From be2c74fdcd0e8d66c3667008ba2561ab5dcc379b Mon Sep 17 00:00:00 2001 From: Richard Biener Date: Thu, 10 Nov 2022 15:04:10 +0100 Subject: [PATCH] Make last DCE remove empty loops The following makes the last DCE pass CD-DCE and in turn the last CD-DCE pass a DCE one. That ensues we remove empty loops that become empty between the two. I've also moved the tail-call pass after DCE since DCE can only improve things here. The two testcases were the only ones scanning cddce3 so I've changed them to scan the dce7 pass that's now in this place. The testcases scanning dce7 also work when that's in the earlier position. PR tree-optimization/84646 * tree-ssa-dce.cc (pass_dce::set_pass_param): Add param wheter to run update-address-taken. (pass_dce::execute): Honor it. * passes.def: Exchange last DCE and CD-DCE invocations. Swap pass_tail_calls and the last DCE. * g++.dg/tree-ssa/pr106922.C: Continue to scan earlier DCE dump. * gcc.dg/tree-ssa/20030808-1.c: Likewise. --- gcc/passes.def | 8 ++++---- gcc/testsuite/g++.dg/tree-ssa/pr106922.C | 4 ++-- gcc/testsuite/gcc.dg/tree-ssa/20030808-1.c | 6 +++--- gcc/tree-ssa-dce.cc | 15 +++++++++++++-- 4 files changed, 22 insertions(+), 11 deletions(-) diff --git a/gcc/passes.def b/gcc/passes.def index 193b579..462e9af 100644 --- a/gcc/passes.def +++ b/gcc/passes.def @@ -346,8 +346,8 @@ along with GCC; see the file COPYING3. If not see NEXT_PASS (pass_ccp, true /* nonzero_p */); NEXT_PASS (pass_warn_restrict); NEXT_PASS (pass_dse); - NEXT_PASS (pass_cd_dce, true /* update_address_taken_p */); - /* After late CD DCE we rewrite no longer addressed locals into SSA + NEXT_PASS (pass_dce, true /* update_address_taken_p */); + /* After late DCE we rewrite no longer addressed locals into SSA form if possible. */ NEXT_PASS (pass_forwprop); NEXT_PASS (pass_sink_code, true /* unsplit edges */); @@ -355,12 +355,12 @@ along with GCC; see the file COPYING3. If not see NEXT_PASS (pass_fold_builtins); NEXT_PASS (pass_optimize_widening_mul); NEXT_PASS (pass_store_merging); - NEXT_PASS (pass_tail_calls); /* If DCE is not run before checking for uninitialized uses, we may get false warnings (e.g., testsuite/gcc.dg/uninit-5.c). However, this also causes us to misdiagnose cases that should be real warnings (e.g., testsuite/gcc.dg/pr18501.c). */ - NEXT_PASS (pass_dce); + NEXT_PASS (pass_cd_dce, false /* update_address_taken_p */); + NEXT_PASS (pass_tail_calls); /* Split critical edges before late uninit warning to reduce the number of false positives from it. */ NEXT_PASS (pass_split_crit_edges); diff --git a/gcc/testsuite/g++.dg/tree-ssa/pr106922.C b/gcc/testsuite/g++.dg/tree-ssa/pr106922.C index 2aec497..4b6a4ad 100644 --- a/gcc/testsuite/g++.dg/tree-ssa/pr106922.C +++ b/gcc/testsuite/g++.dg/tree-ssa/pr106922.C @@ -1,5 +1,5 @@ // { dg-require-effective-target c++20 } -// { dg-options "-O2 -fdump-tree-cddce3" } +// { dg-options "-O2 -fdump-tree-dce7" } template struct __new_allocator { void deallocate(int *, int) { operator delete(0); } @@ -87,4 +87,4 @@ void testfunctionfoo() { } } -// { dg-final { scan-tree-dump-not "m_initialized" "cddce3" } } +// { dg-final { scan-tree-dump-not "m_initialized" "dce7" } } diff --git a/gcc/testsuite/gcc.dg/tree-ssa/20030808-1.c b/gcc/testsuite/gcc.dg/tree-ssa/20030808-1.c index 456f6f2..7d4a138 100644 --- a/gcc/testsuite/gcc.dg/tree-ssa/20030808-1.c +++ b/gcc/testsuite/gcc.dg/tree-ssa/20030808-1.c @@ -1,5 +1,5 @@ /* { dg-do compile } */ -/* { dg-options "-O1 -fdump-tree-cddce3" } */ +/* { dg-options "-O1 -fdump-tree-dce7" } */ extern void abort (void); @@ -33,8 +33,8 @@ delete_dead_jumptables () /* There should be no loads of ->code. If any exist, then we failed to optimize away all the IF statements and the statements feeding their conditions. */ -/* { dg-final { scan-tree-dump-times "->code" 0 "cddce3"} } */ +/* { dg-final { scan-tree-dump-times "->code" 0 "dce7"} } */ /* There should be no IF statements. */ -/* { dg-final { scan-tree-dump-times "if " 0 "cddce3"} } */ +/* { dg-final { scan-tree-dump-times "if " 0 "dce7"} } */ diff --git a/gcc/tree-ssa-dce.cc b/gcc/tree-ssa-dce.cc index 54e5d8c..187d58b 100644 --- a/gcc/tree-ssa-dce.cc +++ b/gcc/tree-ssa-dce.cc @@ -2005,14 +2005,25 @@ class pass_dce : public gimple_opt_pass { public: pass_dce (gcc::context *ctxt) - : gimple_opt_pass (pass_data_dce, ctxt) + : gimple_opt_pass (pass_data_dce, ctxt), update_address_taken_p (false) {} /* opt_pass methods: */ opt_pass * clone () final override { return new pass_dce (m_ctxt); } + void set_pass_param (unsigned n, bool param) final override + { + gcc_assert (n == 0); + update_address_taken_p = param; + } bool gate (function *) final override { return flag_tree_dce != 0; } - unsigned int execute (function *) final override { return tree_ssa_dce (); } + unsigned int execute (function *) final override + { + return (tree_ssa_dce () + | (update_address_taken_p ? TODO_update_address_taken : 0)); + } +private: + bool update_address_taken_p; }; // class pass_dce } // anon namespace -- 2.7.4