Change EmitConstantExpr to allow failure.

IRgen no longer relies on isConstantInitializer, instead we just try
to emit the constant. If that fails then in C we emit an error
unsupported (this occurs when Sema accepted something that it doesn't
know how to fold, and IRgen doesn't know how to emit) and in C++ we
emit a guarded initializer.

This ends up handling a few more cases, because IRgen was actually
able to emit some of the constants Sema accepts but can't Evaluate().
For example, PR3398.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@64780 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 0 deletions

diff --git a/lib/CodeGen/CodeGenModule.h b/lib/CodeGen/CodeGenModule.h
index ff1437c20d..b54ee13df6 100644
--- a/lib/CodeGen/CodeGenModule.h
+++ b/lib/CodeGen/CodeGenModule.h
@@ -247,7 +247,12 @@ public:
                                         const std::string &Name);
 
   void UpdateCompletedType(const TagDecl *D);
+
+  /// EmitConstantExpr - Try to emit the given expression as a
+  /// constant; returns 0 if the expression cannot be emitted as a
+  /// constant.
   llvm::Constant *EmitConstantExpr(const Expr *E, CodeGenFunction *CGF = 0);
+
   llvm::Constant *EmitAnnotateAttr(llvm::GlobalValue *GV,
                                    const AnnotateAttr *AA, unsigned LineNo);