Add memset test verifying the parameters are passed in registers

Author: winstonallo

tests/assembly-llvm/regparm-module-flag.rs

@@ -0,0 +1,23 @@
+//@ assembly-output: emit-asm
+//@ compile-flags: -O -Zregparm=3 -Cunsafe-allow-abi-mismatch=regparm
+//@ only-x86
+
+#![crate_type = "lib"]
+
+use std::ffi::c_void;
+
+unsafe extern "C" {
+    fn memset(p: *mut c_void, val: i32, len: usize) -> *mut c_void;
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn entrypoint(
+    len: usize, val: i32, ptr: *mut c_void
+)  -> *mut c_void {
+    unsafe { memset(ptr, val, len) }
+}
+
+// CHECK: mov{{.*}}eax
+// CHECK: mov{{.*}}ecx
+// CHECK: mov{{.*}}esi
+// CHECK: jmp{{.*}}memset