1#!/usr/bin/env perl
2# SPDX-License-Identifier: GPL-2.0
3
4# Read two files produced by the stackusage script, and show the
5# delta between them.
6#
7# Currently, only shows changes for functions listed in both files. We
8# could add an option to show also functions which have vanished or
9# appeared (which would often be due to gcc making other inlining
10# decisions).
11#
12# Another possible option would be a minimum absolute value for the
13# delta.
14#
15# A third possibility is for sorting by delta, but that can be
16# achieved by piping to sort -k5,5g.
17
18sub read_stack_usage_file {
19    my %su;
20    my $f = shift;
21    open(my $fh, '<', $f)
22	or die "cannot open $f: $!";
23    while (<$fh>) {
24	chomp;
25	my ($file, $func, $size, $type) = split;
26	# Old versions of gcc (at least 4.7) have an annoying quirk in
27	# that a (static) function whose name has been changed into
28	# for example ext4_find_unwritten_pgoff.isra.11 will show up
29	# in the .su file with a name of just "11". Since such a
30	# numeric suffix is likely to change across different
31	# commits/compilers/.configs or whatever else we're trying to
32	# tweak, we can't really track those functions, so we just
33	# silently skip them.
34	#
35	# Newer gcc (at least 5.0) report the full name, so again,
36	# since the suffix is likely to change, we strip it.
37	next if $func =~ m/^[0-9]+$/;
38	$func =~ s/\..*$//;
39	# Line numbers are likely to change; strip those.
40	$file =~ s/:[0-9]+$//;
41	$su{"${file}\t${func}"} = {size => $size, type => $type};
42    }
43    close($fh);
44    return \%su;
45}
46
47@ARGV == 2
48    or die "usage: $0 <old> <new>";
49
50my $old = read_stack_usage_file($ARGV[0]);
51my $new = read_stack_usage_file($ARGV[1]);
52my @common = sort grep {exists $new->{$_}} keys %$old;
53for (@common) {
54    my $x = $old->{$_}{size};
55    my $y = $new->{$_}{size};
56    my $delta = $y - $x;
57    if ($delta) {
58	printf "%s\t%d\t%d\t%+d\n", $_, $x, $y, $delta;
59    }
60}
61