[ThinLTO] Add option to dump value name to GUID mapping

[tejohnson]

Summary

Useful for debugging since we lose this correlation after the permodule
summary/VST is read and until we later materialize source modules in the
function importer.

[mehdi_amini]

That's close to what I implemented locally when I was debugging this code last month.
My plan to have a "nice" solution was to dump a map in a file that could be loaded by other pieces. For instance you could use the map file by doing opt -function-import .... -debug -debug-map-guid=path/to/map and expose an API that convert GUID to name.

[mehdi_amini]

Maybe on the short term it is not worth investing time in this and I won't oppose to add the easy solution you have.

[tejohnson]

In D18555#389713, @joker.eph wrote:

That's close to what I implemented locally when I was debugging this code last month.
My plan to have a "nice" solution was to dump a map in a file that could be loaded by other pieces. For instance you could use the map file by doing opt -function-import .... -debug -debug-map-guid=path/to/map and expose an API that convert GUID to name.

In D18555#389715, @joker.eph wrote:

Maybe on the short term it is not worth investing time in this and I won't oppose to add the easy solution you have.

Yea, I thought about something along those lines too, but decided the simple solution was sufficient for now. Note that this patch would be a subset of that approach anyway since it gives you the map that would be fed back in.

[mehdi_amini]

Well it is not clear to me that it is an intermediate step, because ultimately you need a way to merge the information. I would have tried to address it a thin-link time.

But, ok it is useful enough and there is no other concrete plan right now, so LGTM.

lib/Bitcode/Reader/BitcodeReader.cpp

 #include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/ModuleSummaryIndex.h"
 #include "llvm/IR/OperandTraits.h"
 #include "llvm/IR/Operator.h"
 #include "llvm/IR/ValueHandle.h"
+#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/DataStream.h"
+#include "llvm/Support/Debug.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/raw_ostream.h"
 #include <deque>
 
 using namespace llvm;
 
+static cl::opt<bool> PrintSummaryGUIDs(
+    "print-summary-global-ids", cl::init(false), cl::Hidden,
+    cl::desc(
+        "Print the global id for each value when reading the module summary"));
+
 namespace {
 enum {
   SWITCH_INST_MAGIC = 0x4B5 // May 2012 => 1205 => Hex
 };
 
 class BitcodeReaderValueList {
   std::vector<WeakVH> ValuePtrs;
 
case bitc::VST_CODE_ENTRY: { // VST_CODE_ENTRY: [valueid, namechar x N]
       std::unique_ptr<GlobalValueInfo> GlobalValInfo =
           llvm::make_unique<GlobalValueInfo>();
       assert(!SourceFileName.empty());
       auto VLI = ValueIdToLinkageMap.find(ValueID);
       assert(VLI != ValueIdToLinkageMap.end() &&
              "No linkage found for VST entry?");
       std::string GlobalId = GlobalValue::getGlobalIdentifier(
           ValueName, VLI->second, SourceFileName);
-      TheIndex->addGlobalValueInfo(GlobalId, std::move(GlobalValInfo));
-      ValueIdToCallGraphGUIDMap[ValueID] = GlobalValue::getGUID(GlobalId);
+      uint64_t ValueGUID = GlobalValue::getGUID(GlobalId);
+      if (PrintSummaryGUIDs)
+        dbgs() << "GUID " << ValueGUID << " is " << ValueName << "\n";
+      TheIndex->addGlobalValueInfo(ValueGUID, std::move(GlobalValInfo));
+      ValueIdToCallGraphGUIDMap[ValueID] = ValueGUID;
       ValueName.clear();
       break;
     }
     case bitc::VST_CODE_FNENTRY: {
       // VST_CODE_FNENTRY: [valueid, offset, namechar x N]
       if (convertToString(Record, 2, ValueName))
         return error("Invalid record");
       unsigned ValueID = Record[0];
       uint64_t FuncOffset = Record[1];
       assert(!IsLazy && "Lazy summary read only supported for combined index");
       std::unique_ptr<GlobalValueInfo> FuncInfo =
           llvm::make_unique<GlobalValueInfo>(FuncOffset);
       assert(!SourceFileName.empty());
       auto VLI = ValueIdToLinkageMap.find(ValueID);
       assert(VLI != ValueIdToLinkageMap.end() &&
              "No linkage found for VST entry?");
       std::string FunctionGlobalId = GlobalValue::getGlobalIdentifier(
           ValueName, VLI->second, SourceFileName);
-      TheIndex->addGlobalValueInfo(FunctionGlobalId, std::move(FuncInfo));
-      ValueIdToCallGraphGUIDMap[ValueID] =
-          GlobalValue::getGUID(FunctionGlobalId);
+      uint64_t FunctionGUID = GlobalValue::getGUID(FunctionGlobalId);
+      if (PrintSummaryGUIDs)
+        dbgs() << "GUID " << FunctionGUID << " is " << ValueName << "\n";
+      TheIndex->addGlobalValueInfo(FunctionGUID, std::move(FuncInfo));
+      ValueIdToCallGraphGUIDMap[ValueID] = FunctionGUID;
 
