Scop: generate context on the fly

Now that the fixed parameter values are stored in the Scop,
the context can be generated from these values and
the set of all parameter when needed.

Author: Sven Verdoolaege

tc/core/polyhedral/codegen_llvm.cc

@@ -324,8 +324,7 @@ llvm::Value* CodeGen_TC::getValue(isl::ast_expr expr) {
 
 class LLVMCodegen {
   void collectTensor(const Halide::OutputImageParam& t) {
-    auto sizes =
-        getTensorSizesWithoutLeadingDim(t, scop_.globalParameterContext);
+    auto sizes = getTensorSizesWithoutLeadingDim(t, scop_.context());
     if (not sizes.empty()) {
       args_.emplace_back(
           makePtrToArrayType(halide_cg.llvm_type_of(t.type()), sizes));
@@ -509,7 +508,7 @@ class LLVMCodegen {
       CHECK(condLHS);
       CHECK_EQ(condLHS.get_id(), iterator);
 
-      IslAstExprInterpeter i(scop_.globalParameterContext);
+      IslAstExprInterpeter i(scop_.context());
       auto condRHSVal = i.interpret(cond_expr.get_arg(1));
 
       auto cond = [&]() {

tc/core/polyhedral/cuda/mapped_scop.cc

@@ -855,7 +855,7 @@ std::unique_ptr<MappedScop> makeSpecializedMappedScop(
   // outer schedule dimensions, so the space of a parameter context code is that
   // of a zero-dimensional space.
   auto root = scop->scheduleRoot();
-  updateTopLevelContext(root, scop->globalParameterContext.from_params());
+  updateTopLevelContext(root, scop->context().from_params());
 
   tc::Grid grid = mappedScop.numBlocks;
   tc::Block block = mappedScop.numThreads;
@@ -878,7 +878,7 @@ std::unique_ptr<MappedScop> makeSpecializedMappedScop(
 } // namespace
 
 // Before generating code, make a copy of the scop and insert
-// the globalParameterContext of the original scop as top-level
+// the context of the original scop as top-level
 // context node in schedule tree.
 std::tuple<std::string, tc::Grid, tc::Block> MappedScop::codegen(
     const std::string& specializedName) const {

tc/core/polyhedral/cuda/tighten_launch_bounds.cc

@@ -84,7 +84,7 @@ std::pair<tc::Grid, tc::Block> tightenLaunchBounds(
     const tc::Grid& grid,
     const tc::Block& block) {
   auto root = scop.scheduleRoot();
-  auto params = scop.globalParameterContext;
+  auto params = scop.context();
 
   auto max = [root, params](const mapping::MappingId& id) -> size_t {
     size_t sizetMax = std::numeric_limits<size_t>::max();

tc/core/polyhedral/memory_promotion.cc

@@ -421,10 +421,7 @@ isl::set tensorElementsSet(const Scop& scop, isl::id tensorId) {
         (isl::aff_set(aff) < (minAff + extentAff));
   }
 
-  if (scop.globalParameterContext) {
-    tensorElements =
-        tensorElements.intersect_params(scop.globalParameterContext);
-  }
+  tensorElements = tensorElements.intersect_params(scop.context());
   return tensorElements;
 }
 

tc/core/polyhedral/scop.cc

@@ -47,11 +47,9 @@ ScopUPtr Scop::makeScop(
 
   halide2isl::SymbolTable sym = halide2isl::makeSymbolTable(components);
 
-  auto globalParameterContext = halide2isl::makeParamContext(ctx, sym.params);
-  isl::space paramSpace = globalParameterContext.get_space();
+  isl::space paramSpace = halide2isl::makeParamSpace(ctx, sym.params);
 
   ScopUPtr scop(new Scop());
-  scop->globalParameterContext = globalParameterContext;
   scop->halide.params = sym.params;
   scop->halide.idx = sym.idxVars;
   scop->halide.reductionIdx = sym.reductionVars;

tc/core/polyhedral/scop.h

@@ -64,7 +64,6 @@ struct Scop {
   static std::unique_ptr<Scop> makeScop(const Scop& scop) {
     auto res = std::unique_ptr<Scop>(new Scop());
     res->parameterValues = scop.parameterValues;
-    res->globalParameterContext = scop.globalParameterContext;
     res->halide = scop.halide;
     res->reads = scop.reads;
     res->writes = scop.writes;
@@ -79,10 +78,20 @@ struct Scop {
     return res;
   }
 
-  // Intersect globalParameterContext with extraGlobalParameterContext.
-  inline void intersectContext(isl::set extraGlobalParameterContext) {
-    auto context = globalParameterContext & extraGlobalParameterContext;
-    globalParameterContext = context;
+  // Return a context encapsulating all known information about
+  // the parameters.  In particular, all parameters are known
+  // to be non-negative and the parameters fixed by fixParameters
+  // have a known value.
+  // This context lives in a parameter space.
+  // The scop is not necessarily specialized to its context.
+  // Call specializeToContext to perform this specialization.
+  // The schedule tree of the scop does not necessarily have
+  // a context node.  Call updateTopLevelContext on the schedule tree
+  // to introduce or refine such a context node.
+  isl::set context() const {
+    auto ctx = domain().get_ctx();
+    auto context = halide2isl::makeParamContext(ctx, halide.params);
+    return context.intersect(makeContext(parameterValues));
   }
 
   // Specialize a Scop by fixing the given parameters to the given sizes.
@@ -108,8 +117,9 @@ struct Scop {
     return res;
   }
 
-  // Specialize the Scop with respect to its globalParameterContext.
+  // Specialize the Scop with respect to its context.
   void specializeToContext() {
+    auto globalParameterContext = context();
     domainRef() = domain().intersect_params(globalParameterContext);
     reads = reads.intersect_params(globalParameterContext);
     writes = writes.intersect_params(globalParameterContext);
@@ -135,15 +145,14 @@ struct Scop {
   }
 
   // Fix the values of the specified parameters in the context
-  // to the corresponding specified values and keep track of them
+  // to the corresponding specified values by keeping track of them
   // in parameterValues.
   template <typename T>
   void fixParameters(const std::unordered_map<std::string, T>& sizes) {
     CHECK(parameterValues.size() == 0);
     for (const auto& kvp : sizes) {
       parameterValues.emplace(kvp.first, kvp.second);
     }
-    intersectContext(makeContext(sizes));
   }
 
   // Return the list of parameter values in the same
@@ -491,22 +500,11 @@ struct Scop {
   // of the ScheduleTree "function".
  private:
   isl::union_set& domainRef();
+
  public:
   const isl::union_set domain() const;
   // The parameter values of a specialized Scop.
   std::unordered_map<std::string, int> parameterValues;
-  // A globalParameterContext is kept. This represents (partial)
-  // parameter specialization coming from the outside.
-  // This may be further specialized before codegen.
-  // This globalParameterContext must not give rise to a context node in the
-  // schedule tree.
-  // This globalParameterContext is intersected with the domain of the
-  // ScheduleTree for best possible specialization of polyhedral decisions and
-  // transformations. By the analogy with generalized functions, the
-  // globalParameterContext becomes part of the "support" of the ScheduleTree
-  // "function".
-  // This globalParameterContext lives in a parameter space.
-  isl::set globalParameterContext; // TODO: not too happy about this name
 
   isl::union_map reads;
   isl::union_map writes;