Skip to content

Break out of quantification loop if there is no forward progress #560

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 4 commits into from
Jul 11, 2022
Merged

Break out of quantification loop if there is no forward progress #560

Changes from 1 commit
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
8584cf4
Break out of quantification loop if there is no forward progress
rctcwyvrn Jul 7, 2022
799ee98
Only emit position checking if we have an unbounded quantification
rctcwyvrn Jul 7, 2022
df8f2a6
Quantification does not guarantee forward progress
rctcwyvrn Jul 7, 2022
84e30b5
Cleanup emitting position checking
rctcwyvrn Jul 11, 2022
File filter

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
Prev Previous commit
Cleanup emitting position checking
  • Loading branch information
@rctcwyvrn
rctcwyvrn committed Jul 11, 2022
commit 84e30b5720ea8e178ab6f5c72ce68d2106f063bb
24 changes: 13 additions & 11 deletions Sources/_StringProcessing/ByteCodeGen.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -652,23 +652,25 @@ fileprivate extension Compiler.ByteCodeGen {
// branch min-trip-count
builder.label(loopBody)

var positionReg: PositionRegister? = nil
// if we aren't sure if the child node will have forward progress and
// we have an unbounded quantification,
if (!optimizationsEnabled || !child.guaranteesForwardProgress),
extraTrips == nil
{
positionReg = builder.makePositionRegister()
builder.buildMoveCurrentPosition(into: positionReg!)
// we have an unbounded quantification
let startPosition: PositionRegister?
let emitPositionChecking =
(!optimizationsEnabled || !child.guaranteesForwardProgress) &&
extraTrips == nil

if emitPositionChecking {
startPosition = builder.makePositionRegister()
builder.buildMoveCurrentPosition(into: startPosition!)
} else {
startPosition = nil
}
try emitNode(child)
if (!optimizationsEnabled || !child.guaranteesForwardProgress),
extraTrips == nil
{
if emitPositionChecking {
// in all quantifier cases, no matter what minTrips or extraTrips is,
// if we have a successful non-advancing match, branch to exit because it
// can match an arbitrary number of times
builder.buildCondBranch(to: exit, ifSamePositionAs: positionReg!)
builder.buildCondBranch(to: exit, ifSamePositionAs: startPosition!)
}

if minTrips <= 1 {
Expand Down