re-work comment, refactor returning from function

Author: Jamesbarford

compiler/rustc_codegen_ssa/src/mir/operand.rs

@@ -637,11 +637,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
             mir::Operand::Constant(ref constant) => {
                 let constant_ty = constant.ty();
-                // Make sure that constant SIMD vectors are passed as immediates.
-                // This is needed for some intrinsics.
-                return if constant_ty.is_simd() {
+                // Make sure this type is actually passed as an immediate vector.
+                // (In particular, this excludes packed SIMD vectors.)
+                if constant_ty.is_simd() {
                     let layout = bx.layout_of(constant_ty);
-                    match layout.abi {
+                    return match layout.abi {
                         Abi::Vector { .. } => {
                             let (llval, ty) = self.immediate_const_vector(bx, constant);
                             OperandRef {
@@ -650,10 +650,10 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             }
                         }
                         _ => self.eval_mir_constant_to_operand(bx, constant),
-                    }
-                } else {
-                    self.eval_mir_constant_to_operand(bx, constant)
-                };
+                    };
+                }
+
+                self.eval_mir_constant_to_operand(bx, constant)
             }
         }
     }