Merge pull request #765 from rust-lang/fix/shift

Fix shifting a value of a smaller type to a bigger type

Author: antoyo

build_system/src/test.rs

@@ -714,8 +714,7 @@ fn test_libcore(env: &Env, args: &TestArg) -> Result<(), String> {
     let path = get_sysroot_dir().join("sysroot_src/library/coretests");
     let _ = remove_dir_all(path.join("target"));
     // TODO(antoyo): run in release mode when we fix the failures.
-    // TODO(antoyo): Stop skipping funnel shift tests when those operations are fixed.
-    run_cargo_command(&[&"test", &"--", &"--skip", &"test_funnel_shift"], Some(&path), env, args)?;
+    run_cargo_command(&[&"test"], Some(&path), env, args)?;
     Ok(())
 }
 

src/int.rs

@@ -83,12 +83,11 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
                 let a_size = a_type.get_size();
                 let b_size = b_type.get_size();
                 match a_size.cmp(&b_size) {
-                    std::cmp::Ordering::Less => {
-                        let a = self.context.new_cast(self.location, a, b_type);
-                        a >> b
-                    }
                     std::cmp::Ordering::Equal => a >> b,
-                    std::cmp::Ordering::Greater => {
+                    _ => {
+                        // NOTE: it is OK to cast even if b has a type bigger than a because b has
+                        // been masked by codegen_ssa before calling Builder::lshr or
+                        // Builder::ashr.
                         let b = self.context.new_cast(self.location, b, a_type);
                         a >> b
                     }
@@ -692,12 +691,10 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
                 let a_size = a_type.get_size();
                 let b_size = b_type.get_size();
                 match a_size.cmp(&b_size) {
-                    std::cmp::Ordering::Less => {
-                        let a = self.context.new_cast(self.location, a, b_type);
-                        a << b
-                    }
                     std::cmp::Ordering::Equal => a << b,
-                    std::cmp::Ordering::Greater => {
+                    _ => {
+                        // NOTE: it is OK to cast even if b has a type bigger than a because b has
+                        // been masked by codegen_ssa before calling Builder::shl.
                         let b = self.context.new_cast(self.location, b, a_type);
                         a << b
                     }