[C++ PATCH] Fix ICE in cxx_eval_vec_init_1 (PR c++/84558)

[Jakub Jelinek]

Hi!

The PR70001 optimization in cxx_eval_vec_init_1 uses
initializer_constant_valid_p (eltinit, TREE_TYPE (eltinit))
which doesn't work if eltinit is NULL.  This can happen if
*non_constant_p is true, but ctx->quiet is true as well (for
*non_constant_p && !ctx->quiet we break the cycle early).
No initializer can be treated like a valid initializer and will
have the advantage that we don't repeat the body for every array element
and just do it once.  The caller will ignore the return value anyway
when *non_constant_p.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2018-02-26  Jakub Jelinek  

PR c++/84558
* constexpr.c (cxx_eval_vec_init_1): For reuse, treat NULL eltinit like
a valid constant initializer.  Formatting fixes.

* g++.dg/cpp1y/pr84558.C: New test.

--- gcc/cp/constexpr.c.jj   2018-02-26 10:46:02.162316172 +0100
+++ gcc/cp/constexpr.c  2018-02-26 14:07:38.705532369 +0100
@@ -2959,9 +2959,8 @@ cxx_eval_vec_init_1 (const constexpr_ctx
  if (!lvalue_p (init))
eltinit = move (eltinit);
  eltinit = force_rvalue (eltinit, tf_warning_or_error);
- eltinit = (cxx_eval_constant_expression
-(_ctx, eltinit, lval,
- non_constant_p, overflow_p));
+ eltinit = cxx_eval_constant_expression (_ctx, eltinit, lval,
+ non_constant_p, overflow_p);
}
   if (*non_constant_p && !ctx->quiet)
break;
@@ -2974,12 +2973,13 @@ cxx_eval_vec_init_1 (const constexpr_ctx
   else
CONSTRUCTOR_APPEND_ELT (*p, idx, eltinit);
   /* Reuse the result of cxx_eval_constant_expression call
- from the first iteration to all others if it is a constant
- initializer that doesn't require relocations.  */
+from the first iteration to all others if it is a constant
+initializer that doesn't require relocations.  */
   if (reuse
  && max > 1
- && (initializer_constant_valid_p (eltinit, TREE_TYPE (eltinit))
- == null_pointer_node))
+ && (eltinit == NULL_TREE
+ || (initializer_constant_valid_p (eltinit, TREE_TYPE (eltinit))
+ == null_pointer_node)))
{
  if (new_ctx.ctor != ctx->ctor)
eltinit = new_ctx.ctor;
--- gcc/testsuite/g++.dg/cpp1y/pr84558.C.jj 2018-02-26 14:33:56.575318295 
+0100
+++ gcc/testsuite/g++.dg/cpp1y/pr84558.C2018-02-26 14:33:33.142318527 
+0100
@@ -0,0 +1,6 @@
+// PR c++/84558
+// { dg-do compile { target c++14 } }
+
+struct A { static int i; constexpr A () { i = 0; } };
+struct B { A a[2][3][4]; };
+B b;

Jakub

Re: [C++ PATCH] Fix ICE in cxx_eval_vec_init_1 (PR c++/84558)

[Jason Merrill]

OK.

On Mon, Feb 26, 2018 at 2:57 PM, Jakub Jelinek  wrote:
> Hi!
>
> The PR70001 optimization in cxx_eval_vec_init_1 uses
> initializer_constant_valid_p (eltinit, TREE_TYPE (eltinit))
> which doesn't work if eltinit is NULL.  This can happen if
> *non_constant_p is true, but ctx->quiet is true as well (for
> *non_constant_p && !ctx->quiet we break the cycle early).
> No initializer can be treated like a valid initializer and will
> have the advantage that we don't repeat the body for every array element
> and just do it once.  The caller will ignore the return value anyway
> when *non_constant_p.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2018-02-26  Jakub Jelinek  
>
> PR c++/84558
> * constexpr.c (cxx_eval_vec_init_1): For reuse, treat NULL eltinit 
> like
> a valid constant initializer.  Formatting fixes.
>
> * g++.dg/cpp1y/pr84558.C: New test.
>
> --- gcc/cp/constexpr.c.jj   2018-02-26 10:46:02.162316172 +0100
> +++ gcc/cp/constexpr.c  2018-02-26 14:07:38.705532369 +0100
> @@ -2959,9 +2959,8 @@ cxx_eval_vec_init_1 (const constexpr_ctx
>   if (!lvalue_p (init))
> eltinit = move (eltinit);
>   eltinit = force_rvalue (eltinit, tf_warning_or_error);
> - eltinit = (cxx_eval_constant_expression
> -(_ctx, eltinit, lval,
> - non_constant_p, overflow_p));
> + eltinit = cxx_eval_constant_expression (_ctx, eltinit, lval,
> + non_constant_p, overflow_p);
> }
>if (*non_constant_p && !ctx->quiet)
> break;
> @@ -2974,12 +2973,13 @@ cxx_eval_vec_init_1 (const constexpr_ctx
>else
> CONSTRUCTOR_APPEND_ELT (*p, idx, eltinit);
>/* Reuse the result of cxx_eval_constant_expression call
> - from the first iteration to all others if it is a constant
> - initializer that doesn't require relocations.  */
> +from the first iteration to all others if it is a constant
> +initializer that doesn't require relocations.  */
>if (reuse
>   && max > 1
> - && (initializer_constant_valid_p (eltinit, TREE_TYPE (eltinit))
> - == null_pointer_node))
> + && (eltinit == NULL_TREE
> + || (initializer_constant_valid_p (eltinit, TREE_TYPE (eltinit))
> + == null_pointer_node)))
> {
>   if (new_ctx.ctor != ctx->ctor)
> eltinit = new_ctx.ctor;
> --- gcc/testsuite/g++.dg/cpp1y/pr84558.C.jj 2018-02-26 14:33:56.575318295 
> +0100
> +++ gcc/testsuite/g++.dg/cpp1y/pr84558.C2018-02-26 14:33:33.142318527 
> +0100
> @@ -0,0 +1,6 @@
> +// PR c++/84558
> +// { dg-do compile { target c++14 } }
> +
> +struct A { static int i; constexpr A () { i = 0; } };
> +struct B { A a[2][3][4]; };
> +B b;
>
> Jakub