Rename the 'cretonne' crate to 'cretonne-codegen'.
This fixes the next part of #287.
This commit is contained in:
Dan Gohman
390
lib/codegen/src/regalloc/reload.rs
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390
lib/codegen/src/regalloc/reload.rs
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@@ -0,0 +1,390 @@
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//! Reload pass
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//!
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//! The reload pass runs between the spilling and coloring passes. Its primary responsibility is to
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//! insert `spill` and `fill` instructions such that instruction operands expecting a register will
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//! get a value with register affinity, and operands expecting a stack slot will get a value with
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//! stack affinity.
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//!
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//! The secondary responsibility of the reload pass is to reuse values in registers as much as
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//! possible to minimize the number of `fill` instructions needed. This must not cause the register
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//! pressure limits to be exceeded.
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use cursor::{Cursor, EncCursor};
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use dominator_tree::DominatorTree;
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use entity::{SparseMap, SparseMapValue};
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use ir::{AbiParam, ArgumentLoc, InstBuilder};
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use ir::{Ebb, Function, Inst, Value};
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use isa::RegClass;
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use isa::{ConstraintKind, EncInfo, Encoding, RecipeConstraints, TargetIsa};
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use regalloc::affinity::Affinity;
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use regalloc::live_value_tracker::{LiveValue, LiveValueTracker};
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use regalloc::liveness::Liveness;
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use std::vec::Vec;
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use timing;
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use topo_order::TopoOrder;
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/// Reusable data structures for the reload pass.
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pub struct Reload {
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candidates: Vec<ReloadCandidate>,
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reloads: SparseMap<Value, ReloadedValue>,
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}
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/// Context data structure that gets instantiated once per pass.
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struct Context<'a> {
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cur: EncCursor<'a>,
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// Cached ISA information.
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// We save it here to avoid frequent virtual function calls on the `TargetIsa` trait object.
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encinfo: EncInfo,
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// References to contextual data structures we need.
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domtree: &'a DominatorTree,
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liveness: &'a mut Liveness,
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topo: &'a mut TopoOrder,
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candidates: &'a mut Vec<ReloadCandidate>,
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reloads: &'a mut SparseMap<Value, ReloadedValue>,
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}
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impl Reload {
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/// Create a new blank reload pass.
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pub fn new() -> Self {
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Self {
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candidates: Vec::new(),
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reloads: SparseMap::new(),
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}
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}
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/// Clear all data structures in this reload pass.
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pub fn clear(&mut self) {
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self.candidates.clear();
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self.reloads.clear();
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}
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/// Run the reload algorithm over `func`.
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pub fn run(
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&mut self,
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isa: &TargetIsa,
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func: &mut Function,
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domtree: &DominatorTree,
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liveness: &mut Liveness,
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topo: &mut TopoOrder,
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tracker: &mut LiveValueTracker,
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) {
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let _tt = timing::ra_reload();
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dbg!("Reload for:\n{}", func.display(isa));
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let mut ctx = Context {
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cur: EncCursor::new(func, isa),
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encinfo: isa.encoding_info(),
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domtree,
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liveness,
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topo,
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candidates: &mut self.candidates,
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reloads: &mut self.reloads,
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};
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ctx.run(tracker)
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}
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}
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/// A reload candidate.
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///
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/// This represents a stack value that is used by the current instruction where a register is
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/// needed.
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struct ReloadCandidate {
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argidx: usize,
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value: Value,
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regclass: RegClass,
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}
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/// A Reloaded value.
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///
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/// This represents a value that has been reloaded into a register value from the stack.
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struct ReloadedValue {
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stack: Value,
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reg: Value,
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}
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impl SparseMapValue<Value> for ReloadedValue {
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fn key(&self) -> Value {
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self.stack
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}
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}
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impl<'a> Context<'a> {
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fn run(&mut self, tracker: &mut LiveValueTracker) {
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self.topo.reset(self.cur.func.layout.ebbs());
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while let Some(ebb) = self.topo.next(&self.cur.func.layout, self.domtree) {
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self.visit_ebb(ebb, tracker);
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}
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}
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fn visit_ebb(&mut self, ebb: Ebb, tracker: &mut LiveValueTracker) {
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dbg!("Reloading {}:", ebb);
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self.visit_ebb_header(ebb, tracker);
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tracker.drop_dead_params();
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// visit_ebb_header() places us at the first interesting instruction in the EBB.
