<div dir="ltr"><br><div class="gmail_extra"><br><br><div class="gmail_quote">On Mon, Aug 12, 2013 at 6:21 PM, Eric Christopher <span dir="ltr"><<a href="mailto:echristo@gmail.com" target="_blank">echristo@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Author: echristo<br>
Date: Mon Aug 12 20:21:55 2013<br>
New Revision: 188243<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=188243&view=rev" target="_blank">http://llvm.org/viewvc/llvm-project?rev=188243&view=rev</a><br>
Log:<br>
Add the start of DIE hashing for DWARF4 type units and split dwarf<br>
CUs.<br>
<br>
Currently only hashes the name of CUs and the names of any children,<br>
but it's an obvious first step to show the framework. The testcase<br>
should continue to be correct, however, as it's an empty TU.<br>
<br>
Added:<br>
llvm/trunk/test/DebugInfo/X86/fission-hash.ll<br>
Modified:<br>
llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.cpp<br>
llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.h<br>
llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp<br>
<br>
Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.cpp?rev=188243&r1=188242&r2=188243&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.cpp?rev=188243&r1=188242&r2=188243&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.cpp (original)<br>
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.cpp Mon Aug 12 20:21:55 2013<br>
@@ -102,6 +102,92 @@ void DIEHash::addParentContext(DIE *Pare<br>
}<br>
}<br>
<br>
+// Collect all of the attributes for a particular DIE in single structure.<br>
+void DIEHash::collectAttributes(DIE *Die, DIEAttrs Attrs) {<br>
+ const SmallVectorImpl<DIEValue *> &Values = Die->getValues();<br>
+ const DIEAbbrev &Abbrevs = Die->getAbbrev();<br>
+<br>
+#define COLLECT_ATTR(NAME) \<br>
+ Attrs.NAME.Val = Values[i]; \<br>
+ Attrs.NAME.Desc = &Abbrevs.getData()[i];<br>
+<br>
+ for (size_t i = 0, e = Values.size(); i != e; ++i) {<br>
+ DEBUG(dbgs() << "Attribute: "<br>
+ << dwarf::AttributeString(Abbrevs.getData()[i].getAttribute())<br>
+ << " added.\n");<br>
+ switch (Abbrevs.getData()[i].getAttribute()) {<br>
+ case dwarf::DW_AT_name:<br>
+ COLLECT_ATTR(DW_AT_name);<br>
+ break;<br>
+ default:<br>
+ break;<br>
+ }<br>
+ }<br>
+}<br>
+<br>
+// Hash an individual attribute \param Attr based on the type of attribute and<br>
+// the form.<br>
+void DIEHash::hashAttribute(AttrEntry Attr) {<br>
+ const DIEValue *Value = Attr.Val;<br>
+ const DIEAbbrevData *Desc = Attr.Desc;<br>
+<br>
+ // TODO: Add support for types.<br>
+<br>
+ // Add the letter A to the hash.<br>
+ addULEB128('A');<br>
+<br>
+ // Then the attribute code and form.<br>
+ addULEB128(Desc->getAttribute());<br>
+ addULEB128(Desc->getForm());<br>
+<br>
+ // TODO: Add support for additional forms.<br>
+ switch (Desc->getForm()) {<br>
+ case dwarf::DW_FORM_strp:<br>
+ addString(cast<DIEString>(Value)->getString());<br>
+ break;<br>
+ }<br>
+}<br>
+<br>
+// Go through the attributes from \param Attrs in the order specified in 7.27.4<br>
+// and hash them.<br>
+void DIEHash::hashAttributes(DIEAttrs Attrs) {<br>
+#define ADD_ATTR(ATTR) \<br>
+ { \<br>
+ if (ATTR.Val != 0) \<br>
+ hashAttribute(ATTR); \<br>
+ }<br>
+<br>
+ // FIXME: Add the rest.<br>
+ ADD_ATTR(Attrs.DW_AT_name);<br>
+}<br>
+<br>
+// Add all of the attributes for \param Die to the hash.<br>
+void DIEHash::addAttributes(DIE *Die) {<br>
+ DIEAttrs Attrs;<br>
+ memset(&Attrs, 0, sizeof(Attrs));<br></blockquote><div><br></div><div>I'd thought this was equivalent to: <br><br> DIEAttrs Attrs = {};<br><br>is it not? Is there a benefit to writing it with memset?</div><div>
</div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
