Revert r347417 "Re-Reinstate 347294 with a fix for the failures."

This caused a miscompile in Chrome (see crbug.com/908372) that's
illustrated by this small reduction:

  static bool f(int *a, int *b) {
    return !__builtin_constant_p(b - a) || (!(b - a));
  }

  int arr[] = {1,2,3};

  bool g() {
    return f(arr, arr + 3);
  }

  $ clang -O2 -S -emit-llvm a.cc -o -

g() should return true, but after r347417 it became false for some reason.

This also reverts the follow-up commits.

r347417:
> Re-Reinstate 347294 with a fix for the failures.
>
> Don't try to emit a scalar expression for a non-scalar argument to
> __builtin_constant_p().
>
> Third time's a charm!

r347446:
> The result of is.constant() is unsigned.

r347480:
> A __builtin_constant_p() returns 0 with a function type.

r347512:
> isEvaluatable() implies a constant context.
>
> Assume that we're in a constant context if we're asking if the expression can
> be compiled into a constant initializer. This fixes the issue where a
> __builtin_constant_p() in a compound literal was diagnosed as not being
> constant, even though it's always possible to convert the builtin into a
> constant.

r347531:
> A "constexpr" is evaluated in a constant context. Make sure this is reflected
> if a __builtin_constant_p() is a part of a constexpr.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@347656 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 14 deletions

diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index e343949ac1..ec6f084aed 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -2594,8 +2594,8 @@ Expr *Expr::IgnoreParenCasts() {
       E = NTTP->getReplacement();
       continue;
     }
-    if (FullExpr *FE = dyn_cast<FullExpr>(E)) {
-      E = FE->getSubExpr();
+    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(E)) {
+      E = CE->getSubExpr();
       continue;
     }
     return E;
@@ -2619,8 +2619,8 @@ Expr *Expr::IgnoreCasts() {
       E = NTTP->getReplacement();
       continue;
     }
-    if (FullExpr *FE = dyn_cast<FullExpr>(E)) {
-      E = FE->getSubExpr();
+    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(E)) {
+      E = CE->getSubExpr();
       continue;
     }
     return E;
@@ -2648,8 +2648,8 @@ Expr *Expr::IgnoreParenLValueCasts() {
                                   = dyn_cast<SubstNonTypeTemplateParmExpr>(E)) {
       E = NTTP->getReplacement();
       continue;
-    } else if (FullExpr *FE = dyn_cast<FullExpr>(E)) {
-      E = FE->getSubExpr();
+    } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(E)) {
+      E = CE->getSubExpr();
       continue;
     }
     break;
@@ -2920,12 +2920,6 @@ bool Expr::isConstantInitializer(ASTContext &Ctx, bool IsForRef,
 
     break;
   }
-  case ConstantExprClass: {
-    // FIXME: We should be able to return "true" here, but it can lead to extra
-    // error messages. E.g. in Sema/array-init.c.
-    const Expr *Exp = cast<ConstantExpr>(this)->getSubExpr();
-    return Exp->isConstantInitializer(Ctx, false, Culprit);
-  }
   case CompoundLiteralExprClass: {
     // This handles gcc's extension that allows global initializers like
     // "struct x {int x;} x = (struct x) {};".
@@ -2965,8 +2959,8 @@ bool Expr::isConstantInitializer(ASTContext &Ctx, bool IsForRef,
           const Expr *Elt = ILE->getInit(ElementNo++);
           if (Field->isBitField()) {
             // Bitfields have to evaluate to an integer.
-            EvalResult Result;
-            if (!Elt->EvaluateAsInt(Result, Ctx)) {
+            llvm::APSInt ResultTmp;
+            if (!Elt->EvaluateAsInt(ResultTmp, Ctx)) {
               if (Culprit)
                 *Culprit = Elt;
               return false;