Hello. Following patch introduces FORTRAN_LOOP_PREHEADER predictor for all Fortran loops that are transformed to:
[Evaluate loop bounds and step] dovar = from; if ((step > 0) ? (dovar <= to) : (dovar => to)) { for (;;) { body; cycle_label: cond = (dovar == to); dovar += step; if (cond) goto end_label; } } end_label: The first condition can be predicted as satisfied in most situations. I've also measured the predictor on SPEC2006 and was 99%, which I've picked up as the hitrate. The patch is pre-approved by Honza. Patch survives reg&bootstrap on x86_64-linux-gnu. Installed as r237533. Martin
>From 6072b4e4a215b876da99ebb37132852bdfd033ee Mon Sep 17 00:00:00 2001 From: marxin <mli...@suse.cz> Date: Wed, 15 Jun 2016 14:45:12 +0200 Subject: [PATCH 2/2] Introduce fortran loop preheader gcc/ChangeLog: 2016-06-15 Martin Liska <mli...@suse.cz> * predict.def: Add fortran loop preheader predictor. * gimple-fold.c (gimple_fold_stmt_to_constant_1): Properly fold IFN_BUILTIN_EXPECT with a known constant argument. gcc/fortran/ChangeLog: 2016-06-15 Martin Liska <mli...@suse.cz> * trans-stmt.c (gfc_trans_simple_do): Predict the edge. gcc/testsuite/ChangeLog: 2016-06-16 Martin Liska <mli...@suse.cz> * gfortran.dg/predict-1.f90: New test. --- gcc/fortran/trans-stmt.c | 4 +++- gcc/gimple-fold.c | 8 ++++++++ gcc/predict.def | 6 ++++++ gcc/testsuite/gfortran.dg/predict-1.f90 | 12 ++++++++++++ 4 files changed, 29 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/gfortran.dg/predict-1.f90 diff --git a/gcc/fortran/trans-stmt.c b/gcc/fortran/trans-stmt.c index 7d3cf8c..84bf749 100644 --- a/gcc/fortran/trans-stmt.c +++ b/gcc/fortran/trans-stmt.c @@ -1938,7 +1938,9 @@ gfc_trans_simple_do (gfc_code * code, stmtblock_t *pblock, tree dovar, else cond = fold_build2_loc (loc, GE_EXPR, boolean_type_node, dovar, to); - tmp = fold_build3_loc (loc, COND_EXPR, void_type_node, cond, tmp, + + tmp = fold_build3_loc (loc, COND_EXPR, void_type_node, + gfc_likely (cond, PRED_FORTRAN_LOOP_PREHEADER), tmp, build_empty_stmt (loc)); gfc_add_expr_to_block (pblock, tmp); diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c index 885367e..fa03e89 100644 --- a/gcc/gimple-fold.c +++ b/gcc/gimple-fold.c @@ -5250,6 +5250,14 @@ gimple_fold_stmt_to_constant_1 (gimple *stmt, tree (*valueize) (tree), case IFN_UBSAN_CHECK_MUL: subcode = MULT_EXPR; break; + case IFN_BUILTIN_EXPECT: + { + tree arg0 = gimple_call_arg (stmt, 0); + tree op0 = (*valueize) (arg0); + if (TREE_CODE (op0) == INTEGER_CST) + return op0; + return NULL_TREE; + } default: return NULL_TREE; } diff --git a/gcc/predict.def b/gcc/predict.def index 3e3a43a..a0d0ba9 100644 --- a/gcc/predict.def +++ b/gcc/predict.def @@ -199,3 +199,9 @@ DEF_PREDICTOR (PRED_FORTRAN_INVALID_BOUND, "Fortran invalid bound", \ which in turn has an optional argument. */ DEF_PREDICTOR (PRED_FORTRAN_ABSENT_DUMMY, "Fortran absent dummy", \ HITRATE (60), 0) + +/* Fortran DO statement generates a pre-header guard: + empty = (step > 0 ? to < from : to > from), which can be predicted + to be very likely. */ +DEF_PREDICTOR (PRED_FORTRAN_LOOP_PREHEADER, "Fortran loop preheader", \ + HITRATE (99), 0) diff --git a/gcc/testsuite/gfortran.dg/predict-1.f90 b/gcc/testsuite/gfortran.dg/predict-1.f90 new file mode 100644 index 0000000..81f0436 --- /dev/null +++ b/gcc/testsuite/gfortran.dg/predict-1.f90 @@ -0,0 +1,12 @@ +! { dg-do compile } +! { dg-options "-O2 -fdump-tree-profile_estimate" } + +subroutine test(block, array) +integer :: i, block(9), array(2) + +do i = array(1), array(2) + block(i) = i +end do +end subroutine test + +! { dg-final { scan-tree-dump-times "Fortran loop preheader heuristics of edge\[^:\]*: 99.0%" 1 "profile_estimate" } } -- 2.8.3