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Diffstat (limited to 'contrib/llvm/lib/CodeGen/AsmPrinter/DIEHash.cpp')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/AsmPrinter/DIEHash.cpp | 424 |
1 files changed, 424 insertions, 0 deletions
diff --git a/contrib/llvm/lib/CodeGen/AsmPrinter/DIEHash.cpp b/contrib/llvm/lib/CodeGen/AsmPrinter/DIEHash.cpp new file mode 100644 index 000000000000..15ade3c96dfe --- /dev/null +++ b/contrib/llvm/lib/CodeGen/AsmPrinter/DIEHash.cpp @@ -0,0 +1,424 @@ +//===-- llvm/CodeGen/DIEHash.cpp - Dwarf Hashing Framework ----------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file contains support for DWARF4 hashing of DIEs. +// +//===----------------------------------------------------------------------===// + +#include "DIEHash.h" +#include "ByteStreamer.h" +#include "DwarfDebug.h" +#include "llvm/ADT/ArrayRef.h" +#include "llvm/ADT/StringRef.h" +#include "llvm/BinaryFormat/Dwarf.h" +#include "llvm/CodeGen/AsmPrinter.h" +#include "llvm/CodeGen/DIE.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/Endian.h" +#include "llvm/Support/MD5.h" +#include "llvm/Support/raw_ostream.h" + +using namespace llvm; + +#define DEBUG_TYPE "dwarfdebug" + +/// \brief Grabs the string in whichever attribute is passed in and returns +/// a reference to it. +static StringRef getDIEStringAttr(const DIE &Die, uint16_t Attr) { + // Iterate through all the attributes until we find the one we're + // looking for, if we can't find it return an empty string. + for (const auto &V : Die.values()) + if (V.getAttribute() == Attr) + return V.getDIEString().getString(); + + return StringRef(""); +} + +/// \brief Adds the string in \p Str to the hash. This also hashes +/// a trailing NULL with the string. +void DIEHash::addString(StringRef Str) { + DEBUG(dbgs() << "Adding string " << Str << " to hash.\n"); + Hash.update(Str); + Hash.update(makeArrayRef((uint8_t)'\0')); +} + +// FIXME: The LEB128 routines are copied and only slightly modified out of +// LEB128.h. + +/// \brief Adds the unsigned in \p Value to the hash encoded as a ULEB128. +void DIEHash::addULEB128(uint64_t Value) { + DEBUG(dbgs() << "Adding ULEB128 " << Value << " to hash.\n"); + do { + uint8_t Byte = Value & 0x7f; + Value >>= 7; + if (Value != 0) + Byte |= 0x80; // Mark this byte to show that more bytes will follow. + Hash.update(Byte); + } while (Value != 0); +} + +void DIEHash::addSLEB128(int64_t Value) { + DEBUG(dbgs() << "Adding ULEB128 " << Value << " to hash.\n"); + bool More; + do { + uint8_t Byte = Value & 0x7f; + Value >>= 7; + More = !((((Value == 0) && ((Byte & 0x40) == 0)) || + ((Value == -1) && ((Byte & 0x40) != 0)))); + if (More) + Byte |= 0x80; // Mark this byte to show that more bytes will follow. + Hash.update(Byte); + } while (More); +} + +/// \brief Including \p Parent adds the context of Parent to the hash.. +void DIEHash::addParentContext(const DIE &Parent) { + + DEBUG(dbgs() << "Adding parent context to hash...\n"); + + // [7.27.2] For each surrounding type or namespace beginning with the + // outermost such construct... + SmallVector<const DIE *, 1> Parents; + const DIE *Cur = &Parent; + while (Cur->getParent()) { + Parents.push_back(Cur); + Cur = Cur->getParent(); + } + assert(Cur->getTag() == dwarf::DW_TAG_compile_unit || + Cur->getTag() == dwarf::DW_TAG_type_unit); + + // Reverse iterate over our list to go from the outermost construct to the + // innermost. + for (SmallVectorImpl<const DIE *>::reverse_iterator I = Parents.rbegin(), + E = Parents.rend(); + I != E; ++I) { + const DIE &Die = **I; + + // ... Append the letter "C" to the sequence... + addULEB128('C'); + + // ... Followed by the DWARF tag of the construct... + addULEB128(Die.getTag()); + + // ... Then the name, taken from the DW_AT_name attribute. + StringRef Name = getDIEStringAttr(Die, dwarf::DW_AT_name); + DEBUG(dbgs() << "... adding context: " << Name << "\n"); + if (!Name.empty()) + addString(Name); + } +} + +// Collect all of the attributes for a particular DIE in single structure. +void DIEHash::collectAttributes(const DIE &Die, DIEAttrs &Attrs) { + + for (const auto &V : Die.values()) { + DEBUG(dbgs() << "Attribute: " + << dwarf::AttributeString(V.getAttribute()) + << " added.