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ce93beb88e
Rely on the assembler to finalize the layout of the DWARF/Itanium
exception-handling LSDA. Rather than calculate the exact size of each
thing in the LSDA, use assembler directives:
To emit the offset to the TTBase label:
.uleb128 .Lttbase0-.Lttbaseref0
.Lttbaseref0:
To emit the size of the call site table:
.uleb128 .Lcst_end0-.Lcst_begin0
.Lcst_begin0:
... call site table entries ...
.Lcst_end0:
To align the type info table:
... action table ...
.balign 4
.long _ZTIi
.long _ZTIl
.Lttbase0:
Using assembler directives simplifies the compiler and allows switching
the encoding of offsets in the call site table from udata4 to uleb128 for
a large code size savings. (This commit does not change the encoding.)
The combination of the uleb128 followed by a balign creates an unfortunate
dependency cycle that the assembler must sometimes resolve either by
padding an LEB or by inserting zero padding before the type table. See
PR35809 or GNU as bug 4029.
Patch by Ryan Prichard!
llvm-svn: 324749
96 lines
3.1 KiB
C++
96 lines
3.1 KiB
C++
//===-- DwarfException.h - Dwarf Exception Framework -----------*- 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 contains support for writing dwarf exception info into asm files.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIB_CODEGEN_ASMPRINTER_DWARFEXCEPTION_H
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#define LLVM_LIB_CODEGEN_ASMPRINTER_DWARFEXCEPTION_H
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#include "EHStreamer.h"
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#include "llvm/CodeGen/AsmPrinter.h"
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#include "llvm/MC/MCDwarf.h"
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namespace llvm {
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class MachineFunction;
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class ARMTargetStreamer;
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class LLVM_LIBRARY_VISIBILITY DwarfCFIExceptionBase : public EHStreamer {
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protected:
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DwarfCFIExceptionBase(AsmPrinter *A);
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/// Per-function flag to indicate if frame CFI info should be emitted.
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bool shouldEmitCFI;
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/// Per-module flag to indicate if .cfi_section has beeen emitted.
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bool hasEmittedCFISections;
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void markFunctionEnd() override;
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void endFragment() override;
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};
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class LLVM_LIBRARY_VISIBILITY DwarfCFIException : public DwarfCFIExceptionBase {
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/// Per-function flag to indicate if .cfi_personality should be emitted.
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bool shouldEmitPersonality;
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/// Per-function flag to indicate if .cfi_personality must be emitted.
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bool forceEmitPersonality;
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/// Per-function flag to indicate if .cfi_lsda should be emitted.
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bool shouldEmitLSDA;
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/// Per-function flag to indicate if frame moves info should be emitted.
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bool shouldEmitMoves;
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public:
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//===--------------------------------------------------------------------===//
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// Main entry points.
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//
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DwarfCFIException(AsmPrinter *A);
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~DwarfCFIException() override;
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/// Emit all exception information that should come after the content.
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void endModule() override;
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/// Gather pre-function exception information. Assumes being emitted
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/// immediately after the function entry point.
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void beginFunction(const MachineFunction *MF) override;
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/// Gather and emit post-function exception information.
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void endFunction(const MachineFunction *) override;
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void beginFragment(const MachineBasicBlock *MBB,
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ExceptionSymbolProvider ESP) override;
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};
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class LLVM_LIBRARY_VISIBILITY ARMException : public DwarfCFIExceptionBase {
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void emitTypeInfos(unsigned TTypeEncoding, MCSymbol *TTBaseLabel) override;
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ARMTargetStreamer &getTargetStreamer();
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public:
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//===--------------------------------------------------------------------===//
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// Main entry points.
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//
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ARMException(AsmPrinter *A);
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~ARMException() override;
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/// Emit all exception information that should come after the content.
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void endModule() override {}
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/// Gather pre-function exception information. Assumes being emitted
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/// immediately after the function entry point.
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void beginFunction(const MachineFunction *MF) override;
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/// Gather and emit post-function exception information.
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void endFunction(const MachineFunction *) override;
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};
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} // End of namespace llvm
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#endif
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