From e0b059b1dd3c284a256833a564f22b8e6d5a5d5d Mon Sep 17 00:00:00 2001 From: Wilco Dijkstra Date: Thu, 4 Feb 2016 18:23:35 +0000 Subject: [PATCH] This patch fixes an exponential issue in ccmp.c. This patch fixes an exponential issue in ccmp.c. When deciding which ccmp expansion to use, the tree nodes gs0 and gs1 are fully expanded twice. If they contain more CCMP opportunities, their subtrees are also expanded twice. When the trees are complex the expansion takes exponential time and memory. As a workaround in GCC6 compute the cost of the first expansion early, and only try the alternative expansion if the cost is low enough. This rarely affects real code, eg. SPECINT2006 has identical codesize. 2016-02-04 Wilco Dijkstra gcc/ PR target/69619 * ccmp.c (expand_ccmp_expr_1): Avoid evaluating gs0/gs1 twice when complex. gcc/testsuite/ PR target/69619 * gcc.dg/pr69619.c: Add new test. From-SVN: r233145 --- gcc/ChangeLog | 6 ++++++ gcc/ccmp.c | 22 ++++++++++++++-------- gcc/testsuite/ChangeLog | 5 +++++ gcc/testsuite/gcc.dg/pr69619.c | 20 ++++++++++++++++++++ 4 files changed, 45 insertions(+), 8 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/pr69619.c diff --git a/gcc/ChangeLog b/gcc/ChangeLog index c76070f8af1..7c2dae85287 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2016-02-04 Wilco Dijkstra + + PR target/69619 + * ccmp.c (expand_ccmp_expr_1): Avoid evaluating gs0/gs1 + twice when complex. + 2016-02-04 Mike Frysinger * doc/invoke.texi: Delete -mno-fma4. diff --git a/gcc/ccmp.c b/gcc/ccmp.c index 9f1ce295554..6f95acec95b 100644 --- a/gcc/ccmp.c +++ b/gcc/ccmp.c @@ -170,7 +170,7 @@ expand_ccmp_expr_1 (gimple *g, rtx *prep_seq, rtx *gen_seq) int unsignedp0, unsignedp1; rtx_code rcode0, rcode1; int speed_p = optimize_insn_for_speed_p (); - rtx tmp2, ret = NULL_RTX, ret2 = NULL_RTX; + rtx tmp2 = NULL_RTX, ret = NULL_RTX, ret2 = NULL_RTX; unsigned cost1 = MAX_COST; unsigned cost2 = MAX_COST; @@ -183,19 +183,25 @@ expand_ccmp_expr_1 (gimple *g, rtx *prep_seq, rtx *gen_seq) gimple_assign_rhs1 (gs0), gimple_assign_rhs2 (gs0)); - tmp2 = targetm.gen_ccmp_first (&prep_seq_2, &gen_seq_2, rcode1, - gimple_assign_rhs1 (gs1), - gimple_assign_rhs2 (gs1)); - - if (!tmp && !tmp2) - return NULL_RTX; - if (tmp != NULL) { ret = expand_ccmp_next (gs1, code, tmp, &prep_seq_1, &gen_seq_1); cost1 = seq_cost (safe_as_a (prep_seq_1), speed_p); cost1 += seq_cost (safe_as_a (gen_seq_1), speed_p); } + + /* FIXME: Temporary workaround for PR69619. + Avoid exponential compile time due to expanding gs0 and gs1 twice. + If gs0 and gs1 are complex, the cost will be high, so avoid + reevaluation if above an arbitrary threshold. */ + if (tmp == NULL || cost1 < COSTS_N_INSNS (25)) + tmp2 = targetm.gen_ccmp_first (&prep_seq_2, &gen_seq_2, rcode1, + gimple_assign_rhs1 (gs1), + gimple_assign_rhs2 (gs1)); + + if (!tmp && !tmp2) + return NULL_RTX; + if (tmp2 != NULL) { ret2 = expand_ccmp_next (gs0, code, tmp2, &prep_seq_2, diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 66115f01555..f2f73b609fd 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2016-02-04 Wilco Dijkstra + + PR target/69619 + * gcc.dg/pr69619.c: Add new test. + 2016-02-04 Richard Sandiford PR rtl-optimization/69577 diff --git a/gcc/testsuite/gcc.dg/pr69619.c b/gcc/testsuite/gcc.dg/pr69619.c new file mode 100644 index 00000000000..a200bdf310f --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr69619.c @@ -0,0 +1,20 @@ +/* { dg-do compile } */ +/* { dg-options "-O3" } */ + +int a, b, c, d; +int e[100]; +void +fn1 () +{ + int *f = &d; + c = 6; + for (; c; c--) + { + b = 0; + for (; b <= 5; b++) + { + short g = e[(b + 2) * 9 + c]; + *f = *f == a && e[(b + 2) * 9 + c]; + } + } +} -- 2.30.2