From 45b6b9d080ac56917337d73d8f1cd6374b27b05d Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Mon, 6 Oct 2008 06:49:02 +0000
Subject: [PATCH] Add a Expr::isEvaluatable method, eliminate
 isBuiltinConstantExpr which is checking for something that can be
 inconsistent with what we can constant fold.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@57159 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/AST/Expr.h |  8 ++++----
 lib/AST/Expr.cpp         | 11 ++++-------
 lib/AST/ExprConstant.cpp |  7 +++++++
 lib/Sema/SemaDecl.cpp    | 15 +++++----------
 4 files changed, 20 insertions(+), 21 deletions(-)

diff --git a/include/clang/AST/Expr.h b/include/clang/AST/Expr.h
index df7a83bcbf..2b42424803 100644
--- a/include/clang/AST/Expr.h
+++ b/include/clang/AST/Expr.h
@@ -124,6 +124,10 @@ public:
   /// we want to.  If this function returns true, it returns the folded constant
   /// in Result.
   bool tryEvaluate(APValue& Result, ASTContext &Ctx) const;
+  
+  /// isEvaluatable - Call tryEvaluate to see if this expression can be constant
+  /// folded, but discard the result.
+  bool isEvaluatable(ASTContext &Ctx) const;
 
   /// hasGlobalStorage - Return true if this expression has static storage
   /// duration.  This means that the address of this expression is a link-time
@@ -709,10 +713,6 @@ public:
   /// not, return 0.
   unsigned isBuiltinCall() const;
   
-  
-  /// isBuiltinConstantExpr - Return true if this built-in call is constant.
-  bool isBuiltinConstantExpr(ASTContext &Ctx) const;
-  
   SourceLocation getRParenLoc() const { return RParenLoc; }
 
   virtual SourceRange getSourceRange() const { 
diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index 45363d6992..6cdaacd689 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -162,12 +162,6 @@ unsigned CallExpr::isBuiltinCall() const {
 }
 
 
-bool CallExpr::isBuiltinConstantExpr(ASTContext &Ctx) const {
-  unsigned BID = isBuiltinCall();
-  if (!BID) return false;
-  return Ctx.BuiltinInfo.isConstantExpr(BID);
-}
-
 /// getOpcodeStr - Turn an Opcode enum value into the punctuation char it
 /// corresponds to, e.g. "<<=".
 const char *BinaryOperator::getOpcodeStr(Opcode Op) {
@@ -519,8 +513,11 @@ bool Expr::isConstantExpr(ASTContext &Ctx, SourceLocation *Loc) const {
     return true;
   case CallExprClass: {
     const CallExpr *CE = cast<CallExpr>(this);
-    if (CE->isBuiltinConstantExpr(Ctx))
+
+    // Allow any constant foldable calls to builtins.
+    if (CE->isBuiltinCall() && CE->isEvaluatable(Ctx))
       return true;
+    
     if (Loc) *Loc = getLocStart();
     return false;
   }
diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 1506f448aa..af30ceb96c 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -693,3 +693,10 @@ bool Expr::tryEvaluate(APValue &Result, ASTContext &Ctx) const {
       
   return false;
 }
+
+/// isEvaluatable - Call tryEvaluate to see if this expression can be constant
+/// folded, but discard the result.
+bool Expr::isEvaluatable(ASTContext &Ctx) const {
+  APValue V;
+  return tryEvaluate(V, Ctx);
+}
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 74ce855add..125d91cdba 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -879,14 +879,6 @@ bool Sema::CheckAddressConstantExpression(const Expr* Init) {
   case Expr::StringLiteralClass:
   case Expr::ObjCStringLiteralClass:
     return false;
-  case Expr::CallExprClass: {
-    const CallExpr *CE = cast<CallExpr>(Init);
-    if (CE->isBuiltinConstantExpr(Context))
-      return false;
-    Diag(Init->getExprLoc(),
-         diag::err_init_element_not_constant, Init->getSourceRange());
-    return true;
-  }
   case Expr::UnaryOperatorClass: {
     const UnaryOperator *Exp = cast<UnaryOperator>(Init);
 
@@ -1080,8 +1072,11 @@ bool Sema::CheckArithmeticConstantExpression(const Expr* Init) {
     return false;
   case Expr::CallExprClass: {
     const CallExpr *CE = cast<CallExpr>(Init);
-    if (CE->isBuiltinConstantExpr(Context))
+
+    // Allow any constant foldable calls to builtins.
+    if (CE->isBuiltinCall() && CE->isEvaluatable(Context))
       return false;
+    
     Diag(Init->getExprLoc(),
          diag::err_init_element_not_constant, Init->getSourceRange());
     return true;
@@ -1226,7 +1221,7 @@ bool Sema::CheckArithmeticConstantExpression(const Expr* Init) {
     // Okay, the evaluated side evaluates to a constant, so we accept this.
     // Check to see if the other side is obviously not a constant.  If so, 
     // emit a warning that this is a GNU extension.
-    if (FalseSide && !FalseSide->tryEvaluate(Val, Context))
+    if (FalseSide && !FalseSide->isEvaluatable(Context))
       Diag(Init->getExprLoc(), 
            diag::ext_typecheck_expression_not_constant_but_accepted,
            FalseSide->getSourceRange());