         void trace_static_roots();
 
-        /// Collects the young generation, placing survivors in old generation.
-        /// Old generation is used for subsequent new objects.
+        /// Collects the youngest generation, placing survivors in previous generation.
+        /// Young generation objects cannot be kept alive by pointers from older generation.
+        /// Older generation is used for subsequent new objects.
         void collect_young();
 
-        /// Collects old generation; use old generation afterward.
-        /// Error if currently using young generation
+        /// Collects oldest generation; use oldest generation afterward.
+        /// Error if currently using younger generation
         void collect();
 
@@ -58 +59 @@
         GC();
 
-        bool mark;                 ///< The current collection's mark bit
-        bool using_young;          ///< Is the young generation in use?
-
         using Generation = std::vector<GC_Object*>;
-        Generation old;            ///< Old generation
-        Generation young;          ///< Young generation
+        std::vector<Generation> gens;  ///< Set of generations; always at least one
 
         using StaticRoots = std::vector<BaseSyntaxNode*>;
-        StaticRoots static_roots;  ///< Set of static-lifetime roots
+        StaticRoots static_roots;      ///< Set of static-lifetime roots
+
+        bool mark;                     ///< The current collection's mark bit
+        unsigned g;                    ///< The current number generation in use
 };