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Re: [PATCH] Restore defensive check in tree_nop_conversion (also PR89779 "fix")
On Thu, 21 Mar 2019, Jason Merrill wrote:
> On 3/21/19 9:43 AM, Richard Biener wrote:
> > On Thu, 21 Mar 2019, Richard Biener wrote:
> >
> > >
> > > This also avoids the ICE in PR89779 but IMHO is not a real fix.
> > >
> > > Still it restores a previously active check against released SSA names
> > > which now have error_mark_node type rather than NULL. The new way
> > > opens up consolidation so I've adjusted tree_nop_conversion plus
> > > operand_equal_p which got a defensive check at the same time
> > > (and checks for error_mark_node right before that check).
> > >
> > > Bootstrap & regtest running on x86_64-unknown-linux-gnu.
> > >
> > > The testcase comes with the other patch (but still included below).
> >
> > Ugh, looks like my defense installed for released SSA names is now
> > relied upon by the C++ FE via
> >
> > #2 0x0000000001864a96 in tree_strip_nop_conversions (
> > exp=<convert_expr 0x7ffff69bc920>)
> > at /space/rguenther/src/svn/trunk2/gcc/tree.c:12848
> > #3 0x0000000000ab2d2f in iterative_hash_template_arg (
> > arg=<convert_expr 0x7ffff69bc920>, val=3363282904)
> > at /space/rguenther/src/svn/trunk2/gcc/cp/pt.c:1751
> >
> > for
> >
> > <convert_expr 0x7ffff69bc920
> > type <integer_type 0x7ffff68985e8 int public type_6 SI
> > size <integer_cst 0x7ffff689c078 constant 32>
> > unit-size <integer_cst 0x7ffff689c090 constant 4>
> > align:32 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
> > 0x7ffff68985e8 precision:32 min <integer_cst 0x7ffff689c030 -2147483648>
> > max <integer_cst 0x7ffff689c048 2147483647>
> > pointer_to_this <pointer_type 0x7ffff68a19d8>>
> > arg:0 <scope_ref 0x7ffff69d0b40 tree_0
> > arg:0 <template_type_parm 0x7ffff69d17e0 i tree_0 type_0 type_6
> > VOID
> > align:8 warn_if_not_align:0 symtab:0 alias-set -1
> > canonical-type 0x7ffff69d1150
> > index 0 level 1 orig_level 1
> > chain <type_decl 0x7ffff69d2098 i>>
> > arg:1 <identifier_node 0x7ffff69c39c0 c
> > normal local bindings <(nil)>>>>
> >
> > where both the SCOPE_REF and TEMPLATE_TYPE_PARM have NULL
> > TREE_TYPE.
> >
> > So I'll restore the NULL check in tree_nop_conversion.
> >
> > But since the C++ FE overloads almost every tree field possible
> > I wonder whether that STRIP_NOPS in iterative_hash_template_arg
> > is a good idea?
>
> I think it still makes sense; TREE_TYPE of an expression is either a type,
> error_mark_node, or NULL_TREE (for type-dependent expressions in a template).
>
> > Also I hope the FE doesn't call into operand_equal_p with such
> > typed trees.
>
> It shouldn't, we have cp_tree_equal to use instead.
OK, let's see how to use that for PR89790 then...
Richard.