Mercurial > hg > graal-compiler
diff src/share/vm/code/compressedStream.cpp @ 0:a61af66fc99e jdk7-b24
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author | duke |
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date | Sat, 01 Dec 2007 00:00:00 +0000 |
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children | c18cbe5936b8 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/code/compressedStream.cpp Sat Dec 01 00:00:00 2007 +0000 @@ -0,0 +1,281 @@ +/* + * Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +#include "incls/_precompiled.incl" +#include "incls/_compressedStream.cpp.incl" + +// 32-bit one-to-one sign encoding taken from Pack200 +// converts leading sign bits into leading zeroes with trailing sign bit +inline juint CompressedStream::encode_sign(jint value) { + return (value << 1) ^ (value >> 31); +} +inline jint CompressedStream::decode_sign(juint value) { + return (value >> 1) ^ -(jint)(value & 1); +} + +// 32-bit self-inverse encoding of float bits +// converts trailing zeroes (common in floats) to leading zeroes +inline juint CompressedStream::reverse_int(juint i) { + // Hacker's Delight, Figure 7-1 + i = (i & 0x55555555) << 1 | (i >> 1) & 0x55555555; + i = (i & 0x33333333) << 2 | (i >> 2) & 0x33333333; + i = (i & 0x0f0f0f0f) << 4 | (i >> 4) & 0x0f0f0f0f; + i = (i << 24) | ((i & 0xff00) << 8) | ((i >> 8) & 0xff00) | (i >> 24); + return i; +} + + +jint CompressedReadStream::read_signed_int() { + return decode_sign(read_int()); +} + +// Compressing floats is simple, because the only common pattern +// is trailing zeroes. (Compare leading sign bits on ints.) +// Since floats are left-justified, as opposed to right-justified +// ints, we can bit-reverse them in order to take advantage of int +// compression. + +jfloat CompressedReadStream::read_float() { + int rf = read_int(); + int f = reverse_int(rf); + return jfloat_cast(f); +} + +jdouble CompressedReadStream::read_double() { + jint rh = read_int(); + jint rl = read_int(); + jint h = reverse_int(rh); + jint l = reverse_int(rl); + return jdouble_cast(jlong_from(h, l)); +} + +jlong CompressedReadStream::read_long() { + jint low = read_signed_int(); + jint high = read_signed_int(); + return jlong_from(high, low); +} + +CompressedWriteStream::CompressedWriteStream(int initial_size) : CompressedStream(NULL, 0) { + _buffer = NEW_RESOURCE_ARRAY(u_char, initial_size); + _size = initial_size; + _position = 0; +} + +void CompressedWriteStream::grow() { + u_char* _new_buffer = NEW_RESOURCE_ARRAY(u_char, _size * 2); + memcpy(_new_buffer, _buffer, _position); + _buffer = _new_buffer; + _size = _size * 2; +} + +void CompressedWriteStream::write_signed_int(jint value) { + // this encoding, called SIGNED5, is taken from Pack200 + write_int(encode_sign(value)); +} + +void CompressedWriteStream::write_float(jfloat value) { + juint f = jint_cast(value); + juint rf = reverse_int(f); + assert(f == reverse_int(rf), "can re-read same bits"); + write_int(rf); +} + +void CompressedWriteStream::write_double(jdouble value) { + juint h = high(jlong_cast(value)); + juint l = low( jlong_cast(value)); + juint rh = reverse_int(h); + juint rl = reverse_int(l); + assert(h == reverse_int(rh), "can re-read same bits"); + assert(l == reverse_int(rl), "can re-read same bits"); + write_int(rh); + write_int(rl); +} + +void CompressedWriteStream::write_long(jlong value) { + write_signed_int(low(value)); + write_signed_int(high(value)); +} + + +/// The remaining details + +#ifndef PRODUCT +// set this to trigger unit test +void test_compressed_stream(int trace); +bool test_compressed_stream_enabled = false; +#endif + +// This encoding, called UNSIGNED5, is taken from J2SE Pack200. +// It assumes that most values have lots of leading zeroes. +// Very small values, in the range [0..191], code in one byte. +// Any 32-bit value (including negatives) can be coded, in +// up to five bytes. The grammar is: +// low_byte = [0..191] +// high_byte = [192..255] +// any_byte = low_byte | high_byte +// coding = low_byte +// | high_byte low_byte +// | high_byte high_byte low_byte +// | high_byte high_byte high_byte low_byte +// | high_byte high_byte