Hang on Debian ARM64 QEMU Chroot

[noloader]

László Böszörményi of Debian reports a hang near "BlumBlumShub validation suite running..." when testing under Debian QEMU Chroot for ARM64. The hang is present under GCC 5.1, but is not present under Clang on the same machine.

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The issue is present with both -std=c++03, -std=c++11. Following GCC miscompiles my code when optimizing..., its also present with -fno-strict-aliasing. On other platforms and compilers, using the following produces no findings or problems: -Wall -Wextra -Wstrict-aliasing=3 -Wstrict-overflow -Waggressive-loop-optimizations. In fact, that's our "Elevated Warnings" test case (with a few more warnings added.

The issue appears to related to inlining. The issue is present with -free and -findirect-inlining. Building with -fno-inline or -fno-devirtualize resolves it at the expense of performance.

An additional issue is the GDB debugger does not work. It can start the program and even attach to the process, but that's about it. It can't break, and it does not provide symbols. LLDB is not available on this platform.

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The hang is not present in GCC's compile farm using gcc113.fsffrance.org or gcc115.fsffrance.org:

$ uname -a
Linux gcc113 3.13.0-57-generic #95-Ubuntu SMP Fri Jun 19 09:31:00 UTC 2015 aarch64 aarch64 aarch64 GNU/Linux
$ gcc --version
gcc (Ubuntu/Linaro 4.8.4-2ubuntu1~14.04) 4.8.4
Copyright (C) 2013 Free Software Foundation, Inc.

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The hang is present on a LeMaker HiKey:

$ uname -a
Linux hikey 3.18.0-linaro-hikey #1 SMP PREEMPT Mon Nov 30 00:11:03 UTC 2015 aarch64 GNU/Linux
$ gcc --version
gcc (Debian/Linaro 4.9.2-10) 4.9.2
Copyright (C) 2014 Free Software Foundation, Inc.

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A HTC Desire 510 and a Samsung Galaxy Core-Prime with a Cortex-A53 (ARMv8-a) were ordered for additional on-device testing. But both devices did not live up to their press releases, and they came with 32-bit ARMv7.

A DragonBoard 410c kit and LeMaker HiKey were ordered for additional on-device testing.

[noloader]

Cleared at Commit 3941be18891a6a87