       ValueName.clear();
       break;
     }
     case bitc::VST_CODE_COMBINED_GVDEFENTRY: {
       // VST_CODE_COMBINED_GVDEFENTRY: [valueid, offset, guid]
       unsigned ValueID = Record[0];
       uint64_t GlobalValSummaryOffset = Record[1];

test/Transforms/FunctionImport/funcimport.ll

 ; Do setup work for all below tests: generate bitcode and combined index
 ; RUN: llvm-as -module-summary %s -o %t.bc
 ; RUN: llvm-as -module-summary %p/Inputs/funcimport.ll -o %t2.bc
-; RUN: llvm-lto -thinlto -o %t3 %t.bc %t2.bc
+; RUN: llvm-lto -thinlto -print-summary-global-ids -o %t3 %t.bc %t2.bc 2>&1 | FileCheck %s --check-prefix=GUID
 
 ; Do the import now
 ; RUN: opt -function-import -stats -print-imports -summary-file %t3.thinlto.bc %t.bc -S 2>&1 | FileCheck %s --check-prefix=CHECK --check-prefix=INSTLIMDEF
 ; "-stats" requires +Asserts.
 ; REQUIRES: asserts
 
 ; Test import with smaller instruction limit
 ; RUN: opt -function-import -summary-file %t3.thinlto.bc %t.bc -import-instr-limit=5 -S | FileCheck %s --check-prefix=CHECK --check-prefix=INSTLIM5

 declare void @weakfunc(...) #1
 
 ; INSTLIMDEF-DAG: Import funcwithpersonality
 ; INSTLIMDEF-DAG: define available_externally hidden void @funcwithpersonality.llvm.2() personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
 ; INSTLIM5-DAG: declare hidden void @funcwithpersonality.llvm.2()
 
 ; INSTLIMDEF-DAG: Import globalfunc2
 ; INSTLIMDEF-DAG: 11 function-import - Number of functions imported
+
+; The GUID values should be stable unless the global identifier scheme
+; is changed.
+; GUID-DAG: GUID 18438612909910340889 is weakalias
+; GUID-DAG: GUID 10419849736188691048 is referenceglobals
+; GUID-DAG: GUID 9779356664709680872 is weakfunc
+; GUID-DAG: GUID 15822663052811949562 is main
+; GUID-DAG: GUID 1794834399867852914 is referencecommon
+; GUID-DAG: GUID 12695095382722328222 is analias
+; GUID-DAG: GUID 11460932053523480915 is referencestatics
+; GUID-DAG: GUID 17082925359558765443 is linkoncealias
+; GUID-DAG: GUID 16956293738471118660 is setfuncptr
+; GUID-DAG: GUID 800887449839734011 is callfuncptr
+; GUID-DAG: GUID 12108029313449967842 is funcwithpersonality
+; GUID-DAG: GUID 16956293738471118660 is setfuncptr
+; GUID-DAG: GUID 15894399990123115248 is staticfunc2
+; GUID-DAG: GUID 1233668236132380018 is __gxx_personality_v0
+; GUID-DAG: GUID 11460932053523480915 is referencestatics
+; GUID-DAG: GUID 8332887114342655934 is globalfunc1
+; GUID-DAG: GUID 2602152165807499502 is globalfunc2
+; GUID-DAG: GUID 9342344237287280920 is P
+; GUID-DAG: GUID 17578217388980876465 is staticvar
+; GUID-DAG: GUID 3013670425691502549 is commonvar
+; GUID-DAG: GUID 18438612909910340889 is weakalias
+; GUID-DAG: GUID 13921022463002872889 is staticfunc
+; GUID-DAG: GUID 9779356664709680872 is weakfunc
+; GUID-DAG: GUID 10419849736188691048 is referenceglobals
+; GUID-DAG: GUID 8769477226392140800 is weakvar
+; GUID-DAG: GUID 16489816843137310249 is staticconstvar
+; GUID-DAG: GUID 12695095382722328222 is analias
+; GUID-DAG: GUID 12887606300320728018 is globalvar
+; GUID-DAG: GUID 1794834399867852914 is referencecommon
+; GUID-DAG: GUID 17082925359558765443 is linkoncealias
+; GUID-DAG: GUID 800887449839734011 is callfuncptr
+; GUID-DAG: GUID 7812846502172333492 is linkoncefunc