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.

llvm-svn: 347656

1 files changed, 7 insertions, 12 deletions

diff --git a/clang/lib/Analysis/CFG.cpp b/clang/lib/Analysis/CFG.cpp
index 96130c25be8..cfda27dd37a 100644
--- a/clang/lib/Analysis/CFG.cpp
+++ b/clang/lib/Analysis/CFG.cpp
@@ -1039,13 +1039,11 @@ private:
     if (!areExprTypesCompatible(Expr1, Expr2))
       return {};
 
-    Expr::EvalResult L1Result, L2Result;
-    if (!Expr1->EvaluateAsInt(L1Result, *Context) ||
-        !Expr2->EvaluateAsInt(L2Result, *Context))
-      return {};
+    llvm::APSInt L1, L2;
 
-    llvm::APSInt L1 = L1Result.Val.getInt();
-    llvm::APSInt L2 = L2Result.Val.getInt();
+    if (!Expr1->EvaluateAsInt(L1, *Context) ||
+        !Expr2->EvaluateAsInt(L2, *Context))
+      return {};
 
     // Can't compare signed with unsigned or with different bit width.
     if (L1.isSigned() != L2.isSigned() || L1.getBitWidth() != L2.getBitWidth())
@@ -1136,16 +1134,13 @@ private:
           case BO_And: {
             // If either operand is zero, we know the value
             // must be false.
-            Expr::EvalResult LHSResult;
-            if (Bop->getLHS()->EvaluateAsInt(LHSResult, *Context)) {
-              llvm::APSInt IntVal = LHSResult.Val.getInt();
+            llvm::APSInt IntVal;
+            if (Bop->getLHS()->EvaluateAsInt(IntVal, *Context)) {
               if (!IntVal.getBoolValue()) {
                 return TryResult(false);
               }
             }
-            Expr::EvalResult RHSResult;
-            if (Bop->getRHS()->EvaluateAsInt(RHSResult, *Context)) {
-              llvm::APSInt IntVal = RHSResult.Val.getInt();
+            if (Bop->getRHS()->EvaluateAsInt(IntVal, *Context)) {
               if (!IntVal.getBoolValue()) {
                 return TryResult(false);
               }