+ collectAttributes(Die, Attrs);<br>
+ hashAttributes(Attrs);<br>
+}<br>
+<br>
+// Compute the hash of a DIE. This is based on the type signature computation<br>
+// given in section 7.27 of the DWARF4 standard. It is the md5 hash of a<br>
+// flattened description of the DIE.<br>
+void DIEHash::computeHash(DIE *Die) {<br>
+<br>
+ // Append the letter 'D', followed by the DWARF tag of the DIE.<br>
+ addULEB128('D');<br>
+ addULEB128(Die->getTag());<br>
+<br>
+ // Add each of the attributes of the DIE.<br>
+ addAttributes(Die);<br>
+<br>
+ // Then hash each of the children of the DIE.<br>
+ for (std::vector<DIE *>::const_iterator I = Die->getChildren().begin(),<br>
+ E = Die->getChildren().end();<br>
+ I != E; ++I)<br>
+ computeHash(*I);<br>
+}<br>
+<br>
/// This is based on the type signature computation given in section 7.27 of the<br>
/// DWARF4 standard. It is the md5 hash of a flattened description of the DIE<br>
/// with the exception that we are hashing only the context and the name of the<br>
@@ -129,6 +215,24 @@ uint64_t DIEHash::computeDIEODRSignature<br>
MD5::MD5Result Result;<br>
Hash.final(Result);<br>
<br>
+ // ... take the least significant 8 bytes and return those. Our MD5<br>
+ // implementation always returns its results in little endian, swap bytes<br>
+ // appropriately.<br>
+ return *reinterpret_cast<support::ulittle64_t *>(Result + 8);<br>
+}<br>
+<br>
+/// This is based on the type signature computation given in section 7.27 of the<br>
+/// DWARF4 standard. It is an md5 hash of the flattened description of the DIE<br>
+/// with the inclusion of the full CU and all top level CU entities.<br>
+uint64_t DIEHash::computeCUSignature(DIE *Die) {<br>
+<br>
+ // Hash the DIE.<br>
+ computeHash(Die);<br>
+<br>
+ // Now return the result.<br>
+ MD5::MD5Result Result;<br>
+ Hash.final(Result);<br>
+<br>
// ... take the least significant 8 bytes and return those. Our MD5<br>
// implementation always returns its results in little endian, swap bytes<br>
// appropriately.<br>
<br>
Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.h?rev=188243&r1=188242&r2=188243&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.h?rev=188243&r1=188242&r2=188243&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.h (original)<br>
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DIEHash.h Mon Aug 12 20:21:55 2013<br>
@@ -20,15 +20,35 @@ class CompileUnit;<br>
/// \brief An object containing the capability of hashing and adding hash<br>
/// attributes onto a DIE.<br>
class DIEHash {<br>
+ // The entry for a particular attribute.<br>
+ struct AttrEntry {<br>
+ const DIEValue *Val;<br>
+ const DIEAbbrevData *Desc;<br>
+ };<br>
+<br>
+ // Collection of all attributes used in hashing a particular DIE.<br>
+ struct DIEAttrs {<br>
+ AttrEntry DW_AT_name;<br>
+ };<br>
+<br>
public:<br>
/// \brief Computes the ODR signature<br>
uint64_t computeDIEODRSignature(DIE *Die);<br>
<br>
+ /// \brief Computes the CU signature<br>
+ uint64_t computeCUSignature(DIE *Die);<br>
+<br>
// Helper routines to process parts of a DIE.<br>
- private:<br>
+private:<br>
/// \brief Adds the parent context of \param Die to the hash.<br>
void addParentContext(DIE *Die);<br>
-<br>
+<br>
+ /// \brief Adds the attributes of \param Die to the hash.<br>
+ void addAttributes(DIE *Die);<br>
+<br>
+ /// \brief Computes the full DWARF4 7.27 hash of the DIE.<br>
+ void computeHash(DIE *Die);<br>
+<br>
// Routines that add DIEValues to the hash.<br>
private:<br>
/// \brief Encodes and adds \param Value to the hash as a ULEB128.<br>
@@ -36,7 +56,17 @@ private:<br>
<br>
/// \brief Adds \param Str to the hash and includes a NULL byte.<br>
void addString(StringRef Str);<br>
