Index: llvm/docs/LangRef.rst
===================================================================
--- llvm/docs/LangRef.rst
+++ llvm/docs/LangRef.rst
@@ -14868,7 +14868,7 @@
 
 ::
 
-      declare void @llvm.trap() noreturn nounwind
+      declare void @llvm.trap() cold noreturn nounwind
 
 Overview:
 """""""""
Index: llvm/include/llvm/IR/Intrinsics.td
===================================================================
--- llvm/include/llvm/IR/Intrinsics.td
+++ llvm/include/llvm/IR/Intrinsics.td
@@ -90,6 +90,10 @@
 
 def IntrNoReturn : IntrinsicProperty;
 
+// IntrCold - Calls to this intrinsic are cold.
+// Parallels the cold attribute on LLVM IR functions.
+def IntrCold : IntrinsicProperty;
+
 // IntrNoduplicate - Calls to this intrinsic cannot be duplicated.
 // Parallels the noduplicate attribute on LLVM IR functions.
 def IntrNoDuplicate : IntrinsicProperty;
@@ -867,7 +871,7 @@
 //
 def int_flt_rounds : Intrinsic<[llvm_i32_ty]>,
                      GCCBuiltin<"__builtin_flt_rounds">;
-def int_trap : Intrinsic<[], [], [IntrNoReturn]>,
+def int_trap : Intrinsic<[], [], [IntrNoReturn, IntrCold]>,
                GCCBuiltin<"__builtin_trap">;
 def int_debugtrap : Intrinsic<[]>,
                     GCCBuiltin<"__builtin_debugtrap">;
Index: llvm/lib/Transforms/IPO/HotColdSplitting.cpp
===================================================================
--- llvm/lib/Transforms/IPO/HotColdSplitting.cpp
+++ llvm/lib/Transforms/IPO/HotColdSplitting.cpp
@@ -98,36 +98,27 @@
   return !(isa<ReturnInst>(I) || isa<IndirectBrInst>(I));
 }
 
-static bool exceptionHandlingFunctions(const CallInst *CI) {
-  auto F = CI->getCalledFunction();
-  if (!F)
-    return false;
-  auto FName = F->getName();
-  return FName == "__cxa_begin_catch" ||
-         FName == "__cxa_free_exception" ||
-         FName == "__cxa_allocate_exception" ||
-         FName == "__cxa_begin_catch" ||
-         FName == "__cxa_end_catch";
-}
-
-static bool unlikelyExecuted(const BasicBlock &BB) {
-  if (blockEndsInUnreachable(BB))
-    return true;
+bool unlikelyExecuted(const BasicBlock &BB) {
   // Exception handling blocks are unlikely executed.
   if (BB.isEHPad())
     return true;
+
+  if (blockEndsInUnreachable(BB)) {
+    // Calls to noreturn functions are followed by an unreachable inst, but
+    // the call itself may be warm (e.g. longjmp, or exit).
+    if (auto *CI =
+            dyn_cast_or_null<CallInst>(BB.getTerminator()->getPrevNode()))
+      if (CI->hasFnAttr(Attribute::NoReturn) && !CI->hasFnAttr(Attribute::Cold))
+        return false;
+    return true;
+  }
+
   for (const Instruction &I : BB)
-    if (const CallInst *CI = dyn_cast<CallInst>(&I)) {
-      // The block is cold if it calls functions tagged as cold or noreturn.
-      if (CI->hasFnAttr(Attribute::Cold) ||
-          CI->hasFnAttr(Attribute::NoReturn) ||
-          exceptionHandlingFunctions(CI))
+    if (const CallInst *CI = dyn_cast<CallInst>(&I))
+      // The block is cold if it calls a cold function.
+      if (CI->hasFnAttr(Attribute::Cold))
         return true;
 
-      // Assume that inline assembly is hot code.
-      if (isa<InlineAsm>(CI->getCalledValue()))
-        return false;
-    }
   return false;
 }
 
Index: llvm/test/Feature/intrinsics.ll
===================================================================
--- llvm/test/Feature/intrinsics.ll
+++ llvm/test/Feature/intrinsics.ll
@@ -70,4 +70,4 @@
 }
 
