mirror of
https://github.com/c64scene-ar/llvm-6502.git
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fc1a161d76
Refactor the TableGen'erated fixed length disassemblmer to use a table-driven state machine rather than a massive set of nested switch() statements. As a result, the ARM Disassembler (ARMDisassembler.cpp) builds much more quickly and generates a smaller end result. For a Release+Asserts build on a 16GB 3.4GHz i7 iMac w/ SSD: Time to compile at -O2 (averaged w/ hot caches): Previous: 35.5s New: 8.9s TEXT size: Previous: 447,251 New: 297,661 Builds in 25% of the time previously required and generates code 66% of the size. Execution time of the disassembler is only slightly slower (7% disassembling 10 million ARM instructions, 19.6s vs 21.0s). The new implementation has not yet been tuned, however, so the performance should almost certainly be recoverable should it become a concern. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161888 91177308-0d34-0410-b5e6-96231b3b80d8
96 lines
2.7 KiB
C++
96 lines
2.7 KiB
C++
//===- llvm/Support/LEB128.h - [SU]LEB128 utility functions -----*- C++ -*-===//
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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 file declares some utility functions for encoding SLEB128 and
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// ULEB128 values.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SYSTEM_LEB128_H
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#define LLVM_SYSTEM_LEB128_H
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#include <llvm/Support/raw_ostream.h>
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namespace llvm {
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/// Utility function to encode a SLEB128 value to an output stream.
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static inline void encodeSLEB128(int64_t Value, raw_ostream &OS) {
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bool More;
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do {
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uint8_t Byte = Value & 0x7f;
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// NOTE: this assumes that this signed shift is an arithmetic right shift.
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Value >>= 7;
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More = !((((Value == 0 ) && ((Byte & 0x40) == 0)) ||
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((Value == -1) && ((Byte & 0x40) != 0))));
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if (More)
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Byte |= 0x80; // Mark this byte that that more bytes will follow.
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OS << char(Byte);
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} while (More);
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}
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/// Utility function to encode a ULEB128 value to an output stream.
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static inline void encodeULEB128(uint64_t Value, raw_ostream &OS,
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unsigned Padding = 0) {
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do {
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uint8_t Byte = Value & 0x7f;
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Value >>= 7;
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if (Value != 0 || Padding != 0)
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Byte |= 0x80; // Mark this byte that that more bytes will follow.
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OS << char(Byte);
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} while (Value != 0);
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// Pad with 0x80 and emit a null byte at the end.
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if (Padding != 0) {
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for (; Padding != 1; --Padding)
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OS << '\x80';
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OS << '\x00';
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}
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}
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/// Utility function to encode a ULEB128 value to a buffer. Returns
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/// the length in bytes of the encoded value.
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static inline unsigned encodeULEB128(uint64_t Value, uint8_t *p,
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unsigned Padding = 0) {
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uint8_t *orig_p = p;
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do {
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uint8_t Byte = Value & 0x7f;
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Value >>= 7;
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if (Value != 0 || Padding != 0)
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Byte |= 0x80; // Mark this byte that that more bytes will follow.
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*p++ = Byte;
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} while (Value != 0);
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// Pad with 0x80 and emit a null byte at the end.
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if (Padding != 0) {
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for (; Padding != 1; --Padding)
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*p++ = '\x80';
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*p++ = '\x00';
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}
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return (unsigned)(p - orig_p);
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}
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/// Utility function to decode a ULEB128 value.
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static inline uint64_t decodeULEB128(const uint8_t *p, unsigned *n = 0) {
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const uint8_t *orig_p = p;
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uint64_t Value = 0;
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unsigned Shift = 0;
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do {
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Value += (*p & 0x7f) << Shift;
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Shift += 7;
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} while (*p++ >= 128);
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if (n)
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*n = (unsigned)(p - orig_p);
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return Value;
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}
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} // namespace llvm
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#endif // LLVM_SYSTEM_LEB128_H
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