On Thu, 12 Mar 2020, Jakub Jelinek wrote:
> Hi!
>
> As the testcase shows, if DSE decides to head trim {mem{set,cpy,move},strncpy}
> and the call has lhs, it is incorrect to leave the lhs as is, because it
> will then point to the adjusted address (base + head_trim) instead of the
> original base.
> The following patch fixes that by dropping the lhs of the call and assigning
> lhs the original base in a following statement.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK, but I don't see where you need anything additional frmo gimplify.h?
Thanks,
Richard.
> 2020-03-12 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/94130
> * tree-ssa-dse.c: Include gimplify.h.
> (increment_start_addr): If stmt has lhs, drop the lhs from call and
> set it after the call to the original value of the first argument.
> Formatting fixes.
> (decrement_count): Formatting fix.
>
> * gcc.c-torture/execute/pr94130.c: New test.
>
> --- gcc/tree-ssa-dse.c.jj 2020-03-03 11:04:46.367821907 +0100
> +++ gcc/tree-ssa-dse.c 2020-03-11 13:57:38.671845186 +0100
> @@ -38,6 +38,7 @@ along with GCC; see the file COPYING3.
> #include "tree-ssa-dse.h"
> #include "builtins.h"
> #include "gimple-fold.h"
> +#include "gimplify.h"
>
> /* This file implements dead store elimination.
>
> @@ -422,29 +423,38 @@ decrement_count (gimple *stmt, int decre
> gcc_assert (TREE_CODE (*countp) == INTEGER_CST);
> *countp = wide_int_to_tree (TREE_TYPE (*countp), (TREE_INT_CST_LOW
> (*countp)
> - decrement));
> -
> }
>
> static void
> increment_start_addr (gimple *stmt, tree *where, int increment)
> {
> + if (tree lhs = gimple_call_lhs (stmt))
> + if (where == gimple_call_arg_ptr (stmt, 0))
> + {
> + gassign *newop = gimple_build_assign (lhs, unshare_expr (*where));
> + gimple_stmt_iterator gsi = gsi_for_stmt (stmt);
> + gsi_insert_after (&gsi, newop, GSI_SAME_STMT);
> + gimple_call_set_lhs (stmt, NULL_TREE);
> + update_stmt (stmt);
> + }
> +
> if (TREE_CODE (*where) == SSA_NAME)
> {
> tree tem = make_ssa_name (TREE_TYPE (*where));
> gassign *newop
> - = gimple_build_assign (tem, POINTER_PLUS_EXPR, *where,
> + = gimple_build_assign (tem, POINTER_PLUS_EXPR, *where,
> build_int_cst (sizetype, increment));
> gimple_stmt_iterator gsi = gsi_for_stmt (stmt);
> gsi_insert_before (&gsi, newop, GSI_SAME_STMT);
> *where = tem;
> - update_stmt (gsi_stmt (gsi));
> + update_stmt (stmt);
> return;
> }
>
> *where = build_fold_addr_expr (fold_build2 (MEM_REF, char_type_node,
> - *where,
> - build_int_cst (ptr_type_node,
> - increment)));
> + *where,
> + build_int_cst (ptr_type_node,
> + increment)));
> }
>
> /* STMT is builtin call that writes bytes in bitmap ORIG, some bytes are dead
> --- gcc/testsuite/gcc.c-torture/execute/pr94130.c.jj 2020-03-11
> 14:01:49.431180291 +0100
> +++ gcc/testsuite/gcc.c-torture/execute/pr94130.c 2020-03-11
> 14:01:37.654352419 +0100
> @@ -0,0 +1,16 @@
> +/* PR tree-optimization/94130 */
> +
> +int
> +main ()
> +{
> + int a[8];
> + char *b = __builtin_memset (a, 0, sizeof (a));
> + a[0] = 1;
> + a[1] = 2;
> + a[2] = 3;
> + if (b != (char *) a)
> + __builtin_abort ();
> + else
> + asm volatile ("" : : "g" (a) : "memory");
> + return 0;
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
