[Pseudo Probe] Use the name from debug info to compute GUID in probe …

…desc

This is to fix a GUID mismatch while decoding pseudo probe, a GUID from the inline tree is not in the GUID2FuncDescMap. It turned out that frontend could change the function name making it different from the one in debug info(https://reviews.llvm.org/D111009). Here change to use the function name from debug info to be consistent with the probe name from the inline stack.

Reviewed By: hoy, wenlei

Differential Revision: https://reviews.llvm.org/D146657

llvm/include/llvm/IR/MDBuilder.h

@@ -78,7 +78,7 @@ class MDBuilder {
   MDNode *createFunctionSectionPrefix(StringRef Prefix);
 
   /// Return metadata containing the pseudo probe descriptor for a function.
-  MDNode *createPseudoProbeDesc(uint64_t GUID, uint64_t Hash, Function *F);
+  MDNode *createPseudoProbeDesc(uint64_t GUID, uint64_t Hash, StringRef FName);
 
   /// Return metadata containing llvm statistics.
   MDNode *

llvm/lib/IR/MDBuilder.cpp

@@ -336,12 +336,12 @@ MDNode *MDBuilder::createIrrLoopHeaderWeight(uint64_t Weight) {
 }
 
 MDNode *MDBuilder::createPseudoProbeDesc(uint64_t GUID, uint64_t Hash,
-                                         Function *F) {
+                                         StringRef FName) {
   auto *Int64Ty = Type::getInt64Ty(Context);
   SmallVector<Metadata *, 3> Ops(3);
   Ops[0] = createConstant(ConstantInt::get(Int64Ty, GUID));
   Ops[1] = createConstant(ConstantInt::get(Int64Ty, Hash));
-  Ops[2] = createString(F->getName());
+  Ops[2] = createString(FName);
   return MDNode::get(Context, Ops);
 }
 

llvm/lib/Transforms/IPO/SampleProfileProbe.cpp

@@ -286,9 +286,16 @@ uint32_t SampleProfileProber::getCallsiteId(const Instruction *Call) const {
 void SampleProfileProber::instrumentOneFunc(Function &F, TargetMachine *TM) {
   Module *M = F.getParent();
   MDBuilder MDB(F.getContext());
-  // Compute a GUID without considering the function's linkage type. This is
-  // fine since function name is the only key in the profile database.
-  uint64_t Guid = Function::getGUID(F.getName());
+  // Since the GUID from probe desc and inline stack are computed seperately, we
+  // need to make sure their names are consistent, so here also use the name
+  // from debug info.
+  StringRef FName = F.getName();
+  if (auto *SP = F.getSubprogram()) {
+    FName = SP->getLinkageName();
+    if (FName.empty())
+      FName = SP->getName();
+  }
+  uint64_t Guid = Function::getGUID(FName);
 
   // Assign an artificial debug line to a probe that doesn't come with a real
   // line. A probe not having a debug line will get an incomplete inline
@@ -371,7 +378,7 @@ void SampleProfileProber::instrumentOneFunc(Function &F, TargetMachine *TM) {
   // - FunctionHash.
   // - FunctionName
   auto Hash = getFunctionHash();
-  auto *MD = MDB.createPseudoProbeDesc(Guid, Hash, &F);
+  auto *MD = MDB.createPseudoProbeDesc(Guid, Hash, FName);
   auto *NMD = M->getNamedMetadata(PseudoProbeDescMetadataName);
   assert(NMD && "llvm.pseudo_probe_desc should be pre-created");
   NMD->addOperand(MD);