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while let Some(inst) = self.cur.current_inst() {
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let encoding = self.cur.func.encodings[inst];
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if encoding.is_legal() {
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self.visit_inst(ebb, inst, encoding, tracker);
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tracker.drop_dead(inst);
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} else {
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self.cur.next_inst();
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}
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}
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}
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/// Process the EBB parameters. Move to the next instruction in the EBB to be processed
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fn visit_ebb_header(&mut self, ebb: Ebb, tracker: &mut LiveValueTracker) {
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let (liveins, args) = tracker.ebb_top(
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ebb,
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&self.cur.func.dfg,
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self.liveness,
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&self.cur.func.layout,
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self.domtree,
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);
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if self.cur.func.layout.entry_block() == Some(ebb) {
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debug_assert_eq!(liveins.len(), 0);
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self.visit_entry_params(ebb, args);
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} else {
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self.visit_ebb_params(ebb, args);
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}
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}
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/// Visit the parameters on the entry block.
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/// These values have ABI constraints from the function signature.
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fn visit_entry_params(&mut self, ebb: Ebb, args: &[LiveValue]) {
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debug_assert_eq!(self.cur.func.signature.params.len(), args.len());
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self.cur.goto_first_inst(ebb);
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for (arg_idx, arg) in args.iter().enumerate() {
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let abi = self.cur.func.signature.params[arg_idx];
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match abi.location {
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ArgumentLoc::Reg(_) => {
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if arg.affinity.is_stack() {
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// An incoming register parameter was spilled. Replace the parameter value
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// with a temporary register value that is immediately spilled.
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let reg = self.cur.func.dfg.replace_ebb_param(
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arg.value,
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abi.value_type,
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);
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let affinity = Affinity::abi(&abi, self.cur.isa);
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self.liveness.create_dead(reg, ebb, affinity);
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self.insert_spill(ebb, arg.value, reg);
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}
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}
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ArgumentLoc::Stack(_) => {
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debug_assert!(arg.affinity.is_stack());
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}
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ArgumentLoc::Unassigned => panic!("Unexpected ABI location"),
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}
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}
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}
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fn visit_ebb_params(&mut self, ebb: Ebb, _args: &[LiveValue]) {
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self.cur.goto_first_inst(ebb);
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}
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/// Process the instruction pointed to by `pos`, and advance the cursor to the next instruction
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/// that needs processing.
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fn visit_inst(
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&mut self,
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ebb: Ebb,
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inst: Inst,
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encoding: Encoding,
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tracker: &mut LiveValueTracker,
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) {
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self.cur.use_srcloc(inst);
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// Get the operand constraints for `inst` that we are trying to satisfy.
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let constraints = self.encinfo.operand_constraints(encoding).expect(
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"Missing instruction encoding",
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);
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// Identify reload candidates.
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debug_assert!(self.candidates.is_empty());
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self.find_candidates(inst, constraints);
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// Insert fill instructions before `inst` and replace `cand.value` with the filled value.
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for cand in self.candidates.iter_mut() {
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if let Some(reload) = self.reloads.get(cand.value) {
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cand.value = reload.reg;
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continue;
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}
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let reg = self.cur.ins().fill(cand.value);
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let fill = self.cur.built_inst();
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self.reloads.insert(ReloadedValue {
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stack: cand.value,
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reg: reg,
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});
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cand.value = reg;
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// Create a live range for the new reload.
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let affinity = Affinity::Reg(cand.regclass.into());
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self.liveness.create_dead(reg, fill, affinity);
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self.liveness.extend_locally(
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reg,
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ebb,
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inst,
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&self.cur.func.layout,
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);
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}
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// Rewrite instruction arguments.
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//
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// Only rewrite those arguments that were identified as candidates. This leaves EBB
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// arguments on branches as-is without rewriting them. A spilled EBB argument needs to stay
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// spilled because the matching EBB parameter is going to be in the same virtual register
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// and therefore the same stack slot as the EBB argument value.
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if !self.candidates.is_empty() {
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let args = self.cur.func.dfg.inst_args_mut(inst);
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while let Some(cand) = self.candidates.pop() {
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args[cand.argidx] = cand.value;
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}
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}
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// TODO: Reuse reloads for future instructions.
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self.reloads.clear();
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let (_throughs, _kills, defs) =
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tracker.process_inst(inst, &self.cur.func.dfg, self.liveness);
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// Advance to the next instruction so we can insert any spills after the instruction.
