[dev.garbage] all: merge dev.cc into dev.garbage

The garbage collector is now written in Go.
There is plenty to clean up (just like on dev.cc).

all.bash passes on darwin/amd64, darwin/386, linux/amd64, linux/386.

TBR=rlh
R=austin, rlh, bradfitz
CC=golang-codereviews
https://codereview.appspot.com/173250043

1 files changed, 7 insertions, 67 deletions

diff --git a/src/runtime/mgc0.h b/src/runtime/mgc0.h
index 519d7206e..dd0c46024 100644
--- a/src/runtime/mgc0.h
+++ b/src/runtime/mgc0.h
@@ -2,81 +2,21 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Garbage collector (GC)
+// Used by cmd/gc.
 
 enum {
-	// Four bits per word (see #defines below).
 	gcBits = 4,
-	wordsPerBitmapByte = 8/gcBits,
-
-	// GC type info programs.
-	// The programs allow to store type info required for GC in a compact form.
-	// Most importantly arrays take O(1) space instead of O(n).
-	// The program grammar is:
-	//
-	// Program = {Block} "insEnd"
-	// Block = Data | Array
-	// Data = "insData" DataSize DataBlock
-	// DataSize = int // size of the DataBlock in bit pairs, 1 byte
-	// DataBlock = binary // dense GC mask (2 bits per word) of size ]DataSize/4[ bytes
-	// Array = "insArray" ArrayLen Block "insArrayEnd"
-	// ArrayLen = int // length of the array, 8 bytes (4 bytes for 32-bit arch)
-	//
-	// Each instruction (insData, insArray, etc) is 1 byte.
-	// For example, for type struct { x []byte; y [20]struct{ z int; w *byte }; }
-	// the program looks as:
-	//
-	// insData 3 (BitsMultiWord BitsSlice BitsScalar)
-	//	insArray 20 insData 2 (BitsScalar BitsPointer) insArrayEnd insEnd
-	//
-	// Total size of the program is 17 bytes (13 bytes on 32-bits).
-	// The corresponding GC mask would take 43 bytes (it would be repeated
-	// because the type has odd number of words).
+	BitsPerPointer = 2,
+	BitsDead = 0,
+	BitsScalar = 1,
+	BitsPointer = 2,
+	BitsMask = 3,
+	PointersPerByte = 8/BitsPerPointer,
 	insData = 1,
 	insArray,
 	insArrayEnd,
 	insEnd,
 
-	// Pointer map
-	BitsPerPointer	= 2,
-	BitsMask	= (1<<BitsPerPointer)-1,
-	PointersPerByte	= 8/BitsPerPointer,
-
-	// If you change these, also change scanblock.
-	// scanblock does "if(bits == BitsScalar || bits == BitsDead)" as "if(bits <= BitsScalar)".
-	BitsDead	= 0,
-	BitsScalar	= 1,                                // 01
-	BitsPointer	= 2,                                // 10
-	BitsCheckMarkXor = 1,                               // 10
-	BitsScalarMarked = BitsScalar ^ BitsCheckMarkXor,   // 00
-	BitsPointerMarked = BitsPointer ^ BitsCheckMarkXor, // 11
-
-	BitsMultiWord	= 3,
-	// BitsMultiWord will be set for the first word of a multi-word item.
-	// When it is set, one of the following will be set for the second word.
-	// NOT USED ANYMORE: BitsString	= 0,
-	// NOT USED ANYMORE: BitsSlice	= 1,
-	BitsIface	= 2,
-	BitsEface	= 3,
-
 	// 64 bytes cover objects of size 1024/512 on 64/32 bits, respectively.
 	MaxGCMask	= 65536, // TODO(rsc): change back to 64
 };
-
-// Bits in per-word bitmap.
-// #defines because we shift the values beyond 32 bits.
-//
-// Each word in the bitmap describes wordsPerBitmapWord words
-// of heap memory.  There are 4 bitmap bits dedicated to each heap word,
-// so on a 64-bit system there is one bitmap word per 16 heap words.
-//
-// The bitmap starts at mheap.arena_start and extends *backward* from
-// there.  On a 64-bit system the off'th word in the arena is tracked by
-// the off/16+1'th word before mheap.arena_start.  (On a 32-bit system,
-// the only difference is that the divisor is 8.)
-enum {
-	bitBoundary = 1, // boundary of an object
-	bitMarked = 2, // marked object
-	bitMask = bitBoundary | bitMarked,
-	bitPtrMask = BitsMask<<2,
-};