From: Richard Biener Date: Tue, 15 May 2018 11:30:29 +0000 (+0000) Subject: tree-ssa-dse.c (dse_classify_store): Remove use_stmt parameter, add by_clobber_p... X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=afe3cc7388efa78fe9a5bd914e0a83b20ea6ab9e;p=gcc.git tree-ssa-dse.c (dse_classify_store): Remove use_stmt parameter, add by_clobber_p one. 2018-05-15 Richard Biener * tree-ssa-dse.c (dse_classify_store): Remove use_stmt parameter, add by_clobber_p one. Change algorithm to collect all defs representing uses we need to walk and try reducing them to a single one before failing. (dse_dom_walker::dse_optimize_stmt): Adjust. * gcc.dg/tree-ssa/ssa-dse-31.c: New testcase. From-SVN: r260253 --- diff --git a/gcc/ChangeLog b/gcc/ChangeLog index f5da0ebc740..ecb524195ba 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,11 @@ +2018-05-15 Richard Biener + + * tree-ssa-dse.c (dse_classify_store): Remove use_stmt parameter, + add by_clobber_p one. Change algorithm to collect all defs + representing uses we need to walk and try reducing them to + a single one before failing. + (dse_dom_walker::dse_optimize_stmt): Adjust. + 2018-05-13 Mark Wielaard * dwarf2out.c (dwarf_OP): Handle DW_OP_addrx and DW_OP_constx. diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 90839ae9428..fe012a4d87e 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,7 @@ +2018-05-15 Richard Biener + + * gcc.dg/tree-ssa/ssa-dse-31.c: New testcase. + 2018-05-15 Prathamesh Kulkarni PR tree-optimization/83648 diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-31.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-31.c new file mode 100644 index 00000000000..9ea9268fe1d --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-31.c @@ -0,0 +1,16 @@ +/* { dg-do compile } */ +/* { dg-options "-O -fdump-tree-dse1-details" } */ + +void g(); +void f(int n, char *p) +{ + *p = 0; + if (n) + { + *p = 1; + g(); + } + *p = 2; +} + +/* { dg-final { scan-tree-dump-times "Deleted dead store" 1 "dse1" } } */ diff --git a/gcc/tree-ssa-dse.c b/gcc/tree-ssa-dse.c index 9220fea7f2e..126592a1d13 100644 --- a/gcc/tree-ssa-dse.c +++ b/gcc/tree-ssa-dse.c @@ -516,18 +516,21 @@ live_bytes_read (ao_ref use_ref, ao_ref *ref, sbitmap live) } /* A helper of dse_optimize_stmt. - Given a GIMPLE_ASSIGN in STMT that writes to REF, find a candidate - statement *USE_STMT that may prove STMT to be dead. - Return TRUE if the above conditions are met, otherwise FALSE. */ + Given a GIMPLE_ASSIGN in STMT that writes to REF, classify it + according to downstream uses and defs. Sets *BY_CLOBBER_P to true + if only clobber statements influenced the classification result. + Returns the classification. */ static dse_store_status -dse_classify_store (ao_ref *ref, gimple *stmt, gimple **use_stmt, - bool byte_tracking_enabled, sbitmap live_bytes) +dse_classify_store (ao_ref *ref, gimple *stmt, + bool byte_tracking_enabled, sbitmap live_bytes, + bool *by_clobber_p = NULL) { gimple *temp; unsigned cnt = 0; - *use_stmt = NULL; + if (by_clobber_p) + *by_clobber_p = true; /* Find the first dominated statement that clobbers (part of) the memory stmt stores to with no intermediate statement that may use @@ -551,7 +554,7 @@ dse_classify_store (ao_ref *ref, gimple *stmt, gimple **use_stmt, else defvar = gimple_vdef (temp); defvar_def = temp; - temp = NULL; + auto_vec defs; FOR_EACH_IMM_USE_STMT (use_stmt, ui, defvar) { cnt++; @@ -569,9 +572,8 @@ dse_classify_store (ao_ref *ref, gimple *stmt, gimple **use_stmt, See gcc.c-torture/execute/20051110-*.c. */ else if (gimple_code (use_stmt) == GIMPLE_PHI) { - if (temp - /* Make sure we are not in a loop latch block. */ - || gimple_bb (stmt) == gimple_bb (use_stmt) + /* Make sure we are not in a loop latch block. */ + if (gimple_bb (stmt) == gimple_bb (use_stmt) || dominated_by_p (CDI_DOMINATORS, gimple_bb (stmt), gimple_bb (use_stmt)) /* We can look through PHIs to regions post-dominating @@ -589,7 +591,7 @@ dse_classify_store (ao_ref *ref, gimple *stmt, gimple **use_stmt, && !dominated_by_p (CDI_DOMINATORS, gimple_bb (defvar_def), gimple_bb (use_stmt))) - temp = use_stmt; + defs.safe_push (use_stmt); } /* If the statement is a use the store is not dead. */ else if (ref_maybe_used_by_stmt_p (use_stmt, ref)) @@ -597,7 +599,8 @@ dse_classify_store (ao_ref *ref, gimple *stmt, gimple **use_stmt, /* Handle