Do not unnecessarily eval consts in codegen

Author: compiler-errors

src/base.rs

@@ -785,8 +785,10 @@ fn codegen_stmt<'tcx>(
                 }
                 Rvalue::Repeat(ref operand, times) => {
                     let operand = codegen_operand(fx, operand);
-                    let times =
-                        fx.monomorphize(times).eval_target_usize(fx.tcx, ParamEnv::reveal_all());
+                    let times = fx
+                        .monomorphize(times)
+                        .try_to_target_usize(fx.tcx)
+                        .expect("expected monomorphic const in codegen");
                     if operand.layout().size.bytes() == 0 {
                         // Do nothing for ZST's
                     } else if fx.clif_type(operand.layout().ty) == Some(types::I8) {
@@ -944,7 +946,10 @@ fn codegen_stmt<'tcx>(
 fn codegen_array_len<'tcx>(fx: &mut FunctionCx<'_, '_, 'tcx>, place: CPlace<'tcx>) -> Value {
     match *place.layout().ty.kind() {
         ty::Array(_elem_ty, len) => {
-            let len = fx.monomorphize(len).eval_target_usize(fx.tcx, ParamEnv::reveal_all()) as i64;
+            let len = fx
+                .monomorphize(len)
+                .try_to_target_usize(fx.tcx)
+                .expect("expected monomorphic const in codegen") as i64;
             fx.bcx.ins().iconst(fx.pointer_type, len)
         }
         ty::Slice(_elem_ty) => place.to_ptr_unsized().1,

src/debuginfo/types.rs

@@ -44,7 +44,7 @@ impl DebugContext {
                 type_dbg,
                 ty,
                 *elem_ty,
-                len.eval_target_usize(tcx, ty::ParamEnv::reveal_all()),
+                len.try_to_target_usize(tcx).expect("expected monomorphic const in codegen"),
             ),
             // ty::Slice(_) | ty::Str
             // ty::Dynamic

src/intrinsics/simd.rs

@@ -131,9 +131,8 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
 
             let idx = generic_args[2]
                 .expect_const()
-                .eval(fx.tcx, ty::ParamEnv::reveal_all(), span)
-                .unwrap()
-                .1
+                .try_to_valtree()
+                .expect("expected monomorphic const in codegen")
                 .unwrap_branch();
 
             assert_eq!(x.layout(), y.layout());

src/unsize.rs

@@ -24,10 +24,10 @@ pub(crate) fn unsized_info<'tcx>(
     let (source, target) =
         fx.tcx.struct_lockstep_tails_for_codegen(source, target, ParamEnv::reveal_all());
     match (&source.kind(), &target.kind()) {
-        (&ty::Array(_, len), &ty::Slice(_)) => fx
-            .bcx
-            .ins()
-            .iconst(fx.pointer_type, len.eval_target_usize(fx.tcx, ParamEnv::reveal_all()) as i64),
+        (&ty::Array(_, len), &ty::Slice(_)) => fx.bcx.ins().iconst(
+            fx.pointer_type,
+            len.try_to_target_usize(fx.tcx).expect("expected monomorphic const in codegen") as i64,
+        ),
         (&ty::Dynamic(data_a, _, src_dyn_kind), &ty::Dynamic(data_b, _, target_dyn_kind))
             if src_dyn_kind == target_dyn_kind =>
         {