high_byte high_byte any_byte +// Each high_byte contributes six bits of payload. +// The encoding is one-to-one (except for integer overflow) +// and easy to parse and unparse. + +jint CompressedReadStream::read_int_mb(jint b0) { + int pos = position() - 1; + u_char* buf = buffer() + pos; + assert(buf[0] == b0 && b0 >= L, "correctly called"); + jint sum = b0; + // must collect more bytes: b[1]...b[4] + int lg_H_i = lg_H; + for (int i = 0; ; ) { + jint b_i = buf[++i]; // b_i = read(); ++i; + sum += b_i << lg_H_i; // sum += b[i]*(64**i) + if (b_i < L || i == MAX_i) { + set_position(pos+i+1); + return sum; + } + lg_H_i += lg_H; + } +} + +void CompressedWriteStream::write_int_mb(jint value) { + debug_only(int pos1 = position()); + juint sum = value; + for (int i = 0; ; ) { + if (sum < L || i == MAX_i) { + // remainder is either a "low code" or the 5th byte + assert(sum == (u_char)sum, "valid byte"); + write((u_char)sum); + break; + } + sum -= L; + int b_i = L + (sum % H); // this is a "high code" + sum >>= lg_H; // extracted 6 bits + write(b_i); ++i; + } + +#ifndef PRODUCT + if (test_compressed_stream_enabled) { // hack to enable this stress test + test_compressed_stream_enabled = false; + test_compressed_stream(0); + } +#endif +} + + +#ifndef PRODUCT +/// a unit test (can be run by hand from a debugger) + +// Avoid a VS2005 compiler stack overflow w/ fastdebug build. +// The following pragma optimize turns off optimization ONLY +// for this block (a matching directive turns it back on later). +// These directives can be removed once the MS VS.NET 2005 +// compiler stack overflow is fixed. +#if _MSC_VER >=1400 && !defined(_WIN64) +#pragma optimize("", off) +#endif + +// generator for an "interesting" set of critical values +enum { stretch_limit = (1<<16) * (64-16+1) }; +static jlong stretch(jint x, int bits) { + // put x[high 4] into place + jlong h = (jlong)((x >> (16-4))) << (bits - 4); + // put x[low 12] into place, sign extended + jlong l = ((jlong)x << (64-12)) >> (64-12); + // move l upwards, maybe + l <<= (x >> 16); + return h ^ l; +} + +void test_compressed_stream(int trace) { + CompressedWriteStream bytes(stretch_limit * 100); + jint n; + int step = 0, fails = 0; +#define CHECKXY(x, y, fmt) { \ + ++step; \ + int xlen = (pos = decode.position()) - lastpos; lastpos = pos; \ + if (trace > 0 && (step % trace) == 0) { \ + tty->print_cr("step %d, n=%08x: value=" fmt " (len=%d)", \ + step, n, x, xlen); } \ + if (x != y) { \ + tty->print_cr("step %d, n=%d: " fmt " != " fmt, step, n, x, y); \ + fails++; \ + } } + for (n = 0; n < (1<<8); n++) { + jbyte x = (jbyte)n; + bytes.write_byte(x); ++step; + } + for (n = 0; n < stretch_limit; n++) { + jint x = (jint)stretch(n, 32); + bytes.write_int(x); ++step; + bytes.write_signed_int(x); ++step; + bytes.write_float(jfloat_cast(x)); ++step; + } + for (n = 0; n < stretch_limit; n++) { + jlong x = stretch(n, 64); + bytes.write_long(x); ++step; + bytes.write_double(jdouble_cast(x)); ++step; + } + int length = bytes.position(); + if (trace != 0) + tty->print_cr("set up test of %d stream values, size %d", step, length); + step = 0; + // now decode it all + CompressedReadStream decode(bytes.buffer()); + int pos, lastpos = decode.position(); + for (n = 0; n < (1<<8); n++) { + jbyte x = (jbyte)n; + jbyte y = decode.read_byte(); + CHECKXY(x, y, "%db"); + } + for (n = 0; n < stretch_limit; n++) { + jint x = (jint)stretch(n, 32); + jint y1 = decode.read_int(); + CHECKXY(x, y1, "%du"); + jint y2 = decode.read_signed_int(); + CHECKXY(x, y2, "%di"); + jint y3 = jint_cast(decode.read_float()); + CHECKXY(x, y3, "%df"); + } + for (n = 0; n < stretch_limit; n++) { + jlong x = stretch(n, 64); + jlong y1 = decode.read_long(); + CHECKXY(x, y1, INT64_FORMAT "l"); + jlong y2 = jlong_cast(decode.read_double()); + CHECKXY(x, y2, INT64_FORMAT "d"); + } + int length2 = decode.position(); + if (trace != 0) + tty->print_cr("finished test of %d stream values, size %d", step, length2); + guarantee(length == length2, "bad length"); + guarantee(fails == 0, "test failures"); +} + +#if _MSC_VER >=1400 && !defined(_WIN64) +#pragma optimize("", on) +#endif + +#endif // PRODUCT