diff --git a/.gitignore b/.gitignore
index c848c14..544ec62 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 # Ignored folders #
+/cache/
 /lib/
 /obj/
 /bin/
diff --git a/tests/regres/cause/cause.go b/tests/regres/cause/cause.go
new file mode 100644
index 0000000..7f2fedb
--- /dev/null
+++ b/tests/regres/cause/cause.go
@@ -0,0 +1,33 @@
+// Copyright 2019 The SwiftShader Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package cause provides functions for building wrapped errors.
+package cause
+
+import (
+	"fmt"
+)
+
+// errWithCause is an error that wrap an inner error with additional info.
+type errWithCause struct {
+	cause error
+	msg   string
+}
+
+func (e errWithCause) Error() string { return fmt.Sprintf("%s. Cause: %v", e.msg, e.cause) }
+
+// Wrap returns a new error wrapping cause with the additional message.
+func Wrap(cause error, msg string, args ...interface{}) error {
+	return errWithCause{cause, fmt.Sprintf(msg, args...)}
+}
diff --git a/tests/regres/git/git.go b/tests/regres/git/git.go
new file mode 100644
index 0000000..9842b5c
--- /dev/null
+++ b/tests/regres/git/git.go
@@ -0,0 +1,141 @@
+// Copyright 2019 The SwiftShader Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package git provides functions for interacting with Git.
+package git
+
+import (
+	"encoding/hex"
+	"fmt"
+	"io/ioutil"
+	"net/url"
+	"os"
+	"os/exec"
+	"time"
+
+	"../cause"
+	"../shell"
+)
+
+const (
+	gitTimeout = time.Minute * 5 // timeout for a git operation
+)
+
+var exe string
+
+func init() {
+	path, err := exec.LookPath("git")
+	if err != nil {
+		panic(cause.Wrap(err, "Couldn't find path to git executable"))
+	}
+	exe = path
+}
+
+// Hash is a 20 byte, git object hash.
+type Hash [20]byte
+
+func (h Hash) String() string { return hex.EncodeToString(h[:]) }
+
+// ParseHash returns a Hash from a hexadecimal string.
+func ParseHash(s string) Hash {
+	b, _ := hex.DecodeString(s)
+	h := Hash{}
+	copy(h[:], b)
+	return h
+}
+
+// Add calls 'git add <file>'.
+func Add(project, file string) error {
+	if err := shell.Shell(gitTimeout, exe, project, "add", file); err != nil {
+		return err
+	}
+	return nil
+}
+
+// CommitFlags advanced flags for Commit
+type CommitFlags struct {
+	Name  string // Used for author and committer
+	Email string // Used for author and committer
+}
+
+// Commit calls 'git commit -m <msg> --author <author>'.
+func Commit(project, msg string, flags CommitFlags) error {
+	args := []string{}
+	if flags.Name != "" {
+		args = append(args, "-c", "user.name="+flags.Name)
+	}
+	if flags.Email != "" {
+		args = append(args, "-c", "user.email="+flags.Email)
+	}
+	args = append(args, "commit", "-m", msg)
+	return shell.Shell(gitTimeout, exe, project, args...)
+}
+
+// PushFlags advanced flags for Commit
+type PushFlags struct {
+	Username string // Used for authentication when uploading
+	Password string // Used for authentication when uploading
+}
+
+// Push pushes the local branch to remote.
+func Push(project, remote, localBranch, remoteBranch string, flags PushFlags) error {
+	args := []string{}
+	if flags.Username != "" {
+		f, err := ioutil.TempFile("", "regres-cookies.txt")
+		if err != nil {
+			return cause.Wrap(err, "Couldn't create cookie file")
+		}
+		defer f.Close()
+		defer os.Remove(f.Name())
+		u, err := url.Parse(remote)
+		if err != nil {
+			return cause.Wrap(err, "Couldn't parse url '%v'", remote)
+		}
+		f.WriteString(fmt.Sprintf("%v	FALSE	/	TRUE	2147483647	o	%v=%v\n", u.Host, flags.Username, flags.Password))
+		f.Close()
+		args = append(args, "-c", "http.cookiefile="+f.Name())
+	}
+	args = append(args, "push", remote, localBranch+":"+remoteBranch)
+	return shell.Shell(gitTimeout, exe, project, args...)
+}
+
+// Checkout performs a git checkout of the given commit into path.
+func Checkout(path, url string, commit Hash) error {
+	if err := os.MkdirAll(path, 0777); err != nil {
+		return cause.Wrap(err, "mkdir '"+path+"' failed")
+	}
+
+	for _, cmds := range [][]string{
+		{"init"},
+		{"remote", "add", "origin", url},
+		{"fetch", "origin", commit.String()},
+		{"checkout", commit.String()},
+	} {
+		if err := shell.Shell(gitTimeout, exe, path, cmds...); err != nil {
+			os.RemoveAll(path)
+			return err
+		}
+	}
+
+	return nil
+}
+
+// FetchRefHash returns the git hash of the given ref.
+func FetchRefHash(ref, url string) (Hash, error) {
+	out, err := shell.Exec(gitTimeout, exe, "", nil, "ls-remote", url, ref)
+	if err != nil {
+		return Hash{}, err
+	}
+	return ParseHash(string(out)), nil
+}
diff --git a/tests/regres/main.go b/tests/regres/main.go
new file mode 100644
index 0000000..93b5594
--- /dev/null
+++ b/tests/regres/main.go
@@ -0,0 +1,1119 @@
+// Copyright 2019 The SwiftShader Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Regres is a tool that detects test regressions with SwiftShader changes.
+//
+// Regres monitors changes that have been put up for review with Gerrit.
+// Once a new patchset has been found, regres will checkout, build and test the
+// change against the parent changelist. Any differences in results are reported
+// as a review comment on the change.
+//
+// Once a day regres will also test another, larger set of tests, and post the
+// full test results as a Gerrit changelist. The CI test lists can be based from
+// this daily test list, so testing can be limited to tests that were known to
+// pass.
