[PATCH] D157432: [clang][ConstExprEmitter] handle Unary Not on integers

[Nick Desaulniers via Phabricator via cfe-commits]

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Consider the following statement:

  int x = ~0;

With the following AST:

  `-VarDecl 0x5647bdb12d60 <x.c:1:1, col:10> col:5 x 'int' cinit
    `-UnaryOperator 0x5647bdb12e30 <col:9, col:10> 'int' prefix '~' cannot overflow
      `-IntegerLiteral 0x5647bdb12e10 <col:10> 'int' 0

Return the evaluation of the subexpression bitwise inverted.

Link: https://github.com/ClangBuiltLinux/linux/issues/1906


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D157432

Files:
  clang/lib/CodeGen/CGExprConstant.cpp


Index: clang/lib/CodeGen/CGExprConstant.cpp
===================================================================
--- clang/lib/CodeGen/CGExprConstant.cpp
+++ clang/lib/CodeGen/CGExprConstant.cpp
@@ -1394,6 +1394,13 @@
     return nullptr;
   }
 
+  llvm::Constant *VisitUnaryNot(UnaryOperator *U, QualType T) {
+    if (llvm::Constant *C = Visit(U->getSubExpr(), T))
+      if (auto *CI = dyn_cast<llvm::ConstantInt>(C))
+        return llvm::ConstantInt::get(CGM.getLLVMContext(), ~CI->getValue());
+    return nullptr;
+  }
+
   // Utility methods
   llvm::Type *ConvertType(QualType T) {
     return CGM.getTypes().ConvertType(T);


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