[c++1z] N4295: fold-expressions.

This is a new form of expression of the form:

  (expr op ... op expr)

where one of the exprs is a parameter pack. It expands into

  (expr1 op (expr2onwards op ... op expr))

(and likewise if the pack is on the right). The non-pack operand can be
omitted; in that case, an empty pack gives a fallback value or an error,
depending on the operator.

llvm-svn: 221573

1 files changed, 45 insertions, 0 deletions

diff --git a/clang/test/CodeGenCXX/cxx1z-fold-expression.cpp b/clang/test/CodeGenCXX/cxx1z-fold-expression.cpp
new file mode 100644
index 00000000000..7677fc0e18f
--- /dev/null
+++ b/clang/test/CodeGenCXX/cxx1z-fold-expression.cpp
@@ -0,0 +1,45 @@
+// RUN: %clang_cc1 -std=c++1z -triple %itanium_abi_triple -emit-llvm -o - %s | FileCheck %s
+
+template<int> struct A {};
+template<int ...N> void foldr(A<(N + ...)>);
+template<int ...N> void foldl(A<(... + N)>);
+template<int ...N> void foldr1(A<(N + ... + 1)>);
+template<int ...N> void foldl1(A<(1 + ... + N)>);
+void use() {
+  foldr<1, 2, 3>({});
+  foldl<1, 2, 3>({});
+  foldr1<1, 2, 3>({});
+  foldl1<1, 2, 3>({});
+  // CHECK-DAG: @_Z5foldrIJLi1ELi2ELi3EEEv1AIXfrplT_EE(
+  // CHECK-DAG: @_Z5foldlIJLi1ELi2ELi3EEEv1AIXflplT_EE(
+  // CHECK-DAG: @_Z6foldr1IJLi1ELi2ELi3EEEv1AIXfxplT_Li1EEE(
+  // CHECK-DAG: @_Z6foldl1IJLi1ELi2ELi3EEEv1AIXfxplLi1ET_EE(
+}
+
+template<int ...N> using Foldr = A<(N + ...)>;
+template<int ...N> using Foldl = A<(... + N)>;
+template<int ...N> using Foldr1 = A<(N + ... + 1)>;
+template<int ...N> using Foldl1 = A<(1 + ... + N)>;
+
+template<int ...A> struct Partial {
+  template<int ...B> void foldr(Foldr<A..., B..., A..., B...>);
+  template<int ...B> void foldl(Foldr<A..., B..., A..., B...>);
+  template<int ...B> void foldr1(Foldr1<A..., B..., A..., B...>);
+  template<int ...B> void foldl1(Foldl1<A..., B..., A..., B...>);
+};
+void use(Partial<1, 2> p) {
+  p.foldr<3, 4>({});
+  p.foldl<3, 4>({});
+  p.foldr1<3, 4>({});
+  p.foldl1<3, 4>({});
+  // CHECK-DAG: @_ZN7PartialIJLi1ELi2EEE5foldrIJLi3ELi4EEEEv1AIXplLi1EplLi2EfxplT_plLi1EplLi2EfrplT_EE(
+  // CHECK-DAG: @_ZN7PartialIJLi1ELi2EEE5foldlIJLi3ELi4EEEEv1AIXplLi1EplLi2EfxplT_plLi1EplLi2EfrplT_EE(
+  // CHECK-DAG: @_ZN7PartialIJLi1ELi2EEE6foldr1IJLi3ELi4EEEEv1AIXplLi1EplLi2EfxplT_plLi1EplLi2EfxplT_Li1EEE(
+  // CHECK-DAG: @_ZN7PartialIJLi1ELi2EEE6foldl1IJLi3ELi4EEEEv1AIXfxplplplfxplplplLi1ELi1ELi2ET_Li1ELi2ET_EE(
+}
+
+extern int n;
+template<int ...N> void f() {
+  (n = ... = N);
+}
+template void f<>();