This fixes the case where we only late during insertion are able to
simplify an expression (when we re-instantiated range-info on all
SSA names). We can't do anything here but give up since we'd end up
with a SSA name with two values which for sure will eventually end up
confusing elimination.
Hopefully for GCC 8 I can fix all this by re-writing SCCVN to RPO style
iteration.
Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
Richard.
2017-03-02 Richard Biener <rguent...@suse.de>
PR tree-optimization/79777
* tree-ssa-pre.c (eliminate_insert): Give up if we simplify
the to insert expression to sth existing.
* gcc.dg/torture/pr79777.c: New testcase.
Index: gcc/tree-ssa-pre.c
===================================================================
*** gcc/tree-ssa-pre.c (revision 245803)
--- gcc/tree-ssa-pre.c (working copy)
*************** eliminate_insert (gimple_stmt_iterator *
*** 4133,4143 ****
else
res = gimple_build (&stmts, gimple_assign_rhs_code (stmt),
TREE_TYPE (val), leader);
! gsi_insert_seq_before (gsi, stmts, GSI_SAME_STMT);
! VN_INFO_GET (res)->valnum = val;
! if (TREE_CODE (leader) == SSA_NAME)
! gimple_set_plf (SSA_NAME_DEF_STMT (leader), NECESSARY, true);
pre_stats.insertions++;
if (dump_file && (dump_flags & TDF_DETAILS))
--- 4133,4174 ----
else
res = gimple_build (&stmts, gimple_assign_rhs_code (stmt),
TREE_TYPE (val), leader);
! if (TREE_CODE (res) != SSA_NAME
! || SSA_NAME_IS_DEFAULT_DEF (res)
! || gimple_bb (SSA_NAME_DEF_STMT (res)))
! {
! gimple_seq_discard (stmts);
! /* During propagation we have to treat SSA info conservatively
! and thus we can end up simplifying the inserted expression
! at elimination time to sth not defined in stmts. */
! /* But then this is a redundancy we failed to detect. Which means
! res now has two values. That doesn't play well with how
! we track availability here, so give up. */
! if (dump_file && (dump_flags & TDF_DETAILS))
! {
! if (TREE_CODE (res) == SSA_NAME)
! res = eliminate_avail (res);
! if (res)
! {
! fprintf (dump_file, "Failed to insert expression for value ");
! print_generic_expr (dump_file, val, 0);
! fprintf (dump_file, " which is really fully redundant to ");
! print_generic_expr (dump_file, res, 0);
! fprintf (dump_file, "\n");
! }
! }
!
! return NULL_TREE;
! }
! else
! {
! gsi_insert_seq_before (gsi, stmts, GSI_SAME_STMT);
! VN_INFO_GET (res)->valnum = val;
!
! if (TREE_CODE (leader) == SSA_NAME)
! gimple_set_plf (SSA_NAME_DEF_STMT (leader), NECESSARY, true);
! }
pre_stats.insertions++;
if (dump_file && (dump_flags & TDF_DETAILS))
Index: gcc/testsuite/gcc.dg/torture/pr79777.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr79777.c (nonexistent)
--- gcc/testsuite/gcc.dg/torture/pr79777.c (working copy)
***************
*** 0 ****
--- 1,38 ----
+ /* { dg-do compile } */
+
+ typedef unsigned short __u16;
+ typedef unsigned int __u32;
+ typedef unsigned char u8;
+ typedef unsigned int u32;
+ typedef __u16 __le16;
+ typedef __u32 __le32;
+ typedef u32 secno;
+ struct bplus_internal_node {
+ __le32 file_secno;
+ __le32 down;
+ };
+ struct bplus_header {
+ u8 n_used_nodes;
+ __le16 first_free;
+ union {
+ struct bplus_internal_node internal[0];
+ }
+ u;
+ };
+
+ __u16 __fswab16(__u16 val);
+ __u32 __fswab32(__u32 val);
+ void hpfs_ea_remove (__u32);
+
+ void hpfs_truncate_btree(secno f, int fno, unsigned secs, struct bplus_header
*btree)
+ {
+ int i, j;
+ for (i = 0; i < btree->n_used_nodes; i++)
+ if ((__builtin_constant_p((__u32)((
__u32)(__le32)(btree->u.internal[i].file_secno))) ? ((__u32)( (((__u32)((
__u32)(__le32)(btree->u.internal[i].file_secno)) & (__u32)0x000000ffUL) << 24)
| (((__u32)(( __u32)(__le32)(btree->u.internal[i].file_secno)) &
(__u32)0x0000ff00UL) << 8) | (((__u32)((
__u32)(__le32)(btree->u.internal[i].file_secno)) & (__u32)0x00ff0000UL) >> 8) |
(((__u32)(( __u32)(__le32)(btree->u.internal[i].file_secno)) &
(__u32)0xff000000UL) >> 24))) : __fswab32((
__u32)(__le32)(btree->u.internal[i].file_secno))) >= secs) goto f;
+ return;
+ f:
+ for (j = i + 1; j < btree->n_used_nodes; j++)
+ hpfs_ea_remove((__builtin_constant_p((__u32)((
__u32)(__le32)(btree->u.internal[j].down))) ? ((__u32)( (((__u32)((
__u32)(__le32)(btree->u.internal[j].down)) & (__u32)0x000000ffUL) << 24) |
(((__u32)(( __u32)(__le32)(btree->u.internal[j].down)) & (__u32)0x0000ff00UL)
<< 8) | (((__u32)(( __u32)(__le32)(btree->u.internal[j].down)) &
(__u32)0x00ff0000UL) >> 8) | (((__u32)((
__u32)(__le32)(btree->u.internal[j].down)) & (__u32)0xff000000UL) >> 24))) :
__fswab32(( __u32)(__le32)(btree->u.internal[j].down))));
+ btree->n_used_nodes = i + 1;
+ btree->first_free = (( __le16)(__builtin_constant_p((__u16)((8 + 8 *
btree->n_used_nodes))) ? ((__u16)( (((__u16)((8 + 8 * btree->n_used_nodes)) &
(__u16)0x00ffU) << 8) | (((__u16)((8 + 8 * btree->n_used_nodes)) &
(__u16)0xff00U) >> 8))) : __fswab16((8 + 8 * btree->n_used_nodes))));
+ }
