[Builtins] Overload __builtin_operator_new/delete to allow forwarding to usual allocation/deallocation functions.

Summary:
Libc++'s default allocator uses `__builtin_operator_new` and `__builtin_operator_delete` in order to allow the calls to new/delete to be ellided. However, libc++ now needs to support over-aligned types in the default allocator. In order to support this without disabling the existing optimization Clang needs to support calling the aligned new overloads from the builtins.

See llvm.org/PR22634 for more information about the libc++ bug.

This patch changes `__builtin_operator_new`/`__builtin_operator_delete` to call any usual `operator new`/`operator delete` function. It does this by performing overload resolution with the arguments passed to the builtin to determine which allocation function to call. If the selected function is not a usual allocation function a diagnostic is issued.

One open issue is if the `align_val_t` overloads should be considered "usual" when `LangOpts::AlignedAllocation` is disabled.


In order to allow libc++ to detect this new behavior the value for `__has_builtin(__builtin_operator_new)` has been updated to `201802`.

Reviewers: rsmith, majnemer, aaron.ballman, erik.pilkington, bogner, ahatanak

Reviewed By: rsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D43047

llvm-svn: 328134

1 files changed, 71 insertions, 0 deletions

diff --git a/clang/test/CodeGenCXX/builtin-operator-new-delete.cpp b/clang/test/CodeGenCXX/builtin-operator-new-delete.cpp
new file mode 100644
index 00000000000..712805a6239
--- /dev/null
+++ b/clang/test/CodeGenCXX/builtin-operator-new-delete.cpp
@@ -0,0 +1,71 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown %s  \
+// RUN:     -faligned-allocation -fsized-deallocation -emit-llvm -o - \
+// RUN:    | FileCheck %s
+
+typedef __SIZE_TYPE__ size_t;
+
+// Declare an 'operator new' template to tickle a bug in __builtin_operator_new.
+template<typename T> void *operator new(size_t, int (*)(T));
+
+// Ensure that this declaration doesn't cause operator new to lose its
+// 'noalias' attribute.
+void *operator new(size_t);
+
+namespace std {
+  struct nothrow_t {};
+  enum class align_val_t : size_t { __zero = 0,
+                                  __max = (size_t)-1 };
+}
+std::nothrow_t nothrow;
+
+// Declare the reserved placement operators.
+void *operator new(size_t, void*) throw();
+void operator delete(void*, void*) throw();
+void *operator new[](size_t, void*) throw();
+void operator delete[](void*, void*) throw();
+
+// Declare the replaceable global allocation operators.
+void *operator new(size_t, const std::nothrow_t &) throw();
+void *operator new[](size_t, const std::nothrow_t &) throw();
+void operator delete(void *, const std::nothrow_t &) throw();
+void operator delete[](void *, const std::nothrow_t &) throw();
+
+// Declare some other placement operators.
+void *operator new(size_t, void*, bool) throw();
+void *operator new[](size_t, void*, bool) throw();
+
+
+// CHECK-LABEL: define void @test_basic(
+extern "C" void test_basic() {
+  // CHECK: call i8* @_Znwm(i64 4) [[ATTR_BUILTIN_NEW:#[^ ]*]]
+  // CHECK: call void @_ZdlPv({{.*}}) [[ATTR_BUILTIN_DELETE:#[^ ]*]]
+  // CHECK: ret void
+  __builtin_operator_delete(__builtin_operator_new(4));
+}
+// CHECK: declare noalias i8* @_Znwm(i64) [[ATTR_NOBUILTIN:#[^ ]*]]
+// CHECK: declare void @_ZdlPv(i8*) [[ATTR_NOBUILTIN_NOUNWIND:#[^ ]*]]
+
+// CHECK-LABEL: define void @test_aligned_alloc(
+extern "C" void test_aligned_alloc() {
+  // CHECK: call i8* @_ZnwmSt11align_val_t(i64 4, i64 4) [[ATTR_BUILTIN_NEW:#[^ ]*]]
+  // CHECK: call void @_ZdlPvSt11align_val_t({{.*}}, i64 4) [[ATTR_BUILTIN_DELETE:#[^ ]*]]
+  __builtin_operator_delete(__builtin_operator_new(4, std::align_val_t(4)), std::align_val_t(4));
+}
+// CHECK: declare noalias i8* @_ZnwmSt11align_val_t(i64, i64) [[ATTR_NOBUILTIN:#[^ ]*]]
+// CHECK: declare void @_ZdlPvSt11align_val_t(i8*, i64) [[ATTR_NOBUILTIN_NOUNWIND:#[^ ]*]]
+
+
+// CHECK-LABEL: define void @test_sized_delete(
+extern "C" void test_sized_delete() {
+  // CHECK: call i8* @_Znwm(i64 4) [[ATTR_BUILTIN_NEW:#[^ ]*]]
+  // CHECK: call void @_ZdlPvm({{.*}}, i64 4) [[ATTR_BUILTIN_DELETE:#[^ ]*]]
+  __builtin_operator_delete(__builtin_operator_new(4), 4);
+}
+// CHECK: declare void @_ZdlPvm(i8*, i64) [[ATTR_NOBUILTIN_UNWIND:#[^ ]*]]
+
+
+// CHECK-DAG: attributes [[ATTR_NOBUILTIN]] = {{[{].*}} nobuiltin {{.*[}]}}
+// CHECK-DAG: attributes [[ATTR_NOBUILTIN_NOUNWIND]] = {{[{].*}} nobuiltin nounwind {{.*[}]}}
+
+// CHECK-DAG: attributes [[ATTR_BUILTIN_NEW]] = {{[{].*}} builtin {{.*[}]}}
+// CHECK-DAG: attributes [[ATTR_BUILTIN_DELETE]] = {{[{].*}} builtin {{.*[}]}}