From 284827f32bd8d06ca1ab8a949bf96088612b1504 Mon Sep 17 00:00:00 2001 From: David Stenberg Date: Tue, 15 Oct 2019 11:14:35 +0000 Subject: [PATCH] [DebugInfo] Add interface for pre-calculating the size of emitted DWARF Summary: DWARF's DW_OP_entry_value operation has two operands; the first is a ULEB128 operand that specifies the size of the second operand, which is a DWARF block. This means that we need to be able to pre-calculate and emit the size of DWARF expressions before emitting them. There is currently no interface for doing this in DwarfExpression, so this patch introduces that. When implementing this I initially thought about running through DwarfExpression's emission two times; first with a temporary buffer to emit the expression, in order to being able to calculate the size of that emitted data. However, DwarfExpression is a quite complex state machine, so I decided against that, as it seemed like the two runs could get out of sync, resulting in incorrect size operands. Therefore I have implemented this in a way that we only have to run DwarfExpression once. The idea is to emit DWARF to a temporary buffer, for which it is possible to query the size. The data in the temporary buffer can then be emitted to DwarfExpression's main output. In the case of DIEDwarfExpression, a temporary DIE is used. The values are all allocated using the same BumpPtrAllocator as for all other DIEs, and the values are then transferred to the real value list. In the case of DebugLocDwarfExpression, the temporary buffer is implemented using a BufferByteStreamer which emits to a buffer in the DwarfExpression object. Reviewers: aprantl, vsk, NikolaPrica, djtodoro Reviewed By: aprantl Subscribers: hiraditya, llvm-commits Tags: #debug-info, #llvm Differential Revision: https://reviews.llvm.org/D67768 llvm-svn: 374879 --- llvm/include/llvm/CodeGen/DIE.h | 12 ++++ llvm/lib/CodeGen/AsmPrinter/ByteStreamer.h | 10 +-- llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp | 36 ++++++++-- llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h | 70 ++++++++++++++++--- llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp | 29 +++++--- 5 files changed, 130 insertions(+), 27 deletions(-) diff --git a/llvm/include/llvm/CodeGen/DIE.h b/llvm/include/llvm/CodeGen/DIE.h index 684f9e40ca5a..e8e7504a6cda 100644 --- a/llvm/include/llvm/CodeGen/DIE.h +++ b/llvm/include/llvm/CodeGen/DIE.h @@ -550,6 +550,14 @@ public: return *static_cast(Last ? Last->Next.getPointer() : nullptr); } + void takeNodes(IntrusiveBackList &Other) { + for (auto &N : Other) { + N.Next.setPointerAndInt(&N, true); + push_back(N); + } + Other.Last = nullptr; + } + class const_iterator; class iterator : public iterator_facade_base { @@ -685,6 +693,10 @@ public: return addValue(Alloc, DIEValue(Attribute, Form, std::forward(Value))); } + /// Take ownership of the nodes in \p Other, and append them to the back of + /// the list. + void takeValues(DIEValueList &Other) { List.takeNodes(Other.List); } + value_range values() { return make_range(value_iterator(List.begin()), value_iterator(List.end())); } diff --git a/llvm/lib/CodeGen/AsmPrinter/ByteStreamer.h b/llvm/lib/CodeGen/AsmPrinter/ByteStreamer.h index 55e609686531..09f7496cd4ef 100644 --- a/llvm/lib/CodeGen/AsmPrinter/ByteStreamer.h +++ b/llvm/lib/CodeGen/AsmPrinter/ByteStreamer.h @@ -75,16 +75,16 @@ private: SmallVectorImpl &Buffer; std::vector &Comments; +public: /// Only verbose textual output needs comments. This will be set to /// true for that case, and false otherwise. If false, comments passed in to /// the emit methods will be ignored. - bool GenerateComments; + const bool GenerateComments; -public: BufferByteStreamer(SmallVectorImpl &Buffer, - std::vector &Comments, - bool GenerateComments) - : Buffer(Buffer), Comments(Comments), GenerateComments(GenerateComments) {} + std::vector &Comments, bool GenerateComments) + : Buffer(Buffer), Comments(Comments), GenerateComments(GenerateComments) { + } void EmitInt8(uint8_t Byte, const Twine &Comment) override { Buffer.push_back(Byte); if (GenerateComments) diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp index 82c8b955e13e..7d7cadcce176 100644 --- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp +++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp @@ -170,26 +170,26 @@ static const char *const DbgTimerDescription = "DWARF Debug Writer"; static constexpr unsigned ULEB128PadSize = 4; void DebugLocDwarfExpression::emitOp(uint8_t Op, const char *Comment) { - BS.EmitInt8( + getActiveStreamer().EmitInt8( Op, Comment ? Twine(Comment) + " " + dwarf::OperationEncodingString(Op) : dwarf::OperationEncodingString(Op)); } void DebugLocDwarfExpression::emitSigned(int64_t Value) { - BS.EmitSLEB128(Value, Twine(Value)); + getActiveStreamer().EmitSLEB128(Value, Twine(Value)); } void DebugLocDwarfExpression::emitUnsigned(uint64_t Value) { - BS.EmitULEB128(Value, Twine(Value)); + getActiveStreamer().EmitULEB128(Value, Twine(Value)); } void DebugLocDwarfExpression::emitData1(uint8_t Value) { - BS.EmitInt8(Value, Twine(Value)); + getActiveStreamer().EmitInt8(Value, Twine(Value)); } void DebugLocDwarfExpression::emitBaseTypeRef(uint64_t Idx) { assert(Idx < (1ULL << (ULEB128PadSize * 7)) && "Idx wont fit"); - BS.EmitULEB128(Idx, Twine(Idx), ULEB128PadSize); + getActiveStreamer().EmitULEB128(Idx, Twine(Idx), ULEB128PadSize); } bool DebugLocDwarfExpression::isFrameRegister(const TargetRegisterInfo &TRI, @@ -198,6 +198,32 @@ bool DebugLocDwarfExpression::isFrameRegister(const TargetRegisterInfo &TRI, return false; } +void DebugLocDwarfExpression::enableTemporaryBuffer() { + assert(!IsBuffering && "Already buffering?"); + if (!TmpBuf) + TmpBuf = std::make_unique(OutBS.GenerateComments); + IsBuffering = true; +} + +void DebugLocDwarfExpression::disableTemporaryBuffer() { IsBuffering = false; } + +unsigned DebugLocDwarfExpression::getTemporaryBufferSize() { + return TmpBuf ? TmpBuf->Bytes.size() : 0; +} + +void DebugLocDwarfExpression::commitTemporaryBuffer() { + if (!TmpBuf) + return; + for (auto Byte : enumerate(TmpBuf->Bytes)) { + const char *Comment = (Byte.index() < TmpBuf->Comments.size()) + ? TmpBuf->Comments[Byte.index()].c_str() + : ""; + OutBS.EmitInt8(Byte.value(), Comment); + } + TmpBuf->Bytes.clear(); + TmpBuf->Comments.clear(); +} + const DIType *DbgVariable::getType() const { return getVariable()->getType(); } diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h index 9f9baf8c1a19..a4b566669c2a 100644 --- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h +++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h @@ -13,6 +13,7 @@ #ifndef LLVM_LIB_CODEGEN_ASMPRINTER_DWARFEXPRESSION_H #define LLVM_LIB_CODEGEN_ASMPRINTER_DWARFEXPRESSION_H +#include "ByteStreamer.h" #include "llvm/ADT/ArrayRef.h" #include "llvm/ADT/None.h" #include "llvm/ADT/Optional.h" @@ -26,7 +27,6 @@ namespace llvm { class AsmPrinter; class APInt; -class ByteStreamer; class DwarfCompileUnit; class DIELoc; class TargetRegisterInfo; @@ -95,6 +95,13 @@ public: /// Base class containing the logic for constructing DWARF expressions /// independently of whether they are emitted into a DIE or into a .debug_loc /// entry. +/// +/// Some DWARF operations, e.g. DW_OP_entry_value, need to calculate the size +/// of a succeeding DWARF block before the latter is emitted to the output. +/// To handle such cases, data can conditionally be emitted to a temporary +/// buffer, which can later on be committed to the main output. The size of the +/// temporary buffer is queryable, allowing for the size of the data to be +/// emitted before the data is committed. class DwarfExpression { protected: /// Holds information about all subregisters comprising a register location. @@ -178,6 +185,22 @@ protected: virtual void emitBaseTypeRef(uint64_t Idx) = 0; + /// Start emitting data to the temporary buffer. The data stored in the + /// temporary buffer can be committed to the main output using + /// commitTemporaryBuffer(). + virtual void enableTemporaryBuffer() = 0; + + /// Disable emission to the temporary buffer. This does not commit data + /// in the temporary buffer to the main output. + virtual void disableTemporaryBuffer() = 0; + + /// Return the emitted size, in number of bytes, for the data stored in the + /// temporary buffer. + virtual unsigned getTemporaryBufferSize() = 0; + + /// Commit the data stored in the temporary buffer to the main output. + virtual void commitTemporaryBuffer() = 0; + /// Emit a normalized unsigned constant. void emitConstu(uint64_t