Re: [PATCH] Fix PR3713

[Richard Biener <richard dot guenther at gmail dot com>]

On Wed, Jan 16, 2013 at 4:57 PM, Richard Biener <rguenther@suse.de> wrote:
>
> This fixes PR3713 by properly propagating ->has_constants in SCCVN.
> With that we are able to simplify (unsigned) Bar & 1 properly.
> Only copyprop later turns the call into a direct one though,
> so I'm testing the important fact - that Bar is inlined and eliminated
> by IPA inlining.
>
> Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
>
> Unless this is somehow a regression (which I doubt) this has to
> wait for stage1 (even though it's pretty safe and at most exposes
> existing bugs in SCCVN).

Committed as r196771.

Richard.

> Richard.
>
> 2013-01-16  Richard Biener  <rguenther@suse.de>
>
>         PR tree-optimization/3713
>         * tree-ssa-sccvn.c (visit_copy): Simplify.  Always propagate
>         has_constants and expr.
>         (stmt_has_constants): Properly valueize SSA names when deciding
>         whether the stmt has constants.
>
>         * g++.dg/ipa/devirt-11.C: New testcase.
>
> Index: gcc/tree-ssa-sccvn.c
> ===================================================================
> *** gcc/tree-ssa-sccvn.c        (revision 195240)
> --- gcc/tree-ssa-sccvn.c        (working copy)
> *************** static tree valueize_expr (tree expr);
> *** 2653,2670 ****
>   static bool
>   visit_copy (tree lhs, tree rhs)
>   {
> -   /* Follow chains of copies to their destination.  */
> -   while (TREE_CODE (rhs) == SSA_NAME
> -        && SSA_VAL (rhs) != rhs)
> -     rhs = SSA_VAL (rhs);
> -
>     /* The copy may have a more interesting constant filled expression
>        (we don't, since we know our RHS is just an SSA name).  */
> !   if (TREE_CODE (rhs) == SSA_NAME)
> !     {
> !       VN_INFO (lhs)->has_constants = VN_INFO (rhs)->has_constants;
> !       VN_INFO (lhs)->expr = VN_INFO (rhs)->expr;
> !     }
>
>     return set_ssa_val_to (lhs, rhs);
>   }
> --- 2653,2665 ----
>   static bool
>   visit_copy (tree lhs, tree rhs)
>   {
>     /* The copy may have a more interesting constant filled expression
>        (we don't, since we know our RHS is just an SSA name).  */
> !   VN_INFO (lhs)->has_constants = VN_INFO (rhs)->has_constants;
> !   VN_INFO (lhs)->expr = VN_INFO (rhs)->expr;
> !
> !   /* And finally valueize.  */
> !   rhs = SSA_VAL (rhs);
>
>     return set_ssa_val_to (lhs, rhs);
>   }
> *************** expr_has_constants (tree expr)
> *** 3063,3087 ****
>   static bool
>   stmt_has_constants (gimple stmt)
>   {
>     if (gimple_code (stmt) != GIMPLE_ASSIGN)
>       return false;
>
>     switch (get_gimple_rhs_class (gimple_assign_rhs_code (stmt)))
>       {
> !     case GIMPLE_UNARY_RHS:
> !       return is_gimple_min_invariant (gimple_assign_rhs1 (stmt));
>
>       case GIMPLE_BINARY_RHS:
> !       return (is_gimple_min_invariant (gimple_assign_rhs1 (stmt))
> !             || is_gimple_min_invariant (gimple_assign_rhs2 (stmt)));
> !     case GIMPLE_TERNARY_RHS:
> !       return (is_gimple_min_invariant (gimple_assign_rhs1 (stmt))
> !             || is_gimple_min_invariant (gimple_assign_rhs2 (stmt))
> !             || is_gimple_min_invariant (gimple_assign_rhs3 (stmt)));
>       case GIMPLE_SINGLE_RHS:
>         /* Constants inside reference ops are rarely interesting, but
>          it can take a lot of looking to find them.  */
> !       return is_gimple_min_invariant (gimple_assign_rhs1 (stmt));
>       default:
>         gcc_unreachable ();
>       }
> --- 3058,3095 ----
>   static bool
>   stmt_has_constants (gimple stmt)
>   {
> +   tree tem;
> +
>     if (gimple_code (stmt) != GIMPLE_ASSIGN)
>       return false;
>
>     switch (get_gimple_rhs_class (gimple_assign_rhs_code (stmt)))
>       {
> !     case GIMPLE_TERNARY_RHS:
> !       tem = gimple_assign_rhs3 (stmt);
> !       if (TREE_CODE (tem) == SSA_NAME)
> !       tem = SSA_VAL (tem);
> !       if (is_gimple_min_invariant (tem))
> !       return true;
> !       /* Fallthru.  */
>
>       case GIMPLE_BINARY_RHS:
> !       tem = gimple_assign_rhs2 (stmt);
> !       if (TREE_CODE (tem) == SSA_NAME)
> !       tem = SSA_VAL (tem);
> !       if (is_gimple_min_invariant (tem))
> !       return true;
> !       /* Fallthru.  */
> !
>       case GIMPLE_SINGLE_RHS:
>         /* Constants inside reference ops are rarely interesting, but
>          it can take a lot of looking to find them.  */
> !     case GIMPLE_UNARY_RHS:
> !       tem = gimple_assign_rhs1 (stmt);
> !       if (TREE_CODE (tem) == SSA_NAME)
> !       tem = SSA_VAL (tem);
> !       return is_gimple_min_invariant (tem);
> !
>       default:
>         gcc_unreachable ();
>       }
> Index: gcc/testsuite/g++.dg/ipa/devirt-11.C
> ===================================================================
> *** gcc/testsuite/g++.dg/ipa/devirt-11.C        (revision 0)
> --- gcc/testsuite/g++.dg/ipa/devirt-11.C        (working copy)
> ***************
> *** 0 ****
> --- 1,22 ----
> + // { dg-do compile }
> + // { dg-options "-std=c++11 -O -fdump-ipa-inline" }
> +
> + class Foo
> + {
> + public:
> +   void Bar() const
> +     {
> +       __builtin_puts ("Howdy!");
> +     }
> + };
> +
> + int main()
> + {
> +   Foo x;
> +   auto y = &Foo::Bar;
> +   (x.*y)();
> +   return 0;
> + }
> +
> + // { dg-final { scan-ipa-dump "Inlined 1 calls, eliminated 1 functions" "inline" } }
> + // { dg-final { cleanup-ipa-dump "inline" } }