[MS] Fix prologue this adjustment when 'this' is passed indirectly

Move the logic for doing this from the ABI argument lowering into
EmitParmDecl, which runs for all parameters. Our codegen is slightly
suboptimal in this case, as we may leave behind a dead store after
optimization, but it's 32-bit inalloca, and this fixes the bug in a
robust way.

Fixes PR30293

llvm-svn: 280836

1 files changed, 23 insertions, 0 deletions

diff --git a/clang/test/CodeGenCXX/microsoft-abi-vtables-multiple-nonvirtual-inheritance-this-adjustment.cpp b/clang/test/CodeGenCXX/microsoft-abi-vtables-multiple-nonvirtual-inheritance-this-adjustment.cpp
index aaee39c51db..b97c432f5e0 100644
--- a/clang/test/CodeGenCXX/microsoft-abi-vtables-multiple-nonvirtual-inheritance-this-adjustment.cpp
+++ b/clang/test/CodeGenCXX/microsoft-abi-vtables-multiple-nonvirtual-inheritance-this-adjustment.cpp
@@ -177,3 +177,26 @@ void fop(C &c) {
 }
 
 }
+
+namespace pr30293 {
+struct NonTrivial {
+  ~NonTrivial();
+  int x;
+};
+struct A { virtual void f(); };
+struct B { virtual void __cdecl g(NonTrivial); };
+struct C final : A, B {
+  void f() override;
+  void __cdecl g(NonTrivial) override;
+};
+C *whatsthis;
+void C::f() { g(NonTrivial()); }
+void C::g(NonTrivial o) {
+  whatsthis = this;
+}
+
+// BITCODE-LABEL: define void @"\01?g@C@pr30293@@UAAXUNonTrivial@2@@Z"(<{ i8*, %"struct.pr30293::NonTrivial" }>* inalloca)
+// BITCODE: %[[this1:[^ ]*]] = load i8*, i8** %[[thisaddr:[^ ]*]], align 4
+// BITCODE-NEXT: %[[this2:[^ ]*]] = getelementptr inbounds i8, i8* %[[this1]], i32 -4
+// BITCODE-NEXT: store i8* %[[this2]], i8** %[[thisaddr]], align 4
+}