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128 lines
4.0 KiB
C
128 lines
4.0 KiB
C
/*===-- semispace.c - Simple semi-space copying garbage collector ---------===*\
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|*
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|* The LLVM Compiler Infrastructure
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|*
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|* This file is distributed under the University of Illinois Open Source
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|* License. See LICENSE.TXT for details.
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|*
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|*===----------------------------------------------------------------------===*|
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|*
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|* This garbage collector is an extremely simple copying collector. It splits
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|* the managed region of memory into two pieces: the current space to allocate
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|* from, and the copying space. When the portion being allocated from fills up,
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|* a garbage collection cycle happens, which copies all live blocks to the other
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|* half of the managed space.
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|*
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\*===----------------------------------------------------------------------===*/
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#include "../GCInterface.h"
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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/* AllocPtr - This points to the next byte that is available for allocation.
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*/
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static char *AllocPtr;
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/* AllocEnd - This points to the first byte not available for allocation. When
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* AllocPtr passes this, we have run out of space.
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*/
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static char *AllocEnd;
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/* CurSpace/OtherSpace - These pointers point to the two regions of memory that
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* we switch between. The unallocated portion of the CurSpace is known to be
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* zero'd out, but the OtherSpace contains junk.
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*/
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static void *CurSpace, *OtherSpace;
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/* SpaceSize - The size of each space. */
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static unsigned SpaceSize;
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/* llvm_gc_initialize - Allocate the two spaces that we plan to switch between.
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*/
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void llvm_gc_initialize(unsigned InitialHeapSize) {
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SpaceSize = InitialHeapSize/2;
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CurSpace = AllocPtr = calloc(1, SpaceSize);
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OtherSpace = malloc(SpaceSize);
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AllocEnd = AllocPtr + SpaceSize;
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}
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/* We always want to inline the fast path, but never want to inline the slow
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* path.
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*/
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void *llvm_gc_allocate(unsigned Size) __attribute__((always_inline));
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static void* llvm_gc_alloc_slow(unsigned Size) __attribute__((noinline));
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void *llvm_gc_allocate(unsigned Size) {
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char *OldAP = AllocPtr;
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char *NewEnd = OldAP+Size;
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if (NewEnd > AllocEnd)
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return llvm_gc_alloc_slow(Size);
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AllocPtr = NewEnd;
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return OldAP;
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}
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static void* llvm_gc_alloc_slow(unsigned Size) {
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llvm_gc_collect();
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if (AllocPtr+Size > AllocEnd) {
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fprintf(stderr, "Garbage collector ran out of memory "
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"allocating object of size: %d\n", Size);
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exit(1);
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}
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return llvm_gc_allocate(Size);
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}
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static void process_pointer(void **Root, void *Meta) {
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printf("process_root[0x%p] = 0x%p\n", (void*) Root, (void*) *Root);
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}
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void llvm_gc_collect() {
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// Clear out the space we will be copying into.
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// FIXME: This should do the copy, then clear out whatever space is left.
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memset(OtherSpace, 0, SpaceSize);
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printf("Garbage collecting!!\n");
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llvm_cg_walk_gcroots(process_pointer);
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abort();
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}
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/* We use no read/write barriers */
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void *llvm_gc_read(void *ObjPtr, void **FieldPtr) { return *FieldPtr; }
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void llvm_gc_write(void *V, void *ObjPtr, void **FieldPtr) { *FieldPtr = V; }
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/*===----------------------------------------------------------------------===**
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* FIXME: This should be in a code-generator specific library, but for now this
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* will work for all code generators.
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*/
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typedef struct FrameMap FrameMap;
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struct FrameMap {
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int32_t NumRoots; // Number of roots in stack frame.
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int32_t NumMeta; // Number of metadata descriptors. May be < NumRoots.
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void *Meta[]; // May be absent for roots without metadata.
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};
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typedef struct StackEntry StackEntry;
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struct StackEntry {
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StackEntry *Next; // Caller's stack entry.
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const FrameMap *Map; // Pointer to constant FrameMap.
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void *Roots[]; // Stack roots (in-place array).
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};
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StackEntry *llvm_gc_root_chain;
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void llvm_cg_walk_gcroots(void (*FP)(void **Root, void *Meta)) {
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StackEntry *R;
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for (R = llvm_gc_root_chain; R; R = R->Next) {
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unsigned i, e;
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for (i = 0, e = R->Map->NumMeta; i != e; ++i)
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FP(&R->Roots[i], R->Map->Meta[i]);
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for (e = R->Map->NumRoots; i != e; ++i)
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FP(&R->Roots[i], NULL);
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}
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}
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/* END FIXME! */
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