Add a utility to reduce GlobalISel tests

[volkan]

Summary

This patch adds a script to reduce GlobalISel failures using bugpoint.

[qcolombet]

Hi Volkan,

Disclaimer: I have looked at the patch at all.

Could this be extended to reduce any isel related bug?

Cheers,
-Quentin

[MatzeB]

Out of interest: Could you explain what this is doing exactly (as the comment at the beginning of the script isn't too specific about what is happening here)? At a first glance it seems to inject a custom command into bugpoint and checks the output for that "LLVM ERROR:" regex? Or is there something else?

[volkan]

In D41876#971552, @qcolombet wrote:

Hi Volkan,

Disclaimer: I have looked at the patch at all.

Could this be extended to reduce any isel related bug?

Cheers,
-Quentin

Yes, it can be extended to reduce the other ISel problems by adding a regex and the specific arguments for llc.

[volkan]

In D41876#971561, @MatzeB wrote:

Out of interest: Could you explain what this is doing exactly (as the comment at the beginning of the script isn't too specific about what is happening here)? At a first glance it seems to inject a custom command into bugpoint and checks the output for that "LLVM ERROR:" regex? Or is there something else?

That’s correct. It runs llc to get the error message using a regex and creates a custom command to check that specific error. Then, it runs bugpoint with the custom command.

I’ll update the description.

[volkan]

Added a comment about how the script works.

[bogner]

In D41876#971616, @volkan wrote:

In D41876#971552, @qcolombet wrote:

Could this be extended to reduce any isel related bug?

Yes, it can be extended to reduce the other ISel problems by adding a regex and the specific arguments for llc.

I'm guessing the answer is no since you'd have to update the regex as well, but would it make sense to allow llc arguments to be passed through from the command line or something like that?

[volkan]

In D41876#972547, @bogner wrote:

In D41876#971616, @volkan wrote:

In D41876#971552, @qcolombet wrote:

Could this be extended to reduce any isel related bug?

Yes, it can be extended to reduce the other ISel problems by adding a regex and the specific arguments for llc.

I'm guessing the answer is no since you'd have to update the regex as well, but would it make sense to allow llc arguments to be passed through from the command line or something like that?

I thought we could have a regex, argument list pair for each error type.

[qcolombet]

In D41876#972584, @volkan wrote:

In D41876#972547, @bogner wrote:

In D41876#971616, @volkan wrote:

In D41876#971552, @qcolombet wrote:

Could this be extended to reduce any isel related bug?

Yes, it can be extended to reduce the other ISel problems by adding a regex and the specific arguments for llc.

I'm guessing the answer is no since you'd have to update the regex as well, but would it make sense to allow llc arguments to be passed through from the command line or something like that?

I thought we could have a regex, argument list pair for each error type.

I didn't mean to have my comment hold on this patch. I think it is already an improvement and should push it to take advantage of it now. We can improve things further later as we see fit.

[bogner]

Agreed, it doesn't hurt to have this in as is.