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self.cur.next_inst();
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// Rewrite register defs that need to be spilled.
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//
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// Change:
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//
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// v2 = inst ...
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//
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// Into:
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//
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// v7 = inst ...
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// v2 = spill v7
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//
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// That way, we don't need to rewrite all future uses of v2.
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for (lv, op) in defs.iter().zip(constraints.outs) {
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if lv.affinity.is_stack() && op.kind != ConstraintKind::Stack {
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let value_type = self.cur.func.dfg.value_type(lv.value);
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let reg = self.cur.func.dfg.replace_result(lv.value, value_type);
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self.liveness.create_dead(reg, inst, Affinity::new(op));
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self.insert_spill(ebb, lv.value, reg);
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}
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}
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// Same thing for spilled call return values.
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let retvals = &defs[constraints.outs.len()..];
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if !retvals.is_empty() {
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let sig = self.cur.func.dfg.call_signature(inst).expect(
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"Extra results on non-call instruction",
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);
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for (i, lv) in retvals.iter().enumerate() {
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let abi = self.cur.func.dfg.signatures[sig].returns[i];
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debug_assert!(abi.location.is_reg());
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if lv.affinity.is_stack() {
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let reg = self.cur.func.dfg.replace_result(lv.value, abi.value_type);
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self.liveness.create_dead(
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reg,
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inst,
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Affinity::abi(&abi, self.cur.isa),
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);
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self.insert_spill(ebb, lv.value, reg);
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}
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}
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}
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}
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// Find reload candidates for `inst` and add them to `self.candidates`.
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//
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// These are uses of spilled values where the operand constraint requires a register.
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fn find_candidates(&mut self, inst: Inst, constraints: &RecipeConstraints) {
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let args = self.cur.func.dfg.inst_args(inst);
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for (argidx, (op, &arg)) in constraints.ins.iter().zip(args).enumerate() {
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if op.kind != ConstraintKind::Stack && self.liveness[arg].affinity.is_stack() {
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self.candidates.push(ReloadCandidate {
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argidx,
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value: arg,
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regclass: op.regclass,
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})
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}
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}
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// If we only have the fixed arguments, we're done now.
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let offset = constraints.ins.len();
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if args.len() == offset {
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return;
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}
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let var_args = &args[offset..];
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// Handle ABI arguments.
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if let Some(sig) = self.cur.func.dfg.call_signature(inst) {
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handle_abi_args(
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self.candidates,
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&self.cur.func.dfg.signatures[sig].params,
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var_args,
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offset,
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self.cur.isa,
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self.liveness,
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);
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} else if self.cur.func.dfg[inst].opcode().is_return() {
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handle_abi_args(
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self.candidates,
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&self.cur.func.signature.returns,
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var_args,
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offset,
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self.cur.isa,
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self.liveness,
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);
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}
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}
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/// Insert a spill at `pos` and update data structures.
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///
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/// - Insert `stack = spill reg` at `pos`, and assign an encoding.
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/// - Move the `stack` live range starting point to the new instruction.
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/// - Extend the `reg` live range to reach the new instruction.
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fn insert_spill(&mut self, ebb: Ebb, stack: Value, reg: Value) {
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self.cur.ins().with_result(stack).spill(reg);
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let inst = self.cur.built_inst();
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// Update live ranges.
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self.liveness.move_def_locally(stack, inst);
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self.liveness.extend_locally(
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reg,
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ebb,
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inst,
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&self.cur.func.layout,
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);
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}
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}
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/// Find reload candidates in the instruction's ABI variable arguments. This handles both
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/// return values and call arguments.
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fn handle_abi_args(
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candidates: &mut Vec<ReloadCandidate>,
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abi_types: &[AbiParam],
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var_args: &[Value],
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offset: usize,
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isa: &TargetIsa,
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liveness: &Liveness,
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) {
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debug_assert_eq!(abi_types.len(), var_args.len());
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for ((abi, &arg), argidx) in abi_types.iter().zip(var_args).zip(offset..) {
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if abi.location.is_reg() {
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let lv = liveness.get(arg).expect("Missing live range for ABI arg");
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if lv.affinity.is_stack() {
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candidates.push(ReloadCandidate {
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argidx,
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value: arg,
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regclass: isa.regclass_for_abi_type(abi.value_type),
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});
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}
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}
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}
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}
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Block a user