 ; CHECK: attributes #0 = { nounwind readnone speculatable }
-; CHECK: attributes #1 = { noreturn nounwind }
+; CHECK: attributes #1 = { cold noreturn nounwind }
Index: llvm/test/Transforms/HotColdSplit/noreturn.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/HotColdSplit/noreturn.ll
@@ -0,0 +1,53 @@
+; RUN: opt -hotcoldsplit -S < %s | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.14.0"
+
+%struct.__jmp_buf_tag = type { [8 x i64], i32, %struct.__sigset_t }
+%struct.__sigset_t = type { [16 x i64] }
+
+; Don't outline noreturn calls which aren't explicitly marked cold.
+
+; CHECK-LABEL: define {{.*}}@foo(
+; CHECK-NOT: foo.cold.1
+define void @foo(i32, %struct.__jmp_buf_tag*) {
+  %3 = icmp eq i32 %0, 0
+  tail call void @_Z10sideeffectv()
+  br i1 %3, label %5, label %4
+
+; <label>:4:                                      ; preds = %2
+  tail call void @longjmp(%struct.__jmp_buf_tag* %1, i32 0)
+  unreachable
+
+; <label>:5:                                      ; preds = %2
+  ret void
+}
+
+; Do outline noreturn calls marked cold.
+
+; CHECK-LABEL: define {{.*}}@bar(
+; CHECK: call {{.*}}@bar.cold.1(
+
+; CHECK-LABEL: define {{.*}}@bar.cold.1(
+; CHECK: call {{.*}}@llvm.trap(
+define void @bar(i32) {
+  %2 = icmp eq i32 %0, 0
+  tail call void @_Z10sideeffectv()
+  br i1 %2, label %sink, label %exit
+
+sink:
+  tail call void @_Z10sideeffectv()
+  tail call void @_Z10sideeffectv()
+  tail call void @_Z10sideeffectv()
+  call void @llvm.trap()
+  unreachable
+
+exit:
+  ret void
+}
+
+declare void @llvm.trap() noreturn cold
+
+declare void @_Z10sideeffectv()
+
+declare void @longjmp(%struct.__jmp_buf_tag*, i32) noreturn nounwind
Index: llvm/test/Transforms/HotColdSplit/outline-cold-asm.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/HotColdSplit/outline-cold-asm.ll
@@ -0,0 +1,27 @@
+; RUN: opt -hotcoldsplit -S < %s | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.14.0"
+
+; CHECK-LABEL: define {{.*}}@fun(
+; CHECK: call {{.*}}@fun.cold.1(
+
+; CHECK-LABEL: define {{.*}}@fun.cold.1(
+; CHECK: asm ""
+
+define void @fun() {
+entry:
+  br i1 undef, label %if.then, label %if.else
+
+if.then:
+  ret void
+
+if.else:
+  call void asm "", ""()
+  call void @sink()
+  call void @sink()
+  call void @sink()
+  ret void
+}
+
+declare void @sink() cold
Index: llvm/test/Transforms/SimplifyCFG/switch-on-const-select.ll
===================================================================
--- llvm/test/Transforms/SimplifyCFG/switch-on-const-select.ll
+++ llvm/test/Transforms/SimplifyCFG/switch-on-const-select.ll
@@ -138,4 +138,4 @@
 declare void @bees.b() nounwind
 
 ; CHECK: attributes [[$NUW]] = { nounwind }
-; CHECK: attributes #1 = { noreturn nounwind }
+; CHECK: attributes #1 = { cold noreturn nounwind }
Index: llvm/utils/TableGen/CodeGenIntrinsics.h
===================================================================
--- llvm/utils/TableGen/CodeGenIntrinsics.h
+++ llvm/utils/TableGen/CodeGenIntrinsics.h
@@ -124,6 +124,9 @@
   /// True if the intrinsic is no-return.
   bool isNoReturn;
 
+  /// True if the intrinsic is cold.
+  bool isCold;
+
   /// True if the intrinsic is marked as convergent.
   bool isConvergent;
 
Index: llvm/utils/TableGen/CodeGenTarget.cpp
===================================================================
--- llvm/utils/TableGen/CodeGenTarget.cpp
+++ llvm/utils/TableGen/CodeGenTarget.cpp
@@ -536,6 +536,7 @@
   isCommutative = false;
   canThrow = false;
   isNoReturn = false;
+  isCold = false;
   isNoDuplicate = false;
   isConvergent = false;
   isSpeculatable = false;
@@ -682,6 +683,8 @@
       isConvergent = true;
     else if (Property->getName() == "IntrNoReturn")
       isNoReturn = true;
+    else if (Property->getName() == "IntrCold")
+      isCold = true;
     else if (Property->getName() == "IntrSpeculatable")
       isSpeculatable = true;
     else if (Property->getName() == "IntrHasSideEffects")
Index: llvm/utils/TableGen/IntrinsicEmitter.cpp
===================================================================
--- llvm/utils/TableGen/IntrinsicEmitter.cpp
+++ llvm/utils/TableGen/IntrinsicEmitter.cpp
@@ -489,6 +489,9 @@
     if (L->isNoReturn != R->isNoReturn)
       return R->isNoReturn;
 
+    if (L->isCold != R->isCold)
+      return R->isCold;
+
     if (L->isConvergent != R->isConvergent)
       return R->isConvergent;
 
@@ -622,7 +625,7 @@
 
     if (!intrinsic.canThrow ||
         intrinsic.ModRef != CodeGenIntrinsic::ReadWriteMem ||
-        intrinsic.isNoReturn || intrinsic.isNoDuplicate ||
+        intrinsic.isNoReturn || intrinsic.isCold || intrinsic.isNoDuplicate ||
         intrinsic.isConvergent || intrinsic.isSpeculatable) {
       OS << "      const Attribute::AttrKind Atts[] = {";
       bool addComma = false;
@@ -636,6 +639,12 @@
         OS << "Attribute::NoReturn";
         addComma = true;
       }
+      if (intrinsic.isCold) {
+        if (addComma)
+          OS << ",";
+        OS << "Attribute::Cold";
+        addComma = true;
+      }
       if (intrinsic.isNoDuplicate) {
         if (addComma)
           OS << ",";