add codegen test

Author: erikdesjardins

src/test/codegen/zst-offset.rs

@@ -0,0 +1,29 @@
+// compile-flags: -C no-prepopulate-passes
+
+#![crate_type = "lib"]
+
+// Hack to get the correct size for the length part in slices
+// CHECK: @helper([[USIZE:i[0-9]+]] %_1)
+#[no_mangle]
+pub fn helper(_: usize) {
+}
+
+// Check that we correctly generate a GEP for a ZST that is not included in Scalar layout
+// CHECK-LABEL: @scalar_layout
+#[no_mangle]
+pub fn scalar_layout(s: &(u64, ())) {
+// CHECK: [[X0:%[0-9]+]] = bitcast i64* %s to i8*
+// CHECK-NEXT: [[X1:%[0-9]+]] = getelementptr i8, i8* [[X0]], [[USIZE]] 8
+    let x = &s.1;
+    &x; // keep variable in an alloca
+}
+
+// Check that we correctly generate a GEP for a ZST that is not included in ScalarPair layout
+// CHECK-LABEL: @scalarpair_layout
+#[no_mangle]
+pub fn scalarpair_layout(s: &(u64, u32, ())) {
+// CHECK: [[X0:%[0-9]+]] = bitcast { i64, i32 }* %s to i8*
+// CHECK-NEXT: [[X1:%[0-9]+]] = getelementptr i8, i8* [[X0]], [[USIZE]] 12
+    let x = &s.2;
+    &x; // keep variable in an alloca
+}