Value); @@ -308,31 +331,62 @@ public: /// DwarfExpression implementation for .debug_loc entries. class DebugLocDwarfExpression final : public DwarfExpression { - ByteStreamer &BS; + + struct TempBuffer { + SmallString<32> Bytes; + std::vector Comments; + BufferByteStreamer BS; + + TempBuffer(bool GenerateComments) : BS(Bytes, Comments, GenerateComments) {} + }; + + std::unique_ptr TmpBuf; + BufferByteStreamer &OutBS; + bool IsBuffering = false; + + /// Return the byte streamer that currently is being emitted to. + ByteStreamer &getActiveStreamer() { return IsBuffering ? TmpBuf->BS : OutBS; } void emitOp(uint8_t Op, const char *Comment = nullptr) override; void emitSigned(int64_t Value) override; void emitUnsigned(uint64_t Value) override; void emitData1(uint8_t Value) override; void emitBaseTypeRef(uint64_t Idx) override; + + void enableTemporaryBuffer() override; + void disableTemporaryBuffer() override; + unsigned getTemporaryBufferSize() override; + void commitTemporaryBuffer() override; + bool isFrameRegister(const TargetRegisterInfo &TRI, unsigned MachineReg) override; - public: - DebugLocDwarfExpression(unsigned DwarfVersion, ByteStreamer &BS, DwarfCompileUnit &CU) - : DwarfExpression(DwarfVersion, CU), BS(BS) {} + DebugLocDwarfExpression(unsigned DwarfVersion, BufferByteStreamer &BS, + DwarfCompileUnit &CU) + : DwarfExpression(DwarfVersion, CU), OutBS(BS) {} }; /// DwarfExpression implementation for singular DW_AT_location. class DIEDwarfExpression final : public DwarfExpression { -const AsmPrinter &AP; - DIELoc &DIE; + const AsmPrinter &AP; + DIELoc &OutDIE; + DIELoc TmpDIE; + bool IsBuffering = false; + + /// Return the DIE that currently is being emitted to. + DIELoc &getActiveDIE() { return IsBuffering ? TmpDIE : OutDIE; } void emitOp(uint8_t Op, const char *Comment = nullptr) override; void emitSigned(int64_t Value) override; void emitUnsigned(uint64_t Value) override; void emitData1(uint8_t Value) override; void emitBaseTypeRef(uint64_t Idx) override; + + void enableTemporaryBuffer() override; + void disableTemporaryBuffer() override; + unsigned getTemporaryBufferSize() override; + void commitTemporaryBuffer() override; + bool isFrameRegister(const TargetRegisterInfo &TRI, unsigned MachineReg) override; public: @@ -340,7 +394,7 @@ public: DIELoc *finalize() { DwarfExpression::finalize(); - return &DIE; + return &OutDIE; } }; diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp index be743a52cc63..ae11dc851395 100644 --- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp +++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp @@ -47,31 +47,42 @@ using namespace llvm; #define DEBUG_TYPE "dwarfdebug" DIEDwarfExpression::DIEDwarfExpression(const AsmPrinter &AP, - DwarfCompileUnit &CU, - DIELoc &DIE) - : DwarfExpression(AP.getDwarfVersion(), CU), AP(AP), - DIE(DIE) {} + DwarfCompileUnit &CU, DIELoc &DIE) + : DwarfExpression(AP.getDwarfVersion(), CU), AP(AP), OutDIE(DIE) {} void DIEDwarfExpression::emitOp(uint8_t Op, const char* Comment) { - CU.addUInt(DIE, dwarf::DW_FORM_data1, Op); + CU.addUInt(getActiveDIE(), dwarf::DW_FORM_data1, Op); } void DIEDwarfExpression::emitSigned(int64_t Value) { - CU.addSInt(DIE, dwarf::DW_FORM_sdata, Value); + CU.addSInt(getActiveDIE(), dwarf::DW_FORM_sdata, Value); } void DIEDwarfExpression::emitUnsigned(uint64_t Value) { - CU.addUInt(DIE, dwarf::DW_FORM_udata, Value); + CU.addUInt(getActiveDIE(), dwarf::DW_FORM_udata, Value); } void DIEDwarfExpression::emitData1(uint8_t Value) { - CU.addUInt(DIE, dwarf::DW_FORM_data1, Value); + CU.addUInt(getActiveDIE(), dwarf::DW_FORM_data1, Value); } void DIEDwarfExpression::emitBaseTypeRef(uint64_t Idx) { - CU.addBaseTypeRef(DIE, Idx); + CU.addBaseTypeRef(getActiveDIE(), Idx); } +void DIEDwarfExpression::enableTemporaryBuffer() { + assert(!IsBuffering && "Already buffering?"); + IsBuffering = true; +} + +void DIEDwarfExpression::disableTemporaryBuffer() { IsBuffering = false; } + +unsigned DIEDwarfExpression::getTemporaryBufferSize() { + return TmpDIE.ComputeSize(&AP); +} + +void DIEDwarfExpression::commitTemporaryBuffer() { OutDIE.takeValues(TmpDIE); } + bool DIEDwarfExpression::isFrameRegister(const TargetRegisterInfo &TRI, unsigned MachineReg) { return MachineReg == TRI.getFrameRegister(*AP.MF);