Add FileCheck annotations to dataflow-const-prop tests

tests/mir-opt/dataflow-const-prop/if.rs

@@ -1,12 +1,28 @@
-// skip-filecheck
 // unit-test: DataflowConstProp
 
 // EMIT_MIR if.main.DataflowConstProp.diff
+// CHECK-LABEL: fn main(
 fn main() {
+    // CHECK: debug b => [[b:_.*]];
+    // CHECK: debug c => [[c:_.*]];
+    // CHECK: debug d => [[d:_.*]];
+    // CHECK: debug e => [[e:_.*]];
+
     let a = 1;
+
+    // CHECK: switchInt(const true) -> [0: {{bb[0-9]+}}, otherwise: [[bb_first_true:bb[0-9]+]]];
+    // CHECK: [[bb_first_true]]: {
+    // CHECK: [[b]] = const 2_i32;
     let b = if a == 1 { 2 } else { 3 };
+
+    // CHECK: [[c]] = const 3_i32;
     let c = b + 1;
 
+    // CHECK: switchInt(const true) -> [0: {{bb[0-9]+}}, otherwise: [[bb_second_true:bb[0-9]+]]];
+    // CHECK: [[bb_second_true]]: {
+    // CHECK: [[d]] = const 1_i32;
     let d = if a == 1 { a } else { a + 1 };
+
+    // CHECK: [[e]] = const 2_i32;
     let e = d + 1;
 }

tests/mir-opt/dataflow-const-prop/inherit_overflow.rs

@@ -1,11 +1,14 @@
-// skip-filecheck
 // EMIT_MIR_FOR_EACH_PANIC_STRATEGY
 // unit-test: DataflowConstProp
 // compile-flags: -Zmir-enable-passes=+Inline
 
 // EMIT_MIR inherit_overflow.main.DataflowConstProp.diff
+// CHECK-LABEL: fn main(
 fn main() {
     // After inlining, this will contain a `CheckedBinaryOp`.
     // Propagating the overflow is ok as codegen will just skip emitting the panic.
+
+    // CHECK: {{_.*}} = const (0_u8, true);
+    // CHECK-LABEL: assert(!const true,
     let _ = <u8 as std::ops::Add>::add(255, 1);
 }

tests/mir-opt/dataflow-const-prop/issue_81605.rs

@@ -1,9 +1,12 @@
-// skip-filecheck
 // unit-test: DataflowConstProp
 
 // EMIT_MIR issue_81605.f.DataflowConstProp.diff
+
+// CHECK-LABEL: fn f
 fn f() -> usize {
+    // CHECK: switchInt(const true) -> [0: {{bb[0-9]+}}, otherwise: {{bb[0-9]+}}];
     1 + if true { 1 } else { 2 }
+    // CHECK: _0 = const 2_usize;
 }
 
 fn main() {