[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, 14 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 92c4426..4100471 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -3729,6 +3729,17 @@ Value *LibCallSimplifier::optimizePuts(CallInst *CI, IRBuilderBase &B) {
   return nullptr;
 }
 
+Value *LibCallSimplifier::optimizeExit(CallInst *CI) {
+
+  // Mark 'exit' as cold if its not exit(0) (success).
+  const APInt *C;
+  if (!CI->hasFnAttr(Attribute::Cold) &&
+      match(CI->getArgOperand(0), m_APInt(C)) && !C->isZero()) {
+    CI->addFnAttr(Attribute::Cold);
+  }
+  return nullptr;
+}
+
 Value *LibCallSimplifier::optimizeBCopy(CallInst *CI, IRBuilderBase &B) {
   // bcopy(src, dst, n) -> llvm.memmove(dst, src, n)
   return copyFlags(*CI, B.CreateMemMove(CI->getArgOperand(1), Align(1),
@@ -4084,6 +4095,9 @@ Value *LibCallSimplifier::optimizeCall(CallInst *CI, IRBuilderBase &Builder) {
     case LibFunc_vfprintf:
     case LibFunc_fiprintf:
       return optimizeErrorReporting(CI, Builder, 0);
+    case LibFunc_exit:
+    case LibFunc_Exit:
+      return optimizeExit(CI);
     default:
       return nullptr;
     }