[llvm-commits] [polly] r149263 - /polly/trunk/lib/ScheduleOptimizer.cpp

[Tobias Grosser]

Author: grosser
Date: Mon Jan 30 13:38:43 2012
New Revision: 149263

URL: http://llvm.org/viewvc/llvm-project?rev=149263&view=rev
Log:
Scheduler: Simplify dependences by default (only isl)

This speeds up the scheduler by orders of magnitude and in addition yields often
to a better schedule.

With this we can compile all polybench kernels with less than 5x compile time
overhead. In general the overhead is even less than 2-3x.  This is still with
running a lot of redundant passes and no compile time tuning at all. There are
several obvious areas where we can improve here further.

There are also two test cases where we cannot find a schedule any more (cholesky
and another). I will look into them later on.

With this we have a very solid base line from which we can start to optimize
further.

Modified:
    polly/trunk/lib/ScheduleOptimizer.cpp

Modified: polly/trunk/lib/ScheduleOptimizer.cpp
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/lib/ScheduleOptimizer.cpp?rev=149263&r1=149262&r2=149263&view=diff
==============================================================================
--- polly/trunk/lib/ScheduleOptimizer.cpp (original)
+++ polly/trunk/lib/ScheduleOptimizer.cpp Mon Jan 30 13:38:43 2012
@@ -50,6 +50,11 @@
 	      cl::desc("Disable tiling in the scheduler"), cl::Hidden,
               cl::location(polly::DisablePollyTiling), cl::init(false));
 
+static cl::opt<std::string>
+SimplifyDeps("polly-opt-simplify-deps",
+             cl::desc("Dependences should be simplified (yes/no)"),
+             cl::Hidden, cl::init("yes"));
+
 namespace {
 
   class IslScheduleOptimizer : public ScopPass {
@@ -410,8 +415,7 @@
                           | Dependences::TYPE_WAR
                           | Dependences::TYPE_WAW;
 
-  isl_union_map *validity = D->getDependences(dependencyKinds);
-  isl_union_map *proximity = D->getDependences(dependencyKinds);
+  isl_union_map *dependences = D->getDependences(dependencyKinds);
   isl_union_set *domain = NULL;
 
   for (Scop::iterator SI = S.begin(), SE = S.end(); SI != SE; ++SI)
@@ -426,6 +430,27 @@
   if (!domain)
     return false;
 
+  // Simplify the dependences by removing the constraints introduced by the
+  // domains. This can speed up the scheduling time significantly, as large
+  // constant coefficients will be removed from the dependences. The
+  // introduction of some additional dependences reduces the possible
+  // transformations, but in most cases, such transformation do not seem to be
+  // interesting anyway. In some cases this option may stop the scheduler to
+  // find any schedule.
+  if (SimplifyDeps == "yes") {
+    dependences = isl_union_map_gist_domain(dependences,
+                                            isl_union_set_copy(domain));
+    dependences = isl_union_map_gist_range(dependences,
+                                           isl_union_set_copy(domain));
+  } else if (SimplifyDeps != "no") {
+    errs() << "warning: Option -polly-opt-simplify-deps should either be 'yes' "
+              "or 'no'. Falling back to default: 'yes'\n";
+  }
+
+  isl_schedule *schedule;
+  isl_union_map *proximity = isl_union_map_copy(dependences);
+  isl_union_map *validity = dependences;
+
   DEBUG(dbgs() << "\n\nCompute schedule from: ");
   DEBUG(dbgs() << "Domain := "; isl_union_set_dump(domain); dbgs() << ";\n");
   DEBUG(dbgs() << "Proximity := "; isl_union_map_dump(proximity);
@@ -433,8 +458,6 @@
   DEBUG(dbgs() << "Validity := "; isl_union_map_dump(validity);
         dbgs() << ";\n");
 
-  isl_schedule *schedule;
-
   isl_options_set_schedule_max_constant_term(S.getIslCtx(), CONSTANT_BOUND);
   isl_options_set_schedule_maximize_band_depth(S.getIslCtx(), 1);
   schedule  = isl_union_set_compute_schedule(domain, validity, proximity);