\n"); + switch (V.getAttribute()) { +#define HANDLE_DIE_HASH_ATTR(NAME) \ + case dwarf::NAME: \ + Attrs.NAME = V; \ + break; +#include "DIEHashAttributes.def" + default: + break; + } + } +} + +void DIEHash::hashShallowTypeReference(dwarf::Attribute Attribute, + const DIE &Entry, StringRef Name) { + // append the letter 'N' + addULEB128('N'); + + // the DWARF attribute code (DW_AT_type or DW_AT_friend), + addULEB128(Attribute); + + // the context of the tag, + if (const DIE *Parent = Entry.getParent()) + addParentContext(*Parent); + + // the letter 'E', + addULEB128('E'); + + // and the name of the type. + addString(Name); + + // Currently DW_TAG_friends are not used by Clang, but if they do become so, + // here's the relevant spec text to implement: + // + // For DW_TAG_friend, if the referenced entry is the DW_TAG_subprogram, + // the context is omitted and the name to be used is the ABI-specific name + // of the subprogram (e.g., the mangled linker name). +} + +void DIEHash::hashRepeatedTypeReference(dwarf::Attribute Attribute, + unsigned DieNumber) { + // a) If T is in the list of [previously hashed types], use the letter + // 'R' as the marker + addULEB128('R'); + + addULEB128(Attribute); + + // and use the unsigned LEB128 encoding of [the index of T in the + // list] as the attribute value; + addULEB128(DieNumber); +} + +void DIEHash::hashDIEEntry(dwarf::Attribute Attribute, dwarf::Tag Tag, + const DIE &Entry) { + assert(Tag != dwarf::DW_TAG_friend && "No current LLVM clients emit friend " + "tags. Add support here when there's " + "a use case"); + // Step 5 + // If the tag in Step 3 is one of [the below tags] + if ((Tag == dwarf::DW_TAG_pointer_type || + Tag == dwarf::DW_TAG_reference_type || + Tag == dwarf::DW_TAG_rvalue_reference_type || + Tag == dwarf::DW_TAG_ptr_to_member_type) && + // and the referenced type (via the [below attributes]) + // FIXME: This seems overly restrictive, and causes hash mismatches + // there's a decl/def difference in the containing type of a + // ptr_to_member_type, but it's what DWARF says, for some reason. + Attribute == dwarf::DW_AT_type) { + // ... has a DW_AT_name attribute, + StringRef Name = getDIEStringAttr(Entry, dwarf::DW_AT_name); + if (!Name.empty()) { + hashShallowTypeReference(Attribute, Entry, Name); + return; + } + } + + unsigned &DieNumber = Numbering[&Entry]; + if (DieNumber) { + hashRepeatedTypeReference(Attribute, DieNumber); + return; + } + + // otherwise, b) use the letter 'T' as the marker, ... + addULEB128('T'); + + addULEB128(Attribute); + + // ... process the type T recursively by performing Steps 2 through 7, and + // use the result as the attribute value. + DieNumber = Numbering.size(); + computeHash(Entry); +} + +// Hash all of the values in a block like set of values. This assumes that +// all of the data is going to be added as integers. +void DIEHash::hashBlockData(const DIE::const_value_range &Values) { + for (const auto &V : Values) + Hash.update((uint64_t)V.getDIEInteger().getValue()); +} + +// Hash the contents of a loclistptr class. +void DIEHash::hashLocList(const DIELocList &LocList) { + HashingByteStreamer Streamer(*this); + DwarfDebug &DD = *AP->getDwarfDebug(); + const DebugLocStream &Locs = DD.getDebugLocs(); + for (const auto &Entry : Locs.getEntries(Locs.getList(LocList.getValue()))) + DD.emitDebugLocEntry(Streamer, Entry); +} + +// Hash an individual attribute \param Attr based on the type of attribute and +// the form. +void DIEHash::hashAttribute(const DIEValue &Value, dwarf::Tag Tag) { + dwarf::Attribute Attribute = Value.getAttribute(); + + // Other attribute values use the letter 'A' as the marker, and the value + // consists of the form code (encoded as an unsigned LEB128 value) followed by + // the encoding of the value according to the form code. To ensure + // reproducibility of the signature, the set of forms used in the signature + // computation is limited to the following: DW_FORM_sdata, DW_FORM_flag, + // DW_FORM_string, and DW_FORM_block. + + switch (Value.getType()) { + case DIEValue::isNone: + llvm_unreachable("Expected valid DIEValue"); + + // 7.27 Step 3 + // ... An attribute that refers to another type entry T is processed as + // follows: + case DIEValue::isEntry: + hashDIEEntry(Attribute, Tag, Value.getDIEEntry().getEntry()); + break; + case DIEValue::isInteger: { + addULEB128('A'); + addULEB128(Attribute); + switch (Value.getForm()) { + case dwarf::DW_FORM_data1: + case dwarf::DW_FORM_data2: + case dwarf::DW_FORM_data4: + case dwarf::DW_FORM_data8: + case dwarf::DW_FORM_udata: + case dwarf::DW_FORM_sdata: + addULEB128(dwarf::DW_FORM_sdata); + addSLEB128((int64_t)Value.getDIEInteger().getValue()); + break; + // DW_FORM_flag_present is just flag with a value of one. We still give it a + // value so just use the value. + case dwarf::DW_FORM_flag_present: + case dwarf::DW_FORM_flag: + addULEB128(dwarf::DW_FORM_flag); + addULEB128((int64_t)Value.getDIEInteger().getValue()); + break; + default: + llvm_unreachable("Unknown integer form!"); + } + break; + } + case DIEValue::isString: + addULEB128('A'); + addULEB128(Attribute); + addULEB128(dwarf::DW_FORM_string); + addString(Value.getDIEString().getString()); + break; + case DIEValue::isInlineString: + addULEB128('A'); + addULEB128(Attribute); + addULEB128(dwarf::DW_FORM_string); + addString(Value.getDIEInlineString().getString()); + break; + case DIEValue::isBlock: + case DIEValue::isLoc: + case DIEValue::isLocList: + addULEB128('A'); + addULEB128(Attribute); + addULEB128(dwarf::DW_FORM_block); + if (Value.getType() == DIEValue::isBlock) { + addULEB128(Value.getDIEBlock().ComputeSize(AP)); + hashBlockData(Value.getDIEBlock().values()); + } else if (Value.getType() == DIEValue::isLoc) { + addULEB128(Value.getDIELoc().ComputeSize(AP)); + hashBlockData(Value.getDIELoc().values()); + } else { + // We could add the block length, but that would take + // a bit of work and not add a lot of uniqueness + // to the hash in some way we could test. + hashLocList(Value.getDIELocList()); + } + break; + // FIXME: It's uncertain whether or not we should handle this at the moment. + case DIEValue::isExpr: + case DIEValue::isLabel: + case DIEValue::isDelta: + llvm_unreachable("Add support for additional value types."); + } +} + +// Go through the attributes from \param Attrs in the order specified in 7.27.4 +// and hash them. +void DIEHash::hashAttributes(const DIEAttrs &Attrs, dwarf::Tag Tag) { +#define HANDLE_DIE_HASH_ATTR(NAME) \ + { \ + if (Attrs.NAME) \ + hashAttribute(Attrs.NAME, Tag); \ + } +#include "DIEHashAttributes.def" + // FIXME: Add the extended attributes. +} + +// Add all of the attributes for \param Die to the hash. +void DIEHash::addAttributes(const DIE &Die) { + DIEAttrs Attrs = {}; + collectAttributes(Die, Attrs); + hashAttributes(Attrs, Die.getTag()); +} + +void DIEHash::hashNestedType(const DIE &Die, StringRef Name) { + // 7.27 Step 7 + // ... append the letter 'S', + addULEB128('S'); + + // the tag of C, + addULEB128(Die.getTag()); + + // and the name. + addString(Name); +} + +// Compute the hash of a DIE. This is based on the type signature computation +// given in section 7.27 of the DWARF4 standard. It is the md5 hash of a +// flattened description of the DIE. +void DIEHash::computeHash(const DIE &Die) { + // Append the letter 'D', followed by the DWARF tag of the DIE. + addULEB128('D'); + addULEB128(Die.getTag()); + + // Add each of the attributes of the DIE. + addAttributes(Die); + + // Then hash each of the children of the DIE. + for (auto &C : Die.children()) { + // 7.27 Step 7 + // If C is a nested type entry or a member function entry, ... + if (isType(C.getTag()) || C.getTag() == dwarf::DW_TAG_subprogram) { + StringRef Name = getDIEStringAttr(C, dwarf::DW_AT_name); + // ... and has a DW_AT_name attribute + if (!Name.empty()) { + hashNestedType(C, Name); + continue; + } + } + computeHash(C); + } + + // Following the last (or if there are no children), append a zero byte. + Hash.update(makeArrayRef((uint8_t)'\0')); +} + +/// This is based on the type signature computation given in section 7.27 of the +/// DWARF4 standard. It is an md5 hash of the flattened description of the DIE +/// with the inclusion of the full CU and all top level CU entities. +// TODO: Initialize the type chain at 0 instead of 1 for CU signatures. +uint64_t DIEHash::computeCUSignature(StringRef DWOName, const DIE &Die) { + Numbering.clear(); + Numbering[&Die] = 1; + + if (!DWOName.empty()) + Hash.update(DWOName); + // Hash the DIE. + computeHash(Die); + + // Now return the result. + MD5::MD5Result Result; + Hash.final(Result); + + // ... take the least significant 8 bytes and return those. Our MD5 + // implementation always returns its results in little endian, so we actually + // need the "high" word. + return Result.high(); +} + +/// This is based on the type signature computation given in section 7.27 of the +/// DWARF4 standard. It is an md5 hash of the flattened description of the DIE +/// with the inclusion of additional forms not specifically called out in the +/// standard. +uint64_t DIEHash::computeTypeSignature(const DIE &Die) { + Numbering.clear(); + Numbering[&Die] = 1; + + if (const DIE *Parent = Die.getParent()) + addParentContext(*Parent); + + // Hash the DIE. + computeHash(Die); + + // Now return the result. + MD5::MD5Result Result; + Hash.final(Result); + + // ... take the least significant 8 bytes and return those. Our MD5 + // implementation always returns its results in little endian, so we actually + // need the "high" word. + return Result.high(); +} |