[CodeExtractor] Mark functions noreturn when applicable

This eliminates the outlining penalty for llvm.trap/unreachable, because
callers no longer have to emit cleanup/ret instructions after calling an
outlined `noreturn` function.

rdar://45523626

llvm-svn: 346421

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/CodeExtractor.cpp b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
index 419e1db08bf..41c3632c82a 100644
--- a/llvm/lib/Transforms/Utils/CodeExtractor.cpp
+++ b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
@@ -1330,6 +1330,13 @@ Function *CodeExtractor::extractCodeRegion() {
       DVI->eraseFromParent();
   }
 
+  // Mark the new function `noreturn` if applicable.
+  bool doesNotReturn = none_of(*newFunction, [](const BasicBlock &BB) {
+    return isa<ReturnInst>(BB.getTerminator());
+  });
+  if (doesNotReturn)
+    newFunction->setDoesNotReturn();
+
   LLVM_DEBUG(if (verifyFunction(*newFunction))
                  report_fatal_error("verifyFunction failed!"));
   return newFunction;