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+
+	"./cause"
+	"./git"
+	"./shell"
+
+	gerrit "github.com/andygrunwald/go-gerrit"
+)
+
+const (
+	gitURL                  = "https://swiftshader.googlesource.com/SwiftShader"
+	gerritURL               = "https://swiftshader-review.googlesource.com/"
+	reportHeader            = "Regres report:"
+	dataVersion             = 1
+	changeUpdateFrequency   = time.Minute * 5
+	changeQueryFrequency    = time.Minute * 5
+	testTimeout             = time.Minute * 5  // timeout for a single test
+	buildTimeout            = time.Minute * 10 // timeout for a build
+	dailyUpdateTestListHour = 5                // 5am
+	fullTestList            = "tests/regres/full-tests.json"
+	ciTestList              = "tests/regres/ci-tests.json"
+)
+
+var (
+	numParallelTests = runtime.NumCPU()
+
+	deqpPath      = flag.String("deqp", "", "path to the deqp build directory")
+	cacheDir      = flag.String("cache", "cache", "path to the output cache directory")
+	gerritEmail   = flag.String("email", "$SS_REGRES_EMAIL", "gerrit email address for posting regres results")
+	gerritUser    = flag.String("user", "$SS_REGRES_USER", "gerrit username for posting regres results")
+	gerritPass    = flag.String("pass", "$SS_REGRES_PASS", "gerrit password for posting regres results")
+	keepCheckouts = flag.Bool("keep", false, "don't delete checkout directories after use")
+	dryRun        = flag.Bool("dry", false, "don't post regres reports to gerrit")
+	maxProcMemory = flag.Uint64("max-proc-mem", shell.MaxProcMemory, "maximum virtual memory per child process")
+)
+
+func main() {
+	if runtime.GOOS != "linux" {
+		log.Fatal("regres only currently runs on linux")
+	}
+
+	flag.ErrHelp = errors.New("regres is a tool to detect regressions between versions of SwiftShader")
+	flag.Parse()
+
+	shell.MaxProcMemory = *maxProcMemory
+
+	r := regres{
+		deqpBuild:     *deqpPath,
+		cacheRoot:     *cacheDir,
+		gerritEmail:   os.ExpandEnv(*gerritEmail),
+		gerritUser:    os.ExpandEnv(*gerritUser),
+		gerritPass:    os.ExpandEnv(*gerritPass),
+		keepCheckouts: *keepCheckouts,
+		dryRun:        *dryRun,
+	}
+
+	if err := r.run(); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(-1)
+	}
+}
+
+type regres struct {
+	deqpBuild     string // path to the build directory of deqp
+	cmake         string // path to cmake
+	make          string // path to make
+	cacheRoot     string // path to the regres cache directory
+	gerritEmail   string // gerrit email address used for posting results
+	gerritUser    string // gerrit username used for posting results
+	gerritPass    string // gerrit password used for posting results
+	keepCheckouts bool   // don't delete source & build checkouts after testing
+	dryRun        bool   // don't post any reviews
+	maxProcMemory uint64 // max virtual memory for child processes
+}
+
+// resolveDirs ensures that the necessary directories used can be found, and
+// expands them to absolute paths.
+func (r *regres) resolveDirs() error {
+	for _, path := range []*string{
+		&r.deqpBuild,
+		&r.cacheRoot,
+	} {
+		abs, err := filepath.Abs(*path)
+		if err != nil {
+			return cause.Wrap(err, "Couldn't find path '%v'", *path)
+		}
+		if _, err := os.Stat(abs); err != nil {
+			return cause.Wrap(err, "Couldn't find path '%v'", abs)
+		}
+		*path = abs
+	}
+	return nil
+}
+
+// resolveExes resolves all external executables used by regres.
+func (r *regres) resolveExes() error {
+	type exe struct {
+		name string
+		path *string
+	}
+	for _, e := range []exe{
+		{"cmake", &r.cmake},
+		{"make", &r.make},
+	} {
+		path, err := exec.LookPath(e.name)
+		if err != nil {
+			return cause.Wrap(err, "Couldn't find path to %s", e.name)
+		}
+		*e.path = path
+	}
+	return nil
+}
+
+// run performs the main processing loop for the regress tool. It:
+// * Scans for open and recently updated changes in gerrit using queryChanges()
+//   and changeInfo.update().
+// * Builds the most recent patchset and the commit's parent CL using
+//   r.newTest(<hash>).lazyRun().
+// * Compares the results of the tests using compare().
+// * Posts the results of the compare to gerrit as a review.
+// * Repeats the above steps until the process is interrupted.
+func (r *regres) run() error {
+	if err := r.resolveExes(); err != nil {
+		return cause.Wrap(err, "Couldn't resolve all exes")
+	}
+
+	if err := r.resolveDirs(); err != nil {
+		return cause.Wrap(err, "Couldn't resolve all directories")
+	}
+
+	client, err := gerrit.NewClient(gerritURL, nil)
+	if err != nil {
+		return cause.Wrap(err, "Couldn't create gerrit client")
+	}
+	if r.gerritUser != "" {
+		client.Authentication.SetBasicAuth(r.gerritUser, r.gerritPass)
+	}
+
+	changes := map[string]*changeInfo{} // Change ID -> changeInfo
+	lastUpdatedTestLists := toDate(time.Now())
+	lastQueriedChanges := time.Time{}
+
+	for {
+		if now := time.Now(); toDate(now) != lastUpdatedTestLists && now.Hour() >= dailyUpdateTestListHour {
+			lastUpdatedTestLists = toDate(now)
+			if err := r.updateTestLists(client); err != nil {
+				log.Println(err.Error())
+			}
+		}
+
+		// Update list of tracked changes.
+		if time.Since(lastQueriedChanges) > changeQueryFrequency {
+			lastQueriedChanges = time.Now()
+			if err := queryChanges(client, changes); err != nil {
+				log.Println(err.Error())
+			}
+		}
+
+		// Update change info.
