diff options
Diffstat (limited to 'compiler/src/dotty/tools/dotc/core/tasty/TreeBuffer.scala')
| -rw-r--r-- | compiler/src/dotty/tools/dotc/core/tasty/TreeBuffer.scala | 188 |
1 files changed, 188 insertions, 0 deletions
diff --git a/compiler/src/dotty/tools/dotc/core/tasty/TreeBuffer.scala b/compiler/src/dotty/tools/dotc/core/tasty/TreeBuffer.scala new file mode 100644 index 000000000..6c7982d78 --- /dev/null +++ b/compiler/src/dotty/tools/dotc/core/tasty/TreeBuffer.scala @@ -0,0 +1,188 @@ +package dotty.tools +package dotc +package core +package tasty + +import util.Util.{bestFit, dble} +import TastyBuffer.{Addr, AddrWidth} +import config.Printers.pickling +import ast.untpd.Tree + +class TreeBuffer extends TastyBuffer(50000) { + + private final val ItemsOverOffsets = 2 + private val initialOffsetSize = bytes.length / (AddrWidth * ItemsOverOffsets) + private var offsets = new Array[Int](initialOffsetSize) + private var isRelative = new Array[Boolean](initialOffsetSize) + private var delta: Array[Int] = _ + private var numOffsets = 0 + + /** A map from trees to the address at which a tree is pickled. */ + private val treeAddrs = new java.util.IdentityHashMap[Tree, Any] // really: Addr | Null + + def registerTreeAddr(tree: Tree): Addr = treeAddrs.get(tree) match { + case null => treeAddrs.put(tree, currentAddr); currentAddr + case addr: Addr => addr + } + + def addrOfTree(tree: Tree): Option[Addr] = treeAddrs.get(tree) match { + case null => None + case addr: Addr => Some(addr) + } + + private def offset(i: Int): Addr = Addr(offsets(i)) + + private def keepOffset(relative: Boolean): Unit = { + if (numOffsets == offsets.length) { + offsets = dble(offsets) + isRelative = dble(isRelative) + } + offsets(numOffsets) = length + isRelative(numOffsets) = relative + numOffsets += 1 + } + + /** Reserve space for a reference, to be adjusted later */ + def reserveRef(relative: Boolean): Addr = { + val addr = currentAddr + keepOffset(relative) + reserveAddr() + addr + } + + /** Write reference right adjusted into freshly reserved field. */ + def writeRef(target: Addr) = { + keepOffset(relative = false) + fillAddr(reserveAddr(), target) + } + + /** Fill previously reserved field with a reference */ + def fillRef(at: Addr, target: Addr, relative: Boolean) = { + val addr = if (relative) target.relativeTo(at) else target + fillAddr(at, addr) + } + + /** The amount by which the bytes at the given address are shifted under compression */ + def deltaAt(at: Addr): Int = { + val idx = bestFit(offsets, numOffsets, at.index - 1) + if (idx < 0) 0 else delta(idx) + } + + /** The address to which `x` is translated under compression */ + def adjusted(x: Addr): Addr = x - deltaAt(x) + + /** Compute all shift-deltas */ + private def computeDeltas() = { + delta = new Array[Int](numOffsets) + var lastDelta = 0 + var i = 0 + while (i < numOffsets) { + val off = offset(i) + val skippedOff = skipZeroes(off) + val skippedCount = skippedOff.index - off.index + assert(skippedCount < AddrWidth, s"unset field at position $off") + lastDelta += skippedCount + delta(i) = lastDelta + i += 1 + } + } + + /** The absolute or relative adjusted address at index `i` of `offsets` array*/ + private def adjustedOffset(i: Int): Addr = { + val at = offset(i) + val original = getAddr(at) + if (isRelative(i)) { + val start = skipNat(at) + val len1 = original + delta(i) - deltaAt(original + start.index) + val len2 = adjusted(original + start.index) - adjusted(start).index + assert(len1 == len2, + s"adjusting offset #$i: $at, original = $original, len1 = $len1, len2 = $len2") + len1 + } else adjusted(original) + } + + /** Adjust all offsets according to previously computed deltas */ + private def adjustOffsets(): Unit = { + for (i <- 0 until numOffsets) { + val corrected = adjustedOffset(i) + fillAddr(offset(i), corrected) + } + } + + /** Adjust deltas to also take account references that will shrink (and thereby + * generate additional zeroes that can be skipped) due to previously + * computed adjustments. + */ + private def adjustDeltas(): Int = { + val delta1 = new Array[Int](delta.length) + var lastDelta = 0 + var i = 0 + while (i < numOffsets) { + val corrected = adjustedOffset(i) + lastDelta += AddrWidth - TastyBuffer.natSize(corrected.index) + delta1(i) = lastDelta + i += 1 + } + val saved = + if (numOffsets == 0) 0 + else delta1(numOffsets - 1) - delta(numOffsets - 1) + delta = delta1 + saved + } + + /** Compress pickle buffer, shifting bytes to close all skipped zeroes. */ + private def compress(): Int = { + var lastDelta = 0 + var start = 0 + var i = 0 + var wasted = 0 + def shift(end: Int) = + Array.copy(bytes, start, bytes, start - lastDelta, end - start) + while (i < numOffsets) { + val next = offsets(i) + shift(next) + start = next + delta(i) - lastDelta + val pastZeroes = skipZeroes(Addr(next)).index + assert(pastZeroes >= start, s"something's wrong: eliminated non-zero") + wasted += (pastZeroes - start) + lastDelta = delta(i) + i += 1 + } + shift(length) + length -= lastDelta + wasted + } + + def adjustTreeAddrs(): Unit = { + val it = treeAddrs.keySet.iterator + while (it.hasNext) { + val tree = it.next + treeAddrs.get(tree) match { + case addr: Addr => treeAddrs.put(tree, adjusted(addr)) + case addrs: List[Addr] => treeAddrs.put(tree, addrs.map(adjusted)) + } + } + } + + /** Final assembly, involving the following steps: + * - compute deltas + * - adjust deltas until additional savings are < 1% of total + * - adjust offsets according to the adjusted deltas + * - shrink buffer, skipping zeroes. + */ + def compactify(): Unit = { + val origLength = length + computeDeltas() + //println(s"offsets: ${offsets.take(numOffsets).deep}") + //println(s"deltas: ${delta.take(numOffsets).deep}") + var saved = 0 + do { + saved = adjustDeltas() + pickling.println(s"adjusting deltas, saved = $saved") + } while (saved > 0 && length / saved < 100) + adjustOffsets() + adjustTreeAddrs() + val wasted = compress() + pickling.println(s"original length: $origLength, compressed to: $length, wasted: $wasted") // DEBUG, for now. + } +} |