From fc1a161d76f5cc0204bed3bce3e27cf36ac76d22 Mon Sep 17 00:00:00 2001 From: Jim Grosbach Date: Tue, 14 Aug 2012 19:06:05 +0000 Subject: Switch the fixed-length disassembler to be table-driven. 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 --- include/llvm/MC/MCFixedLenDisassembler.h | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) create mode 100644 include/llvm/MC/MCFixedLenDisassembler.h (limited to 'include/llvm/MC/MCFixedLenDisassembler.h') diff --git a/include/llvm/MC/MCFixedLenDisassembler.h b/include/llvm/MC/MCFixedLenDisassembler.h new file mode 100644 index 0000000..22b3c32 --- /dev/null +++ b/include/llvm/MC/MCFixedLenDisassembler.h @@ -0,0 +1,32 @@ +//===-- llvm/MC/MCFixedLenDisassembler.h - Decoder driver -------*- C++ -*-===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// Fixed length disassembler decoder state machine driver. +//===----------------------------------------------------------------------===// +#ifndef MCFIXEDLENDISASSEMBLER_H +#define MCFIXEDLENDISASSEMBLER_H + +namespace llvm { + +namespace MCD { +// Disassembler state machine opcodes. +enum DecoderOps { + OPC_ExtractField = 1, // OPC_ExtractField(uint8_t Start, uint8_t Len) + OPC_FilterValue, // OPC_FilterValue(uleb128 Val, uint16_t NumToSkip) + OPC_CheckField, // OPC_CheckField(uint8_t Start, uint8_t Len, + // uleb128 Val, uint16_t NumToSkip) + OPC_CheckPredicate, // OPC_CheckPredicate(uleb128 PIdx, uint16_t NumToSkip) + OPC_Decode, // OPC_Decode(uleb128 Opcode, uleb128 DIdx) + OPC_SoftFail, // OPC_SoftFail(uleb128 PMask, uleb128 NMask) + OPC_Fail // OPC_Fail() +}; + +} // namespace MCDecode +} // namespace llvm + +#endif -- cgit v1.1