Update codegen.swift

Author: xwu

test/IRGen/temporary_allocation/codegen.swift

@@ -1,6 +1,7 @@
 // RUN: %target-swift-frontend -primary-file %s -O -emit-ir | %FileCheck %s --check-prefixes=CHECK,CHECK-LARGE-ALLOC,CHECK-LARGE-ALLOC-%target-vendor
 // RUN: %target-swift-frontend -primary-file %s -O -emit-ir | %FileCheck %s --check-prefix=CHECK-LARGE-STACK-ALLOC -DWORD=i%target-ptrsize
 // RUN: %target-swift-frontend -primary-file %s -O -emit-ir | %FileCheck %s --check-prefix=CHECK-LARGE-HEAP-ALLOC -DWORD=i%target-ptrsize
+// REQUIRES: CPU=x86_64
 
 @_silgen_name("blackHole")
 func blackHole(_ value: UnsafeMutableRawPointer?) -> Void