+		for _, change := range changes {
+			if time.Since(change.lastUpdated) > changeUpdateFrequency {
+				change.lastUpdated = time.Now()
+				err := change.update(client)
+				if err != nil {
+					log.Println(cause.Wrap(err, "Couldn't update info for change '%s'", change.id))
+				}
+			}
+		}
+
+		// Find the change with the highest priority.
+		var change *changeInfo
+		numPending := 0
+		for _, c := range changes {
+			if c.pending {
+				numPending++
+				if change == nil || c.priority > change.priority {
+					change = c
+				}
+			}
+		}
+
+		if change == nil {
+			// Everything up to date. Take a break.
+			log.Println("Nothing to do. Sleeping")
+			time.Sleep(time.Minute)
+			continue
+		}
+
+		log.Printf("%d changes queued for testing\n", numPending)
+
+		log.Printf("Testing change '%s'\n", change.id)
+
+		// Get the test results for the latest patchset in the change.
+		latest, err := r.newTest(ciTestList, change.latest).lazyRun()
+		if err != nil {
+			log.Println(cause.Wrap(err, "Failed to test changelist '%s'", change.latest))
+			time.Sleep(time.Minute)
+			continue
+		}
+
+		// Get the test results for the changes's parent changelist.
+		parent, err := r.newTest(ciTestList, change.parent).lazyRun()
+		if err != nil {
+			log.Println(cause.Wrap(err, "Failed to test changelist '%s'", change.parent))
+			time.Sleep(time.Minute)
+			continue
+		}
+
+		// Compare the latest patchset to the change's parent commit.
+		msg := compare(parent, latest)
+
+		// Always include the reportHeader in the message.
+		// changeInfo.update() uses this header to detect whether a patchset has
+		// already got a test result.
+		msg = reportHeader + "\n\n" + msg
+
+		if r.dryRun {
+			log.Printf("DRY RUN: add review to change '%v':\n%v\n", change.id, msg)
+		} else {
+			log.Printf("Posting review to '%s'\n", change.id)
+			_, _, err = client.Changes.SetReview(change.id, change.latest.String(), &gerrit.ReviewInput{
+				Message: msg,
+				Tag:     "autogenerated:regress",
+			})
+			if err != nil {
+				return cause.Wrap(err, "Failed to post comments on change '%s'", change.id)
+			}
+		}
+		change.pending = false
+	}
+}
+
+func (r *regres) updateTestLists(client *gerrit.Client) error {
+	log.Println("Updating test lists")
+
+	headHash, err := git.FetchRefHash("HEAD", gitURL)
+	if err != nil {
+		return cause.Wrap(err, "Could not get hash of master HEAD")
+	}
+
+	// Get the full test results for latest master.
+	t := r.newTest(fullTestList, headHash)
+
+	// Keep the checked out directory after the test is run. We want this so
+	// we can build a new patchset containing the updated test lists.
+	t.keepCheckouts = true
+	if !r.keepCheckouts {
+		defer os.RemoveAll(t.srcDir)
+	}
+
+	if _, err := t.run(); err != nil {
+		return cause.Wrap(err, "Failed to test changelist '%s'", headHash)
+	}
+
+	// Stage all the updated test files.
+	for _, path := range t.writtenTestLists {
+		log.Println("Staging", path)
+		git.Add(t.srcDir, path)
+	}
+
+	log.Println("Checking for existing test list")
+	results, _, err := client.Changes.QueryChanges(&gerrit.QueryChangeOptions{
+		QueryOptions: gerrit.QueryOptions{
+			Query: []string{fmt.Sprintf(`status:open+owner:"%v"`, r.gerritEmail)},
+			Limit: 1,
+		},
+	})
+	if err != nil {
+		return cause.Wrap(err, "Failed to checking for existing test list")
+	}
+
+	commitMsg := strings.Builder{}
+	commitMsg.WriteString("Regres: Update test lists @ " + headHash.String()[:8])
+	if results != nil && len(*results) > 0 {
+		// Reuse gerrit change ID if there's already a change up for review.
+		id := (*results)[0].ChangeID
+		commitMsg.WriteString("\n\n")
+		commitMsg.WriteString("Change-Id: " + id)
+	}
+
+	if err := git.Commit(t.srcDir, commitMsg.String(), git.CommitFlags{
+		Name:  "SwiftShader Regression Bot",
+		Email: r.gerritEmail,
+	}); err != nil {
+		return cause.Wrap(err, "Failed to commit test results")
+	}
+
+	if r.dryRun {
+		log.Printf("DRY RUN: post results for review")
+	} else {
+		log.Println("Pushing test results for review")
+		if err := git.Push(t.srcDir, gitURL, "HEAD", "refs/for/master", git.PushFlags{
+			Username: r.gerritUser,
+			Password: r.gerritPass,
+		}); err != nil {
+			return cause.Wrap(err, "Failed to push test results for review")
+		}
+		log.Println("Test results posted for review")
+	}
+
+	return nil
+}
+
+// changeInfo holds the important information about a single, open change in
+// gerrit.
+type changeInfo struct {
+	id          string    // Gerrit change ID.
+	pending     bool      // Is this change waiting a test for the latest patchset?
+	priority    int       // Calculated priority based on Gerrit labels.
+	latest      git.Hash  // Git hash of the latest patchset in the change.
+	parent      git.Hash  // Git hash of the changelist this change is based on.
+	lastUpdated time.Time // Time the change was last fetched.
+}
+
+// queryChanges updates the changes map by querying gerrit for the latest open
+// changes.
