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Check the top-level register class for available registers.

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Fixes #165.

The constraint solver's schedule_move() function sometimes need to use
an extra available register when the moves to be scheduled contains
cycles.

The pending moves have associated register classes that come from the
constraint programming. Since the moves have hard-coded to and from
registers, these register classes are only meant to indicate the
register sizes. In particular, we can use the whole top-level register
class when scavenging for a spare register to break a cycle.
This commit is contained in:
Jakob Stoklund Olesen
2017-10-03 12:18:55 -07:00
parent 739d414d18
commit fb0999ce33
3 changed files with 48 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files

51
lib/cretonne/src/regalloc/solver.rs
View File

@@ -679,7 +679,7 @@ impl Solver {
/// a register.
///
/// Returns the number of spills that had to be emitted.
pub fn schedule_moves(&mut self, regs: &AllocatableSet) -> usize {
pub fn schedule_moves(&mut self, regs: &AllocatableSet, reginfo: &RegInfo) -> usize {
self.collect_moves();
let mut avail = regs.clone();
@@ -724,9 +724,17 @@ impl Solver {
.0;
self.moves.swap(i, i + j);
// Check the top-level register class for an available register. It is an axiom of the
// register allocator that we can move between all registers in the top-level RC.
let m = self.moves[i].clone();
if let Some(reg) = avail.iter(m.rc).next() {
dbg!("breaking cycle at {} with available register %{}", m, reg);
let toprc = reginfo.toprc(m.rc);
if let Some(reg) = avail.iter(toprc).next() {
dbg!(
"breaking cycle at {} with available {} register {}",
m,
toprc,
reginfo.display_regunit(reg)
);
// Alter the move so it is guaranteed to be picked up when we loop. It is important
// that this move is scheduled immediately, otherwise we would have multiple moves
@@ -737,7 +745,7 @@ impl Solver {
// next iteration.
self.moves.push(Assignment {
value: m.value,
rc: m.rc,
rc: toprc,
from: reg,
to: m.to,
});
@@ -746,7 +754,7 @@ impl Solver {
// may have to move two S-registers out of the way before we can resolve a cycle
// involving a D-register.
} else {
panic!("Not enough registers in {} to schedule moves", m.rc);
panic!("Not enough registers in {} to schedule moves", toprc);
}
}
@@ -779,9 +787,8 @@ impl fmt::Display for Solver {
mod tests {
use entity::EntityRef;
use ir::Value;
use isa::{TargetIsa, RegClass, RegUnit};
use isa::{TargetIsa, RegClass, RegUnit, RegInfo};
use regalloc::AllocatableSet;
use std::borrow::Borrow;
use super::{Solver, Assignment};
// Make an arm32 `TargetIsa`, if possible.
@@ -796,12 +803,10 @@ mod tests {
}
// Get a register class by name.
fn rc_by_name(isa: &TargetIsa, name: &str) -> RegClass {
isa.register_info()
.classes
.iter()
.find(|rc| rc.name == name)
.expect("Can't find named register class.")
fn rc_by_name(reginfo: &RegInfo, name: &str) -> RegClass {
reginfo.classes.iter().find(|rc| rc.name == name).expect(
"Can't find named register class.",
)
}
// Construct a move.
@@ -817,8 +822,8 @@ mod tests {
#[test]
fn simple_moves() {
let isa = arm32().expect("This test requires arm32 support");
let isa = isa.borrow();
let gpr = rc_by_name(isa, "GPR");
let reginfo = isa.register_info();
let gpr = rc_by_name(&reginfo, "GPR");
let r0 = gpr.unit(0);
let r1 = gpr.unit(1);
let r2 = gpr.unit(2);
@@ -833,7 +838,7 @@ mod tests {
solver.reassign_in(v10, gpr, r1, r0);
solver.inputs_done();
assert!(solver.quick_solve().is_ok());
assert_eq!(solver.schedule_moves(&regs), 0);
assert_eq!(solver.schedule_moves(&regs, &reginfo), 0);
assert_eq!(solver.moves(), &[mov(v10, gpr, r1, r0)]);
// A bit harder: r0, r1 need to go in r1, r2.
@@ -843,7 +848,7 @@ mod tests {
solver.reassign_in(v11, gpr, r1, r2);
solver.inputs_done();
assert!(solver.quick_solve().is_ok());
assert_eq!(solver.schedule_moves(&regs), 0);
assert_eq!(solver.schedule_moves(&regs, &reginfo), 0);
assert_eq!(
solver.moves(),
&[mov(v11, gpr, r1, r2), mov(v10, gpr, r0, r1)]
@@ -855,7 +860,7 @@ mod tests {
solver.reassign_in(v11, gpr, r1, r0);
solver.inputs_done();
assert!(solver.quick_solve().is_ok());
assert_eq!(solver.schedule_moves(&regs), 0);
assert_eq!(solver.schedule_moves(&regs, &reginfo), 0);
assert_eq!(
solver.moves(),
&[
@@ -869,9 +874,9 @@ mod tests {
#[test]
fn harder_move_cycles() {
let isa = arm32().expect("This test requires arm32 support");
let isa = isa.borrow();
let s = rc_by_name(isa, "S");
let d = rc_by_name(isa, "D");
let reginfo = isa.register_info();
let s = rc_by_name(&reginfo, "S");
let d = rc_by_name(&reginfo, "D");
let d0 = d.unit(0);
let d1 = d.unit(1);
let d2 = d.unit(2);
@@ -894,7 +899,7 @@ mod tests {
solver.reassign_in(v12, s, s3, s1);
solver.inputs_done();
assert!(solver.quick_solve().is_ok());
assert_eq!(solver.schedule_moves(&regs), 0);
assert_eq!(solver.schedule_moves(&regs, &reginfo), 0);
assert_eq!(
solver.moves(),
&[
@@ -915,7 +920,7 @@ mod tests {
solver.reassign_in(v10, d, d1, d0);
solver.inputs_done();
assert!(solver.quick_solve().is_ok());
assert_eq!(solver.schedule_moves(&regs), 0);
assert_eq!(solver.schedule_moves(&regs, &reginfo), 0);
assert_eq!(
solver.moves(),
&[