From d822f3d585da1f9be6ab62245073625385a0e34f Mon Sep 17 00:00:00 2001 From: Bin Cheng Date: Thu, 23 Feb 2017 22:02:01 +0000 Subject: [PATCH] re PR tree-optimization/79663 (r244815 causes 10% regression for spec1k/172.mgrid on AArch64) 2017-01-21 Bin Cheng PR tree-optimization/79663 * tree-predcom.c (combine_chains): Process refs in reverse order only for ZERO length chains, and add explaining comment. From-SVN: r245689 --- gcc/ChangeLog | 6 ++++++ gcc/tree-predcom.c | 53 +++++++++++++++++++++++++--------------------- 2 files changed, 35 insertions(+), 24 deletions(-) diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 37ae06af4f3..906607f4123 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2017-02-23 Bin Cheng + + PR tree-optimization/79663 + * tree-predcom.c (combine_chains): Process refs in reverse order + only for ZERO length chains, and add explaining comment. + 2017-02-23 Jeff Law PR tree-optimization/79578 diff --git a/gcc/tree-predcom.c b/gcc/tree-predcom.c index 9723e9c4066..57d8f7d207c 100644 --- a/gcc/tree-predcom.c +++ b/gcc/tree-predcom.c @@ -2283,7 +2283,7 @@ combine_chains (chain_p ch1, chain_p ch2) enum tree_code op = ERROR_MARK; bool swap = false; chain_p new_chain; - unsigned i; + int i, j, num; gimple *root_stmt; tree rslt_type = NULL_TREE; @@ -2305,6 +2305,9 @@ combine_chains (chain_p ch1, chain_p ch2) return NULL; } + ch1->combined = true; + ch2->combined = true; + if (swap) std::swap (ch1, ch2); @@ -2317,39 +2320,41 @@ combine_chains (chain_p ch1, chain_p ch2) new_chain->length = ch1->length; gimple *insert = NULL; - auto_vec tmp_refs; - gcc_assert (ch1->refs.length () == ch2->refs.length ()); - /* Process in reverse order so dominance point is ready when it comes - to the root ref. */ - for (i = ch1->refs.length (); i > 0; i--) + num = ch1->refs.length (); + i = (new_chain->length == 0) ? num - 1 : 0; + j = (new_chain->length == 0) ? -1 : 1; + /* For ZERO length chain, process refs in reverse order so that dominant + position is ready when it comes to the root ref. + For non-ZERO length chain, process refs in order. See PR79663. */ + for (; num > 0; num--, i += j) { - r1 = ch1->refs[i - 1]; - r2 = ch2->refs[i - 1]; + r1 = ch1->refs[i]; + r2 = ch2->refs[i]; nw = XCNEW (struct dref_d); nw->distance = r1->distance; - nw->stmt = stmt_combining_refs (r1, r2, i == 1 ? insert : NULL); - /* Record dominance point where root combined stmt should be inserted - for chains with 0 length. Though all root refs dominate following - refs, it's possible the combined stmt doesn't. See PR70754. */ - if (ch1->length == 0 + /* For ZERO length chain, insert combined stmt of root ref at dominant + position. */ + nw->stmt = stmt_combining_refs (r1, r2, i == 0 ? insert : NULL); + /* For ZERO length chain, record dominant position where combined stmt + of root ref should be inserted. In this case, though all root refs + dominate following ones, it's possible that combined stmt doesn't. + See PR70754. */ + if (new_chain->length == 0 && (insert == NULL || stmt_dominates_stmt_p (nw->stmt, insert))) insert = nw->stmt; - tmp_refs.safe_push (nw); + new_chain->refs.safe_push (nw); } - - /* Restore the order for new chain's refs. */ - for (i = tmp_refs.length (); i > 0; i--) - new_chain->refs.safe_push (tmp_refs[i - 1]); - - ch1->combined = true; - ch2->combined = true; - - /* For chains with 0 length, has_max_use_after must be true since root - combined stmt must dominates others. */ if (new_chain->length == 0) { + /* Restore the order for ZERO length chain's refs. */ + num = new_chain->refs.length () >> 1; + for (i = 0, j = new_chain->refs.length () - 1; i < num; i++, j--) + std::swap (new_chain->refs[i], new_chain->refs[j]); + + /* For ZERO length chain, has_max_use_after must be true since root + combined stmt must dominates others. */ new_chain->has_max_use_after = true; return new_chain; }