[Bug middle-end/67285] New: ICE with (rdiv (POW:s @0 REAL_CST@1) @0)

[Bug middle-end/67285] New: ICE with (rdiv (POW:s @0 REAL_CST@1) @0)

[hs.naveen2u at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67285

            Bug ID: 67285
           Summary: ICE with (rdiv (POW:s @0 REAL_CST@1) @0)
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hs.naveen2u at gmail dot com
  Target Milestone: ---

The following pattern should work as expected:-

+ /* Simplify pow(x,c) / x -> pow(x,c-1). */
+ (simplify
+  (rdiv (POW:s @0 REAL_CST@1) @0)
+  (if (!TREE_OVERFLOW (@1))
+   (POW @0 (minus @1 { build_one_cst (type); }))))

However, it generates the following error:-
internal compiler error: tree check: expected ssa_name, have var_decl in
simplify_builtin_call, at tree-ssa-forwprop.c:1259

Its due to REAL_CST@1

[Bug middle-end/67285] ICE with (rdiv (POW:s @0 REAL_CST@1) @0)

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67285

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2015-08-20
                 CC|                            |mpolacek at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Testcase?

[Bug middle-end/67285] ICE with (rdiv (POW:s @0 REAL_CST@1) @0)

[hs.naveen2u at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67285

--- Comment #2 from hs.naveen2u at gmail dot com ---
Created attachment 36226
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36226&action=edit
Testcase to reproduce the issue

aarch64-thunder-elf-gcc pr67285.c -O2 -funsafe-math-optimizations

[Bug middle-end/67285] ICE with (rdiv (POW:s @0 REAL_CST@1) @0)

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67285

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Mine.

[Bug middle-end/67285] ICE with (rdiv (POW:s @0 REAL_CST@1) @0)

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67285

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
There are two issues here - one is side-effects (virtual definition) and one
is dependences (virtual uses).  The first one you hit with -fmath-errno,
the second you hit with -frounding-math.

On GENERIC there can be nothing "inbetween" components of the matched
expression
so things are usually fine.

On GIMPLE there can be random statements inbetween the statements composing
the matched expression.  Like

  _1 = pow (x, 2)
  fesetround();
  _2 = _1 / x;

we may not move pow () across fesetround () with -frounding-math, thus we
may not generate the expression replacement at the point of the _2 definition.

The actual ICE is about our failure to keep the virtual operand SSA form
up-to-date in fold_stmt.  As we generally do not want to do IL walks to
find a suitable VUSE/DEF we can use for that (apart from looking at the
current statement) we generally have to fail doing the expression replacement.

Implementation-wise the easiest is to "fail" when we are trying to generate
a builtin function call which is not CONST.  That doesn't avoid all
questionable
transforms but at least should avoid the ICEs due to non-up-to-date virtual
operand form.

There are cases we could relax (like replacing a call with another call),
but let's do that separately.

Note that this will require -fno-math-errno for any late transforms regarding
to math builtins.

[Bug middle-end/67285] ICE with (rdiv (POW:s @0 REAL_CST@1) @0)

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67285

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
Author: rguenth
Date: Fri Aug 21 08:06:20 2015
New Revision: 227053

URL: https://gcc.gnu.org/viewcvs?rev=227053&root=gcc&view=rev
Log:
2015-08-21  Richard Biener  <rguenther@suse.de>

        PR middle-end/67285
        * gimple-fold.c (replace_stmt_with_simplification): Assert
        seq is empty when replacing a call with itself but different
        arguments.
        * gimple-match-head.c (maybe_push_res_to_seq): When pushing
        a call require that it is const.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/gimple-fold.c
    trunk/gcc/gimple-match-head.c

[Bug middle-end/67285] ICE with (rdiv (POW:s @0 REAL_CST@1) @0)

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67285

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed.