* Ping: PR tree-opt/33615 [1/2] Hoisting of throwing expression for -fnon-call-exceptions
@ 2007-10-07 18:50 Richard Sandiford
2007-10-08 0:48 ` Zdenek Dvorak
0 siblings, 1 reply; 2+ messages in thread
From: Richard Sandiford @ 2007-10-07 18:50 UTC (permalink / raw)
To: gcc-patches
http://gcc.gnu.org/ml/gcc-patches/2007-10/msg00085.html
This didn't draw any comment from maintainers. Andrew commented that it
might be a good idea to set TREE_SIDE_EFFECTS for things that can throw,
but I don't know whether that'd be easier to maintain than the new
(function) predicate suggested in the covering patch. Either way,
I hope the patch as-is is strict progress.
Dan approved part 2 (thanks), but I thought I'd better wait on part 1
before checking it in.
Richard
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Ping: PR tree-opt/33615 [1/2] Hoisting of throwing expression for -fnon-call-exceptions
2007-10-07 18:50 Ping: PR tree-opt/33615 [1/2] Hoisting of throwing expression for -fnon-call-exceptions Richard Sandiford
@ 2007-10-08 0:48 ` Zdenek Dvorak
0 siblings, 0 replies; 2+ messages in thread
From: Zdenek Dvorak @ 2007-10-08 0:48 UTC (permalink / raw)
To: Richard Sandiford; +Cc: gcc-patches
Hello,
> http://gcc.gnu.org/ml/gcc-patches/2007-10/msg00085.html
>
> This didn't draw any comment from maintainers. Andrew commented that it
> might be a good idea to set TREE_SIDE_EFFECTS for things that can throw,
> but I don't know whether that'd be easier to maintain than the new
> (function) predicate suggested in the covering patch. Either way,
> I hope the patch as-is is strict progress.
the patch is OK, but see the notes below.
> Index: gcc/tree-ssa-loop-im.c
> ===================================================================
> --- gcc/tree-ssa-loop-im.c 2007-10-01 23:23:16.000000000 +0100
> +++ gcc/tree-ssa-loop-im.c 2007-10-01 23:39:36.000000000 +0100
> @@ -260,7 +260,8 @@ movement_possibility (tree stmt)
>
> rhs = GIMPLE_STMT_OPERAND (stmt, 1);
>
> - if (TREE_SIDE_EFFECTS (rhs))
> + if (TREE_SIDE_EFFECTS (rhs)
> + || tree_could_throw_p (rhs))
> return MOVE_IMPOSSIBLE;
>
> if (TREE_CODE (lhs) != SSA_NAME
The check for
if (stmt_ends_bb_p (stmt))
return MOVE_IMPOSSIBLE;
was supposed to prevent this optimization for expressions throwing
exceptions. However, we do not create edges to exit for exceptions that
are not caught locally; which seems somewhat wrong, certainly this
can cause problems also for other code hoisting optimizations.
Zdenek
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2007-10-07 18:50 Ping: PR tree-opt/33615 [1/2] Hoisting of throwing expression for -fnon-call-exceptions Richard Sandiford
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