Merge tag 'upstream/1.4' into debian-experimental

* tag 'upstream/1.4':
  Imported Upstream version 1.4

1 files changed, 621 insertions, 0 deletions

diff --git a/src/runtime/malloc.h b/src/runtime/malloc.h
new file mode 100644
index 000000000..adb8d3d67
--- /dev/null
+++ b/src/runtime/malloc.h
@@ -0,0 +1,621 @@
+// 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.
+
+// Memory allocator, based on tcmalloc.
+// http://goog-perftools.sourceforge.net/doc/tcmalloc.html
+
+// The main allocator works in runs of pages.
+// Small allocation sizes (up to and including 32 kB) are
+// rounded to one of about 100 size classes, each of which
+// has its own free list of objects of exactly that size.
+// Any free page of memory can be split into a set of objects
+// of one size class, which are then managed using free list
+// allocators.
+//
+// The allocator's data structures are:
+//
+//	FixAlloc: a free-list allocator for fixed-size objects,
+//		used to manage storage used by the allocator.
+//	MHeap: the malloc heap, managed at page (4096-byte) granularity.
+//	MSpan: a run of pages managed by the MHeap.
+//	MCentral: a shared free list for a given size class.
+//	MCache: a per-thread (in Go, per-P) cache for small objects.
+//	MStats: allocation statistics.
+//
+// Allocating a small object proceeds up a hierarchy of caches:
+//
+//	1. Round the size up to one of the small size classes
+//	   and look in the corresponding MCache free list.
+//	   If the list is not empty, allocate an object from it.
+//	   This can all be done without acquiring a lock.
+//
+//	2. If the MCache free list is empty, replenish it by
+//	   taking a bunch of objects from the MCentral free list.
+//	   Moving a bunch amortizes the cost of acquiring the MCentral lock.
+//
+//	3. If the MCentral free list is empty, replenish it by
+//	   allocating a run of pages from the MHeap and then
+//	   chopping that memory into a objects of the given size.
+//	   Allocating many objects amortizes the cost of locking
+//	   the heap.
+//
+//	4. If the MHeap is empty or has no page runs large enough,
+//	   allocate a new group of pages (at least 1MB) from the
+//	   operating system.  Allocating a large run of pages
+//	   amortizes the cost of talking to the operating system.
+//
+// Freeing a small object proceeds up the same hierarchy:
+//
+//	1. Look up the size class for the object and add it to
+//	   the MCache free list.
+//
+//	2. If the MCache free list is too long or the MCache has
+//	   too much memory, return some to the MCentral free lists.
+//
+//	3. If all the objects in a given span have returned to
+//	   the MCentral list, return that span to the page heap.
+//
+//	4. If the heap has too much memory, return some to the
+//	   operating system.
+//
+//	TODO(rsc): Step 4 is not implemented.
+//
+// Allocating and freeing a large object uses the page heap
+// directly, bypassing the MCache and MCentral free lists.
+//
+// The small objects on the MCache and MCentral free lists
+// may or may not be zeroed.  They are zeroed if and only if
+// the second word of the object is zero.  A span in the
+// page heap is zeroed unless s->needzero is set. When a span
+// is allocated to break into small objects, it is zeroed if needed
+// and s->needzero is set. There are two main benefits to delaying the
+// zeroing this way:
+//
+//	1. stack frames allocated from the small object lists
+//	   or the page heap can avoid zeroing altogether.
+//	2. the cost of zeroing when reusing a small object is
+//	   charged to the mutator, not the garbage collector.
+//
+// This C code was written with an eye toward translating to Go
+// in the future.  Methods have the form Type_Method(Type *t, ...).
+
+typedef struct MCentral	MCentral;
+typedef struct MHeap	MHeap;
+typedef struct MSpan	MSpan;
+typedef struct MStats	MStats;
+typedef struct MLink	MLink;
+typedef struct GCStats	GCStats;
+
+enum
+{
+	PageShift	= 13,
+	PageSize	= 1<<PageShift,
+	PageMask	= PageSize - 1,
+};
+typedef	uintptr	pageID;		// address >> PageShift
+
+enum
+{
+	// Computed constant.  The definition of MaxSmallSize and the
+	// algorithm in msize.c produce some number of different allocation
+	// size classes.  NumSizeClasses is that number.  It's needed here
+	// because there are static arrays of this length; when msize runs its
+	// size choosing algorithm it double-checks that NumSizeClasses agrees.
+	NumSizeClasses = 67,
+
+	// Tunable constants.
+	MaxSmallSize = 32<<10,
+
+	// Tiny allocator parameters, see "Tiny allocator" comment in malloc.goc.
+	TinySize = 16,
+	TinySizeClass = 2,
+
+	FixAllocChunk = 16<<10,		// Chunk size for FixAlloc
+	MaxMHeapList = 1<<(20 - PageShift),	// Maximum page length for fixed-size list in MHeap.
+	HeapAllocChunk = 1<<20,		// Chunk size for heap growth
+
+	// Per-P, per order stack segment cache size.
+	StackCacheSize = 32*1024,
+	// Number of orders that get caching.  Order 0 is FixedStack
+	// and each successive order is twice as large.
+	NumStackOrders = 3,
+
+	// Number of bits in page to span calculations (4k pages).
+	// On Windows 64-bit we limit the arena to 32GB or 35 bits (see below for reason).
+	// On other 64-bit platforms, we limit the arena to 128GB, or 37 bits.
+	// On 32-bit, we don't bother limiting anything, so we use the full 32-bit address.
+#ifdef _64BIT
+#ifdef GOOS_windows
+	// Windows counts memory used by page table into committed memory
+	// of the process, so we can't reserve too much memory.
+	// See http://golang.org/issue/5402 and http://golang.org/issue/5236.
+	MHeapMap_Bits = 35 - PageShift,
+#else
+	MHeapMap_Bits = 37 - PageShift,
+#endif
+#else
+	MHeapMap_Bits = 32 - PageShift,
+#endif
+
+	// Max number of threads to run garbage collection.
+	// 2, 3, and 4 are all plausible maximums depending
+	// on the hardware details of the machine.  The garbage
+	// collector scales well to 32 cpus.
+	MaxGcproc = 32,
+};
+
+// Maximum memory allocation size, a hint for callers.
+// This must be a #define instead of an enum because it
+// is so large.
+#ifdef _64BIT
+#define	MaxMem	(1ULL<<(MHeapMap_Bits+PageShift))	/* 128 GB or 32 GB */
+#else
+#define	MaxMem	((uintptr)-1)
+#endif
+
+// A generic linked list of blocks.  (Typically the block is bigger than sizeof(MLink).)
+struct MLink
+{
+	MLink *next;
+};
+
+// sysAlloc obtains a large chunk of zeroed memory from the
+// operating system, typically on the order of a hundred kilobytes
+// or a megabyte.
+// NOTE: sysAlloc returns OS-aligned memory, but the heap allocator
+// may use larger alignment, so the caller must be careful to realign the
+// memory obtained by sysAlloc.
+//
+// SysUnused notifies the operating system that the contents
+// of the memory region are no longer needed and can be reused
+// for other purposes.
+// SysUsed notifies the operating system that the contents
+// of the memory region are needed again.
+//
+// SysFree returns it unconditionally; this is only used if
+// an out-of-memory error has been detected midway through
+// an allocation.  It is okay if SysFree is a no-op.
+//
+// SysReserve reserves address space without allocating memory.
+// If the pointer passed to it is non-nil, the caller wants the
+// reservation there, but SysReserve can still choose another
+// location if that one is unavailable.  On some systems and in some
+// cases SysReserve will simply check that the address space is
+// available and not actually reserve it.  If SysReserve returns
+// non-nil, it sets *reserved to true if the address space is
+// reserved, false if it has merely been checked.
+// NOTE: SysReserve returns OS-aligned memory, but the heap allocator
+// may use larger alignment, so the caller must be careful to realign the
+// memory obtained by sysAlloc.
+//
+// SysMap maps previously reserved address space for use.
+// The reserved argument is true if the address space was really
+// reserved, not merely checked.
+//
+// SysFault marks a (already sysAlloc'd) region to fault
+// if accessed.  Used only for debugging the runtime.
+
+void*	runtime·sysAlloc(uintptr nbytes, uint64 *stat);
+void	runtime·SysFree(void *v, uintptr nbytes, uint64 *stat);
+void	runtime·SysUnused(void *v, uintptr nbytes);
+void	runtime·SysUsed(void *v, uintptr nbytes);
+void	runtime·SysMap(void *v, uintptr nbytes, bool reserved, uint64 *stat);
+void*	runtime·SysReserve(void *v, uintptr nbytes, bool *reserved);
+void	runtime·SysFault(void *v, uintptr nbytes);
+
+// FixAlloc is a simple free-list allocator for fixed size objects.
