[Clang Interpreter] Initial patch for the constexpr interpreter

Summary:
This patch introduces the skeleton of the constexpr interpreter,
capable of evaluating a simple constexpr functions consisting of
if statements. The interpreter is described in more detail in the
RFC. Further patches will add more features.

Reviewers: Bigcheese, jfb, rsmith

Subscribers: bruno, uenoku, ldionne, Tyker, thegameg, tschuett, dexonsmith, mgorny, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64146

llvm-svn: 370531

1 files changed, 11 insertions, 0 deletions

diff --git a/clang/test/AST/Interp/cond.cpp b/clang/test/AST/Interp/cond.cpp
new file mode 100644
index 00000000000..8a5a318c216
--- /dev/null
+++ b/clang/test/AST/Interp/cond.cpp
@@ -0,0 +1,11 @@
+// RUN: %clang_cc1 -std=c++17 -fsyntax-only -fforce-experimental-new-constant-interpreter %s -verify
+// RUN: %clang_cc1 -std=c++17 -fsyntax-only %s -verify
+// expected-no-diagnostics
+
+constexpr int cond_then_else(int a, int b) {
+  if (a < b) {
+    return b - a;
+  } else {
+    return a - b;
+  }
+}