Implement __builtin_LINE() et. al. to support source location capture.

Summary:
This patch implements the source location builtins `__builtin_LINE(), `__builtin_FUNCTION()`, `__builtin_FILE()` and `__builtin_COLUMN()`. These builtins are needed to implement [`std::experimental::source_location`](https://rawgit.com/cplusplus/fundamentals-ts/v2/main.html#reflection.src_loc.creation).

With the exception of `__builtin_COLUMN`, GCC also implements these builtins, and Clangs behavior is intended to match as closely as possible. 

Reviewers: rsmith, joerg, aaron.ballman, bogner, majnemer, shafik, martong

Reviewed By: rsmith

Subscribers: rnkovacs, loskutov, riccibruno, mgorny, kunitoki, alexr, majnemer, hfinkel, cfe-commits

Differential Revision: https://reviews.llvm.org/D37035

llvm-svn: 360937

1 files changed, 10 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index 777e1dc8938..62c4da0383c 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -16,6 +16,7 @@
 #include "CGObjCRuntime.h"
 #include "CodeGenFunction.h"
 #include "CodeGenModule.h"
+#include "ConstantEmitter.h"
 #include "TargetInfo.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclObjC.h"
@@ -640,12 +641,20 @@ public:
   Value *VisitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *E) {
     return EmitLoadOfLValue(E);
   }
+  Value *VisitSourceLocExpr(SourceLocExpr *SLE) {
+    auto &Ctx = CGF.getContext();
+    APValue Evaluated =
+        SLE->EvaluateInContext(Ctx, CGF.CurSourceLocExprScope.getDefaultExpr());
+    return ConstantEmitter(CGF.CGM, &CGF)
+        .emitAbstract(SLE->getLocation(), Evaluated, SLE->getType());
+  }
 
   Value *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
+    CodeGenFunction::CXXDefaultArgExprScope Scope(CGF, DAE);
     return Visit(DAE->getExpr());
   }
   Value *VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE) {
-    CodeGenFunction::CXXDefaultInitExprScope Scope(CGF);
+    CodeGenFunction::CXXDefaultInitExprScope Scope(CGF, DIE);
     return Visit(DIE->getExpr());
   }
   Value *VisitCXXThisExpr(CXXThisExpr *TE) {