On Tue, Jun 4, 2019 at 5:24 PM Feng Xue OS <f...@os.amperecomputing.com> wrote: > > Some changes on documentation.
Please name the option -ffinite-loops (plural), the patch is OK with this change if you also adjust > + /* If the loop has any non-EH exit, we can assume it will terminate. */ > + FOR_EACH_VEC_ELT (exits, i, ex) > + if (!(ex->flags & EDGE_EH)) > + { to look for "normal" edges only - in addition to EDGE_EH you want to ignore EDGE_FAKE and EDGE_ABNORMAL. EDGE_FAKE are inserted by connect_infiinite_loops_to_exit and EDGE_ABNORMAL can appear with setjmp/longjmp and friends. I think this change also warrants mentioning in gcc-10/changes.html. Thanks, Richard. > Feng > > ---- > diff --git a/gcc/ChangeLog b/gcc/ChangeLog > index 37aab79..4fdc5c8 100644 > --- a/gcc/ChangeLog > +++ b/gcc/ChangeLog > @@ -1,3 +1,16 @@ > +2019-06-04 Feng Xue <f...@os.amperecomputing.com> > + > + PR tree-optimization/89713 > + * doc/invoke.texi (-ffinite-loop): Document new option. > + * common.opt (-ffinite-loop): New option. > + * tree-ssa-dce.c (mark_stmt_if_obviously_necessary): Mark > + IFN_GOACC_LOOP calls as necessary. > + * tree-ssa-loop-niter.c (finite_loop): Assume loop with an exit is > + finite. > + * omp-offload.c (oacc_xform_loop): Skip lowering if return value of > + IFN_GOACC_LOOP call is not used. > + * opts.c (default_options_table): Enable -ffinite-loop at -O2+. > + > 2019-06-04 Alan Modra <amo...@gmail.com> > > PR target/90689 > diff --git a/gcc/common.opt b/gcc/common.opt > index 0e72fd0..f570815 100644 > --- a/gcc/common.opt > +++ b/gcc/common.opt > @@ -1437,6 +1437,10 @@ ffinite-math-only > Common Report Var(flag_finite_math_only) Optimization SetByCombined > Assume no NaNs or infinities are generated. > > +ffinite-loop > +Common Report Var(flag_finite_loop) Optimization > +Assume that loops with an exit will terminate and not loop indefinitely. > + > ffixed- > Common Joined RejectNegative Var(common_deferred_options) Defer > -ffixed-<register> Mark <register> as being unavailable to the compiler. > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi > index 91c9bb8..2cb0b9a 100644 > --- a/gcc/doc/invoke.texi > +++ b/gcc/doc/invoke.texi > @@ -412,6 +412,7 @@ Objective-C and Objective-C++ Dialects}. > -fdevirtualize-at-ltrans -fdse @gol > -fearly-inlining -fipa-sra -fexpensive-optimizations -ffat-lto-objects > @gol > -ffast-math -ffinite-math-only -ffloat-store > -fexcess-precision=@var{style} @gol > +-ffinite-loop @gol > -fforward-propagate -ffp-contract=@var{style} -ffunction-sections @gol > -fgcse -fgcse-after-reload -fgcse-las -fgcse-lm -fgraphite-identity @gol > -fgcse-sm -fhoist-adjacent-loads -fif-conversion @gol > @@ -8282,6 +8283,7 @@ also turns on the following optimization flags: > -fdelete-null-pointer-checks @gol > -fdevirtualize -fdevirtualize-speculatively @gol > -fexpensive-optimizations @gol > +-ffinite-loop @gol > -fgcse -fgcse-lm @gol > -fhoist-adjacent-loads @gol > -finline-small-functions @gol > @@ -9503,6 +9505,15 @@ that may set @code{errno} but are otherwise free of > side effects. This flag is > enabled by default at @option{-O2} and higher if @option{-Os} is not also > specified. > > +@item -ffinite-loop > +@opindex ffinite-loop > +@opindex fno-finite-loop > +Assume that a loop with an exit will eventually take the exit and not loop > +indefinitely. This allows the compiler to remove loops that otherwise have > +no side-effects, not considering eventual endless looping as such. > + > +This option is enabled by default at @option{-O2}. > + > @item -ftree-dominator-opts > @opindex ftree-dominator-opts > Perform a variety of simple scalar cleanups (constant/copy > diff --git a/gcc/omp-offload.c b/gcc/omp-offload.c > index 97ae47b..369122f 100644 > --- a/gcc/omp-offload.c > +++ b/gcc/omp-offload.c > @@ -300,7 +300,7 @@ oacc_xform_loop (gcall *call) > tree chunk_size = NULL_TREE; > unsigned mask = (unsigned) TREE_INT_CST_LOW (gimple_call_arg (call, 5)); > tree lhs = gimple_call_lhs (call); > - tree type = TREE_TYPE (lhs); > + tree type = NULL_TREE; > tree diff_type = TREE_TYPE (range); > tree r = NULL_TREE; > gimple_seq seq = NULL; > @@ -308,6 +308,15 @@ oacc_xform_loop (gcall *call) > unsigned outer_mask = mask & (~mask + 1); // Outermost partitioning > unsigned inner_mask = mask & ~outer_mask; // Inner partitioning (if any) > > + /* Skip lowering if return value of IFN_GOACC_LOOP call is not used. */ > + if (!lhs) > + { > + gsi_replace_with_seq (&gsi, seq, true); > + return; > + } > + > + type = TREE_TYPE (lhs); > + > #ifdef ACCEL_COMPILER > chunk_size = gimple_call_arg (call, 4); > if (integer_minus_onep (chunk_size) /* Force static allocation. */ > diff --git a/gcc/opts.c b/gcc/opts.c > index 64f94ac..0db9dda 100644 > --- a/gcc/opts.c > +++ b/gcc/opts.c > @@ -494,6 +494,7 @@ static const struct default_options > default_options_table[] = > { OPT_LEVELS_2_PLUS, OPT_fdevirtualize, NULL, 1 }, > { OPT_LEVELS_2_PLUS, OPT_fdevirtualize_speculatively, NULL, 1 }, > { OPT_LEVELS_2_PLUS, OPT_fexpensive_optimizations, NULL, 1 }, > + { OPT_LEVELS_2_PLUS, OPT_ffinite_loop, NULL, 1 }, > { OPT_LEVELS_2_PLUS, OPT_fgcse, NULL, 1 }, > { OPT_LEVELS_2_PLUS, OPT_fhoist_adjacent_loads, NULL, 1 }, > { OPT_LEVELS_2_PLUS, OPT_findirect_inlining, NULL, 1 }, > diff --git a/gcc/testsuite/g++.dg/tree-ssa/empty-loop.C > b/gcc/testsuite/g++.dg/tree-ssa/empty-loop.C > new file mode 100644 > index 0000000..e374155 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/tree-ssa/empty-loop.C > @@ -0,0 +1,33 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O2 -fdump-tree-cddce2 -ffinite-loop" } */ > + > +#include <string> > +#include <vector> > +#include <list> > +#include <set> > +#include <map> > + > +using namespace std; > + > +int foo (vector<string> &v, list<string> &l, set<string> &s, map<int, > string> &m) > +{ > + for (vector<string>::iterator it = v.begin (); it != v.end (); ++it) > + it->length(); > + > + for (list<string>::iterator it = l.begin (); it != l.end (); ++it) > + it->length(); > + > + for (map<int, string>::iterator it = m.begin (); it != m.end (); ++it) > + it->first + it->second.length(); > + > + for (set<string>::iterator it0 = s.begin (); it0 != s.end(); ++it0) > + for (vector<string>::reverse_iterator it1 = v.rbegin(); it1 != v.rend(); > ++it1) > + { > + it0->length(); > + it1->length(); > + } > + > + return 0; > +} > +/* { dg-final { scan-tree-dump-not "if" "cddce2"} } */ > + > diff --git a/gcc/testsuite/gcc.dg/const-1.c b/gcc/testsuite/gcc.dg/const-1.c > index a5b2b16..13e3451 100644 > --- a/gcc/testsuite/gcc.dg/const-1.c > +++ b/gcc/testsuite/gcc.dg/const-1.c > @@ -1,5 +1,5 @@ > /* { dg-do compile { target nonpic } } */ > -/* { dg-options "-O2 -Wsuggest-attribute=const" } */ > +/* { dg-options "-O2 -Wsuggest-attribute=const -fno-finite-loop" } */ > > extern int extern_const(int a) __attribute__ ((const)); > > diff --git a/gcc/testsuite/gcc.dg/graphite/graphite.exp > b/gcc/testsuite/gcc.dg/graphite/graphite.exp > index ea61446..b294b9c 100644 > --- a/gcc/testsuite/gcc.dg/graphite/graphite.exp > +++ b/gcc/testsuite/gcc.dg/graphite/graphite.exp > @@ -56,7 +56,7 @@ set vect_files [lsort [glob -nocomplain > $srcdir/$subdir/vect-*.c ] ] > > # Tests to be compiled. > set dg-do-what-default compile > -dg-runtest $scop_files "" "-O2 -fgraphite -fdump-tree-graphite-all" > +dg-runtest $scop_files "" "-O2 -fgraphite -fdump-tree-graphite-all > -fno-finite-loop" > dg-runtest $id_files "" "-O2 -fgraphite-identity -ffast-math > -fdump-tree-graphite-details" > > # Tests to be run. > diff --git a/gcc/testsuite/gcc.dg/loop-unswitch-1.c > b/gcc/testsuite/gcc.dg/loop-unswitch-1.c > index f6fc41d..735eeef 100644 > --- a/gcc/testsuite/gcc.dg/loop-unswitch-1.c > +++ b/gcc/testsuite/gcc.dg/loop-unswitch-1.c > @@ -1,6 +1,6 @@ > /* For PR rtl-optimization/27735 */ > /* { dg-do compile } */ > -/* { dg-options "-O2 -funswitch-loops -fdump-tree-unswitch-details" } */ > +/* { dg-options "-O2 -funswitch-loops -fdump-tree-unswitch-details > -fno-finite-loop" } */ > > void set_color(void); > void xml_colorize_line(unsigned int *p, int state) > diff --git a/gcc/testsuite/gcc.dg/predict-9.c > b/gcc/testsuite/gcc.dg/predict-9.c > index 7e5ba08..3710eef 100644 > --- a/gcc/testsuite/gcc.dg/predict-9.c > +++ b/gcc/testsuite/gcc.dg/predict-9.c > @@ -1,5 +1,5 @@ > /* { dg-do compile } */ > -/* { dg-options "-O2 -fdisable-tree-evrp -fdump-tree-profile_estimate" } */ > +/* { dg-options "-O2 -fdisable-tree-evrp -fdump-tree-profile_estimate > -fno-finite-loop" } */ > > extern int global; > extern int global2; > diff --git a/gcc/testsuite/gcc.dg/pure-2.c b/gcc/testsuite/gcc.dg/pure-2.c > index fe6e2bc..6ac372b 100644 > --- a/gcc/testsuite/gcc.dg/pure-2.c > +++ b/gcc/testsuite/gcc.dg/pure-2.c > @@ -1,5 +1,5 @@ > /* { dg-do compile } */ > -/* { dg-options "-O2 -Wsuggest-attribute=pure" } */ > +/* { dg-options "-O2 -Wsuggest-attribute=pure -fno-finite-loop" } */ > /* { dg-add-options bind_pic_locally } */ > > extern int extern_const(int a) __attribute__ ((pure)); > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/20040211-1.c > b/gcc/testsuite/gcc.dg/tree-ssa/20040211-1.c > index d289e5d..e4d331e 100644 > --- a/gcc/testsuite/gcc.dg/tree-ssa/20040211-1.c > +++ b/gcc/testsuite/gcc.dg/tree-ssa/20040211-1.c > @@ -1,5 +1,5 @@ > /* { dg-do compile } */ > -/* { dg-options "-O2 -fdump-tree-cddce2" } */ > +/* { dg-options "-O2 -fdump-tree-cddce2 -fno-finite-loop" } */ > > struct rtx_def; > typedef struct rtx_def *rtx; > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/dce-2.c > b/gcc/testsuite/gcc.dg/tree-ssa/dce-2.c > new file mode 100644 > index 0000000..ffca49c > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/tree-ssa/dce-2.c > @@ -0,0 +1,37 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O2 -fdump-tree-cddce1 -ffinite-loop" } */ > + > +typedef struct list { > + char pad[15]; > + struct list *next; > +} list; > + > +int data; > + > +list *head, *tail; > + > +int __attribute__((pure)) pfn (int); > + > +int foo (unsigned u, int s) > +{ > + unsigned i; > + list *p; > + int j; > + > + for (i = 0; i < u; i += 2) > + ; > + > + for (p = head; p; p = p->next) > + ; > + > + for (j = data; j & s; j = pfn (j + 3)) > + ; > + > + for (p = head; p != tail; p = p->next) > + for (j = data + 1; j > s; j = pfn (j + 2)) > + ; > + > + return 0; > +} > +/* { dg-final { scan-tree-dump-not "if" "cddce1"} } */ > + > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/loop-10.c > b/gcc/testsuite/gcc.dg/tree-ssa/loop-10.c > index a29c9fb..c605005 100644 > --- a/gcc/testsuite/gcc.dg/tree-ssa/loop-10.c > +++ b/gcc/testsuite/gcc.dg/tree-ssa/loop-10.c > @@ -1,5 +1,5 @@ > /* { dg-do compile } */ > -/* { dg-options "-O2 -fdump-tree-optimized" } */ > +/* { dg-options "-O2 -fdump-tree-optimized -fno-finite-loop" } */ > /* { dg-require-effective-target int32plus } */ > > int bar (void); > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/split-path-6.c > b/gcc/testsuite/gcc.dg/tree-ssa/split-path-6.c > index e9b4f26..7c47906 100644 > --- a/gcc/testsuite/gcc.dg/tree-ssa/split-path-6.c > +++ b/gcc/testsuite/gcc.dg/tree-ssa/split-path-6.c > @@ -1,5 +1,5 @@ > /* { dg-do compile } */ > -/* { dg-options "-O2 -fsplit-paths -fno-tree-cselim > -fdump-tree-split-paths-details -w" } */ > +/* { dg-options "-O2 -fsplit-paths -fno-tree-cselim > -fdump-tree-split-paths-details -w -fno-finite-loop" } */ > > struct __sFILE > { > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-thread-12.c > b/gcc/testsuite/gcc.dg/tree-ssa/ssa-thread-12.c > index d829b04..b7a3d77 100644 > --- a/gcc/testsuite/gcc.dg/tree-ssa/ssa-thread-12.c > +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-thread-12.c > @@ -1,5 +1,5 @@ > /* { dg-do compile } */ > -/* { dg-options "-O2 -fdump-tree-thread2-details -fdump-tree-thread3-details > -fdump-tree-thread4-details" } */ > +/* { dg-options "-O2 -fdump-tree-thread2-details -fdump-tree-thread3-details > -fdump-tree-thread4-details -fno-finite-loop" } */ > /* { dg-final { scan-tree-dump "FSM" "thread2" } } */ > /* { dg-final { scan-tree-dump "FSM" "thread3" } } */ > /* { dg-final { scan-tree-dump "FSM" "thread4" { xfail *-*-* } } } */ > diff --git a/gcc/tree-ssa-dce.c b/gcc/tree-ssa-dce.c > index 2478219..179605e 100644 > --- a/gcc/tree-ssa-dce.c > +++ b/gcc/tree-ssa-dce.c > @@ -245,6 +245,17 @@ mark_stmt_if_obviously_necessary (gimple *stmt, bool > aggressive) > mark_stmt_necessary (stmt, true); > return; > } > + /* IFN_GOACC_LOOP calls are necessary in that they are used to > + represent parameter (i.e. step, bound) of a lowered OpenACC > + partitioned loop. But this kind of partitioned loop might not > + survive from aggressive loop removal for it has loop exit and > + is assumed to be finite. Therefore, we need to explicitly mark > + these calls. (An example is libgomp.oacc-c-c++-common/pr84955.c) > */ > + if (gimple_call_internal_p (stmt, IFN_GOACC_LOOP)) > + { > + mark_stmt_necessary (stmt, true); > + return; > + } > if (!gimple_call_lhs (stmt)) > return; > break; > diff --git a/gcc/tree-ssa-loop-niter.c b/gcc/tree-ssa-loop-niter.c > index 470b6a2..c25cb1d 100644 > --- a/gcc/tree-ssa-loop-niter.c > +++ b/gcc/tree-ssa-loop-niter.c > @@ -2798,6 +2798,27 @@ finite_loop_p (struct loop *loop) > loop->num); > return true; > } > + > + if (flag_finite_loop) > + { > + unsigned i; > + vec<edge> exits = get_loop_exit_edges (loop); > + edge ex; > + > + /* If the loop has any non-EH exit, we can assume it will terminate. */ > + FOR_EACH_VEC_ELT (exits, i, ex) > + if (!(ex->flags & EDGE_EH)) > + { > + exits.release (); > + if (dump_file) > + fprintf (dump_file, "Assume loop %i to be finite: it has an > exit " > + "and -ffinite-loop is on.\n", loop->num); > + return true; > + } > + > + exits.release (); > + } > + > return false; > } > > diff --git a/libgomp/testsuite/libgomp.oacc-c-c++-common/pr84955-1.c > b/libgomp/testsuite/libgomp.oacc-c-c++-common/pr84955-1.c > new file mode 100644 > index 0000000..845268b > --- /dev/null > +++ b/libgomp/testsuite/libgomp.oacc-c-c++-common/pr84955-1.c > @@ -0,0 +1,31 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O2 -fdump-tree-cddce2 -ffinite-loop" } */ > + > +int > +f1 (void) > +{ > + int i, j; > + > +#pragma acc parallel loop tile(2,3) > + for (i = 1; i < 10; i++) > + for (j = 1; j < 10; j++) > + for (;;) > + ; > + > + return i + j; > +} > + > +int > +f2 (void) > +{ > + int i, j, k; > + > +#pragma acc parallel loop tile(2,3) > + for (i = 1; i < 10; i++) > + for (j = 1; j < 10; j++) > + for (k = 1; k < 10; k++) > + ; > + > + return i + j; > +} > +/* { dg-final { scan-tree-dump-not "if" "cddce2"} } */