[TLI] Add support for inferring attr `cold` on `exit`/`abort`

`abort` can be assumed always cold and assume non-zero `exit` status
as a `cold` path as well.

Closes #101003

1 files changed, 12 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
index 0c45bd8..898e5b0 100644
--- a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
@@ -48,6 +48,7 @@ STATISTIC(NumNoAlias, "Number of function returns inferred as noalias");
 STATISTIC(NumNoUndef, "Number of function returns inferred as noundef returns");
 STATISTIC(NumReturnedArg, "Number of arguments inferred as returned");
 STATISTIC(NumWillReturn, "Number of functions inferred as willreturn");
+STATISTIC(NumCold, "Number of functions inferred as cold");
 
 static bool setDoesNotAccessMemory(Function &F) {
   if (F.doesNotAccessMemory())
@@ -57,6 +58,14 @@ static bool setDoesNotAccessMemory(Function &F) {
   return true;
 }
 
+static bool setIsCold(Function &F) {
+  if (F.hasFnAttribute(Attribute::Cold))
+    return false;
+  F.addFnAttr(Attribute::Cold);
+  ++NumCold;
+  return true;
+}
+
 static bool setOnlyAccessesInaccessibleMemory(Function &F) {
   if (F.onlyAccessesInaccessibleMemory())
     return false;
@@ -1087,6 +1096,9 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
     Changed |= setOnlyWritesMemory(F, 0);
     Changed |= setDoesNotThrow(F);
     break;
+  case LibFunc_abort:
+    Changed |= setIsCold(F);
+    break;
   // int __nvvm_reflect(const char *)
   case LibFunc_nvvm_reflect:
     Changed |= setRetAndArgsNoUndef(F);