Fix the bug by enabling extension for bool returns on x86_64

Author: saethlin

compiler/rustc_target/src/callconv/x86_64.rs

@@ -244,7 +244,10 @@ where
                 if arg.layout.is_aggregate() {
                     let size = arg.layout.size;
                     arg.cast_to(cast_target(cls, size));
-                } else if is_arg || cx.target_spec().is_like_darwin {
+                } else if is_arg || cx.target_spec().is_like_darwin
+                    // Always extend bool returns
+                    || (!is_arg && arg.layout.layout.backend_repr.is_bool())
+                {
                     arg.extend_integer_width_to(32);
                 }
             }

tests/codegen-llvm/some-abis-do-extend-params-to-32-bits.rs

@@ -134,7 +134,7 @@ pub extern "C" fn c_arg_i32(_a: i32) {}
 #[no_mangle]
 pub extern "C" fn c_arg_i64(_a: i64) {}
 
-// x86_64-linux:                                    i1 @c_ret_bool()
+// x86_64-linux:    zeroext i1 @c_ret_bool()
 // x86_64-uefi:     zeroext i1 @c_ret_bool()
 // i686:            zeroext i1 @c_ret_bool()
 // aarch64-apple:   zeroext i1 @c_ret_bool()