Extract cost checker from inliner.

Author: cjgillot

compiler/rustc_mir_transform/src/cost_checker.rs

@@ -0,0 +1,94 @@
+use rustc_middle::mir::visit::*;
+use rustc_middle::mir::*;
+use rustc_middle::ty::{self, ParamEnv, TyCtxt};
+
+const INSTR_COST: usize = 5;
+const CALL_PENALTY: usize = 25;
+const LANDINGPAD_PENALTY: usize = 50;
+const RESUME_PENALTY: usize = 45;
+
+/// Verify that the callee body is compatible with the caller.
+#[derive(Clone)]
+pub(crate) struct CostChecker<'b, 'tcx> {
+    tcx: TyCtxt<'tcx>,
+    param_env: ParamEnv<'tcx>,
+    cost: usize,
+    callee_body: &'b Body<'tcx>,
+    instance: ty::Instance<'tcx>,
+}
+
+impl<'b, 'tcx> CostChecker<'b, 'tcx> {
+    pub fn new(
+        tcx: TyCtxt<'tcx>,
+        param_env: ParamEnv<'tcx>,
+        instance: ty::Instance<'tcx>,
+        callee_body: &'b Body<'tcx>,
+    ) -> CostChecker<'b, 'tcx> {
+        CostChecker { tcx, param_env, callee_body, instance, cost: 0 }
+    }
+
+    pub fn cost(&self) -> usize {
+        self.cost
+    }
+}
+
+impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
+    fn visit_statement(&mut self, statement: &Statement<'tcx>, _: Location) {
+        // Don't count StorageLive/StorageDead in the inlining cost.
+        match statement.kind {
+            StatementKind::StorageLive(_)
+            | StatementKind::StorageDead(_)
+            | StatementKind::Deinit(_)
+            | StatementKind::Nop => {}
+            _ => self.cost += INSTR_COST,
+        }
+    }
+
+    fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, _: Location) {
+        let tcx = self.tcx;
+        match terminator.kind {
+            TerminatorKind::Drop { ref place, unwind, .. } => {
+                // If the place doesn't actually need dropping, treat it like a regular goto.
+                let ty = self.instance.instantiate_mir(
+                    tcx,
+                    ty::EarlyBinder::bind(&place.ty(self.callee_body, tcx).ty),
+                );
+                if ty.needs_drop(tcx, self.param_env) {
+                    self.cost += CALL_PENALTY;
+                    if let UnwindAction::Cleanup(_) = unwind {
+                        self.cost += LANDINGPAD_PENALTY;
+                    }
+                } else {
+                    self.cost += INSTR_COST;
+                }
+            }
+            TerminatorKind::Call { func: Operand::Constant(ref f), unwind, .. } => {
+                let fn_ty =
+                    self.instance.instantiate_mir(tcx, ty::EarlyBinder::bind(&f.const_.ty()));
+                self.cost += if let ty::FnDef(def_id, _) = *fn_ty.kind() && tcx.is_intrinsic(def_id) {
+                    // Don't give intrinsics the extra penalty for calls
+                    INSTR_COST
+                } else {
+                    CALL_PENALTY
+                };
+                if let UnwindAction::Cleanup(_) = unwind {
+                    self.cost += LANDINGPAD_PENALTY;
+                }
+            }
+            TerminatorKind::Assert { unwind, .. } => {
+                self.cost += CALL_PENALTY;
+                if let UnwindAction::Cleanup(_) = unwind {
+                    self.cost += LANDINGPAD_PENALTY;
+                }
+            }
+            TerminatorKind::UnwindResume => self.cost += RESUME_PENALTY,
+            TerminatorKind::InlineAsm { unwind, .. } => {
+                self.cost += INSTR_COST;
+                if let UnwindAction::Cleanup(_) = unwind {
+                    self.cost += LANDINGPAD_PENALTY;
+                }
+            }
+            _ => self.cost += INSTR_COST,
+        }
+    }
+}

compiler/rustc_mir_transform/src/inline.rs

@@ -14,6 +14,7 @@ use rustc_session::config::OptLevel;
 use rustc_target::abi::FieldIdx;
 use rustc_target::spec::abi::Abi;
 
+use crate::cost_checker::CostChecker;
 use crate::simplify::{remove_dead_blocks, CfgSimplifier};
 use crate::util;
 use crate::MirPass;
@@ -22,11 +23,6 @@ use std::ops::{Range, RangeFrom};
 
 pub(crate) mod cycle;
 
