Check in an EARLY START on a simple copying collector

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@13698 91177308-0d34-0410-b5e6-96231b3b80d8

runtime/GC/SemiSpace/Makefile

@@ -0,0 +1,19 @@
+##===- runtime/GC/SemiSpace/Makefile -----------------------*- Makefile -*-===##
+# 
+#                     The LLVM Compiler Infrastructure
+#
+# This file was developed by the LLVM research group and is distributed under
+# the University of Illinois Open Source License. See LICENSE.TXT for details.
+# 
+##===----------------------------------------------------------------------===##
+
+LEVEL = ../../..
+BYTECODE_LIBRARY=1
+#SHARED_LIBRARY=1
+#DONT_BUILD_RELINKED=1
+LIBRARYNAME=gcsemispace
+
+EXPORTED_SYMBOL_FILE = $(SourceDir)/../gc_exported_symbols.lst
+
+include $(LEVEL)/Makefile.common
+

runtime/GC/SemiSpace/semispace.c

@@ -0,0 +1,98 @@
+/*===-- semispace.c - Simple semi-space copying garbage collector ---------===*\
+|*
+|*                     The LLVM Compiler Infrastructure
+|*
+|* This file was developed by the LLVM research group and is distributed under
+|* the University of Illinois Open Source License. See LICENSE.TXT for details.
+|* 
+|*===----------------------------------------------------------------------===*|
+|* 
+|* This garbage collector is an extremely simple copying collector.  It splits
+|* the managed region of memory into two pieces: the current space to allocate
+|* from, and the copying space.  When the portion being allocated from fills up,
+|* a garbage collection cycle happens, which copies all live blocks to the other
+|* half of the managed space.
+|*
+\*===----------------------------------------------------------------------===*/
+
+#include "../GCInterface.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+/* FIXME: This should be in a code-generator specific library!
+ */
+typedef struct GCRoot {
+  void **RootPtr;
+  void *Meta;
+} GCRoot;
+
+typedef struct GCRoots {
+  struct GCRoots *Next;
+  unsigned NumRoots;
+  GCRoot RootRecords[];
+} GCRoots;
+GCRoots *llvm_gc_root_chain;
+
+static void llvm_cg_walk_gcroots(void (*FP)(void **Root, void *Meta)) {
+  GCRoots *R = llvm_gc_root_chain;
+  for (; R; R = R->Next) {
+    unsigned i, e;
+    for (i = 0, e = R->NumRoots; i != e; ++i)
+      FP(R->RootRecords[i].RootPtr, R->RootRecords[i].Meta);
+  }
+}
+/* END FIXME! */
+
+
+
+/* We use no read/write barriers */
+void *llvm_gc_read(void **P) { return *P; }
+void llvm_gc_write(void *V, void **P) { *P = V; }
+
+
+/* AllocPtr - This points to the next byte that is available for allocation.
+ */
+static char *AllocPtr;
+
+/* AllocEnd - This points to the first byte not available for allocation.  When
+ * AllocPtr passes this, we have run out of space.
+ */
+static char *AllocEnd;
+
+void llvm_gc_initialize() {
+  AllocPtr = calloc(1, 1000);
+  AllocEnd = AllocPtr + 1000;
+}
+
+/* We always want to inline the fast path, but never want to inline the slow
+ * path.
+ */
+void *llvm_gc_allocate(unsigned Size) __attribute__((always_inline));
+static void* llvm_gc_alloc_slow(unsigned Size) __attribute__((noinline));
+
+void *llvm_gc_allocate(unsigned Size) {
+  char *OldAP = AllocPtr;
+  char *NewEnd = OldAP+Size;
+  if (NewEnd > AllocEnd)
+    return llvm_gc_alloc_slow(Size);
+  AllocPtr = NewEnd;
+  return OldAP;
+}
+
+static void* llvm_gc_alloc_slow(unsigned Size) {
+  llvm_gc_collect();
+  return llvm_gc_allocate(Size);
+}
+
+
+static void process_root(void **Root, void *Meta) {
+  printf("process_root[0x%X] = 0x%X\n", Root, *Root);
+}
+
+void llvm_gc_collect() {
+  printf("Garbage collecting!!\n");
+  llvm_cg_walk_gcroots(process_root);
+  abort();
+
+  /* TODO: Iterate through roots. */
+}