+// Malloc uses a FixAlloc wrapped around sysAlloc to manages its
+// MCache and MSpan objects.
+//
+// Memory returned by FixAlloc_Alloc is not zeroed.
+// The caller is responsible for locking around FixAlloc calls.
+// Callers can keep state in the object but the first word is
+// smashed by freeing and reallocating.
+struct FixAlloc
+{
+	uintptr	size;
+	void	(*first)(void *arg, byte *p);	// called first time p is returned
+	void*	arg;
+	MLink*	list;
+	byte*	chunk;
+	uint32	nchunk;
+	uintptr	inuse;	// in-use bytes now
+	uint64*	stat;
+};
+
+void	runtime·FixAlloc_Init(FixAlloc *f, uintptr size, void (*first)(void*, byte*), void *arg, uint64 *stat);
+void*	runtime·FixAlloc_Alloc(FixAlloc *f);
+void	runtime·FixAlloc_Free(FixAlloc *f, void *p);
+
+
+// Statistics.
+// Shared with Go: if you edit this structure, also edit type MemStats in mem.go.
+struct MStats
+{
+	// General statistics.
+	uint64	alloc;		// bytes allocated and still in use
+	uint64	total_alloc;	// bytes allocated (even if freed)
+	uint64	sys;		// bytes obtained from system (should be sum of xxx_sys below, no locking, approximate)
+	uint64	nlookup;	// number of pointer lookups
+	uint64	nmalloc;	// number of mallocs
+	uint64	nfree;  // number of frees
+
+	// Statistics about malloc heap.
+	// protected by mheap.lock
+	uint64	heap_alloc;	// bytes allocated and still in use
+	uint64	heap_sys;	// bytes obtained from system
+	uint64	heap_idle;	// bytes in idle spans
+	uint64	heap_inuse;	// bytes in non-idle spans
+	uint64	heap_released;	// bytes released to the OS
+	uint64	heap_objects;	// total number of allocated objects
+
+	// Statistics about allocation of low-level fixed-size structures.
+	// Protected by FixAlloc locks.
+	uint64	stacks_inuse;	// this number is included in heap_inuse above
+	uint64	stacks_sys;	// always 0 in mstats
+	uint64	mspan_inuse;	// MSpan structures
+	uint64	mspan_sys;
+	uint64	mcache_inuse;	// MCache structures
+	uint64	mcache_sys;
+	uint64	buckhash_sys;	// profiling bucket hash table
+	uint64	gc_sys;
+	uint64	other_sys;
+
+	// Statistics about garbage collector.
+	// Protected by mheap or stopping the world during GC.
+	uint64	next_gc;	// next GC (in heap_alloc time)
+	uint64  last_gc;	// last GC (in absolute time)
+	uint64	pause_total_ns;
+	uint64	pause_ns[256];  // circular buffer of recent GC pause lengths
+	uint64	pause_end[256]; // circular buffer of recent GC end times (nanoseconds since 1970)
+	uint32	numgc;
+	bool	enablegc;
+	bool	debuggc;
+
+	// Statistics about allocation size classes.
+	
+	struct MStatsBySize {
+		uint32 size;
+		uint64 nmalloc;
+		uint64 nfree;
+	} by_size[NumSizeClasses];
+	
+	uint64	tinyallocs;	// number of tiny allocations that didn't cause actual allocation; not exported to Go directly
+};
+
+
+#define mstats runtime·memstats
+extern MStats mstats;
+void	runtime·updatememstats(GCStats *stats);
+void	runtime·ReadMemStats(MStats *stats);
+
+// Size classes.  Computed and initialized by InitSizes.
+//
+// SizeToClass(0 <= n <= MaxSmallSize) returns the size class,
+//	1 <= sizeclass < NumSizeClasses, for n.
+//	Size class 0 is reserved to mean "not small".
+//
+// class_to_size[i] = largest size in class i
+// class_to_allocnpages[i] = number of pages to allocate when
+//	making new objects in class i
+
+int32	runtime·SizeToClass(int32);
+uintptr	runtime·roundupsize(uintptr);
+extern	int32	runtime·class_to_size[NumSizeClasses];
+extern	int32	runtime·class_to_allocnpages[NumSizeClasses];
+extern	int8	runtime·size_to_class8[1024/8 + 1];
+extern	int8	runtime·size_to_class128[(MaxSmallSize-1024)/128 + 1];
+extern	void	runtime·InitSizes(void);
+
+typedef struct MCacheList MCacheList;
+struct MCacheList
+{
+	MLink *list;
+	uint32 nlist;
+};
+
+typedef struct StackFreeList StackFreeList;
+struct StackFreeList
+{
+	MLink *list;  // linked list of free stacks
+	uintptr size; // total size of stacks in list
+};
+
+typedef struct SudoG SudoG;
+
+// Per-thread (in Go, per-P) cache for small objects.
