[Bug tree-optimization/65217] __builtin_unreachable in if statement causes bad assembly generation

[law at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65217

Jeffrey A. Law law at redhat dot com changed:

   What|Removed |Added

 Status|REOPENED|RESOLVED
 CC||law at redhat dot com
 Resolution|--- |FIXED

--- Comment #5 from Jeffrey A. Law law at redhat dot com ---
Resolved again :-)

[Bug tree-optimization/65217] __builtin_unreachable in if statement causes bad assembly generation

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65217

Richard Biener rguenth at gcc dot gnu.org changed:

   What|Removed |Added

   Keywords||missed-optimization, xfail
 Status|RESOLVED|REOPENED
   Last reconfirmed||2015-04-27
 CC||law at gcc dot gnu.org,
   ||rguenth at gcc dot gnu.org
  Component|c   |tree-optimization
 Resolution|FIXED   |---
 Ever confirmed|0   |1

--- Comment #3 from Richard Biener rguenth at gcc dot gnu.org ---
It was only fixed by luck due to us folding all stmts in forwprop which turns

  if (_3 != n_1(D))

into the canonical

  if (n_1(D) != _3)

and then DOM recording the proper equality via record_equality by _always_
swapping operands due to

  else if (is_gimple_min_invariant (x)
   /* ???  When threading over backedges the following is important
  for correctness.  See PR61757.  */
   || (loop_depth_of_name (x) = loop_depth_of_name (y)))

and its '==' part.

For non-canonical order (in GCC 4.9 and earlier) that swapping turned it into
the unfortunate direction.

That equality decides whether we propagate _3 into the return value on the
else branch (where n_1(D) == _3) or leave it as n_1(D) (good for this case).

I am about to commit a patch that does not perform this kind of random swapping
(and will XFAIL the testcase).

[Bug tree-optimization/65217] __builtin_unreachable in if statement causes bad assembly generation

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65217

--- Comment #4 from Jeffrey A. Law law at gcc dot gnu.org ---
Author: law
Date: Tue Apr 28 04:01:28 2015
New Revision: 222499

URL: https://gcc.gnu.org/viewcvs?rev=222499root=gccview=rev
Log:
PR tree-optimization/65217
* tree-ssa-dom.c (record_equality): Given two SSA_NAMEs, if just one
of them has a single use, make sure it is the LHS of the implied
copy.

PR tree-optimization/65217
* gcc.target/i386/pr65217.c: Remove XFAIL.

Modified:
trunk/gcc/ChangeLog
trunk/gcc/testsuite/ChangeLog
trunk/gcc/testsuite/gcc.target/i386/pr65217.c
trunk/gcc/tree-ssa-dom.c