[Bug translator/25549] Systemtap unable to find many probe points available in code compiled with LTO enable

["wcohen at redhat dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=25549

--- Comment #8 from William Cohen <wcohen at redhat dot com> ---
I locally built a elfutils-0.179-2.fc30.src.rpm with the proposed patch and
installed the resulting rpms.  The patch does make things work better.

For the simple reproducer:

[wcohen@cervelo BUILDROOT]$ stap -L
'process("./pr25549").statement("main@*:*")'
process("/home/wcohen/rpmbuild/BUILDROOT/pr25549").statement("main@/home/wcohen/rpmbuild/BUILDROOT/pr25549.cxx:4")
$argc:int $argv:char**
process("/home/wcohen/rpmbuild/BUILDROOT/pr25549").statement("main@/home/wcohen/rpmbuild/BUILDROOT/pr25549.cxx:6")
$argc:int $argv:char**
[wcohen@cervelo BUILDROOT]$ stap -L
'process("./pr25549.lto").statement("main@*:*")'
process("/home/wcohen/rpmbuild/BUILDROOT/pr25549.lto").statement("main@/home/wcohen/rpmbuild/BUILDROOT/pr25549.cxx:4")
$argc:int $argv:char**
process("/home/wcohen/rpmbuild/BUILDROOT/pr25549.lto").statement("main@/home/wcohen/rpmbuild/BUILDROOT/pr25549.cxx:6")
$argc:int $argv:char**

For the original example that caused the PR to be filed there are many more
probe (21694 vs 1196) for the lto version, but still an order of magnitude less
than the non-lto version (255842):

[wcohen@cervelo BUILDROOT]$ stap -v -L
'process("./binutils-2.31.1-29.fc30_gcc_o2_lto_g_.x86_64/usr/bin/ld").statement("*@*:*")'
|wc
Pass 1: parsed user script and 577 library scripts using
1279164virt/1049920res/13264shr/1036408data kb, in 2230usr/260sys/2499real ms.
Pass 2: analyzed script: 21694 probes, 0 functions, 0 embeds, 0 globals using
2078028virt/1843376res/14204shr/1835272data kb, in 11060usr/270sys/11552real
ms.
  21694  477333 10389959
[wcohen@cervelo BUILDROOT]$ stap -v -L
'process("./binutils-2.31.1-29.fc30_gcc_o2__g_.x86_64/usr/bin/ld").statement("*@*:*")'
|wc
Pass 1: parsed user script and 577 library scripts using
1279164virt/1049904res/13252shr/1036408data kb, in 2170usr/270sys/2459real ms.
Pass 2: analyzed script: 255842 probes, 0 functions, 0 embeds, 0 globals using
1958204virt/1729244res/14192shr/1715448data kb, in 90860usr/10320sys/101800real
ms.
 255842 3891737 96145934

It would be expected that the lto version would be optimized so there are fewer
probe points, but 90% reduction in probe points seems unlikely given the
relative sizes of the binaries:

[wcohen@cervelo BUILDROOT]$ ls -l
./binutils-2.31.1-29.fc30_gcc_o2__g_.x86_64/usr/bin/ld
-rwxr-xr-x. 2 wcohen wcohen 3941264 Oct 14  2019
./binutils-2.31.1-29.fc30_gcc_o2__g_.x86_64/usr/bin/ld
[wcohen@cervelo BUILDROOT]$ ls -l
./binutils-2.31.1-29.fc30_gcc_o2_lto_g_.x86_64/usr/bin/ld
-rwxr-xr-x. 2 wcohen wcohen 2215376 Oct 14  2019
./binutils-2.31.1-29.fc30_gcc_o2_lto_g_.x86_64/usr/bin/ld

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