+// No locking needed because it is per-thread (per-P).
+struct MCache
+{
+	// The following members are accessed on every malloc,
+	// so they are grouped here for better caching.
+	int32 next_sample;		// trigger heap sample after allocating this many bytes
+	intptr local_cachealloc;	// bytes allocated (or freed) from cache since last lock of heap
+	// Allocator cache for tiny objects w/o pointers.
+	// See "Tiny allocator" comment in malloc.goc.
+	byte*	tiny;
+	uintptr	tinysize;
+	uintptr	local_tinyallocs;	// number of tiny allocs not counted in other stats
+	// The rest is not accessed on every malloc.
+	MSpan*	alloc[NumSizeClasses];	// spans to allocate from
+
+	StackFreeList stackcache[NumStackOrders];
+
+	SudoG*	sudogcache;
+
+	void*	gcworkbuf;
+
+	// Local allocator stats, flushed during GC.
+	uintptr local_nlookup;		// number of pointer lookups
+	uintptr local_largefree;	// bytes freed for large objects (>MaxSmallSize)
+	uintptr local_nlargefree;	// number of frees for large objects (>MaxSmallSize)
+	uintptr local_nsmallfree[NumSizeClasses];	// number of frees for small objects (<=MaxSmallSize)
+};
+
+MSpan*	runtime·MCache_Refill(MCache *c, int32 sizeclass);
+void	runtime·MCache_ReleaseAll(MCache *c);
+void	runtime·stackcache_clear(MCache *c);
+void	runtime·gcworkbuffree(void *b);
+
+enum
+{
+	KindSpecialFinalizer = 1,
+	KindSpecialProfile = 2,
+	// Note: The finalizer special must be first because if we're freeing
+	// an object, a finalizer special will cause the freeing operation
+	// to abort, and we want to keep the other special records around
+	// if that happens.
+};
+
+typedef struct Special Special;
+struct Special
+{
+	Special*	next;	// linked list in span
+	uint16		offset;	// span offset of object
+	byte		kind;	// kind of Special
+};
+
+// The described object has a finalizer set for it.
+typedef struct SpecialFinalizer SpecialFinalizer;
+struct SpecialFinalizer
+{
+	Special		special;
+	FuncVal*	fn;
+	uintptr		nret;
+	Type*		fint;
+	PtrType*	ot;
+};
+
+// The described object is being heap profiled.
+typedef struct Bucket Bucket; // from mprof.h
+typedef struct SpecialProfile SpecialProfile;
+struct SpecialProfile
+{
+	Special	special;
+	Bucket*	b;
+};
+
+// An MSpan is a run of pages.
+enum
+{
+	MSpanInUse = 0, // allocated for garbage collected heap
+	MSpanStack,     // allocated for use by stack allocator
+	MSpanFree,
+	MSpanListHead,
+	MSpanDead,
+};
+struct MSpan
+{
+	MSpan	*next;		// in a span linked list
+	MSpan	*prev;		// in a span linked list
+	pageID	start;		// starting page number
+	uintptr	npages;		// number of pages in span
+	MLink	*freelist;	// list of free objects
+	// sweep generation:
+	// if sweepgen == h->sweepgen - 2, the span needs sweeping
+	// if sweepgen == h->sweepgen - 1, the span is currently being swept
+	// if sweepgen == h->sweepgen, the span is swept and ready to use
+	// h->sweepgen is incremented by 2 after every GC
+	uint32	sweepgen;
+	uint16	ref;		// capacity - number of objects in freelist
+	uint8	sizeclass;	// size class
+	bool	incache;	// being used by an MCache
+	uint8	state;		// MSpanInUse etc
+	uint8	needzero;	// needs to be zeroed before allocation
+	uintptr	elemsize;	// computed from sizeclass or from npages
+	int64   unusedsince;	// First time spotted by GC in MSpanFree state
+	uintptr npreleased;	// number of pages released to the OS
+	byte	*limit;		// end of data in span
+	Mutex	specialLock;	// guards specials list
+	Special	*specials;	// linked list of special records sorted by offset.