-<br>
+<br>
+ /// \brief Collects the attributes of DIE \param Die into the \param Attrs<br>
+ /// structure.<br>
+ void collectAttributes(DIE *Die, DIEAttrs Attrs);<br>
+<br>
+ /// \brief Hashes the attributes in \param Attrs in order.<br>
+ void hashAttributes(DIEAttrs Attrs);<br>
+<br>
+ /// \brief Hashes an individual attribute.<br>
+ void hashAttribute(AttrEntry Attr);<br>
+<br>
private:<br>
MD5 Hash;<br>
};<br>
<br>
Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=188243&r1=188242&r2=188243&view=diff" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=188243&r1=188242&r2=188243&view=diff</a><br>
==============================================================================<br>
--- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)<br>
+++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Mon Aug 12 20:21:55 2013<br>
@@ -67,6 +67,11 @@ GenerateODRHash("generate-odr-hash", cl:<br>
cl::desc("Add an ODR hash to external type DIEs."),<br>
cl::init(false));<br>
<br>
+static cl::opt<bool><br>
+GenerateCUHash("generate-cu-hash", cl::Hidden,<br>
+ cl::desc("Add the CU hash as the dwo_id."),<br>
+ cl::init(false));<br>
+<br>
namespace {<br>
enum DefaultOnOff {<br>
Default,<br>
@@ -1024,14 +1029,19 @@ void DwarfDebug::finalizeModuleInfo() {<br>
// If we're splitting the dwarf out now that we've got the entire<br>
// CU then construct a skeleton CU based upon it.<br>
if (useSplitDwarf()) {<br>
+ uint64_t ID = 0;<br>
+ if (GenerateCUHash) {<br>
+ DIEHash CUHash;<br>
+ ID = CUHash.computeCUSignature(TheCU->getCUDie());<br>
+ }<br>
// This should be a unique identifier when we want to build .dwp files.<br>
TheCU->addUInt(TheCU->getCUDie(), dwarf::DW_AT_GNU_dwo_id,<br>
- dwarf::DW_FORM_data8, 0);<br>
+ dwarf::DW_FORM_data8, ID);<br>
// Now construct the skeleton CU associated.<br>
CompileUnit *SkCU = constructSkeletonCU(CUI->first);<br>
// This should be a unique identifier when we want to build .dwp files.<br>
SkCU->addUInt(SkCU->getCUDie(), dwarf::DW_AT_GNU_dwo_id,<br>
- dwarf::DW_FORM_data8, 0);<br>
+ dwarf::DW_FORM_data8, ID);<br>
}<br>
}<br>
<br>
<br>
Added: llvm/trunk/test/DebugInfo/X86/fission-hash.ll<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/fission-hash.ll?rev=188243&view=auto" target="_blank">http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/X86/fission-hash.ll?rev=188243&view=auto</a><br>
==============================================================================<br>
--- llvm/trunk/test/DebugInfo/X86/fission-hash.ll (added)<br>
+++ llvm/trunk/test/DebugInfo/X86/fission-hash.ll Mon Aug 12 20:21:55 2013<br>
@@ -0,0 +1,15 @@<br>
+; RUN: llc -split-dwarf=Enable -generate-cu-hash -O0 %s -mtriple=x86_64-unknown-linux-gnu -filetype=obj -o %t<br>
+; RUN: llvm-dwarfdump -debug-dump=all %t | FileCheck %s<br>
+<br>
+; The source is an empty file.<br>
+<br>
+; CHECK: DW_AT_GNU_dwo_id [DW_FORM_data8] (0x356a7d50a77f5177)<br>
+; CHECK: DW_AT_GNU_dwo_id [DW_FORM_data8] (0x356a7d50a77f5177)<br>
+<br>
+!<a href="http://llvm.dbg.cu" target="_blank">llvm.dbg.cu</a> = !{!0}<br>
+!llvm.module.flags = !{!3}<br>
+<br>
+!0 = metadata !{i32 786449, metadata !1, i32 12, metadata !"clang version 3.4 (trunk 188230) (llvm/trunk 188234)", i1 false, metadata !"", i32 0, metadata !2, metadata !2, metadata !2, metadata !2, metadata !2, metadata !"foo.dwo"} ; [ DW_TAG_compile_unit ] [/usr/local/google/home/echristo/tmp/foo.c] [DW_LANG_C99]<br>
+!1 = metadata !{metadata !"foo.c", metadata !"/usr/local/google/home/echristo/tmp"}<br>
+!2 = metadata !{i32 0}<br>
+!3 = metadata !{i32 2, metadata !"Dwarf Version", i32 3}<br>
<br>
<br>
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</blockquote></div><br></div></div>