FileCheck casts.

Author: cjgillot

tests/mir-opt/casts.redundant.PreCodegen.after.mir

@@ -7,15 +7,19 @@
       let mut _2: *const &u8;
       let mut _3: *const &u8;
       scope 1 (inlined generic_cast::<&u8, &u8>) {
-          debug x => _1;
+          debug x => _3;
+          let mut _4: *const &u8;
       }
 
       bb0: {
           StorageLive(_2);
           StorageLive(_3);
           _3 = _1;
--         _2 = _3 as *const &u8 (PtrToPtr);
-+         _2 = _3;
+          StorageLive(_4);
+          _4 = _3;
+-         _2 = move _4 as *const &u8 (PtrToPtr);
++         _2 = move _4;
+          StorageDead(_4);
           StorageDead(_3);
           _0 = _2;
           StorageDead(_2);

tests/mir-opt/casts.roundtrip.PreCodegen.after.mir

@@ -0,0 +1,21 @@
+- // MIR for `roundtrip` before InstSimplify
++ // MIR for `roundtrip` after InstSimplify
+  
+  fn roundtrip(_1: *const u8) -> *const u8 {
+      debug x => _1;
+      let mut _0: *const u8;
+      let mut _2: *mut u8;
+      let mut _3: *const u8;
+  
+      bb0: {
+          StorageLive(_2);
+          StorageLive(_3);
+          _3 = _1;
+          _2 = move _3 as *mut u8 (PtrToPtr);
+          _0 = move _2 as *const u8 (PointerCoercion(MutToConstPointer));
+          StorageDead(_3);
+          StorageDead(_2);
+          return;
+      }
+  }
+  

tests/mir-opt/casts.rs

@@ -0,0 +1,25 @@
+// unit-test: InstSimplify
+// compile-flags: -Zinline-mir
+#![crate_type = "lib"]
+
+#[inline(always)]
+fn generic_cast<T, U>(x: *const T) -> *const U {
+    x as *const U
+}
+
+// EMIT_MIR casts.redundant.InstSimplify.diff
+pub fn redundant<'a, 'b: 'a>(x: *const &'a u8) -> *const &'a u8 {
+    // CHECK-LABEL: fn redundant(
+    // CHECK: inlined generic_cast
+    // CHECK-NOT: as
+    generic_cast::<&'a u8, &'b u8>(x) as *const &'a u8
+}
+
+// EMIT_MIR casts.roundtrip.InstSimplify.diff
+pub fn roundtrip(x: *const u8) -> *const u8 {
+    // CHECK-LABEL: fn roundtrip(
+    // CHECK: _3 = _1;
+    // CHECK: _2 = move _3 as *mut u8 (PtrToPtr);
+    // CHECK: _0 = move _2 as *const u8 (PointerCoercion(MutToConstPointer));
+    x as *mut u8 as *const u8
+}