SamplePGO ThinLTO ICP fix for local functions.

Summary:
In SamplePGO, if the profile is collected from non-LTO binary, and used to drive ThinLTO, the indirect call promotion may fail because ThinLTO adjusts local function names to avoid conflicts. There are two places of where the mismatch can happen:

1. thin-link prepends SourceFileName to front of FuncName to build the GUID (GlobalValue::getGlobalIdentifier). Unlike instrumentation FDO, SamplePGO does not use the PGOFuncName scheme and therefore the indirect call target profile data contains a hash of the OriginalName.
2. backend compiler promotes some local functions to global and appends .llvm.{$ModuleHash} to the end of the FuncName to derive PromotedFunctionName

This patch tries at the best effort to find the GUID from the original local function name (in profile), and use that in ICP promotion, and in SamplePGO matching that happens in the backend after importing/inlining:

1. in thin-link, it builds the map from OriginalName to GUID so that when thin-link reads in indirect call target profile (represented by OriginalName), it knows which GUID to import.
2. in backend compiler, if sample profile reader cannot find a profile match for PromotedFunctionName, it will try to find if there is a match for OriginalFunctionName.
3. in backend compiler, we build symbol table entry for OriginalFunctionName and pointer to the same symbol of PromotedFunctionName, so that ICP can find the correct target to promote.

Reviewers: mehdi_amini, tejohnson

Reviewed By: tejohnson

Subscribers: llvm-commits, Prazek

Differential Revision: https://reviews.llvm.org/D30754

llvm-svn: 297757

2 files changed, 16 insertions, 3 deletions

diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 9f1a3d60132..9e87f1aa96d 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -4846,6 +4846,7 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(
   // Keep around the last seen summary to be used when we see an optional
   // "OriginalName" attachement.
   GlobalValueSummary *LastSeenSummary = nullptr;
+  GlobalValue::GUID LastSeenGUID = 0;
   bool Combined = false;
 
   // We can expect to see any number of type ID information records before
@@ -5014,6 +5015,7 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(
       PendingTypeTestAssumeConstVCalls.clear();
       PendingTypeCheckedLoadConstVCalls.clear();
       LastSeenSummary = FS.get();
+      LastSeenGUID = GUID;
       FS->setModulePath(ModuleIdMap[ModuleId]);
       TheIndex.addGlobalValueSummary(GUID, std::move(FS));
       Combined = true;
@@ -5040,6 +5042,7 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(
       AS->setAliasee(AliaseeInModule);
 
       GlobalValue::GUID GUID = getGUIDFromValueId(ValueID).first;
+      LastSeenGUID = GUID;
       TheIndex.addGlobalValueSummary(GUID, std::move(AS));
       Combined = true;
       break;
@@ -5056,6 +5059,7 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(
       LastSeenSummary = FS.get();
       FS->setModulePath(ModuleIdMap[ModuleId]);
       GlobalValue::GUID GUID = getGUIDFromValueId(ValueID).first;
+      LastSeenGUID = GUID;
       TheIndex.addGlobalValueSummary(GUID, std::move(FS));
       Combined = true;
       break;
@@ -5066,8 +5070,10 @@ Error ModuleSummaryIndexBitcodeReader::parseEntireSummary(
       if (!LastSeenSummary)
         return error("Name attachment that does not follow a combined record");
       LastSeenSummary->setOriginalName(OriginalName);
+      TheIndex.addOriginalName(LastSeenGUID, OriginalName);
       // Reset the LastSeenSummary
       LastSeenSummary = nullptr;
+      LastSeenGUID = 0;
       break;
     }
     case bitc::FS_TYPE_TESTS: {
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 9f18375d484..db8079ee22d 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -3708,9 +3708,16 @@ void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
     for (auto &EI : FS->calls()) {
       // If this GUID doesn't have a value id, it doesn't have a function
       // summary and we don't need to record any calls to it.
-      if (!hasValueId(EI.first.getGUID()))
-        continue;
-      NameVals.push_back(getValueId(EI.first.getGUID()));
+      GlobalValue::GUID GUID = EI.first.getGUID();
+      if (!hasValueId(GUID)) {
+        // For SamplePGO, the indirect call targets for local functions will
+        // have its original name annotated in profile. We try to find the
+        // corresponding PGOFuncName as the GUID.
+        GUID = Index.getGUIDFromOriginalID(GUID);
+        if (GUID == 0 || !hasValueId(GUID))
+          continue;
+      }
+      NameVals.push_back(getValueId(GUID));
       if (HasProfileData)
         NameVals.push_back(static_cast<uint8_t>(EI.second.Hotness));
     }