[Bug 1489560] Re: qemu-efi: hangs in kvm mode when built w/ gcc-5

[Thomas Preud'homme]

Ok, I'll build edk2 with bswap dumps enabled and check all the cases
this pass optimizes. There might be many of them so if you manage to
pinpoint it to some specific file or testcase please let me know as it
would make debugging easier.

Best regards

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Title:
  qemu-efi: hangs in kvm mode when built w/ gcc-5

Status in edk2 package in Ubuntu:
  New
Status in gcc-5 package in Ubuntu:
  New

Bug description:
  When I rebuild edk2_0~20150106.5c2d456b-1build1 in wily or sid, KVM-
  accelerated arm64 VMs hang before displaying any console output. I
  bisected this down to a change in gcc (see below).

  Note that this does not impact fully emulated instances. That is, if I
  drop '-enable-kvm' and change '-cpu host' to '-cpu cortex-a57', it
  boots fine.

  Here's the gcc changeset that introduced the issue:

  From 470d5bb5a2aba04db8d9d9dce0c5a3d5efe85882 Mon Sep 17 00:00:00 2001
  From: thopre01 <thopre01 at 138bc75d-0d04-0410-961f-82ee72b054a4>
  Date: Fri, 23 May 2014 03:33:28 +0000
  Subject: [PATCH] 2014-05-23  Thomas Preud'homme  <thomas.preudhomme at arm.com>

          PR tree-optimization/54733
  gcc/
          * tree-ssa-math-opts.c (nop_stats): New "bswap_stats" structure.
          (CMPNOP): Define.
          (find_bswap_or_nop_load): New.
          (find_bswap_1): Renamed to ...
          (find_bswap_or_nop_1): This. Also add support for memory source.
          (find_bswap): Renamed to ...
          (find_bswap_or_nop): This. Also add support for memory source and
          detection of bitwise operations equivalent to load in host endianness.
          (execute_optimize_bswap): Likewise. Also move its leading comment back
          in place and split statement transformation into ...
          (bswap_replace): This.

  gcc/testsuite
          * gcc.dg/optimize-bswapdi-3.c: New test to check extension of bswap
          optimization to support memory sources and bitwise operations
          equivalent to load in host endianness.
          * gcc.dg/optimize-bswaphi-1.c: Likewise.
          * gcc.dg/optimize-bswapsi-2.c: Likewise.
          * gcc.c-torture/execute/bswap-2.c: Likewise.

  
  git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@210843 138bc75d-0d04-0410-961f-82ee72b054a4

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