Fix a major swiftcall ABI bug with trivial C++ class types.

The problem with the previous logic was that there might not be any
explicit copy/move constructor declarations, e.g. if the type is
trivial and we've never type-checked a copy of it.  Relying on Sema's
computation seems much more reliable.

Also, I believe Richard's recommendation is exactly the rule we use
now on the Itanium ABI, modulo the trivial_abi attribute (which this
change of course fixes our handling of in Swift).

This does mean that we have a less portable rule for deciding
indirectness for swiftcall.  I would prefer it if we just applied the
Itanium rule universally under swiftcall, but in the meantime, I need
to fix this bug.

This only arises when defining functions with class-type arguments
in C++, as we do in the Swift runtime.  It doesn't affect normal Swift
operation because we don't import code as C++.

llvm-svn: 328942

1 files changed, 10 insertions, 0 deletions

diff --git a/clang/test/CodeGenCXX/arm-swiftcall.cpp b/clang/test/CodeGenCXX/arm-swiftcall.cpp
index 5c932c77b1d..36a5afad4c6 100644
--- a/clang/test/CodeGenCXX/arm-swiftcall.cpp
+++ b/clang/test/CodeGenCXX/arm-swiftcall.cpp
@@ -113,3 +113,13 @@ TEST(struct_indirect_1)
 
 // Should not be byval.
 // CHECK-LABEL: define {{.*}} void @take_struct_indirect_1({{.*}}*{{( %.*)?}})
+
+// Do a simple standalone test here of a function definition to ensure that
+// we don't have problems due to failure to eagerly synthesize a copy
+// constructor declaration.
+class struct_trivial {
+  int x;
+};
+// CHECK-LABEL define void @test_struct_trivial(i32{{( %.*)?}})
+extern "C" SWIFTCALL
+void test_struct_trivial(struct_trivial triv) {}