+func queryChanges(client *gerrit.Client, changes map[string]*changeInfo) error {
+	log.Println("Checking for latest changes")
+	results, _, err := client.Changes.QueryChanges(&gerrit.QueryChangeOptions{
+		QueryOptions: gerrit.QueryOptions{
+			Query: []string{"status:open+-age:3d"},
+			Limit: 100,
+		},
+	})
+	if err != nil {
+		return cause.Wrap(err, "Failed to get list of changes")
+	}
+
+	ids := map[string]bool{}
+	for _, r := range *results {
+		ids[r.ChangeID] = true
+	}
+
+	// Add new changes
+	for id := range ids {
+		if _, found := changes[id]; !found {
+			log.Printf("Tracking new change '%v'\n", id)
+			changes[id] = &changeInfo{id: id}
+		}
+	}
+
+	// Remove old changes
+	for id := range changes {
+		if found := ids[id]; !found {
+			log.Printf("Untracking change '%v'\n", id)
+			delete(changes, id)
+		}
+	}
+
+	return nil
+}
+
+// update queries gerrit for information about the given change.
+func (c *changeInfo) update(client *gerrit.Client) error {
+	change, _, err := client.Changes.GetChange(c.id, &gerrit.ChangeOptions{
+		AdditionalFields: []string{"CURRENT_REVISION", "CURRENT_COMMIT", "MESSAGES", "LABELS"},
+	})
+	if err != nil {
+		return cause.Wrap(err, "Getting info for change '%s'", c.id)
+	}
+
+	current, ok := change.Revisions[change.CurrentRevision]
+	if !ok {
+		return fmt.Errorf("Couldn't find current revision for change '%s'", c.id)
+	}
+
+	if len(current.Commit.Parents) == 0 {
+		return fmt.Errorf("Couldn't find current commit for change '%s' has no parents(?)", c.id)
+	}
+
+	kokoroPresubmit := change.Labels["Kokoro-Presubmit"].Approved.AccountID != 0
+	codeReviewScore := change.Labels["Code-Review"].Value
+	presubmitReady := change.Labels["Presubmit-Ready"].Approved.AccountID != 0
+
+	c.priority = 0
+	if presubmitReady {
+		c.priority += 10
+	}
+	c.priority += codeReviewScore
+	if kokoroPresubmit {
+		c.priority++
+	}
+
+	// Is the change from a Googler?
+	canTest := strings.HasSuffix(current.Commit.Committer.Email, "@google.com")
+
+	// Has the latest patchset already been tested?
+	if canTest {
+		for _, msg := range change.Messages {
+			if msg.RevisionNumber == current.Number &&
+				strings.Contains(msg.Message, reportHeader) {
+				canTest = false
+				break
+			}
+		}
+	}
+
+	c.pending = canTest
+	c.latest = git.ParseHash(change.CurrentRevision)
+	c.parent = git.ParseHash(current.Commit.Parents[0].Commit)
+
+	return nil
+}
+
+func (r *regres) newTest(testListPath string, commit git.Hash) *test {
+	srcDir := filepath.Join(r.cacheRoot, "src", commit.String())
+	resDir := filepath.Join(r.cacheRoot, "res", commit.String())
+	return &test{
+		r:            r,
+		commit:       commit,
+		srcDir:       srcDir,
+		resDir:       resDir,
+		outDir:       filepath.Join(srcDir, "out"),
+		buildDir:     filepath.Join(srcDir, "build"),
+		testListPath: testListPath,
+	}
+}
+
+type test struct {
+	r             *regres
+	commit        git.Hash // hash of the commit to test
+	srcDir        string   // directory for the SwiftShader checkout
+	resDir        string   // directory for the test results
+	outDir        string   // directory for SwiftShader output
+	buildDir      string   // directory for SwiftShader build
+	keepCheckouts bool     // don't delete source & build checkouts after testing
+	testListPath  string   // relative path to the test list .json file
+
+	writtenTestLists []string // paths to test updated lists that have been written
+}
+
+// lazyRun lazily runs the test t.
+// If the test results are not already cached, then test will setup the test
+// environment, and call t.run().
+// The results of the test will be cached into r.cacheRoot.
+func (t *test) lazyRun() (*CommitTestResults, error) {
+	load := func(data []byte) (interface{}, error) {
+		var res CommitTestResults
+		if err := json.NewDecoder(bytes.NewReader(data)).Decode(&res); err != nil {
+			return nil, err
+		}
+		if res.Version != dataVersion {
+			return nil, errors.New("Data is from an old version")
+		}
+		return &res, nil
+	}
+
+	build := func() ([]byte, interface{}, error) {
+		res, err := t.run()
+
+		if err != nil {
+			return nil, nil, err
+		}
+
+		b := bytes.Buffer{}
+		enc := json.NewEncoder(&b)
+		enc.SetIndent("", "  ")
+		if err := enc.Encode(res); err != nil {
+			return nil, nil, err
+		}
+
+		return b.Bytes(), res, nil
+	}
+
+	res, err := loadOrBuild(filepath.Join(t.resDir, "results.json"), load, build)
+	if err != nil {
+		return nil, err
+	}
+
+	return res.(*CommitTestResults), nil
+}
+
+// run executes the tests for the test environment t.
+// If the source is not cached, run will fetch the commit to be tested,
+// before building it, and then run the required tests.
+func (t *test) run() (*CommitTestResults, error) {
+	if isDir(t.srcDir) && t.keepCheckouts {
+		log.Printf("Reusing source cache for commit '%s'\n", t.commit)
+	} else {
+		log.Printf("Checking out '%s'\n", t.commit)
+		os.RemoveAll(t.srcDir)
+		if err := git.Checkout(t.srcDir, gitURL, t.commit); err != nil {
+			return nil, cause.Wrap(err, "Checking out commit '%s'", t.commit)
+		}
+		log.Printf("Checked out commit '%s'\n", t.commit)
+		if !t.keepCheckouts {
+			defer os.RemoveAll(t.srcDir)
+		}
+	}
+
+	if err := t.build(); err != nil {
+		log.Printf("Warning: Commit '%s' failed to build. %v", t.commit, err)
+		return &CommitTestResults{Version: dataVersion, Built: false}, nil
+	}
+	log.Printf("Built '%s'\n", t.commit)
+
+	// Load the list of tests that need executing.
+	// Note: this list may vary by each commit.
