Second field of ScalarPair can be undef in some cases

1 files changed, 11 insertions, 7 deletions

diff --git a/src/librustc_codegen_llvm/mir/operand.rs b/src/librustc_codegen_llvm/mir/operand.rs
index 1296f5e4b14..f8166ee6491 100644
--- a/src/librustc_codegen_llvm/mir/operand.rs
+++ b/src/librustc_codegen_llvm/mir/operand.rs
@@ -10,7 +10,7 @@
 
 use rustc::mir::interpret::ConstEvalErr;
 use rustc::mir;
-use rustc::mir::interpret::ConstValue;
+use rustc::mir::interpret::{ConstValue, ScalarMaybeUndef};
 use rustc::ty;
 use rustc::ty::layout::{self, Align, LayoutOf, TyLayout};
 use rustc_data_structures::indexed_vec::Idx;
@@ -110,12 +110,16 @@ impl OperandRef<'ll, 'tcx> {
                     a_scalar,
                     layout.scalar_pair_element_llvm_type(bx.cx, 0, true),
                 );
-                let b_llval = scalar_to_llvm(
-                    bx.cx,
-                    b,
-                    b_scalar,
-                    layout.scalar_pair_element_llvm_type(bx.cx, 1, true),
-                );
+                let b_layout = layout.scalar_pair_element_llvm_type(bx.cx, 1, true);
+                let b_llval = match b {
+                    ScalarMaybeUndef::Scalar(b) => scalar_to_llvm(
+                        bx.cx,
+                        b,
+                        b_scalar,
+                        b_layout,
+                    ),
+                    ScalarMaybeUndef::Undef => C_undef(b_layout),
+                };
                 OperandValue::Pair(a_llval, b_llval)
             },
             ConstValue::ByRef(alloc, offset) => {