diff --git a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
--- a/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
+++ b/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
@@ -210,12 +210,11 @@
 // Command line option to enable/disable the warning about a hash mismatch in
 // the profile data for Comdat functions, which often turns out to be false
 // positive due to the pre-instrumentation inline.
-static cl::opt<bool>
-    NoPGOWarnMismatchComdat("no-pgo-warn-mismatch-comdat", cl::init(true),
-                            cl::Hidden,
-                            cl::desc("The option is used to turn on/off "
-                                     "warnings about hash mismatch for comdat "
-                                     "functions."));
+static cl::opt<bool> NoPGOWarnMismatchComdatWeak(
+    "no-pgo-warn-mismatch-comdat-weak", cl::init(true), cl::Hidden,
+    cl::desc("The option is used to turn on/off "
+             "warnings about hash mismatch for comdat "
+             "or weak functions."));
 
 // Command line option to enable/disable select instruction instrumentation.
 static cl::opt<bool>
@@ -287,6 +286,11 @@
     cl::desc("Set the threshold for pgo-verify-bfi: skip the counts whose "
              "profile count value is below."));
 
+static cl::opt<std::string> PGOTraceFuncHash(
+    "pgo-trace-func-hash", cl::init("-"), cl::Hidden,
+    cl::value_desc("function name"),
+    cl::desc("Trace the hash of the function with this name."));
+
 namespace llvm {
 // Command line option to turn on CFG dot dump after profile annotation.
 // Defined in Analysis/BlockFrequencyInfo.cpp:  -pgo-view-counts
@@ -630,6 +634,10 @@
                       << ", High32 CRC = " << JCH.getCRC());
   }
   LLVM_DEBUG(dbgs() << ", Hash = " << FunctionHash << "\n";);
+
+  if (PGOTraceFuncHash != "-" && F.getName().contains(PGOTraceFuncHash))
+    dbgs() << "Funcname=" << F.getName() << ", Hash=" << FunctionHash
+           << " in building " << F.getParent()->getSourceFileName() << "\n";
 }
 
 // Check if we can safely rename this Comdat function.
@@ -1233,10 +1241,11 @@
         IsCS ? NumOfCSPGOMismatch++ : NumOfPGOMismatch++;
         SkipWarning =
             NoPGOWarnMismatch ||
-            (NoPGOWarnMismatchComdat &&
-             (F.hasComdat() ||
+            (NoPGOWarnMismatchComdatWeak &&
+             (F.hasComdat() || F.getLinkage() == GlobalValue::WeakAnyLinkage ||
               F.getLinkage() == GlobalValue::AvailableExternallyLinkage));
-        LLVM_DEBUG(dbgs() << "hash mismatch (skip=" << SkipWarning << ")");
+        LLVM_DEBUG(dbgs() << "hash mismatch (hash= " << FuncInfo.FunctionHash
+                          << " skip=" << SkipWarning << ")");
         // Emit function metadata indicating PGO profile mismatch.
         annotateFunctionWithHashMismatch(F, M->getContext());
       }