[PATCH] D156175: [clang][ConstExprEmitter] handle NullToPointer ImplicitCastExpr

[Nick Desaulniers via Phabricator via cfe-commits]

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Consider the following statement:

  void* foo = ((void *)0);

For the sub-AST:

  | `-ImplicitCastExpr 'const void *' <NullToPointer>
  |   `-CStyleCastExpr 'void *' <NullToPointer>
  |     `-IntegerLiteral 'int' 0

If the subexpression of the cast is itself the NULL constant, then
ImplicitCastExpr should emit the NULL pointer constant.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D156175

Files:
  clang/lib/CodeGen/CGExprConstant.cpp


Index: clang/lib/CodeGen/CGExprConstant.cpp
===================================================================
--- clang/lib/CodeGen/CGExprConstant.cpp
+++ clang/lib/CodeGen/CGExprConstant.cpp
@@ -1127,6 +1127,13 @@
     case CK_ConstructorConversion:
       return Visit(subExpr, destType);
 
+    case CK_NullToPointer: {
+      if (llvm::Constant *C = Visit(subExpr, destType))
+        if (C->isNullValue())
+          return CGM.EmitNullConstant(destType);
+      return nullptr;
+    }
+
     case CK_IntToOCLSampler:
       llvm_unreachable("global sampler variables are not generated");
 
@@ -1183,7 +1190,6 @@
     case CK_IntegralComplexToFloatingComplex:
     case CK_PointerToIntegral:
     case CK_PointerToBoolean:
-    case CK_NullToPointer:
     case CK_IntegralCast:
     case CK_BooleanToSignedIntegral:
     case CK_IntegralToPointer:


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