FileCheck and rename const_prop_fails_gracefully.

Author: cjgillot

tests/mir-opt/const_prop/const_prop_fails_gracefully.rs

@@ -0,0 +1,18 @@
+// EMIT_MIR_FOR_EACH_PANIC_STRATEGY
+// unit-test: ConstProp
+
+#[inline(never)]
+fn read(_: usize) { }
+
+// EMIT_MIR pointer_expose_address.main.ConstProp.diff
+fn main() {
+    // CHECK-LABEL: fn main(
+    // CHECK: [[ptr:_.*]] = const _;
+    // CHECK: [[ref:_.*]] = &raw const (*[[ptr]]);
+    // CHECK: [[x:_.*]] = move [[ref]] as usize (PointerExposeAddress);
+    // CHECK: [[arg:_.*]] = [[x]];
+    // CHECK: = read(move [[arg]])
+    const FOO: &i32 = &1;
+    let x = FOO as *const i32 as usize;
+    read(x);
+}