On Thu, 24 Mar 2022, Jakub Jelinek wrote:
> Hi!
>
> As mentioned in the PR, operand_equal_p already contains some hacks so that
> it can be called already on pre-instantiation C++ trees from templates,
> but the recent change to compare DECL_FIELD_OFFSET in the COMPONENT_REF
> case broke this. Many such COMPONENT_REFs are already punted on earlier
> because they have NULL TREE_TYPE, but in this case the code knows what
> type they have but still uses an IDENTIFIER_NODE as second operand
> of COMPONENT_REF (I think SCOPE_REF is something that could be used too).
>
> The following patch looks at those DECL_FIELD_*OFFSET fields only if
> both field[01] args are FIELD_DECLs and otherwise keeps it to the
> earlier OP_SAME (1) check that guards this whole block.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Richard.
> 2022-03-24 Jakub Jelinek <ja...@redhat.com>
>
> PR c++/105035
> * fold-const.cc (operand_equal_p) <case COMPONENT_REF>: If either
> field0 or field1 is not a FIELD_DECL, return false.
>
> * g++.dg/warn/Wduplicated-cond2.C: New test.
>
> --- gcc/fold-const.cc.jj 2022-03-18 18:32:36.175078948 +0100
> +++ gcc/fold-const.cc 2022-03-23 13:40:49.893266570 +0100
> @@ -3357,8 +3357,11 @@ operand_compare::operand_equal_p (const_
> tree field0 = TREE_OPERAND (arg0, 1);
> tree field1 = TREE_OPERAND (arg1, 1);
>
> - if (!operand_equal_p (DECL_FIELD_OFFSET (field0),
> - DECL_FIELD_OFFSET (field1), flags)
> + /* Non-FIELD_DECL operands can appear in C++ templates. */
> + if (TREE_CODE (field0) != FIELD_DECL
> + || TREE_CODE (field1) != FIELD_DECL
> + || !operand_equal_p (DECL_FIELD_OFFSET (field0),
> + DECL_FIELD_OFFSET (field1), flags)
> || !operand_equal_p (DECL_FIELD_BIT_OFFSET (field0),
> DECL_FIELD_BIT_OFFSET (field1),
> flags))
> --- gcc/testsuite/g++.dg/warn/Wduplicated-cond2.C.jj 2022-03-23
> 13:47:36.041577821 +0100
> +++ gcc/testsuite/g++.dg/warn/Wduplicated-cond2.C 2022-03-23
> 13:46:54.820155190 +0100
> @@ -0,0 +1,29 @@
> +// PR c++/105035
> +// { dg-do compile }
> +// { dg-options "-Wduplicated-cond" }
> +
> +class A {
> + struct B { int c; int f; } e;
> + template <typename> void foo ();
> + void bar ();
> +};
> +
> +template <typename> void
> +A::foo ()
> +{
> + int g;
> + if (&g == &e.c)
> + ;
> + else if (&g == &e.f)
> + ;
> +}
> +
> +void
> +A::bar ()
> +{
> + int g;
> + if (&g == &e.c) // { dg-message "previously used here" }
> + ;
> + else if (&g == &e.c) // { dg-warning "duplicated 'if' condition" }
> + ;
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)
