Bug#918175: internal loop labels are kept as symbols

[Mike Gabriel]

Hi Steinar,

On  Do 03 Jan 2019 23:45:28 CET, Steinar H. Gunderson wrote:

Package: libjpeg62-turbo
Version: 1:1.5.2-2+b1
Severity: normal
Tags: patch upstream

Hi,

When profiling any program that uses libjpeg-turbo, there's a proliferation
of “symbols” that are really internal labels, confusing the profiler:


   3,24%  MJPEG_Encode     libjpeg.so.62.2.0              [.] encode_mcu_huff

   1,89%  MJPEG_Encode     libjpeg.so.62.2.0              [.] compress_data

   1,39%  MJPEG_Encode     libjpeg.so.62.2.0              [.] forward_DCT


Note in particular ..@25..CHECKBUF47_END, which is really part of
jsimd_huff_encode_one_block_sse2, and the same with .BLOOP. This is a known
shortcoming of nasm, but can be stripped out fairly easily, e.g., with
something like

--- libjpeg-turbo-1.5.2.orig/simd/nasm_lt.sh
+++ libjpeg-turbo-1.5.2/simd/nasm_lt.sh
@@ -39,6 +39,7 @@ while [ $# -gt 0 ]; do
         -o*)
             o_opt=yes
             command="$command $1"
+            outfile="$2"
             ;;
         *.asm)
             infile=$1
@@ -53,8 +54,11 @@ done
 if [ "$o_opt" != yes ] ; then
     # By default, NASM creates an output file
     # in the same directory as the input file.
-    outfile="-o `echo $infile | sed -e 's%^.*/%%' -e 's%\.[^.]*$%%'`.o"
-    command="$command $outfile"
+    outfile="`echo $infile | sed -e 's%^.*/%%' -e 's%\.[^.]*$%%'`.o"
+    command="$command -o $outfile"
 fi
+set -e
 echo $command
-exec $command
+$command
+echo strip --discard-locals --wildcard --strip-symbol='?*.*' $outfile
+strip --discard-locals --wildcard --strip-symbol='?*.*' $outfile

After applying said patch and rebuilding, the profile is a lot more readable
and less cluttered:


   2,86%  MJPEG_Encode     libjpeg.so.62.2.0              [.] encode_mcu_huff

Backtracing and disassembling in gdb is also affected by this issue.

-- System Information:
Debian Release: buster/sid
  APT prefers testing-debug
  APT policy: (500, 'testing-debug'), (500, 'testing'), (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.19.11 (SMP w/40 CPU cores)

Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages libjpeg62-turbo depends on:
ii  libc6  2.28-2

libjpeg62-turbo recommends no packages.

libjpeg62-turbo suggests no packages.

-- debconf-show failed

14,50% MJPEG_Encode libjpeg.so.62.2.0 [.] jsimd_fdct_islow_sse2 8,80% MJPEG_Encode nageru [.] memcpy_interleaved_fastpath 8,69% MJPEG_Encode libjpeg.so.62.2.0 [.] ..@25..CHECKBUF47_END 4,51% MJPEG_Encode libc-2.28.so [.] __memmove_avx_unaligned_erms 3,81% MJPEG_Encode libjpeg.so.62.2.0 [.] jsimd_quantize_sse2.quantloop 2,81% Mixer_Audio libzita-resampler.so.1.6.0 [.] Resampler::process 2,54% MJPEG_Encode libjpeg.so.62.2.0 [.] jsimd_convsamp_sse2.convloop 2,44% nageru [unknown] [k] 0xffffffffa280015f 2,31% MHD-connection [unknown] [k] 0xffffffffa280015f 2,09% MJPEG_Encode libjpeg.so.62.2.0 [.] ..@44..CHECKBUF31_END 2,02% QS_Encode [unknown] [k] 0xffffffffa280015f 1,98% Mixer_Audio libzita-resampler.so.1.6.0 [.] VResampler::process 1,57% MJPEG_Encode libjpeg.so.62.2.0 [.] jsimd_huff_encode_one_block_sse2.BLOOP 1,21% MJPEG_Encode libjpeg.so.62.2.0 [.] jsimd_huff_encode_one_block_sse2 16,05% MJPEG_Encode libjpeg.so.62.2.0 [.] jsimd_huff_encode_one_block_sse2 14,38% MJPEG_Encode libjpeg.so.62.2.0 [.] jsimd_fdct_islow_sse2 8,50% MJPEG_Encode nageru [.] memcpy_interleaved_fastpath 4,75% MJPEG_Encode libjpeg.so.62.2.0 [.] jsimd_quantize_sse2 3,71% MJPEG_Encode libc-2.28.so [.] __memmove_avx_unaligned_erms 3,11% MJPEG_Encode libjpeg.so.62.2.0 [.] jsimd_convsamp_sse2 Locale: LANG=en_DK.UTF-8, LC_CTYPE=en_DK.UTF-8 (charmap=UTF-8), LANGUAGE=en_NO:en_US:en_GB:en (charmap=UTF-8)

I'd be happy to apply your patchl, if upstream accepts it.

Greets,
Mike
--

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Sorry for replying so late. Could you bring this up with the upstream maintainers of libjpeg-turbo? I guess you can explain everything much better than me (as you probably had to work around the above problem).

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