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From: "slyfox at inbox dot ru" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/95118] New: gcc-10 and master -O3
 -fopt-info-vec causes gcc to hang
Date: Wed, 13 May 2020 22:09:46 +0000
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X-Bugzilla-Component: tree-optimization
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95118

            Bug ID: 95118
           Summary: gcc-10 and master -O3 -fopt-info-vec causes gcc to
                    hang
           Product: gcc
           Version: 10.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: slyfox at inbox dot ru
  Target Milestone: ---

The bug originally reported by Adrien Dessemond as
https://bugs.gentoo.org/722774 where gzip-1.10's ./configure CFLAGS=3D"-O3 =
-pipe
-march=3Dnative -fomit-frame-pointer -fopt-info-vec -mindirect-branch=3Dthu=
nk
-mindirect-branch-register" makes gcc hang.

Minimal reproducer against gcc-10.1.0 anf gcc-master is:

  // $ cat bug.c
  void a();
  void b() {
    union {
      int c[4];
      long double d;
    } e =3D {{0, 0, 4}};
    a(e.d);
  }

$ /usr/bin/x86_64-pc-linux-gnu-gcc-10.1.0 -o conftest -O3 -fopt-info-vec -c
bug.c
<hung>

Reproducible on the following gcc config against master:

Reading specs from /home/slyfox/dev/git/gcc-native-quick/gcc/specs
COLLECT_GCC=3D/home/slyfox/dev/git/gcc-native-quick/gcc/xgcc
COLLECT_LTO_WRAPPER=3D/home/slyfox/dev/git/gcc-native-quick/gcc/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc/configure --enable-languages=3Dc,c++ --disable-boot=
strap
--with-multilib-list=3Dm64
--prefix=3D/home/slyfox/dev/git/gcc-native-quick/../gcc-native-quick-instal=
led
--disable-nls --without-isl --disable-libsanitizer --disable-libvtv
--disable-libgomp --disable-libstdcxx-pch --disable-libunwind-exceptions
CFLAGS=3D'-O1 ' CXXFLAGS=3D'-O1 ' --with-sysroot=3D/usr/x86_64-HEAD-linux-g=
nu
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.0.0 20200513 (experimental) (GCC)=