From: Jeff Law Date: Tue, 1 Mar 2016 21:46:58 +0000 (-0700) Subject: re PR tree-optimization/69196 (code size regression with jump threading at -O2) X-Git-Tag: basepoints/gcc-7~657 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2a9afc868088221a4edd54e79d1388ab25f7f2fa;p=thirdparty%2Fgcc.git re PR tree-optimization/69196 (code size regression with jump threading at -O2) PR tree-optimization/69196 * tree-ssa-threadbackward.c (fsm_find_control_statement_thread_paths): Do count some PHIs in the thread path against the insn count. Decrease final statement count by one as the control statement in the last block will get removed. Remove special cased code for handling PHIs in the last block. PR tree-optimization/69196 * gcc.dg/tree-ssa/vrp46.c: Twiddle threading params to keep it from duplicating code and spoiling the expected output. From-SVN: r233866 --- diff --git a/gcc/ChangeLog b/gcc/ChangeLog index b758d4265600..c1f25572590e 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,11 @@ +2016-03-01 Jeff Law + + PR tree-optimization/69196 + * tree-ssa-threadbackward.c (fsm_find_control_statement_thread_paths): + Do count some PHIs in the thread path against the insn count. Decrease + final statement count by one as the control statement in the last + block will get removed. Remove special cased code for handling PHIs in the last block. + 2016-03-01 Uros Bizjak PR target/70027 diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 000ece8b63fa..ef8a9875d402 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,9 @@ +2016-03-01 Jeff Law + + PR tree-optimization/69196 + * gcc.dg/tree-ssa/vrp46.c: Twiddle threading params to keep it from + duplicating code and spoiling the expected output. + 2016-03-01 Michael Meissner PR target/70033 diff --git a/gcc/testsuite/gcc.dg/tree-ssa/vrp46.c b/gcc/testsuite/gcc.dg/tree-ssa/vrp46.c index 8923eb404d3d..d3c9ed144f38 100644 --- a/gcc/testsuite/gcc.dg/tree-ssa/vrp46.c +++ b/gcc/testsuite/gcc.dg/tree-ssa/vrp46.c @@ -1,5 +1,5 @@ /* { dg-do compile } */ -/* { dg-options "-O2 -fdump-tree-vrp1" } */ +/* { dg-options "-O2 -fdump-tree-vrp1 --param fsm-scale-path-blocks=1" } */ int func_81 (int); int func_98 (int); diff --git a/gcc/tree-ssa-threadbackward.c b/gcc/tree-ssa-threadbackward.c index 55dbcaddf69f..3028504aefa2 100644 --- a/gcc/tree-ssa-threadbackward.c +++ b/gcc/tree-ssa-threadbackward.c @@ -286,6 +286,37 @@ fsm_find_control_statement_thread_paths (tree name, break; } + /* PHIs in the path will create degenerate PHIS in the + copied path which will then get propagated away, so + looking at just the duplicate path the PHIs would + seem unimportant. + + But those PHIs, because they're assignments to objects + typically with lives that exist outside the thread path, + will tend to generate PHIs (or at least new PHI arguments) + at points where we leave the thread path and rejoin + the original blocks. So we do want to account for them. + + We ignore virtual PHIs. We also ignore cases where BB + has a single incoming edge. That's the most common + degenerate PHI we'll see here. Finally we ignore PHIs + that are associated with the value we're tracking as + that object likely dies. */ + if (EDGE_COUNT (bb->succs) > 1 && EDGE_COUNT (bb->preds) > 1) + { + for (gphi_iterator gsip = gsi_start_phis (bb); + !gsi_end_p (gsip); + gsi_next (&gsip)) + { + gphi *phi = gsip.phi (); + tree dst = gimple_phi_result (phi); + + if (SSA_NAME_VAR (dst) != SSA_NAME_VAR (name) + && !virtual_operand_p (dst)) + ++n_insns; + } + } + for (gsi = gsi_after_labels (bb); !gsi_end_p (gsi); gsi_next_nondebug (&gsi)) @@ -324,6 +355,11 @@ fsm_find_control_statement_thread_paths (tree name, threaded_through_latch = true; } + /* We are going to remove the control statement at the end of the + last block in the threading path. So don't count it against our + statement count. */ + n_insns--; + gimple *stmt = get_gimple_control_stmt ((*path)[0]); gcc_assert (stmt); /* We have found a constant value for ARG. For GIMPLE_SWITCH @@ -352,24 +388,6 @@ fsm_find_control_statement_thread_paths (tree name, == DOMST_NONDOMINATING)) creates_irreducible_loop = true; - /* PHIs in the final target and only the final target will need - to be duplicated. So only count those against the number - of statements. */ - gphi_iterator gsip; - for (gsip = gsi_start_phis (taken_edge->dest); - !gsi_end_p (gsip); - gsi_next (&gsip)) - { - gphi *phi = gsip.phi (); - tree dst = gimple_phi_result (phi); - - /* We consider any non-virtual PHI as a statement since it - count result in a constant assignment or copy - operation. */ - if (!virtual_operand_p (dst)) - ++n_insns; - } - if (path_crosses_loops) { if (dump_file && (dump_flags & TDF_DETAILS))