Mark drop calls in landing pads cold instead of noinline

Now that deferred inlining has been disabled in LLVM,
this shouldn't cause catastrophic size blowup.

src/test/codegen/unwind-landingpad-cold.rs

@@ -0,0 +1,14 @@
+// compile-flags: -Cno-prepopulate-passes
+#![crate_type = "lib"]
+
+// This test checks that drop calls in unwind landing pads
+// get the `cold` attribute.
+
+// CHECK-LABEL: @check_cold
+// CHECK: call void {{.+}}drop_in_place{{.+}} [[ATTRIBUTES:#[0-9]+]]
+// CHECK: attributes [[ATTRIBUTES]] = { cold }
+#[no_mangle]
+pub fn check_cold(f: fn(), x: Box<u32>) {
+    // this may unwind
+    f();
+}

src/test/codegen/unwind-landingpad-inline.rs

@@ -0,0 +1,22 @@
+// no-system-llvm: needs patch for Rust alloc/dealloc functions
+// compile-flags: -Copt-level=3
+#![crate_type = "lib"]
+
+// This test checks that we can inline drop_in_place in
+// unwind landing pads. Without this, the box pointers escape,
+// and LLVM will not optimize out the pointer comparison.
+// See https://github.com/rust-lang/rust/issues/46515
+
+// Everything should be optimized out.
+// CHECK-LABEL: @check_no_escape_in_landingpad
+// CHECK: start:
+// CHECK-NEXT: ret void
+#[no_mangle]
+pub fn check_no_escape_in_landingpad(f: fn()) {
+    let x = &*Box::new(0);
+    let y = &*Box::new(0);
+
+    if x as *const _ == y as *const _ {
+        f();
+    }
+}