On Wed, Dec 28, 2011 at 8:04 PM, Jakub Jelinek <ja...@redhat.com> wrote:
> Hi!
>
> For some calls (like memcpy and other builtins that are known to pass
> through the first argument) we know the value of the lhs, but still
> we shouldn't be replacing the call with just a mere assignment of that
> known value to the LHS SSA_NAME, because the call has other side-effects.
> Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux,
> ok for trunk?
Ok.
Thanks,
Richard.
> 2011-12-28 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/51683
> * tree-ssa-propagate.c (substitute_and_fold): Don't optimize away
> calls with side-effects.
> * tree-ssa-ccp.c (ccp_fold_stmt): Likewise.
>
> * gcc.dg/pr51683.c: New test.
>
> --- gcc/tree-ssa-propagate.c.jj 2011-11-11 20:54:59.000000000 +0100
> +++ gcc/tree-ssa-propagate.c 2011-12-27 12:23:41.334187258 +0100
> @@ -1056,6 +1056,12 @@ substitute_and_fold (ssa_prop_get_value_
> }
> else if (is_gimple_call (def_stmt))
> {
> + int flags = gimple_call_flags (def_stmt);
> +
> + /* Don't optimize away calls that have side-effects. */
> + if ((flags & (ECF_CONST|ECF_PURE)) == 0
> + || (flags & ECF_LOOPING_CONST_OR_PURE))
> + continue;
> if (update_call_from_tree (&gsi, val)
> && maybe_clean_or_replace_eh_stmt (def_stmt, gsi_stmt (gsi)))
> gimple_purge_dead_eh_edges (gimple_bb (gsi_stmt (gsi)));
> --- gcc/tree-ssa-ccp.c.jj 2011-12-19 09:21:07.000000000 +0100
> +++ gcc/tree-ssa-ccp.c 2011-12-27 12:29:48.620880857 +0100
> @@ -1878,6 +1878,7 @@ ccp_fold_stmt (gimple_stmt_iterator *gsi
> case GIMPLE_CALL:
> {
> tree lhs = gimple_call_lhs (stmt);
> + int flags = gimple_call_flags (stmt);
> tree val;
> tree argt;
> bool changed = false;
> @@ -1888,7 +1889,10 @@ ccp_fold_stmt (gimple_stmt_iterator *gsi
> type issues. */
> if (lhs
> && TREE_CODE (lhs) == SSA_NAME
> - && (val = get_constant_value (lhs)))
> + && (val = get_constant_value (lhs))
> + /* Don't optimize away calls that have side-effects. */
> + && (flags & (ECF_CONST|ECF_PURE)) != 0
> + && (flags & ECF_LOOPING_CONST_OR_PURE) == 0)
> {
> tree new_rhs = unshare_expr (val);
> bool res;
> --- gcc/testsuite/gcc.dg/pr51683.c.jj 2011-12-27 12:21:43.662925435 +0100
> +++ gcc/testsuite/gcc.dg/pr51683.c 2011-12-27 12:21:23.000000000 +0100
> @@ -0,0 +1,18 @@
> +/* PR tree-optimization/51683 */
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-optimized" } */
> +
> +static inline void *
> +bar (void *p, void *q, int r)
> +{
> + return __builtin_memcpy (p, q, r);
> +}
> +
> +void *
> +foo (void *p)
> +{
> + return bar ((void *) 0x12345000, p, 256);
> +}
> +
> +/* { dg-final { scan-tree-dump "memcpy" "optimized" } } */
> +/* { dg-final { cleanup-tree-dump "optimized" } } */
>
> Jakub