+	testLists, err := t.loadTestList()
+	if err != nil {
+		return nil, cause.Wrap(err, "Loading test lists")
+	}
+
+	results, err := t.runTests(testLists)
+	if err != nil {
+		return nil, cause.Wrap(err, "Running tests")
+	}
+	log.Printf("Ran tests for '%s'\n", t.commit)
+
+	if t.keepCheckouts {
+		if err := t.writeTestListsByStatus(testLists, results); err != nil {
+			return nil, cause.Wrap(err, "Writing test lists by status")
+		}
+	}
+
+	return results, nil
+}
+
+// loadOrBuild is a helper for building a lazy resolved cache.
+// loadOrBuild attempts to load the file at path. If the file exists and loaded
+// successfully, then load() is called with the file data, and the the result
+// object from load() is returned.
+// If the file does not exist, the file cannot be loaded, or load() returns an
+// error, then build() is called and the byte slice is saved to path, and the
+// object is returned.
+func loadOrBuild(path string,
+	load func([]byte) (interface{}, error),
+	build func() ([]byte, interface{}, error)) (interface{}, error) {
+
+	if data, err := ioutil.ReadFile(path); err == nil {
+		out, err := load(data)
+		if err == nil {
+			return out, nil
+		}
+		log.Printf("Warning: Failed to load '%s': %v", path, err)
+		os.Remove(path) // Delete and rebuild.
+	}
+
+	data, obj, err := build()
+	if err != nil {
+		return nil, err
+	}
+
+	os.MkdirAll(filepath.Dir(path), 0777)
+
+	if err := ioutil.WriteFile(path, data, 0777); err != nil {
+		log.Printf("Warning: Failed to write to '%s': %v", path, err)
+	}
+	return obj, nil
+}
+
+// build builds the SwiftShader source into t.buildDir.
+func (t *test) build() error {
+	log.Printf("Building '%s'\n", t.commit)
+
+	if err := os.MkdirAll(t.buildDir, 0777); err != nil {
+		return cause.Wrap(err, "Failed to create build directory")
+	}
+
+	if err := shell.Shell(buildTimeout, t.r.cmake, t.buildDir,
+		"-DCMAKE_BUILD_TYPE=Release",
+		"-DDCHECK_ALWAYS_ON=1",
+		".."); err != nil {
+		return err
+	}
+
+	if err := shell.Shell(buildTimeout, t.r.make, t.buildDir, fmt.Sprintf("-j%d", runtime.NumCPU())); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// runTests runs all the tests.
+func (t *test) runTests(testLists []TestList) (*CommitTestResults, error) {
+	log.Printf("Running tests for '%s'\n", t.commit)
+	start := time.Now()
+
+	// Wait group that completes once all the tests have finished.
+	wg := sync.WaitGroup{}
+	results := make(chan TestResult, 256)
+
+	numTests := 0
+
+	// For each API that we are testing
+	for _, list := range testLists {
+		// Resolve the test runner
+		var exe string
+		switch list.API {
+		case egl:
+			exe = filepath.Join(t.r.deqpBuild, "modules", "egl", "deqp-egl")
+		case gles2:
+			exe = filepath.Join(t.r.deqpBuild, "modules", "gles2", "deqp-gles2")
+		case gles3:
+			exe = filepath.Join(t.r.deqpBuild, "modules", "gles3", "deqp-gles3")
+		case vulkan:
+			exe = filepath.Join(t.r.deqpBuild, "external", "vulkancts", "modules", "vulkan", "deqp-vk")
+		default:
+			return nil, fmt.Errorf("Unknown API '%v'", list.API)
+		}
+		if !isFile(exe) {
+			return nil, fmt.Errorf("Couldn't find dEQP executable at '%s'", exe)
+		}
+
+		// Build a chan for the test names to be run.
+		tests := make(chan string, len(list.Tests))
+
+		// Start a number of go routines to run the tests.
+		wg.Add(numParallelTests)
+		for i := 0; i < numParallelTests; i++ {
+			go func() {
+				t.deqpTestRoutine(exe, tests, results)
+				wg.Done()
+			}()
+		}
+
+		// Hand the tests to the deqpTestRoutines.
+		for _, t := range list.Tests {
+			tests <- t
+		}
+
+		// Close the tests chan to indicate that there are no more tests to run.
+		// The deqpTestRoutine functions will return once all tests have been
+		// run.
+		close(tests)
+
+		numTests += len(list.Tests)
+	}
+
+	out := CommitTestResults{
+		Version: dataVersion,
+		Built:   true,
+		Tests:   map[string]TestResult{},
+	}
+
+	// Collect the results.
+	finished := make(chan struct{})
+	lastUpdate := time.Now()
+	go func() {
+		start, i := time.Now(), 0
+		for r := range results {
+			i++
+			out.Tests[r.Test] = r
+			if time.Since(lastUpdate) > time.Minute {
+				lastUpdate = time.Now()
+				remaining := numTests - i
+				log.Printf("Ran %d/%d tests (%v%%). Estimated completion in %v.\n",
+					i, numTests, percent(i, numTests),
+					(time.Since(start)/time.Duration(i))*time.Duration(remaining))
+			}
+		}
+		close(finished)
+	}()
+
+	wg.Wait()      // Block until all the deqpTestRoutines have finished.
+	close(results) // Signal no more results.
+	<-finished     // And wait for the result collecting go-routine to finish.
+
+	out.Duration = time.Since(start)
+
+	return &out, nil
+}
+
+func (t *test) writeTestListsByStatus(testLists []TestList, results *CommitTestResults) error {
+	for _, list := range testLists {
+		files := map[Status]*os.File{}
+		ext := filepath.Ext(list.File)
+		name := list.File[:len(list.File)-len(ext)]
+		for _, status := range Statuses {
+			path := filepath.Join(t.srcDir, name+"-"+string(status)+ext)
+			dir := filepath.Dir(path)
+			os.MkdirAll(dir, 0777)
+			f, err := os.Create(path)
+			if err != nil {
+				return cause.Wrap(err, "Couldn't create file '%v'", path)
+			}
+			defer f.Close()
+			files[status] = f
+
+			t.writtenTestLists = append(t.writtenTestLists, path)
+		}
+
+		for _, testName := range list.Tests {
+			if r, found := results.Tests[testName]; found {
+				fmt.Fprintln(files[r.Status], testName)
+			}
+		}
+	}
+
+	return nil
+}
+
+// Status is an enumerator of test results.