+};
+
+void	runtime·MSpan_Init(MSpan *span, pageID start, uintptr npages);
+void	runtime·MSpan_EnsureSwept(MSpan *span);
+bool	runtime·MSpan_Sweep(MSpan *span, bool preserve);
+
+// Every MSpan is in one doubly-linked list,
+// either one of the MHeap's free lists or one of the
+// MCentral's span lists.  We use empty MSpan structures as list heads.
+void	runtime·MSpanList_Init(MSpan *list);
+bool	runtime·MSpanList_IsEmpty(MSpan *list);
+void	runtime·MSpanList_Insert(MSpan *list, MSpan *span);
+void	runtime·MSpanList_InsertBack(MSpan *list, MSpan *span);
+void	runtime·MSpanList_Remove(MSpan *span);	// from whatever list it is in
+
+
+// Central list of free objects of a given size.
+struct MCentral
+{
+	Mutex  lock;
+	int32 sizeclass;
+	MSpan nonempty;	// list of spans with a free object
+	MSpan empty;	// list of spans with no free objects (or cached in an MCache)
+};
+
+void	runtime·MCentral_Init(MCentral *c, int32 sizeclass);
+MSpan*	runtime·MCentral_CacheSpan(MCentral *c);
+void	runtime·MCentral_UncacheSpan(MCentral *c, MSpan *s);
+bool	runtime·MCentral_FreeSpan(MCentral *c, MSpan *s, int32 n, MLink *start, MLink *end, bool preserve);
+
+// Main malloc heap.
+// The heap itself is the "free[]" and "large" arrays,
+// but all the other global data is here too.
+struct MHeap
+{
+	Mutex  lock;
+	MSpan free[MaxMHeapList];	// free lists of given length
+	MSpan freelarge;		// free lists length >= MaxMHeapList
+	MSpan busy[MaxMHeapList];	// busy lists of large objects of given length
+	MSpan busylarge;		// busy lists of large objects length >= MaxMHeapList
+	MSpan **allspans;		// all spans out there
+	MSpan **gcspans;		// copy of allspans referenced by GC marker or sweeper
+	uint32	nspan;
+	uint32	nspancap;
+	uint32	sweepgen;		// sweep generation, see comment in MSpan
+	uint32	sweepdone;		// all spans are swept
+
+	// span lookup
+	MSpan**	spans;
+	uintptr	spans_mapped;
+
+	// range of addresses we might see in the heap
+	byte *bitmap;
+	uintptr bitmap_mapped;
+	byte *arena_start;
+	byte *arena_used;
+	byte *arena_end;
+	bool arena_reserved;
+
+	// central free lists for small size classes.
+	// the padding makes sure that the MCentrals are
+	// spaced CacheLineSize bytes apart, so that each MCentral.lock
+	// gets its own cache line.
+	struct MHeapCentral {
+		MCentral mcentral;
+		byte pad[CacheLineSize];
+	} central[NumSizeClasses];
+
+	FixAlloc spanalloc;	// allocator for Span*
+	FixAlloc cachealloc;	// allocator for MCache*
+	FixAlloc specialfinalizeralloc;	// allocator for SpecialFinalizer*
+	FixAlloc specialprofilealloc;	// allocator for SpecialProfile*
+	Mutex speciallock; // lock for sepcial record allocators.
+
+	// Malloc stats.
