Patchwork [fortran] PR 50690 Disable common function elimination in WORKSHAREs

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Submitter Thomas Koenig
Date Dec. 3, 2011, 8:58 p.m.
Message ID <4EDA8D69.4040004@netcologne.de>
Download mbox | patch
Permalink /patch/129113/
State New
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Comments

Thomas Koenig - Dec. 3, 2011, 8:58 p.m.
Hello world,

the recent discussion has convinced me that there is no way to
mix OMP workshares and common function elimination as practiced by
frontend-passes.c.  This patch therefore disables that
particular optimization within workshares.

Regression-tested.  OK for trunk?

	Thomas

2011-12-02  Thomas Koenig  <tkoenig@gcc.gnu.org>

         PR fortran/50690
         * frontend-passes.c (workshare_level):  New variable.
         (cfe_expr_0):  Don't eliminiat common functions within
         workshares.
         (gfc_code_walker):  Keep track of workshare level.

2011-12-02  Thomas Koenig  <tkoenig@gcc.gnu.org>

         PR fortran/50690
         * gfortran.dg/gomp/workshare2.f90:  New test.
! { dg-do compile }
! { dg-options "-ffrontend-optimize" }
! PR 50690 - this used to ICE because workshare could not handle
! BLOCKs.
! To test for correct execution, run this program (but don't forget
! to unset the stack limit).
program foo
  implicit none
  integer, parameter :: n = 100000000
  real, parameter :: eps = 3e-7
  integer :: i,j
  real :: A(n), B(5), C(n)
  real :: tmp
  B(1) = 3.344
  tmp = B(1)
  do i=1,10
     call random_number(a)
     c = a
     !$omp parallel default(shared)
     !$omp workshare
     A(:) = A(:)*cos(B(1))+A(:)*cos(B(1))
     !$omp end workshare nowait
     !$omp end parallel ! sync is implied here
  end do

  c = c*tmp + c*tmp

  do j=1,n
     if (abs(a(j)-c(j)) > eps) then
        print *,1,j,a(j), c(j)
        call abort
     end if
  end do

  do i=1,10
     call random_number(a)
     c = a
     !$omp parallel workshare default(shared)
     A(:) = A(:)*cos(B(1))+A(:)*cos(B(1))
     !$omp end parallel workshare
  end do

  c = c*tmp + c*tmp
  do j=1,n
     if (abs(a(j)-c(j)) > eps) then
        print *,2,j,a(j), c(j)
        call abort
     end if
  end do

end program foo
Jakub Jelinek - Dec. 3, 2011, 9:39 p.m.
On Sat, Dec 03, 2011 at 09:58:17PM +0100, Thomas Koenig wrote:
> the recent discussion has convinced me that there is no way to
> mix OMP workshares and common function elimination as practiced by
> frontend-passes.c.  This patch therefore disables that
> particular optimization within workshares.
> 
> Regression-tested.  OK for trunk?

I think disabling these optimizations in workshare/parallel workshare
is reasonable, though perhaps you could enable it again in
EXEC_OMP_PARALLEL{,_DO,_SECTIONS} nested in the
EXEC_OMP_WORKSHARE/EXEC_OMP_PARALLEL_WORKSHARE.

E.g. in
  $omp parallel workshare
    a = b
    $omp parallel
      c = cos(d) + cos(d)
    $omp end parallel
    e = f
  $omp end parallel workshare
the body of the inner $omp parallel can be optimized just fine.

	Jakub

Patch

Index: frontend-passes.c
===================================================================
--- frontend-passes.c	(Revision 181809)
+++ frontend-passes.c	(Arbeitskopie)
@@ -66,6 +66,10 @@  static gfc_namespace *current_ns;
 
 static int forall_level;
 
+/* If we are within an OMP WORKSHARE or OMP PARALLEL WORKSHARE.  */
+
+static int workshare_level;
+
 /* Entry point - run all passes for a namespace.  So far, only an
    optimization pass is run.  */
 
@@ -367,6 +371,13 @@  cfe_expr_0 (gfc_expr **e, int *walk_subtrees,
   int i,j;
   gfc_expr *newvar;
 
+  /* Don't do this optimization within WORKSHARES.  */
+  if (workshare_level > 0)
+    {
+      *walk_subtrees = 0;
+      return 0;
+    }
+
   expr_count = 0;
 
   gfc_expr_walker (e, cfe_register_funcs, NULL);
@@ -505,6 +516,7 @@  optimize_namespace (gfc_namespace *ns)
 
   current_ns = ns;
   forall_level = 0;
+  workshare_level = 0;
 
   gfc_code_walker (&ns->code, convert_do_while, dummy_expr_callback, NULL);
   gfc_code_walker (&ns->code, cfe_code, cfe_expr_0, NULL);
@@ -1330,14 +1342,18 @@  gfc_code_walker (gfc_code **c, walk_code_fn_t code
 	      WALK_SUBEXPR (co->ext.dt->extra_comma);
 	      break;
 
+	    case EXEC_OMP_PARALLEL_WORKSHARE:
+	    case EXEC_OMP_WORKSHARE:
+	      workshare_level ++;
+
+	      /* Fall through.  */
+
 	    case EXEC_OMP_DO:
 	    case EXEC_OMP_PARALLEL:
 	    case EXEC_OMP_PARALLEL_DO:
 	    case EXEC_OMP_PARALLEL_SECTIONS:
-	    case EXEC_OMP_PARALLEL_WORKSHARE:
 	    case EXEC_OMP_SECTIONS:
 	    case EXEC_OMP_SINGLE:
-	    case EXEC_OMP_WORKSHARE:
 	    case EXEC_OMP_END_SINGLE:
 	    case EXEC_OMP_TASK:
 	      if (co->ext.omp_clauses)
@@ -1366,6 +1382,10 @@  gfc_code_walker (gfc_code **c, walk_code_fn_t code
 	  if (co->op == EXEC_FORALL)
 	    forall_level --;
 
+	  if (co->op == EXEC_OMP_WORKSHARE
+	      || co->op == EXEC_OMP_PARALLEL_WORKSHARE)
+	    workshare_level --;
+
 	}
     }
   return 0;