+type Status string
+
+const (
+	// Pass is the status of a successful test.
+	Pass = Status("PASS")
+	// Fail is the status of a failed test.
+	Fail = Status("FAIL")
+	// Timeout is the status of a test that failed to complete in the alloted
+	// time.
+	Timeout = Status("TIMEOUT")
+	// Crash is the status of a test that crashed.
+	Crash = Status("CRASH")
+	// NotSupported is the status of a test feature not supported by the driver.
+	NotSupported = Status("NOT_SUPPORTED")
+	// CompatibilityWarning is the status passing test with a warning.
+	CompatibilityWarning = Status("COMPATIBILITY_WARNING")
+	// QualityWarning is the status passing test with a warning.
+	QualityWarning = Status("QUALITY_WARNING")
+)
+
+// Statuses is the full list of status types
+var Statuses = []Status{Pass, Fail, Timeout, Crash, NotSupported, CompatibilityWarning, QualityWarning}
+
+// Failing returns true if the task status requires fixing.
+func (s Status) Failing() bool {
+	switch s {
+	case Fail, Timeout, Crash:
+		return true
+	default:
+		return false
+	}
+}
+
+// CommitTestResults holds the results the tests across all APIs for a given
+// commit. The CommitTestResults structure may be serialized to cache the
+// results.
+type CommitTestResults struct {
+	Version  int
+	Built    bool
+	Tests    map[string]TestResult
+	Duration time.Duration
+}
+
+// compare returns a string describing all differences between two
+// CommitTestResults. This string is used as the report message posted to the
+// gerrit code review.
+func compare(old, new *CommitTestResults) string {
+	switch {
+	case !old.Built && !new.Built:
+		return "Build continues to be broken."
+	case old.Built && !new.Built:
+		return "Build broken."
+	case !old.Built && !new.Built:
+		return "Build now fixed. Cannot compare against broken parent."
+	}
+
+	oldStatusCounts, newStatusCounts := map[Status]int{}, map[Status]int{}
+	totalTests := 0
+
+	broken, fixed, failing, removed, changed := []string{}, []string{}, []string{}, []string{}, []string{}
+
+	for test, new := range new.Tests {
+		old, found := old.Tests[test]
+		switch {
+		case (!found || old.Status == Pass) && new.Status.Failing():
+			broken = append(broken, test)
+		case (found && old.Status.Failing()) && new.Status == Pass:
+			fixed = append(fixed, test)
+		case found && old.Status != new.Status:
+			changed = append(changed, test)
+		case found && old.Status.Failing() && new.Status.Failing():
+			failing = append(failing, test) // Still broken
+		}
+		totalTests++
+		if found {
+			oldStatusCounts[old.Status] = oldStatusCounts[old.Status] + 1
+		}
+		newStatusCounts[new.Status] = newStatusCounts[new.Status] + 1
+	}
+
+	for test := range old.Tests {
+		if _, found := new.Tests[test]; !found {
+			removed = append(removed, test)
+		}
+	}
+
+	sb := strings.Builder{}
+
+	// list prints the list l to sb, truncating after a limit.
+	list := func(l []string) {
+		const max = 10
+		for i, s := range l {
+			sb.WriteString("  ")
+			if i == max {
+				sb.WriteString(fmt.Sprintf("> %d more\n", len(l)-i))
+				break
+			}
+			sb.WriteString(fmt.Sprintf("> %s", s))
+			if n, ok := new.Tests[s]; ok {
+				if o, ok := old.Tests[s]; ok && n != o {
+					sb.WriteString(fmt.Sprintf(" - [%s -> %s]", o.Status, n.Status))
+				} else {
+					sb.WriteString(fmt.Sprintf(" - [%s]", n.Status))
+				}
+			}
+			sb.WriteString("\n")
+		}
+	}
+
+	sb.WriteString(fmt.Sprintf("          Total tests: %d\n", totalTests))
+	for _, s := range []struct {
+		label  string
+		status Status
+	}{
+		{"                 Pass", Pass},
+		{"                 Fail", Fail},
+		{"              Timeout", Timeout},
+		{"                Crash", Crash},
+		{"        Not Supported", NotSupported},
+		{"Compatibility Warning", CompatibilityWarning},
+		{"      Quality Warning", QualityWarning},
+	} {
+		old, new := oldStatusCounts[s.status], newStatusCounts[s.status]
+		if old == 0 && new == 0 {
+			continue
+		}
+		change := percent64(int64(new-old), int64(old))
+		switch {
+		case old == new:
+			sb.WriteString(fmt.Sprintf("%s: %v\n", s.label, new))
+		case change == 0:
+			sb.WriteString(fmt.Sprintf("%s: %v -> %v\n", s.label, old, new))
+		default:
+			sb.WriteString(fmt.Sprintf("%s: %v -> %v (%+d%%)\n", s.label, old, new, change))
+		}
+	}
+
+	if old, new := old.Duration, new.Duration; old != 0 && new != 0 {
+		label := "           Time taken"
+		change := percent64(int64(new-old), int64(old))
+		switch {
+		case old == new:
+			sb.WriteString(fmt.Sprintf("%s: %v\n", label, new))
+		case change == 0:
+			sb.WriteString(fmt.Sprintf("%s: %v -> %v\n", label, old, new))
+		default:
+			sb.WriteString(fmt.Sprintf("%s: %v -> %v (%+d%%)\n", label, old, new, change))
+		}
+	}
+
+	if n := len(broken); n > 0 {
+		sort.Strings(broken)
+		sb.WriteString(fmt.Sprintf("\n--- This change breaks %d tests: ---\n", n))
+		list(broken)
+	}
+	if n := len(fixed); n > 0 {
+		sort.Strings(fixed)
+		sb.WriteString(fmt.Sprintf("\n--- This change fixes %d tests: ---\n", n))
+		list(fixed)
+	}
+	if n := len(removed); n > 0 {
+		sort.Strings(removed)
+		sb.WriteString(fmt.Sprintf("\n--- This change removes %d tests: ---\n", n))
+		list(removed)
+	}
+	if n := len(changed); n > 0 {
+		sort.Strings(changed)
+		sb.WriteString(fmt.Sprintf("\n--- This change alters %d tests: ---\n", n))
+		list(changed)
+	}
+
+	if len(broken) == 0 && len(fixed) == 0 && len(removed) == 0 && len(changed) == 0 {
+		sb.WriteString(fmt.Sprintf("\n--- No change in test results ---\n"))
+	}
+
+	return sb.String()
+}
+
+// TestResult holds the results of a single API test.
