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 <ubiz...@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 <ubiz...@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.
Index: config/i386/i386.c =================================================================== --- config/i386/i386.c (revision 246531) +++ config/i386/i386.c (working copy) @@ -5927,9 +5927,8 @@ ix86_option_override_internal (bool main_args_p, ix86_preferred_stack_boundary = PREFERRED_STACK_BOUNDARY_DEFAULT; if (opts_set->x_ix86_preferred_stack_boundary_arg) { - int min = (TARGET_64BIT_P (opts->x_ix86_isa_flags) - ? (TARGET_SSE_P (opts->x_ix86_isa_flags) ? 4 : 3) : 2); - int max = (TARGET_SEH ? 4 : 12); + int min = TARGET_64BIT_P (opts->x_ix86_isa_flags)? 3 : 2; + int max = TARGET_SEH ? 4 : 12; if (opts->x_ix86_preferred_stack_boundary_arg < min || opts->x_ix86_preferred_stack_boundary_arg > max) Index: testsuite/gcc.target/i386/pr53383-1.c =================================================================== --- testsuite/gcc.target/i386/pr53383-1.c (revision 246531) +++ testsuite/gcc.target/i386/pr53383-1.c (working copy) @@ -1,5 +1,5 @@ /* { dg-do compile } */ -/* { dg-options "-O2 -mno-sse -mpreferred-stack-boundary=3" } */ +/* { dg-options "-O2 -mpreferred-stack-boundary=3" } */ int bar (int x) Index: testsuite/gcc.target/i386/pr53383-2.c =================================================================== --- testsuite/gcc.target/i386/pr53383-2.c (revision 246531) +++ testsuite/gcc.target/i386/pr53383-2.c (working copy) @@ -1,5 +1,5 @@ /* { dg-do compile } */ -/* { dg-options "-O2 -mno-sse -mpreferred-stack-boundary=3 -mincoming-stack-boundary=3" } */ +/* { dg-options "-O2 -mpreferred-stack-boundary=3 -mincoming-stack-boundary=3" } */ int bar (int x) Index: testsuite/gcc.target/i386/pr53383-3.c =================================================================== --- testsuite/gcc.target/i386/pr53383-3.c (revision 246531) +++ testsuite/gcc.target/i386/pr53383-3.c (working copy) @@ -1,5 +1,5 @@ /* { dg-do compile } */ -/* { dg-options "-O2 -mno-sse -mincoming-stack-boundary=3 -mpreferred-stack-boundary=3" } */ +/* { dg-options "-O2 -mincoming-stack-boundary=3 -mpreferred-stack-boundary=3" } */ int bar (int x)