Index: include/llvm/IR/ModuleSummaryIndex.h
===================================================================
--- include/llvm/IR/ModuleSummaryIndex.h
+++ include/llvm/IR/ModuleSummaryIndex.h
@@ -47,7 +47,13 @@
 
 /// \brief Class to accumulate and hold information about a callee.
 struct CalleeInfo {
-  enum class HotnessType : uint8_t { Unknown = 0, Cold = 1, None = 2, Hot = 3 };
+  enum class HotnessType : uint8_t {
+    Unknown = 0,
+    Cold = 1,
+    None = 2,
+    Hot = 3,
+    Critical = 4
+  };
   HotnessType Hotness = HotnessType::Unknown;
 
   CalleeInfo() = default;
Index: lib/Analysis/ModuleSummaryAnalysis.cpp
===================================================================
--- lib/Analysis/ModuleSummaryAnalysis.cpp
+++ lib/Analysis/ModuleSummaryAnalysis.cpp
@@ -266,7 +266,7 @@
   // sample PGO, to enable the same inlines as the profiled optimized binary.
   for (auto &I : F.getImportGUIDs())
     CallGraphEdges[Index.getOrInsertValueInfo(I)].updateHotness(
-        CalleeInfo::HotnessType::Hot);
+        CalleeInfo::HotnessType::Critical);
 
   bool NonRenamableLocal = isNonRenamableLocal(F);
   bool NotEligibleForImport =
Index: lib/Transforms/IPO/FunctionImport.cpp
===================================================================
--- lib/Transforms/IPO/FunctionImport.cpp
+++ lib/Transforms/IPO/FunctionImport.cpp
@@ -64,6 +64,12 @@
     "import-hot-multiplier", cl::init(3.0), cl::Hidden, cl::value_desc("x"),
     cl::desc("Multiply the `import-instr-limit` threshold for hot callsites"));
 
+static cl::opt<float> ImportCriticalMultiplier(
+    "import-critical-multiplier", cl::init(100.0), cl::Hidden,
+    cl::value_desc("x"),
+    cl::desc(
+        "Multiply the `import-instr-limit` threshold for critical callsites"));
+
 // FIXME: This multiplier was not really tuned up.
 static cl::opt<float> ImportColdMultiplier(
     "import-cold-multiplier", cl::init(0), cl::Hidden, cl::value_desc("N"),
@@ -207,6 +213,8 @@
         return ImportHotMultiplier;
       if (Hotness == CalleeInfo::HotnessType::Cold)
         return ImportColdMultiplier;
+      if (Hotness == CalleeInfo::HotnessType::Critical)
+        return ImportCriticalMultiplier;
       return 1.0;
     };
 
Index: test/Bitcode/thinlto-function-summary-callgraph-profile-summary.ll
===================================================================
--- test/Bitcode/thinlto-function-summary-callgraph-profile-summary.ll
+++ test/Bitcode/thinlto-function-summary-callgraph-profile-summary.ll
@@ -29,7 +29,7 @@
 ; CHECK-NEXT:    <VERSION
 ; CHECK-NEXT:    <VALUE_GUID op0=25 op1=123/>
 ; op4=hot1 op6=cold op8=hot2 op10=hot4 op12=none1 op14=hot3 op16=none2 op18=none3 op20=123
-; CHECK-NEXT:    <PERMODULE_PROFILE {{.*}} op4=1 op5=3 op6=5 op7=1 op8=2 op9=3 op10=4 op11=1 op12=6 op13=2 op14=3 op15=3 op16=7 op17=2 op18=8 op19=2 op20=25 op21=3/>
+; CHECK-NEXT:    <PERMODULE_PROFILE {{.*}} op4=1 op5=3 op6=5 op7=1 op8=2 op9=3 op10=4 op11=1 op12=6 op13=2 op14=3 op15=3 op16=7 op17=2 op18=8 op19=2 op20=25 op21=4/>
 ; CHECK-NEXT:  </GLOBALVAL_SUMMARY_BLOCK>
 
 ; CHECK: <STRTAB_BLOCK
Index: test/Bitcode/thinlto-function-summary-callgraph-sample-profile-summary.ll
===================================================================
--- test/Bitcode/thinlto-function-summary-callgraph-sample-profile-summary.ll
+++ test/Bitcode/thinlto-function-summary-callgraph-sample-profile-summary.ll
@@ -29,7 +29,7 @@
 ; CHECK-NEXT:    <VERSION
 ; CHECK-NEXT:    <VALUE_GUID op0=25 op1=123/>
 ; op4=hot1 op6=cold op8=hot2 op10=hot4 op12=none1 op14=hot3 op16=none2 op18=none3 op20=123
-; CHECK-NEXT:    <PERMODULE_PROFILE {{.*}} op4=1 op5=3 op6=5 op7=1 op8=2 op9=3 op10=4 op11=3 op12=6 op13=2 op14=3 op15=3 op16=7 op17=2 op18=8 op19=2 op20=25 op21=3/>
+; CHECK-NEXT:    <PERMODULE_PROFILE {{.*}} op4=1 op5=3 op6=5 op7=1 op8=2 op9=3 op10=4 op11=3 op12=6 op13=2 op14=3 op15=3 op16=7 op17=2 op18=8 op19=2 op20=25 op21=4/>
 ; CHECK-NEXT:  </GLOBALVAL_SUMMARY_BLOCK>
 
 ; CHECK: <STRTAB_BLOCK