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