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Re: [PATCH] Fix handling of const/pure noreturn functions (PR tree-optimization/44485)


On Thu, Aug 26, 2010 at 5:00 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> On this testcase, local_pure_const discovery first determines bar
> is TREE_READONLY/DECL_LOOPING_CONST_OR_PURE_P and only later on
> finds out it is also noreturn (TREE_THIS_VOLATILE).
> flags_from_decl_or_type in that case would not return ECF_CONST, which means
> a call which didn't have vops suddenly needs them and the calling pass of
> fixup_noreturn_call doesn't expect .MEM needs to be renamed.
> Fixed by treating noreturn const or pure as noreturn const/pure looping
> functions. ?I wanted to make sure DECL_LOOPING_CONST_OR_PURE_P is
> going to be set for noreturn const or pure functions declared with
> attribute, but that would be quite difficult (would need to handle that
> in all the pure/const/noreturn attribute handling, and in C and C++ decl
> merging, etc.). ?There are only very few places which check
> DECL_LOOPING_CONST_OR_PURE_P directly, it is easier just to use
> flags_from_decl_or_type there as most of the other places already do.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

Ok.

Thanks,
Richard.

> 2010-08-26 ?Jakub Jelinek ?<jakub@redhat.com>
>
> ? ? ? ?PR tree-optimization/44485
> ? ? ? ?* calls.c (flags_from_decl_or_type): For const or pure
> ? ? ? ?noreturn functions return ECF_LOOPING_CONST_OR_PURE|ECF_NORETURN
> ? ? ? ?together with ECF_CONST resp. ECF_PURE.
> ? ? ? ?* builtins.c (expand_builtin): Use flags_from_decl_or_type
> ? ? ? ?instead of querying flags directly.
> ? ? ? ?* tree-ssa-loop-niter.c (finite_loop_p): Likewise.
> ? ? ? ?* tree-ssa-dce.c (find_obviously_necessary_stmts): Likewise.
>
> ? ? ? ?* gcc.dg/pr44485.c: New test.
>
> --- gcc/calls.c.jj ? ? ?2010-08-16 19:24:16.000000000 +0200
> +++ gcc/calls.c 2010-08-26 12:21:17.000000000 +0200
> @@ -601,7 +601,7 @@ flags_from_decl_or_type (const_tree exp)
> ? ? ? ?flags |= ECF_RETURNS_TWICE;
>
> ? ? ? /* Process the pure and const attributes. ?*/
> - ? ? ?if (TREE_READONLY (exp) && ! TREE_THIS_VOLATILE (exp))
> + ? ? ?if (TREE_READONLY (exp))
> ? ? ? ?flags |= ECF_CONST;
> ? ? ? if (DECL_PURE_P (exp))
> ? ? ? ?flags |= ECF_PURE;
> @@ -616,11 +616,15 @@ flags_from_decl_or_type (const_tree exp)
>
> ? ? ? flags = special_function_p (exp, flags);
> ? ? }
> - ?else if (TYPE_P (exp) && TYPE_READONLY (exp) && ! TREE_THIS_VOLATILE (exp))
> + ?else if (TYPE_P (exp) && TYPE_READONLY (exp))
> ? ? flags |= ECF_CONST;
>
> ? if (TREE_THIS_VOLATILE (exp))
> - ? ?flags |= ECF_NORETURN;
> + ? ?{
> + ? ? ?flags |= ECF_NORETURN;
> + ? ? ?if (flags & (ECF_CONST|ECF_PURE))
> + ? ? ? flags |= ECF_LOOPING_CONST_OR_PURE;
> + ? ?}
>
> ? return flags;
> ?}
> --- gcc/builtins.c.jj ? 2010-08-20 16:51:09.000000000 +0200
> +++ gcc/builtins.c ? ? ?2010-08-26 13:59:07.000000000 +0200
> @@ -5748,6 +5748,7 @@ expand_builtin (tree exp, rtx target, rt
> ? tree fndecl = get_callee_fndecl (exp);
> ? enum built_in_function fcode = DECL_FUNCTION_CODE (fndecl);
> ? enum machine_mode target_mode = TYPE_MODE (TREE_TYPE (exp));
