Add codegen test for array comparision opt

Author: tesuji

tests/assembly/62531-array-cmp.rs

@@ -0,0 +1,21 @@
+// Ensure the asm for array comparisons is properly optimized on x86.
+
+//@ min-llvm-version: 12
+//@ assembly-output: emit-asm
+//@ compile-flags: -C opt-level=2
+//@ only-x86_64
+
+#![crate_type = "lib"]
+
+// CHECK-LABEL: compare
+// CHECK: movb $1, %al
+// CHECK-NEXT: retq
+#[no_mangle]
+pub fn compare() -> bool {
+    let bytes = 12.5f32.to_ne_bytes();
+    bytes == if cfg!(target_endian = "big") {
+        [0x41, 0x48, 0x00, 0x00]
+    } else {
+        [0x00, 0x00, 0x48, 0x41]
+    }
+}