llvm/trunk/utils/bugpoint_gisel_reducer.py

+#!/usr/bin/env python
+
+"""Reduces GlobalISel failures.
+
+This script is a utility to reduce tests that GlobalISel
+fails to compile.
+
+It runs llc to get the error message using a regex and creates
+a custom command to check that specific error. Then, it runs bugpoint
+with the custom command.
+
+"""
+from __future__ import print_function
+import argparse
+import re
+import subprocess
+import sys
+import tempfile
+import os
+
+
+def log(msg):
+    print(msg)
+
+
+def hr():
+    log('-' * 50)
+
+
+def log_err(msg):
+    print('ERROR: {}'.format(msg), file=sys.stderr)
+
+
+def check_path(path):
+    if not os.path.exists(path):
+        log_err('{} does not exist.'.format(path))
+        raise
+    return path
+
+
+def check_bin(build_dir, bin_name):
+    file_name = '{}/bin/{}'.format(build_dir, bin_name)
+    return check_path(file_name)
+
+
+def run_llc(llc, irfile):
+    pr = subprocess.Popen([llc,
+                           '-o',
+                           '-',
+                           '-global-isel',
+                           '-pass-remarks-missed=gisel',
+                           irfile],
+                          stdout=subprocess.PIPE,
+                          stderr=subprocess.PIPE)
+    out, err = pr.communicate()
+    res = pr.wait()
+    if res == 0:
+        return 0
+    re_err = re.compile(
+        r'LLVM ERROR: ([a-z\s]+):.*(G_INTRINSIC[_A-Z]* <intrinsic:@[a-zA-Z0-9\.]+>|G_[A-Z_]+)')
+    match = re_err.match(err)
+    if not match:
+        return 0
+    else:
+        return [match.group(1), match.group(2)]
+
+
+def run_bugpoint(bugpoint_bin, llc_bin, opt_bin, tmp, ir_file):
+    compileCmd = '-compile-command={} -c {} {}'.format(
+        os.path.realpath(__file__), llc_bin, tmp)
+    pr = subprocess.Popen([bugpoint_bin,
+                           '-compile-custom',
+                           compileCmd,
+                           '-opt-command={}'.format(opt_bin),
+                           ir_file])
+    res = pr.wait()
+    if res != 0:
+        log_err("Unable to reduce the test.")
+        raise
+
+
+def run_bugpoint_check():
+    path_to_llc = sys.argv[2]
+    path_to_err = sys.argv[3]
+    path_to_ir = sys.argv[4]
+    with open(path_to_err, 'r') as f:
+        err = f.read()
+        res = run_llc(path_to_llc, path_to_ir)
+        if res == 0:
+            return 0
+        log('GlobalISed failed, {}: {}'.format(res[0], res[1]))
+        if res != err.split(';'):
+            return 0
+        else:
+            return 1
+
+
+def main():
+    # Check if this is called by bugpoint.
+    if len(sys.argv) == 5 and sys.argv[1] == '-c':
+        sys.exit(run_bugpoint_check())
+
+    # Parse arguments.
+    parser = argparse.ArgumentParser(
+        description=__doc__, formatter_class=argparse.RawTextHelpFormatter)
+    parser.add_argument('BuildDir', help="Path to LLVM build directory")
+    parser.add_argument('IRFile', help="Path to the input IR file")
+    args = parser.parse_args()
+
+    # Check if the binaries exist.
+    build_dir = check_path(args.BuildDir)
+    ir_file = check_path(args.IRFile)
+    llc_bin = check_bin(build_dir, 'llc')
+    opt_bin = check_bin(build_dir, 'opt')
+    bugpoint_bin = check_bin(build_dir, 'bugpoint')
+
+    # Run llc to see if GlobalISel fails.
+    log('Running llc...')
+    res = run_llc(llc_bin, ir_file)
+    if res == 0:
+        log_err("Expected failure")
+        raise
+    hr()
+    log('GlobalISel failed, {}: {}.'.format(res[0], res[1]))
+    tmp = tempfile.NamedTemporaryFile()
+    log('Writing error to {} for bugpoint.'.format(tmp.name))
+    tmp.write(';'.join(res))
+    tmp.flush()
+    hr()
+
+    # Run bugpoint.
+    log('Running bugpoint...')
+    run_bugpoint(bugpoint_bin, llc_bin, opt_bin, tmp.name, ir_file)
+    hr()
+    log('Done!')
+    hr()
+    output_file = 'bugpoint-reduced-simplified.bc'
+    log('Run llvm-dis to disassemble the output:')
+    log('$ {}/bin/llvm-dis -o - {}'.format(build_dir, output_file))
+    log('Run llc to reproduce the problem:')
+    log('$ {}/bin/llc -o - -global-isel '
+        '-pass-remarks-missed=gisel {}'.format(build_dir, output_file))
+
+
+if __name__ == '__main__':
+    main()