> + ?int flags;
>
> ? if (DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_MD)
> ? ? return targetm.expand_builtin (exp, target, subtarget, mode, ignore);
> @@ -5770,8 +5771,8 @@ expand_builtin (tree exp, rtx target, rt
> ? ? ?none of its arguments are volatile, we can avoid expanding the
> ? ? ?built-in call and just evaluate the arguments for side-effects. ?*/
> ? if (target == const0_rtx
> - ? ? ?&& (DECL_PURE_P (fndecl) || TREE_READONLY (fndecl))
> - ? ? ?&& !DECL_LOOPING_CONST_OR_PURE_P (fndecl))
> + ? ? ?&& ((flags = flags_from_decl_or_type (fndecl)) & (ECF_CONST | ECF_PURE))
> + ? ? ?&& !(flags & ECF_LOOPING_CONST_OR_PURE))
> ? ? {
> ? ? ? bool volatilep = false;
> ? ? ? tree arg;
> --- gcc/tree-ssa-loop-niter.c.jj ? ? ? ?2010-08-20 16:05:40.000000000 +0200
> +++ gcc/tree-ssa-loop-niter.c ? 2010-08-26 13:59:04.000000000 +0200
> @@ -1970,12 +1970,12 @@ finite_loop_p (struct loop *loop)
> ? edge ex;
> ? struct tree_niter_desc desc;
> ? bool finite = false;
> + ?int flags;
>
> ? if (flag_unsafe_loop_optimizations)
> ? ? return true;
> - ?if ((TREE_READONLY (current_function_decl)
> - ? ? ? || DECL_PURE_P (current_function_decl))
> - ? ? ?&& !DECL_LOOPING_CONST_OR_PURE_P (current_function_decl))
> + ?flags = flags_from_decl_or_type (current_function_decl);
> + ?if ((flags & (ECF_CONST|ECF_PURE)) && !(flags & ECF_LOOPING_CONST_OR_PURE))
> ? ? {
> ? ? ? if (dump_file && (dump_flags & TDF_DETAILS))
> ? ? ? ?fprintf (dump_file, "Found loop %i to be finite: it is within pure or const function.\n",
> --- gcc/tree-ssa-dce.c.jj ? ? ? 2010-07-05 12:37:02.000000000 +0200
> +++ gcc/tree-ssa-dce.c ?2010-08-26 13:59:01.000000000 +0200
> @@ -433,6 +433,7 @@ find_obviously_necessary_stmts (struct e
> ? gimple_stmt_iterator gsi;
> ? edge e;
> ? gimple phi, stmt;
> + ?int flags;
>
> ? FOR_EACH_BB (bb)
> ? ? {
> @@ -454,9 +455,8 @@ find_obviously_necessary_stmts (struct e
>
> ? /* Pure and const functions are finite and thus have no infinite loops in
> ? ? ?them. ?*/
> - ?if ((TREE_READONLY (current_function_decl)
> - ? ? ? || DECL_PURE_P (current_function_decl))
> - ? ? ?&& !DECL_LOOPING_CONST_OR_PURE_P (current_function_decl))
> + ?flags = flags_from_decl_or_type (current_function_decl);
> + ?if ((flags & (ECF_CONST|ECF_PURE)) && !(flags & ECF_LOOPING_CONST_OR_PURE))
> ? ? return;
>
> ? /* Prevent the empty possibly infinite loops from being removed. ?*/
> --- gcc/testsuite/gcc.dg/pr44485.c.jj ? 2010-08-26 13:59:52.000000000 +0200
> +++ gcc/testsuite/gcc.dg/pr44485.c ? ? ?2010-08-26 13:57:32.000000000 +0200
> @@ -0,0 +1,31 @@
> +/* PR tree-optimization/44485 */
> +/* { dg-do compile } */
> +/* { dg-options "-O1 -funsafe-math-optimizations" } */
> +
> +unsigned short b;
> +int bar (unsigned);
> +
> +void
> +baz (void)
> +{
> + ?if (bar (0))
> + ? ?for (b = 0; b < 30; b++)
> + ? ? ?;
> +}
> +
> +int
> +bar (unsigned z)
> +{
> + ?unsigned short c;
> + ?for (; ; z += 1)
> +l1:
> + ? ?if (z)
> + ? ? ?goto l2;
> +l2:
> + ?for (z = 0; z < 9; z++)
> + ? ?if (z)
> + ? ? ?goto l1;
> + ?for (c = 0; c; c = (__UINTPTR_TYPE__) baz)
> + ? ?;
> + ?return 0;
> +}
>
> ? ? ? ?Jakub
>


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