Add regression test for 147485

Author: dianqk

tests/crashes/147485.rs

@@ -0,0 +1,14 @@
+//@ known-bug: #147485
+//@ compile-flags: -g -O
+
+#![crate_type = "lib"]
+
+pub fn f(x: *const usize) -> &'static usize {
+    let mut a = unsafe { &*x };
+    a = unsafe { &*x };
+    a
+}
+
+pub fn g() {
+    f(&0);
+}

tests/mir-opt/debuginfo/ref_prop.remap_debuginfo_locals.ReferencePropagation.diff

@@ -0,0 +1,33 @@
+- // MIR for `remap_debuginfo_locals` before ReferencePropagation
++ // MIR for `remap_debuginfo_locals` after ReferencePropagation
+  
+  fn remap_debuginfo_locals() -> () {
+      let mut _0: ();
+      let _1: &usize;
+      let mut _2: *const usize;
+      let _3: &usize;
+      let _4: usize;
+      let mut _5: &usize;
+      scope 1 (inlined foo) {
+-         debug a => _1;
++         debug a => _5;
+      }
+  
+      bb0: {
+-         StorageLive(_1);
+-         StorageLive(_2);
+-         StorageLive(_3);
+          _5 = const remap_debuginfo_locals::promoted[0];
+-         _3 = &(*_5);
+-         _2 = &raw const (*_3);
+-         // DBG: _1 = &(*_2);
+-         _1 = &(*_2);
+-         StorageDead(_2);
+-         StorageDead(_3);
+-         StorageDead(_1);
++         // DBG: _1 = &(*_5);
+          _0 = const ();
+          return;
+      }
+  }
+  

tests/mir-opt/debuginfo/ref_prop.rs

@@ -0,0 +1,26 @@
+// skip-filecheck
+//@ test-mir-pass: ReferencePropagation
+//@ compile-flags: -g -Zub_checks=false -Zinline-mir -Zmir-enable-passes=+DeadStoreElimination-initial
+
+#![feature(core_intrinsics, custom_mir)]
+#![crate_type = "lib"]
+
+use std::intrinsics::mir::*;
+
+// EMIT_MIR ref_prop.remap_debuginfo_locals.ReferencePropagation.diff
+pub fn remap_debuginfo_locals() {
+    foo(&0);
+}
+
+#[custom_mir(dialect = "runtime", phase = "post-cleanup")]
+#[inline]
+fn foo(x: *const usize) -> &'static usize {
+    mir! {
+        debug a => RET;
+        {
+            RET = &*x;
+            RET = &*x;
+            Return()
+        }
+    }
+}