Don't hardcode IR value numbers in IRGen/objc_block.sil.

Author: kubamracek

test/IRGen/objc_block.sil

@@ -18,13 +18,13 @@ entry(%b : $@convention(block) Foo -> Foo, %x : $Foo):
 }
 // CHECK-LABEL: define{{( protected)?}} swiftcc %T10objc_block3FooC* @call_block(%objc_block*, %T10objc_block3FooC*) {{.*}} {
 // CHECK:       entry:
-// CHECK:         %2 = getelementptr inbounds %objc_block, %objc_block* %0, i32 0, i32 3
-// CHECK:         %3 = load i8*, i8** %2
-// CHECK:         %4 = bitcast i8* %3 to i8* (%objc_block*, i8*)*
-// CHECK:         %5 = bitcast %T10objc_block3FooC* %1 to i8*
-// CHECK:         %6 = call i8* %4(%objc_block* %0, i8* %5)
-// CHECK:         %7 = bitcast i8* %6 to %T10objc_block3FooC*
-// CHECK:         ret %T10objc_block3FooC* %7
+// CHECK:         [[T0:%.*]] = getelementptr inbounds %objc_block, %objc_block* %0, i32 0, i32 3
+// CHECK:         [[T1:%.*]] = load i8*, i8** [[T0]]
+// CHECK:         [[T2:%.*]] = bitcast i8* [[T1]] to i8* (%objc_block*, i8*)*
+// CHECK:         [[T3:%.*]] = bitcast %T10objc_block3FooC* %1 to i8*
+// CHECK:         [[T4:%.*]] = call i8* [[T2]](%objc_block* %0, i8* [[T3]])
+// CHECK:         [[T5:%.*]] = bitcast i8* [[T4]] to %T10objc_block3FooC*
+// CHECK:         ret %T10objc_block3FooC* [[T5]]
 // CHECK:       }
 
 sil @generic : $@convention(thin) <T> (@in T) -> ()