#!/usr/bin/env perl
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# SPDX-License-Identifier: GPL-2.0
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# Read two files produced by the stackusage script, and show the
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# delta between them.
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#
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# Currently, only shows changes for functions listed in both files. We
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# could add an option to show also functions which have vanished or
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# appeared (which would often be due to gcc making other inlining
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# decisions).
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#
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# Another possible option would be a minimum absolute value for the
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# delta.
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#
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# A third possibility is for sorting by delta, but that can be
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# achieved by piping to sort -k5,5g.
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sub read_stack_usage_file {
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my %su;
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my $f = shift;
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open(my $fh, '<', $f)
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or die "cannot open $f: $!";
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while (<$fh>) {
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chomp;
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my ($file, $func, $size, $type) = split;
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# Old versions of gcc (at least 4.7) have an annoying quirk in
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# that a (static) function whose name has been changed into
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# for example ext4_find_unwritten_pgoff.isra.11 will show up
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# in the .su file with a name of just "11". Since such a
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# numeric suffix is likely to change across different
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# commits/compilers/.configs or whatever else we're trying to
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# tweak, we can't really track those functions, so we just
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# silently skip them.
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#
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# Newer gcc (at least 5.0) report the full name, so again,
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# since the suffix is likely to change, we strip it.
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next if $func =~ m/^[0-9]+$/;
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$func =~ s/\..*$//;
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# Line numbers are likely to change; strip those.
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$file =~ s/:[0-9]+$//;
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$su{"${file}\t${func}"} = {size => $size, type => $type};
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}
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close($fh);
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return \%su;
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}
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@ARGV == 2
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or die "usage: $0 <old> <new>";
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my $old = read_stack_usage_file($ARGV[0]);
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my $new = read_stack_usage_file($ARGV[1]);
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my @common = sort grep {exists $new->{$_}} keys %$old;
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for (@common) {
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my $x = $old->{$_}{size};
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my $y = $new->{$_}{size};
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my $delta = $y - $x;
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if ($delta) {
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printf "%s\t%d\t%d\t%+d\n", $_, $x, $y, $delta;
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}
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}
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