Hello!

As argued in the PR [1], limiting -mpreferred-stack-boundary=3 only
for non-SSE 64bit targets represent artificial limitation, restricting
compiler functionality and user freedom.

Attached patch allows -mpreferred-stack-boundary=3 in all cases. The
compiler will align stack when needed, imposing a small runtime
penalty for functions that require 16-byte alignment.

2017-03-28  Uros Bizjak  <ubizjak@gmail.com>

    PR target/53383
    * config/i386/i386.c (ix86_option_override_internal): Always
    allow -mpreferred-stack-boundary=3 for 64-bit targets.

testsuite/ChangeLog:

2017-03-28  Uros Bizjak  <ubizjak@gmail.com>

    PR target/53383
    * gcc.target/i386/pr53383-1.c (dg-options): Remove -mno-sse.
    * gcc.target/i386/pr53383-2.c (dg-options): Ditto.
    * gcc.target/i386/pr53383-3.c (dg-options): Ditto.

Patch was bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.

Committed to mainline SVN.

[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383#c25

Uros.