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98bbd07cc3
Summary: The "single parameter" .file directive appears to be an ELF-only feature that is intended to insert the main source filename into the string table table. I noticed that if you assemble an ELF .s file for COFF, typically it will assert right away on a .file directive near the top of the file. My first change was to make this emit a proper error in the asm parser so that we don't assert so easily. However, COFF actually does have some support for this directive, and if you emit an object file, llvm-mc does not assert. When emitting a COFF object, MC will take those file names and create "debug" symbol table entries for them. I'm not familiar with these kinds of symbol table entries, and I'm not aware of any users of them, but @compnerd added them a while ago. They don't introduce absolute paths, and most main source file paths are short enough that this extra entry shouldn't cause any problems, so I enabled the flag in MCAsmInfoCOFF that indicates that it's supported. This has the side effect of adding an extra debug symbol to every object produced by clang, which is a pretty big functional change. My question is, should we keep the functionality or remove it in the name of symbol table minimalism? Reviewers: mstorsjo, compnerd Subscribers: hiraditya, compnerd, llvm-commits Differential Revision: https://reviews.llvm.org/D55900 llvm-svn: 349976
70 lines
2.2 KiB
C++
70 lines
2.2 KiB
C++
//===- MCAsmInfoCOFF.cpp - COFF asm properties ----------------------------===//
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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 defines target asm properties related what form asm statements
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// should take in general on COFF-based targets
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/MC/MCAsmInfoCOFF.h"
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#include "llvm/MC/MCDirectives.h"
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using namespace llvm;
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void MCAsmInfoCOFF::anchor() {}
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MCAsmInfoCOFF::MCAsmInfoCOFF() {
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// MingW 4.5 and later support .comm with log2 alignment, but .lcomm uses byte
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// alignment.
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COMMDirectiveAlignmentIsInBytes = false;
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LCOMMDirectiveAlignmentType = LCOMM::ByteAlignment;
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HasDotTypeDotSizeDirective = false;
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HasSingleParameterDotFile = true;
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WeakRefDirective = "\t.weak\t";
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HasLinkOnceDirective = true;
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// Doesn't support visibility:
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HiddenVisibilityAttr = HiddenDeclarationVisibilityAttr = MCSA_Invalid;
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ProtectedVisibilityAttr = MCSA_Invalid;
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// Set up DWARF directives
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SupportsDebugInformation = true;
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NeedsDwarfSectionOffsetDirective = true;
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UseIntegratedAssembler = true;
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// At least MSVC inline-asm does AShr.
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UseLogicalShr = false;
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// If this is a COFF target, assume that it supports associative comdats. It's
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// part of the spec.
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HasCOFFAssociativeComdats = true;
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// We can generate constants in comdat sections that can be shared,
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// but in order not to create null typed symbols, we actually need to
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// make them global symbols as well.
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HasCOFFComdatConstants = true;
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}
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void MCAsmInfoMicrosoft::anchor() {}
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MCAsmInfoMicrosoft::MCAsmInfoMicrosoft() = default;
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void MCAsmInfoGNUCOFF::anchor() {}
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MCAsmInfoGNUCOFF::MCAsmInfoGNUCOFF() {
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// If this is a GNU environment (mingw or cygwin), don't use associative
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// comdats for jump tables, unwind information, and other data associated with
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// a function.
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HasCOFFAssociativeComdats = false;
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// We don't create constants in comdat sections for MinGW.
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HasCOFFComdatConstants = false;
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}
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