Clean up CtfeLimit MirPass

Author: bryangarza

compiler/rustc_mir_transform/src/ctfe_limit.rs

@@ -1,92 +1,49 @@
 use crate::MirPass;
 
-use rustc_middle::mir::{BasicBlock, Body, Statement, StatementKind, TerminatorKind};
+use rustc_middle::mir::{BasicBlockData, Body, Statement, StatementKind, TerminatorKind};
 use rustc_middle::ty::TyCtxt;
 
-use tracing::{info, instrument};
-
 pub struct CtfeLimit;
 
 impl<'tcx> MirPass<'tcx> for CtfeLimit {
     #[instrument(skip(self, _tcx, body))]
     fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         let doms = body.basic_blocks.dominators();
-        //info!("Got body with {} basic blocks: {:#?}", body.basic_blocks.len(), body.basic_blocks);
-        //info!("With doms: {doms:?}");
-
-        /*
-        for (index, basic_block) in body.basic_blocks.iter().enumerate() {
-            info!("bb{index}: {basic_block:#?}")
-        }*/
-        for (index, basic_block) in body.basic_blocks.iter().enumerate() {
-            info!(
-                "bb{index} -> successors = {:?}",
-                basic_block.terminator().successors().collect::<Vec<BasicBlock>>()
-            );
-        }
-        for (index, basic_block) in body.basic_blocks.iter().enumerate() {
-            info!("bb{index} -> unwind = {:?}", basic_block.terminator().unwind())
-        }
-
-        let mut dominators = Vec::new();
-        for idom in 0..body.basic_blocks.len() {
-            let mut nodes = Vec::new();
-            for inode in 0..body.basic_blocks.len() {
-                let dom = BasicBlock::from_usize(idom);
-                let node = BasicBlock::from_usize(inode);
-                if doms.is_reachable(dom)
+        let mut indices = Vec::new();
+        for (node, node_data) in body.basic_blocks.iter_enumerated() {
+            if let TerminatorKind::Call { .. } = node_data.terminator().kind {
+                indices.push(node);
+                continue;
+            }
+            // Back edges in a CFG indicate loops
+            for (potential_dom, _) in body.basic_blocks.iter_enumerated() {
+                if doms.is_reachable(potential_dom)
                     && doms.is_reachable(node)
-                    && doms.is_dominated_by(node, dom)
+                    && doms.is_dominated_by(node, potential_dom)
+                    && node_data
+                        .terminator()
+                        .successors()
+                        .into_iter()
+                        .any(|succ| succ == potential_dom)
                 {
-                    //info!("{idom} dominates {inode}");
-                    nodes.push(true);
-                } else {
-                    nodes.push(false);
+                    indices.push(node);
+                    continue;
                 }
             }
-            dominators.push(nodes);
         }
-        /*
-        for idom in 0..body.basic_blocks.len() {
-            print!("{idom} | dom | ");
-            for inode in 0..body.basic_blocks.len() {
-                if dominators[idom][inode] {
-                    print!("{inode} | ");
-                } else {
-                    print!("  | ");
-                }
-            }
-            print!("\n");
-        }
-        */
-
-        for (index, basic_block) in body.basic_blocks_mut().iter_mut().enumerate() {
-            // info!("bb{index}: {basic_block:#?}");
-            //info!("bb{index} -> successors = {:?}", basic_block.terminator().successors().collect::<Vec<BasicBlock>>());
-            let is_back_edge_or_fn_call = 'label: {
-                match basic_block.terminator().kind {
-                    TerminatorKind::Call { .. } => {
-                        break 'label true;
-                    }
-                    _ => (),
-                }
-                for successor in basic_block.terminator().successors() {
-                    let s_index = successor.as_usize();
-                    if dominators[s_index][index] {
-                        info!("{s_index} to {index} is a loop");
-                        break 'label true;
-                    }
-                }
-                false
-            };
-            if is_back_edge_or_fn_call {
-                basic_block.statements.push(Statement {
-                    source_info: basic_block.terminator().source_info,
-                    kind: StatementKind::ConstEvalCounter,
-                });
-                info!("New basic block statements vector: {:?}", basic_block.statements);
-            }
+        for index in indices {
+            insert_counter(
+                body.basic_blocks_mut()
+                    .get_mut(index)
+                    .expect("basic_blocks index {index} should exist"),
+            );
         }
-        info!("With doms: {doms:?}");
     }
 }
+
+fn insert_counter(basic_block_data: &mut BasicBlockData<'_>) {
+    basic_block_data.statements.push(Statement {
+        source_info: basic_block_data.terminator().source_info,
+        kind: StatementKind::ConstEvalCounter,
+    });
+}

src/test/ui/consts/const-eval/stable-metric/ctfe-fn-call.rs

@@ -0,0 +1,33 @@
+// check-pass
+
+const fn foo() {}
+
+const fn call_foo() -> u32 {
+    foo();
+    foo();
+    foo();
+    foo();
+    foo();
+    foo();
+    foo();
+    foo();
+    foo();
+    foo();
+    foo();
+    foo();
+    foo();
+    foo();
+    foo();
+    foo();
+    foo();
+    foo();
+    foo();
+    foo();
+    0
+}
+
+const X: u32 = call_foo();
+
+fn main() {
+    println!("{X}");
+}

src/test/ui/consts/const-eval/stable-metric/ctfe-fn-call.stderr

@@ -0,0 +1,4 @@
+warning: Const eval counter limit (20) has been crossed
+
+warning: 1 warning emitted
+