[PATCH] D123898: Fix crash in ObjC codegen introduced with 5ab6ee75994d645725264e757d67bbb1c96fb2b6

[David Chisnall via Phabricator via cfe-commits]

theraven created this revision.
theraven added reviewers: rjmccall, triplef.
Herald added a project: All.
theraven requested review of this revision.
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5ab6ee75994d645725264e757d67bbb1c96fb2b6 <https://reviews.llvm.org/rG5ab6ee75994d645725264e757d67bbb1c96fb2b6> assumed that if `RValue::isScalar()` returns true then `RValue::getScalarVal` will return a valid value.  This is not the case when the return value is `void` and so void message returns would crash if they hit this path.  This is triggered only for cases where the nil-handling path needs to do something non-trivial (destroy arguments that should be consumed by the callee).


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D123898

Files:
  clang/lib/CodeGen/CGObjCGNU.cpp


Index: clang/lib/CodeGen/CGObjCGNU.cpp
===================================================================
--- clang/lib/CodeGen/CGObjCGNU.cpp
+++ clang/lib/CodeGen/CGObjCGNU.cpp
@@ -2837,11 +2837,13 @@
     // Enter the continuation block and emit a phi if required.
     CGF.EmitBlock(continueBB);
     if (msgRet.isScalar()) {
-      llvm::Value *v = msgRet.getScalarVal();
-      llvm::PHINode *phi = Builder.CreatePHI(v->getType(), 2);
-      phi->addIncoming(v, nonNilPathBB);
-      phi->addIncoming(CGM.EmitNullConstant(ResultType), nilPathBB);
-      msgRet = RValue::get(phi);
+      // If the return type is void, do nothing
+      if (llvm::Value *v = msgRet.getScalarVal()) {
+        llvm::PHINode *phi = Builder.CreatePHI(v->getType(), 2);
+        phi->addIncoming(v, nonNilPathBB);
+        phi->addIncoming(CGM.EmitNullConstant(ResultType), nilPathBB);
+        msgRet = RValue::get(phi);
+      }
     } else if (msgRet.isAggregate()) {
       // Aggregate zeroing is handled in nilCleanupBB when it's required.
     } else /* isComplex() */ {


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