Shuffle things around in preparation for integrating Eli's constant evaluator.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@53074 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 60 insertions, 0 deletions

diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
new file mode 100644
index 0000000000..ea9b106b69
--- /dev/null
+++ b/lib/AST/ExprConstant.cpp
@@ -0,0 +1,60 @@
+//===--- Expr.cpp - Expression Constant Evaluator -------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the Expr constant evaluator.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/AST/APValue.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/Expr.h"
+
+using namespace clang;
+
+
+static bool CalcFakeICEVal(const Expr* Expr,
+                           llvm::APSInt& Result,
+                           ASTContext& Context) {
+  // Calculate the value of an expression that has a calculatable
+  // value, but isn't an ICE. Currently, this only supports
+  // a very narrow set of extensions, but it can be expanded if needed.
+  if (const ParenExpr *PE = dyn_cast<ParenExpr>(Expr))
+    return CalcFakeICEVal(PE->getSubExpr(), Result, Context);
+  
+  if (const CastExpr *CE = dyn_cast<CastExpr>(Expr)) {
+    QualType CETy = CE->getType();
+    if ((CETy->isIntegralType() && !CETy->isBooleanType()) ||
+        CETy->isPointerType()) {
+      if (CalcFakeICEVal(CE->getSubExpr(), Result, Context)) {
+        Result.extOrTrunc(Context.getTypeSize(CETy));
+        // FIXME: This assumes pointers are signed.
+        Result.setIsSigned(CETy->isSignedIntegerType() ||
+                           CETy->isPointerType());
+        return true;
+      }
+    }
+  }
+  
+  if (Expr->getType()->isIntegralType())
+    return Expr->isIntegerConstantExpr(Result, Context);
+  
+  return false;
+}
+
+bool Expr::tryEvaluate(APValue& Result, ASTContext &Ctx) const
+{
+  llvm::APSInt sInt(1);
+  
+  if (CalcFakeICEVal(this, sInt, Ctx)) {
+    Result = APValue(sInt);
+    return true;
+  }
+  
+  return false;
+}