+type TestResult struct {
+	Test   string
+	Status Status
+	Err    string `json:",omitempty"`
+}
+
+func (r TestResult) String() string {
+	if r.Err != "" {
+		return fmt.Sprintf("%s: %s (%s)", r.Test, r.Status, r.Err)
+	}
+	return fmt.Sprintf("%s: %s", r.Test, r.Status)
+}
+
+// Regular expression to parse the output of a dEQP test.
+var parseRE = regexp.MustCompile(`(Fail|Pass|NotSupported|CompatibilityWarning|QualityWarning) \(([\s\S]*)\)`)
+
+// deqpTestRoutine repeatedly runs the dEQP test executable exe with the tests
+// taken from tests. The output of the dEQP test is parsed, and the test result
+// is written to results.
+// deqpTestRoutine only returns once the tests chan has been closed.
+// deqpTestRoutine does not close the results chan.
+func (t *test) deqpTestRoutine(exe string, tests <-chan string, results chan<- TestResult) {
+	for name := range tests {
+		// log.Printf("Running test '%s'\n", name)
+		env := []string{
+			"LD_LIBRARY_PATH=" + t.buildDir + ":" + os.Getenv("LD_LIBRARY_PATH"),
+			"VK_ICD_FILENAMES=" + filepath.Join(t.outDir, "Linux", "vk_swiftshader_icd.json"),
+			"DISPLAY=" + os.Getenv("DISPLAY"),
+			"LIBC_FATAL_STDERR_=1", // Put libc explosions into logs.
+		}
+
+		out, err := shell.Exec(testTimeout, exe, filepath.Dir(exe), env, "--deqp-surface-type=pbuffer", "-n="+name)
+		switch err.(type) {
+		default:
+			results <- TestResult{
+				Test:   name,
+				Status: Crash,
+				Err:    cause.Wrap(err, string(out)).Error(),
+			}
+		case shell.ErrTimeout:
+			results <- TestResult{
+				Test:   name,
+				Status: Timeout,
+				Err:    cause.Wrap(err, string(out)).Error(),
+			}
+		case nil:
+			toks := parseRE.FindStringSubmatch(string(out))
+			if len(toks) < 3 {
+				err := fmt.Sprintf("Couldn't parse test '%v' output:\n%s", name, string(out))
+				log.Println("Warning: ", err)
+				results <- TestResult{Test: name, Status: Fail, Err: err}
+				continue
+			}
+			switch toks[1] {
+			case "Pass":
+				results <- TestResult{Test: name, Status: Pass}
+			case "NotSupported":
+				results <- TestResult{Test: name, Status: NotSupported}
+			case "CompatibilityWarning":
+				results <- TestResult{Test: name, Status: CompatibilityWarning}
+			case "QualityWarning":
+				results <- TestResult{Test: name, Status: CompatibilityWarning}
+			case "Fail":
+				var err string
+				if toks[2] != "Fail" {
+					err = toks[2]
+				}
+				results <- TestResult{Test: name, Status: Fail, Err: err}
+			default:
+				err := fmt.Sprintf("Couldn't parse test output:\n%s", string(out))
+				log.Println("Warning: ", err)
+				results <- TestResult{Test: name, Status: Fail, Err: err}
+			}
+		}
+	}
+}
+
+// API is an enumerator of graphics APIs.
+type API string
+
+const (
+	egl    = API("egl")
+	gles2  = API("gles2")
+	gles3  = API("gles3")
+	vulkan = API("vulkan")
+)
+
+// TestList is a list of tests to be run for a given API.
+type TestList struct {
+	Name  string
+	File  string
+	API   API
+	Tests []string
+}
+
+// loadTestList loads the test list json file.
+// The file is first searched at {Commit}/{t.testListPath}
+// If this cannot be found, then the file is searched at the fallback path
+// {CWD}/{t.testListPath}
+// This allows CLs to alter the list of tests to be run, as well as providing
+// a default set.
+func (t *test) loadTestList() ([]TestList, error) {
+	// find the test.json file in {SwiftShader}/tests/regres
+	root := t.srcDir
+	if isFile(filepath.Join(root, t.testListPath)) {
+		log.Println("Using test list from commit")
+	} else {
+		// Not found there. Search locally.
+		root, _ = os.Getwd()
+		if isFile(filepath.Join(root, t.testListPath)) {
+			log.Println("Using test list from regres")
+		} else {
+			return nil, fmt.Errorf("Could not find test list file '%v'", t.testListPath)
+		}
+	}
+
+	jsonPath := filepath.Join(root, t.testListPath)
+	i, err := ioutil.ReadFile(jsonPath)
+	if err != nil {
+		return nil, cause.Wrap(err, "Couldn't read test list from '%s'", jsonPath)
+	}
+
+	var groups []struct {
+		Name     string
+		API      string
+		TestFile string `json:"tests"`
+	}
+	if err := json.NewDecoder(bytes.NewReader(i)).Decode(&groups); err != nil {
+		return nil, cause.Wrap(err, "Couldn't parse '%s'", jsonPath)
+	}
+
+	dir := filepath.Dir(jsonPath)
+
+	out := make([]TestList, len(groups))
+	for i, group := range groups {
+		path := filepath.Join(dir, group.TestFile)
+		tests, err := ioutil.ReadFile(path)
+		if err != nil {
+			return nil, cause.Wrap(err, "Couldn't read '%s'", tests)
+		}
+		relPath, err := filepath.Rel(root, path)
+		if err != nil {
+			return nil, cause.Wrap(err, "Couldn't get relative path for '%s'", path)
+		}
+		list := TestList{
+			Name: group.Name,
+			File: relPath,
+			API:  API(group.API),
+		}
+		for _, line := range strings.Split(string(tests), "\n") {
+			line = strings.TrimSpace(line)
+			if line != "" && !strings.HasPrefix(line, "#") {
+				list.Tests = append(list.Tests, line)
+			}
+		}
+		sort.Strings(list.Tests)
+		out[i] = list
+	}
+
+	return out, nil
+}
+
+// isDir returns true if path is a file.
