[DependenceInfo] Reset operations counter when setting limit.

When entering the dependence computation and the max_operations is set, the
operations counter may have already exceeded the counter, thus aborting any ISL
computation from the start. The counter is reset at the end of the dependence
calculation such that a follow-up recomputation might succeed, ie. the success
of the first dependence calculation depends on unrelated ISL operations that
happened before, giving it a disadvantage to the following calculations.

This patch resets the operations counter at the beginning of the dependence
recalculation to not depend on previous actions. Otherwise additional
preprocessing of the Scop that aims to improve its schedulability (eg. DeLICM)
do have the effect that DependenceInfo and hence the scheduling fail more
likely, contraproductive to the goal of said preprocessing.

llvm-svn: 277810

diff --git a/polly/lib/Analysis/DependenceInfo.cpp b/polly/lib/Analysis/DependenceInfo.cpp
index aa5eadc..53fee9b 100644 (file)
--- a/polly/lib/Analysis/DependenceInfo.cpp
+++ b/polly/lib/Analysis/DependenceInfo.cpp
@@ -366,8 +366,10 @@ void Dependences::calculateDependences(Scop &S) {
   }
 
   long MaxOpsOld = isl_ctx_get_max_operations(IslCtx.get());
-  if (OptComputeOut)
+  if (OptComputeOut) {
+    isl_ctx_reset_operations(IslCtx.get());
     isl_ctx_set_max_operations(IslCtx.get(), OptComputeOut);
+  }
 
   auto OnErrorStatus = isl_options_get_on_error(IslCtx.get());
   isl_options_set_on_error(IslCtx.get(), ISL_ON_ERROR_CONTINUE);