[PATCH] Fix up bootstrap on i686 --with-arch=corei7 --with-fpmath=sse (PR bootstrap/69677)

[Jakub Jelinek]

Hi!

As mentioned in the PR, the convert_scalars_to_vector hunk is important,
without that we e.g. miscompile simplify-rtx.c.
The following patch restores that hunk and extends disabling of TARGET_STV
also for the 64-bit, but not 128-bit, aligned preferred or incoming stack
boundaries (also non-default).

Bootstrapped/regtested on i686-linux --with-arch=corei7 --with-tune=corei7
--with-fpmath=sse.

Alternatively, it is enough to just adjust stack_alignment_estimated in
there and keep stack_alignment_needed as is, that version has also been
successfully bootstrapped on i686-linux --with-arch=corei7
--with-tune=corei7 --with-fpmath=sse.

2016-02-04  Jakub Jelinek  <ja...@redhat.com>

        PR bootstrap/69677
        * config/i386/i386.c (convert_scalars_to_vector): Readd stack
        alignment fixes.
        (ix86_option_override_internal): Disable TARGET_STV even for
        -m{incoming,preferred}-stack-boundary=3.

--- gcc/config/i386/i386.c.jj   2016-02-04 18:59:38.309204574 +0100
+++ gcc/config/i386/i386.c      2016-02-04 21:54:02.439904261 +0100
@@ -3588,6 +3588,16 @@ convert_scalars_to_vector ()
   bitmap_obstack_release (NULL);
   df_process_deferred_rescans ();
 
+  /* Conversion means we may have 128bit register spills/fills
+     which require aligned stack.  */
+  if (converted_insns)
+    {
+      if (crtl->stack_alignment_needed < 128)
+       crtl->stack_alignment_needed = 128;
+      if (crtl->stack_alignment_estimated < 128)
+       crtl->stack_alignment_estimated = 128;
+    }
+
   return 0;
 }
 
@@ -5443,12 +5453,12 @@ ix86_option_override_internal (bool main
     opts->x_target_flags |= MASK_VZEROUPPER;
   if (!(opts_set->x_target_flags & MASK_STV))
     opts->x_target_flags |= MASK_STV;
-  /* Disable STV if -mpreferred-stack-boundary=2 or
-     -mincoming-stack-boundary=2 - the needed
+  /* Disable STV if -mpreferred-stack-boundary={2,3} or
+     -mincoming-stack-boundary={2,3} - the needed
      stack realignment will be extra cost the pass doesn't take into
      account and the pass can't realign the stack.  */
-  if (ix86_preferred_stack_boundary < 64
-      || ix86_incoming_stack_boundary < 64)
+  if (ix86_preferred_stack_boundary < 128
+      || ix86_incoming_stack_boundary < 128)
     opts->x_target_flags &= ~MASK_STV;
   if (!ix86_tune_features[X86_TUNE_AVX256_UNALIGNED_LOAD_OPTIMAL]
       && !(opts_set->x_target_flags & MASK_AVX256_SPLIT_UNALIGNED_LOAD))

        Jakub