+func isFile(path string) bool {
+	s, err := os.Stat(path)
+	if err != nil {
+		return false
+	}
+	return !s.IsDir()
+}
+
+// isDir returns true if path is a directory.
+func isDir(path string) bool {
+	s, err := os.Stat(path)
+	if err != nil {
+		return false
+	}
+	return s.IsDir()
+}
+
+// percent returns the percentage completion of i items out of n.
+func percent(i, n int) int {
+	return int(percent64(int64(i), int64(n)))
+}
+
+// percent64 returns the percentage completion of i items out of n.
+func percent64(i, n int64) int64 {
+	if n == 0 {
+		return 0
+	}
+	return (100 * i) / n
+}
+
+type date struct {
+	year  int
+	month time.Month
+	day   int
+}
+
+func toDate(t time.Time) date {
+	d := date{}
+	d.year, d.month, d.day = t.Date()
+	return d
+}
diff --git a/tests/regres/shell/shell.go b/tests/regres/shell/shell.go
new file mode 100644
index 0000000..28fae26
--- /dev/null
+++ b/tests/regres/shell/shell.go
@@ -0,0 +1,125 @@
+// Copyright 2019 The SwiftShader Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package shell provides functions for running sub-processes.
+package shell
+
+import (
+	"bytes"
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"strconv"
+	"syscall"
+	"time"
+
+	"../cause"
+)
+
+// MaxProcMemory is the maximum virtual memory per child process
+var MaxProcMemory uint64 = 2 * 1024 * 1024 * 1024 // 2GB
+
+func init() {
+	// As we are going to be running a number of tests concurrently, we need to
+	// limit the amount of virtual memory each test uses, otherwise memory
+	// hungry tests can bring the whole system down into a swapping apocalypse.
+	//
+	// Linux has the setrlimit() function to limit a process (and child's)
+	// virtual memory usage - but we cannot call this from the regres process
+	// as this process may need more memory than the limit allows.
+	//
+	// Unfortunately golang has no native support for setting rlimits for child
+	// processes (https://github.com/golang/go/issues/6603), so we instead wrap
+	// the exec to the test executable with another child regres process using a
+	// special --exec mode:
+	//
+	// [regres] -> [regres --exec <test-exe N args...>] -> [test-exe]
+	//               ^^^^
+	//          (calls rlimit() with memory limit of N bytes)
+
+	if len(os.Args) > 3 && os.Args[1] == "--exec" {
+		exe := os.Args[2]
+		limit, err := strconv.ParseUint(os.Args[3], 10, 64)
+		if err != nil {
+			log.Fatalf("Expected memory limit as 3rd argument. %v\n", err)
+		}
+		if limit > 0 {
+			if err := syscall.Setrlimit(syscall.RLIMIT_AS, &syscall.Rlimit{Cur: limit, Max: limit}); err != nil {
+				log.Fatalln(cause.Wrap(err, "Setrlimit").Error())
+			}
+		}
+		c := exec.Command(exe, os.Args[4:]...)
+		c.Stdin = os.Stdin
+		c.Stdout = os.Stdout
+		c.Stderr = os.Stderr
+		c.Run()
+		os.Exit(c.ProcessState.ExitCode())
+	}
+}
+
+// Shell runs the executable exe with the given arguments, in the working
+// directory wd.
+// If the process does not finish within timeout a errTimeout will be returned.
+func Shell(timeout time.Duration, exe, wd string, args ...string) error {
+	if out, err := Exec(timeout, exe, wd, nil, args...); err != nil {
+		return cause.Wrap(err, "%s", out)
+	}
+	return nil
+}
+
+// Exec runs the executable exe with the given arguments, in the working
+// directory wd, with the custom environment flags.
+// If the process does not finish within timeout a errTimeout will be returned.
+func Exec(timeout time.Duration, exe, wd string, env []string, args ...string) ([]byte, error) {
+	// Shell via regres: --exec N <exe> <args...>
+	// See main() for details.
+	args = append([]string{"--exec", exe, fmt.Sprintf("%v", MaxProcMemory)}, args...)
+	b := bytes.Buffer{}
+	c := exec.Command(os.Args[0], args...)
+	c.Dir = wd
+	c.Env = env
+	c.Stdout = &b
+	c.Stderr = &b
+
+	if err := c.Start(); err != nil {
+		return nil, err
+	}
+
+	res := make(chan error)
+	go func() { res <- c.Wait() }()
+
+	select {
+	case <-time.NewTimer(timeout).C:
+		c.Process.Signal(syscall.SIGINT)
+		time.Sleep(time.Second * 5)
+		if !c.ProcessState.Exited() {
+			c.Process.Kill()
+		}
+		return b.Bytes(), ErrTimeout{exe, timeout}
+	case err := <-res:
+		return b.Bytes(), err
+	}
+}
+
+// ErrTimeout is the error returned when a process does not finish with its
+// permitted time.
+type ErrTimeout struct {
+	process string
+	timeout time.Duration
+}
+
+func (e ErrTimeout) Error() string {
+	return fmt.Sprintf("'%v' did not return after %v", e.process, e.timeout)
+}