-const INSTR_COST: usize = 5;
-const CALL_PENALTY: usize = 25;
-const LANDINGPAD_PENALTY: usize = 50;
-const RESUME_PENALTY: usize = 45;
-
 const TOP_DOWN_DEPTH_LIMIT: usize = 5;
 
 pub struct Inline;
@@ -479,13 +475,7 @@ impl<'tcx> Inliner<'tcx> {
 
         // FIXME: Give a bonus to functions with only a single caller
 
-        let mut checker = CostChecker {
-            tcx: self.tcx,
-            param_env: self.param_env,
-            instance: callsite.callee,
-            callee_body,
-            cost: 0,
-        };
+        let mut checker = CostChecker::new(self.tcx, self.param_env, callsite.callee, callee_body);
 
         // Traverse the MIR manually so we can account for the effects of inlining on the CFG.
         let mut work_list = vec![START_BLOCK];
@@ -530,7 +520,7 @@ impl<'tcx> Inliner<'tcx> {
         // That attribute is often applied to very large functions that exceed LLVM's (very
         // generous) inlining threshold. Such functions are very poor MIR inlining candidates.
         // Always inlining #[inline(always)] functions in MIR, on net, slows down the compiler.
-        let cost = checker.cost;
+        let cost = checker.cost();
         if cost <= threshold {
             debug!("INLINING {:?} [cost={} <= threshold={}]", callsite, cost, threshold);
             Ok(())
@@ -803,81 +793,6 @@ impl<'tcx> Inliner<'tcx> {
     }
 }
 
-/// Verify that the callee body is compatible with the caller.
-///
-/// This visitor mostly computes the inlining cost,
-/// but also needs to verify that types match because of normalization failure.
-struct CostChecker<'b, 'tcx> {
-    tcx: TyCtxt<'tcx>,
-    param_env: ParamEnv<'tcx>,
-    cost: usize,
-    callee_body: &'b Body<'tcx>,
-    instance: ty::Instance<'tcx>,
-}
-
-impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
-    fn visit_statement(&mut self, statement: &Statement<'tcx>, _: Location) {
-        // Don't count StorageLive/StorageDead in the inlining cost.
-        match statement.kind {
-            StatementKind::StorageLive(_)
-            | StatementKind::StorageDead(_)
-            | StatementKind::Deinit(_)
-            | StatementKind::Nop => {}
-            _ => self.cost += INSTR_COST,
-        }
-    }
-
-    fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, _: Location) {
-        let tcx = self.tcx;
-        match terminator.kind {
-            TerminatorKind::Drop { ref place, unwind, .. } => {
-                // If the place doesn't actually need dropping, treat it like a regular goto.
-                let ty = self.instance.instantiate_mir(
-                    tcx,
-                    ty::EarlyBinder::bind(&place.ty(self.callee_body, tcx).ty),
-                );
-                if ty.needs_drop(tcx, self.param_env) {
-                    self.cost += CALL_PENALTY;
-                    if let UnwindAction::Cleanup(_) = unwind {
-                        self.cost += LANDINGPAD_PENALTY;
-                    }
-                } else {
-                    self.cost += INSTR_COST;
-                }
-            }
-            TerminatorKind::Call { func: Operand::Constant(ref f), unwind, .. } => {
-                let fn_ty =
-                    self.instance.instantiate_mir(tcx, ty::EarlyBinder::bind(&f.const_.ty()));
-                self.cost += if let ty::FnDef(def_id, _) = *fn_ty.kind()
-                    && tcx.is_intrinsic(def_id)
-                {
-                    // Don't give intrinsics the extra penalty for calls
-                    INSTR_COST
-                } else {
-                    CALL_PENALTY
-                };
-                if let UnwindAction::Cleanup(_) = unwind {
-                    self.cost += LANDINGPAD_PENALTY;
-                }
-            }
-            TerminatorKind::Assert { unwind, .. } => {
-                self.cost += CALL_PENALTY;
-                if let UnwindAction::Cleanup(_) = unwind {
-                    self.cost += LANDINGPAD_PENALTY;
-                }
-            }
-            TerminatorKind::UnwindResume => self.cost += RESUME_PENALTY,
-            TerminatorKind::InlineAsm { unwind, .. } => {
-                self.cost += INSTR_COST;
-                if let UnwindAction::Cleanup(_) = unwind {
-                    self.cost += LANDINGPAD_PENALTY;
-                }
-            }
-            _ => self.cost += INSTR_COST,
-        }
-    }
-}
-
 /**
  * Integrator.
  *

compiler/rustc_mir_transform/src/lib.rs

@@ -61,6 +61,7 @@ mod const_goto;
 mod const_prop;
 mod const_prop_lint;
 mod copy_prop;
+mod cost_checker;
 mod coverage;
 mod cross_crate_inline;
 mod ctfe_limit;