Rename uneval_consts to required_consts

rust-lang · bors · Apr 24, 2020 · Apr 5, 2020 · Apr 3, 2020 · Apr 5, 2020
commit c1ed7cc95f0aaa75e916fc044cce293f56ad04d3
diff --git a/src/librustc_codegen_ssa/mir/mod.rs b/src/librustc_codegen_ssa/mir/mod.rs
@@ -191,7 +191,7 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 
     fx.per_local_var_debug_info = fx.compute_per_local_var_debug_info();
 
-    for const_ in &mir.uneval_consts {
+    for const_ in &mir.required_consts {
         if let Err(err) = fx.eval_mir_constant(const_) {
             match err {
                 // errored or at least linted

diff --git a/src/librustc_middle/mir/mod.rs b/src/librustc_middle/mir/mod.rs
@@ -156,8 +156,9 @@ pub struct Body<'tcx> {
     /// A span representing this MIR, for error reporting.
     pub span: Span,
 
-    /// Unevaluated consts to evaluate them regardless of being optimized out
-    pub uneval_consts: Vec<Constant<'tcx>>,
+    /// Constants that are required to evaluate successfully for this MIR to be well-formed.
+    /// We hold in this field all the constants we are not able to evaluate yet.
+    pub required_consts: Vec<Constant<'tcx>>,
 
     /// The user may be writing e.g. &[(SOME_CELL, 42)][i].1 and this would get promoted, because
     /// we'd statically know that no thing with interior mutability will ever be available to the
@@ -206,7 +207,7 @@ impl<'tcx> Body<'tcx> {
             spread_arg: None,
             var_debug_info,
             span,
-            uneval_consts: Vec::new(),
+            required_consts: Vec::new(),
             ignore_interior_mut_in_const_validation: false,
             control_flow_destroyed,
             predecessor_cache: PredecessorCache::new(),
@@ -231,7 +232,7 @@ impl<'tcx> Body<'tcx> {
             arg_count: 0,
             spread_arg: None,
             span: DUMMY_SP,
-            uneval_consts: Vec::new(),
+            required_consts: Vec::new(),
             control_flow_destroyed: Vec::new(),
             generator_kind: None,
             var_debug_info: Vec::new(),

diff --git a/src/librustc_middle/mir/visit.rs b/src/librustc_middle/mir/visit.rs
@@ -289,7 +289,7 @@ macro_rules! make_mir_visitor {
 
                 self.visit_span(&$($mutability)? body.span);
 
-                for const_ in &$($mutability)? body.uneval_consts {
+                for const_ in &$($mutability)? body.required_consts {
                     let location = START_BLOCK.start_location();
                     self.visit_constant(const_, location);
                 }

diff --git a/src/librustc_mir/transform/inline.rs b/src/librustc_mir/transform/inline.rs
@@ -124,12 +124,14 @@ impl Inliner<'tcx> {
                 };
 
                 // Copy only unevaluated constants from the callee_body into the caller_body.
-                // Although we are only pushing `ConstKind::Unevaluated` consts to uneval_consts,
-                // here we may not only have `ConstKind::Unevaluated` because we are calling
-                // `subst_and_normalize_erasing_regions`.
-                caller_body.uneval_consts.extend(callee_body.uneval_consts.iter().copied().filter(
-                    |&constant| matches!(constant.literal.val, ConstKind::Unevaluated(_, _, _)),
-                    ));
+                // Although we are only pushing `ConstKind::Unevaluated` consts to
+                // `required_consts`, here we may not only have `ConstKind::Unevaluated`
+                // because we are calling `subst_and_normalize_erasing_regions`.
+                caller_body.required_consts.extend(
+                    callee_body.required_consts.iter().copied().filter(|&constant| {
+                        matches!(constant.literal.val, ConstKind::Unevaluated(_, _, _))
+                    }),
+                );
 
                 let start = caller_body.basic_blocks().len();
                 debug!("attempting to inline callsite {:?} - body={:?}", callsite, callee_body);

diff --git a/src/librustc_mir/transform/mod.rs b/src/librustc_mir/transform/mod.rs
@@ -30,11 +30,11 @@ pub mod no_landing_pads;
 pub mod promote_consts;
 pub mod qualify_min_const_fn;
 pub mod remove_noop_landing_pads;
+pub mod required_consts;
 pub mod rustc_peek;
 pub mod simplify;
 pub mod simplify_branches;
 pub mod simplify_try;
-pub mod uneval_const_set;
 pub mod uninhabited_enum_branching;
 pub mod unreachable_prop;
 
@@ -240,13 +240,13 @@ fn mir_validated(
 
     let mut body = tcx.mir_const(def_id).steal();
 
-    let mut uneval_consts = Vec::new();
-    let mut uneval_const_visitor =
-        self::uneval_const_set::UnevalConstSetVisitor::new(&mut uneval_consts);
+    let mut required_consts = Vec::new();
+    let mut required_consts_visitor =
+        self::required_consts::RequiredConstsVisitor::new(&mut required_consts);
     for (bb, bb_data) in traversal::reverse_postorder(&body) {
-        uneval_const_visitor.visit_basic_block_data(bb, bb_data);
+        required_consts_visitor.visit_basic_block_data(bb, bb_data);
     }
-    body.uneval_consts = uneval_consts;
+    body.required_consts = required_consts;
 
     let promote_pass = promote_consts::PromoteTemps::default();
     run_passes(

diff --git a/src/librustc_mir/transform/required_consts.rs b/src/librustc_mir/transform/required_consts.rs
@@ -0,0 +1,23 @@
+use rustc_middle::mir::visit
6302
::Visitor;
+use rustc_middle::mir::{Constant, Location};
+use rustc_middle::ty::ConstKind;
+
+pub struct RequiredConstsVisitor<'a, 'tcx> {
+    required_consts: &'a mut Vec<Constant<'tcx>>,
+}
+
+impl<'a, 'tcx> RequiredConstsVisitor<'a, 'tcx> {
+    pub fn new(required_consts: &'a mut Vec<Constant<'tcx>>) -> Self {
+        RequiredConstsVisitor { required_consts }
+    }
+}
+
+impl<'a, 'tcx> Visitor<'tcx> for RequiredConstsVisitor<'a, 'tcx> {
+    fn visit_constant(&mut self, constant: &Constant<'tcx>, _: Location) {
+        let const_kind = constant.literal.val;
+
+        if let ConstKind::Unevaluated(_, _, _) = const_kind {
+            self.required_consts.push(*constant);
+        }
+    }
+}
diff --git a/src/librustc_mir/transform/uneval_const_set.rs b/src/librustc_mir/transform/uneval_const_set.rs