+	uint64 largefree;	// bytes freed for large objects (>MaxSmallSize)
+	uint64 nlargefree;	// number of frees for large objects (>MaxSmallSize)
+	uint64 nsmallfree[NumSizeClasses];	// number of frees for small objects (<=MaxSmallSize)
+};
+#define runtime·mheap runtime·mheap_
+extern MHeap runtime·mheap;
+
+void	runtime·MHeap_Init(MHeap *h);
+MSpan*	runtime·MHeap_Alloc(MHeap *h, uintptr npage, int32 sizeclass, bool large, bool needzero);
+MSpan*	runtime·MHeap_AllocStack(MHeap *h, uintptr npage);
+void	runtime·MHeap_Free(MHeap *h, MSpan *s, int32 acct);
+void	runtime·MHeap_FreeStack(MHeap *h, MSpan *s);
+MSpan*	runtime·MHeap_Lookup(MHeap *h, void *v);
+MSpan*	runtime·MHeap_LookupMaybe(MHeap *h, void *v);
+void*	runtime·MHeap_SysAlloc(MHeap *h, uintptr n);
+void	runtime·MHeap_MapBits(MHeap *h);
+void	runtime·MHeap_MapSpans(MHeap *h);
+void	runtime·MHeap_Scavenge(int32 k, uint64 now, uint64 limit);
+
+void*	runtime·persistentalloc(uintptr size, uintptr align, uint64 *stat);
+int32	runtime·mlookup(void *v, byte **base, uintptr *size, MSpan **s);
+uintptr	runtime·sweepone(void);
+void	runtime·markspan(void *v, uintptr size, uintptr n, bool leftover);
+void	runtime·unmarkspan(void *v, uintptr size);
+void	runtime·purgecachedstats(MCache*);
+void	runtime·tracealloc(void*, uintptr, Type*);
+void	runtime·tracefree(void*, uintptr);
+void	runtime·tracegc(void);
+
+int32	runtime·gcpercent;
+int32	runtime·readgogc(void);
+void	runtime·clearpools(void);
+
+enum
+{
+	// flags to malloc
+	FlagNoScan	= 1<<0,	// GC doesn't have to scan object
+	FlagNoZero	= 1<<1, // don't zero memory
+};
+
+void	runtime·mProf_Malloc(void*, uintptr);
+void	runtime·mProf_Free(Bucket*, uintptr, bool);
+void	runtime·mProf_GC(void);
+void	runtime·iterate_memprof(void (**callback)(Bucket*, uintptr, uintptr*, uintptr, uintptr, uintptr));
+int32	runtime·gcprocs(void);
+void	runtime·helpgc(int32 nproc);
+void	runtime·gchelper(void);
+void	runtime·createfing(void);
+G*	runtime·wakefing(void);
+void	runtime·getgcmask(byte*, Type*, byte**, uintptr*);
+
+// NOTE: Layout known to queuefinalizer.
+typedef struct Finalizer Finalizer;
+struct Finalizer
+{
+	FuncVal *fn;	// function to call
+	void *arg;	// ptr to object
+	uintptr nret;	// bytes of return values from fn
+	Type *fint;	// type of first argument of fn
+	PtrType *ot;	// type of ptr to object
+};
+
+typedef struct FinBlock FinBlock;
+struct FinBlock
+{
+	FinBlock *alllink;
+	FinBlock *next;
+	int32 cnt;
+	int32 cap;
+	Finalizer fin[1];
+};
+extern Mutex	runtime·finlock;	// protects the following variables
+extern G*	runtime·fing;
+extern bool	runtime·fingwait;
+extern bool	runtime·fingwake;
+extern FinBlock	*runtime·finq;		// list of finalizers that are to be executed
+extern FinBlock	*runtime·finc;		// cache of free blocks
+
+void	runtime·setprofilebucket_m(void);
+
+bool	runtime·addfinalizer(void*, FuncVal *fn, uintptr, Type*, PtrType*);
+void	runtime·removefinalizer(void*);
+void	runtime·queuefinalizer(byte *p, FuncVal *fn, uintptr nret, Type *fint, PtrType *ot);
+bool	runtime·freespecial(Special *s, void *p, uintptr size, bool freed);
+
+// Information from the compiler about the layout of stack frames.
+struct BitVector
+{
+	int32 n; // # of bits
+	uint8 *bytedata;
+};
+typedef struct StackMap StackMap;
+struct StackMap
+{
+	int32 n; // number of bitmaps
+	int32 nbit; // number of bits in each bitmap
+	uint8 bytedata[]; // bitmaps, each starting on a 32-bit boundary
+};
+// Returns pointer map data for the given stackmap index
+// (the index is encoded in PCDATA_StackMapIndex).
+BitVector	runtime·stackmapdata(StackMap *stackmap, int32 n);
+
+extern	BitVector	runtime·gcdatamask;
+extern	BitVector	runtime·gcbssmask;
+
+// defined in mgc0.go
+void	runtime·gc_m_ptr(Eface*);
+void	runtime·gc_g_ptr(Eface*);
+void	runtime·gc_itab_ptr(Eface*);
+
+void  runtime·setgcpercent_m(void);
+
+// Value we use to mark dead pointers when GODEBUG=gcdead=1.
+#define PoisonGC ((uintptr)0xf969696969696969ULL)
+#define PoisonStack ((uintptr)0x6868686868686868ULL)