Split repeat-operand codegen test

Looks like the output it's looking for can be in different orders, so separate tests will fix that.

Author: scottmcm

tests/codegen/repeat-operand.rs renamed to tests/codegen/repeat-operand-zero-len.rs

@@ -11,10 +11,6 @@
 #[repr(transparent)]
 pub struct Wrapper<T, const N: usize>([T; N]);
 
-// CHECK-LABEL: define {{.+}}do_repeat{{.+}}()
-// CHECK-NEXT: start:
-// CHECK-NOT: alloca
-// CHECK-NEXT: ret void
 // CHECK-LABEL: define {{.+}}do_repeat{{.+}}(i32 noundef %x)
 // CHECK-NEXT: start:
 // CHECK-NOT: alloca
@@ -30,10 +26,3 @@ pub fn trigger_repeat_zero_len() -> Wrapper<u32, 0> {
     // CHECK: call void {{.+}}do_repeat{{.+}}(i32 noundef 4)
     do_repeat(4)
 }
-
-// CHECK-LABEL: @trigger_repeat_zst
-#[no_mangle]
-pub fn trigger_repeat_zst() -> Wrapper<(), 8> {
-    // CHECK: call void {{.+}}do_repeat{{.+}}()
-    do_repeat(())
-}

tests/codegen/repeat-operand-zst-elem.rs

@@ -0,0 +1,28 @@
+//@ compile-flags: -Copt-level=1 -Cno-prepopulate-passes
+
+// This test is here to hit the `Rvalue::Repeat` case in `codegen_rvalue_operand`.
+// It only applies when the resulting array is a ZST, so the test is written in
+// such a way as to keep MIR optimizations from seeing that fact and removing
+// the local and statement altogether. (At the time of writing, no other codegen
+// test hit that code path, nor did a stage 2 build of the compiler.)
+
+#![crate_type = "lib"]
+
+#[repr(transparent)]
+pub struct Wrapper<T, const N: usize>([T; N]);
+
+// CHECK-LABEL: define {{.+}}do_repeat{{.+}}()
+// CHECK-NEXT: start:
+// CHECK-NOT: alloca
+// CHECK-NEXT: ret void
+#[inline(never)]
+pub fn do_repeat<T: Copy, const N: usize>(x: T) -> Wrapper<T, N> {
+    Wrapper([x; N])
+}
+
+// CHECK-LABEL: @trigger_repeat_zst_elem
+#[no_mangle]
+pub fn trigger_repeat_zst_elem() -> Wrapper<(), 8> {
+    // CHECK: call void {{.+}}do_repeat{{.+}}()
+    do_repeat(())
+}