[llvm] r346421 - [CodeExtractor] Mark functions noreturn when applicable

[Vedant Kumar via llvm-commits]

Author: vedantk
Date: Thu Nov  8 09:57:09 2018
New Revision: 346421

URL: http://llvm.org/viewvc/llvm-project?rev=346421&view=rev
Log:
[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

Modified:
    llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp
    llvm/trunk/test/Transforms/HotColdSplit/split-cold-2.ll

Modified: llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp?rev=346421&r1=346420&r2=346421&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/CodeExtractor.cpp Thu Nov  8 09:57:09 2018
@@ -1330,6 +1330,13 @@ Function *CodeExtractor::extractCodeRegi
       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;

Modified: llvm/trunk/test/Transforms/HotColdSplit/split-cold-2.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/HotColdSplit/split-cold-2.ll?rev=346421&r1=346420&r2=346421&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/HotColdSplit/split-cold-2.ll (original)
+++ llvm/trunk/test/Transforms/HotColdSplit/split-cold-2.ll Thu Nov  8 09:57:09 2018
@@ -9,6 +9,9 @@
 ; CHECK: codeRepl:
 ; CHECK-NEXT: call void @fun.cold.1
 
+; CHECK: define {{.*}}@fun.cold.1{{.*}} [[cold_attr:#[0-9]+]]
+; CHECK: attributes [[cold_attr]] = { {{.*}}noreturn
+
 define void @fun() {
 entry:
   br i1 undef, label %if.then, label %if.else