common cases where we can easily build an ao_ref structure for USE_STMT and in doing so we find that the references hit non-live bytes and thus can be ignored. */ - if (byte_tracking_enabled && (!gimple_vdef (use_stmt) || !temp)) + if (byte_tracking_enabled + && (!gimple_vdef (use_stmt) || defs.is_empty ())) { if (is_gimple_assign (use_stmt)) { @@ -613,7 +616,7 @@ dse_classify_store (ao_ref *ref, gimple *stmt, gimple **use_stmt, /* If this statement has a VDEF, then it is the first store we have seen, so walk through it. */ if (gimple_vdef (use_stmt)) - temp = use_stmt; + defs.safe_push (use_stmt); continue; } } @@ -622,17 +625,10 @@ dse_classify_store (ao_ref *ref, gimple *stmt, gimple **use_stmt, fail = true; BREAK_FROM_IMM_USE_STMT (ui); } - /* If this is a store, remember it or bail out if we have - multiple ones (the will be in different CFG parts then). */ + /* If this is a store, remember it as we possibly need to walk the + defs uses. */ else if (gimple_vdef (use_stmt)) - { - if (temp) - { - fail = true; - BREAK_FROM_IMM_USE_STMT (ui); - } - temp = use_stmt; - } + defs.safe_push (use_stmt); } if (fail) @@ -647,25 +643,54 @@ dse_classify_store (ao_ref *ref, gimple *stmt, gimple **use_stmt, /* If we didn't find any definition this means the store is dead if it isn't a store to global reachable memory. In this case just pretend the stmt makes itself dead. Otherwise fail. */ - if (!temp) + if (defs.is_empty ()) { if (ref_may_alias_global_p (ref)) return DSE_STORE_LIVE; - temp = stmt; - break; + if (by_clobber_p) + *by_clobber_p = false; + return DSE_STORE_DEAD; } - if (byte_tracking_enabled && temp) - clear_bytes_written_by (live_bytes, temp, ref); - } - /* Continue walking until we reach a full kill as a single statement - or there are no more live bytes. */ - while (!stmt_kills_ref_p (temp, ref) - && !(byte_tracking_enabled && bitmap_empty_p (live_bytes))); + /* Process defs and remove paths starting with a kill from further + processing. */ + for (unsigned i = 0; i < defs.length (); ++i) + if (stmt_kills_ref_p (defs[i], ref)) + { + if (by_clobber_p && !gimple_clobber_p (defs[i])) + *by_clobber_p = false; + defs.unordered_remove (i); + } + + /* If all defs kill the ref we are done. */ + if (defs.is_empty ()) + return DSE_STORE_DEAD; + /* If more than one def survives fail. */ + if (defs.length () > 1) + { + /* STMT might be partially dead and we may be able to reduce + how many memory locations it stores into. */ + if (byte_tracking_enabled && !gimple_clobber_p (stmt)) + return DSE_STORE_MAYBE_PARTIAL_DEAD; + return DSE_STORE_LIVE; + } + temp = defs[0]; - *use_stmt = temp; - return DSE_STORE_DEAD; + /* Track partial kills. */ + if (byte_tracking_enabled) + { + clear_bytes_written_by (live_bytes, temp, ref); + if (bitmap_empty_p (live_bytes)) + { + if (by_clobber_p && !gimple_clobber_p (temp)) + *by_clobber_p = false; + return DSE_STORE_DEAD; + } + } + } + /* Continue walking until there are no more live bytes. */ + while (1); } @@ -795,11 +820,10 @@ dse_dom_walker::dse_optimize_stmt (gimple_stmt_iterator *gsi) return; } - gimple *use_stmt; enum dse_store_status store_status; m_byte_tracking_enabled = setup_live_bytes_from_ref (&ref, m_live_bytes); - store_status = dse_classify_store (&ref, stmt, &use_stmt, + store_status = dse_classify_store (&ref, stmt, m_byte_tracking_enabled, m_live_bytes); if (store_status == DSE_STORE_LIVE) @@ -823,20 +847,20 @@ dse_dom_walker::dse_optimize_stmt (gimple_stmt_iterator *gsi) if (is_gimple_assign (stmt)) { - gimple *use_stmt; + bool by_clobber_p = false; /* Self-assignments are zombies. */ if (operand_equal_p (gimple_assign_rhs1 (stmt), gimple_assign_lhs (stmt), 0)) - use_stmt = stmt; + ; else { m_byte_tracking_enabled = setup_live_bytes_from_ref (&ref, m_live_bytes); enum dse_store_status store_status; - store_status = dse_classify_store (&ref, stmt, &use_stmt, + store_status = dse_classify_store (&ref, stmt, m_byte_tracking_enabled, - m_live_bytes); + m_live_bytes, &by_clobber_p); if (store_status == DSE_STORE_LIVE) return; @@ -852,7 +876,7 @@ dse_dom_walker::dse_optimize_stmt (gimple_stmt_iterator *gsi) /* But only remove *this_2(D) ={v} {CLOBBER} if killed by another clobber stmt. */ if (gimple_clobber_p (stmt) - && !gimple_clobber_p (use_stmt)) + && !by_clobber_p) return; delete_dead_assignment (gsi);