[ForwardOpTree] Support read-only value uses.

Read-only values (values defined before the SCoP) require special
handing with -polly-analyze-read-only-scalars=true (which is the
default). If active, each use of a value requires a read access.
When a copied value uses a read-only value, we must also ensure that
such a MemoryAccess is available or is created.

Differential Revision: https://reviews.llvm.org/D35764

llvm-svn: 308876

2 files changed, 29 insertions, 2 deletions

diff --git a/polly/lib/Analysis/ScopBuilder.cpp b/polly/lib/Analysis/ScopBuilder.cpp
index f6b929ab73e..cf253bfa8cc 100644
--- a/polly/lib/Analysis/ScopBuilder.cpp
+++ b/polly/lib/Analysis/ScopBuilder.cpp
@@ -32,10 +32,12 @@ STATISTIC(RichScopFound, "Number of Scops containing a loop");
 STATISTIC(InfeasibleScops,
           "Number of SCoPs with statically infeasible context.");
 
-static cl::opt<bool> ModelReadOnlyScalars(
+bool polly::ModelReadOnlyScalars;
+static cl::opt<bool, true> XModelReadOnlyScalars(
     "polly-analyze-read-only-scalars",
     cl::desc("Model read-only scalar values in the scop description"),
-    cl::Hidden, cl::ZeroOrMore, cl::init(true), cl::cat(PollyCategory));
+    cl::location(ModelReadOnlyScalars), cl::Hidden, cl::ZeroOrMore,
+    cl::init(true), cl::cat(PollyCategory));
 
 static cl::opt<bool> UnprofitableScalarAccs(
     "polly-unprofitable-scalar-accs",
@@ -778,6 +780,15 @@ void ScopBuilder::ensureValueWrite(Instruction *Inst) {
 }
 
 void ScopBuilder::ensureValueRead(Value *V, ScopStmt *UserStmt) {
+  // TODO: Make ScopStmt::ensureValueRead(Value*) offer the same functionality
+  // to be able to replace this one. Currently, there is a split responsibility.
+  // In a first step, the MemoryAccess is created, but without the
+  // AccessRelation. In the second step by ScopStmt::buildAccessRelations(), the
+  // AccessRelation is created. At least for scalar accesses, there is no new
+  // information available at ScopStmt::buildAccessRelations(), so we could
+  // create the AccessRelation right away. This is what
+  // ScopStmt::ensureValueRead(Value*) does.
+
   auto *Scope = UserStmt->getSurroundingLoop();
   auto VUse = VirtualUse::create(scop.get(), UserStmt, Scope, V, false);
   switch (VUse.getKind()) {
diff --git a/polly/lib/Analysis/ScopInfo.cpp b/polly/lib/Analysis/ScopInfo.cpp
index 6defb4f1bb9..c1a30b9bad4 100644
--- a/polly/lib/Analysis/ScopInfo.cpp
+++ b/polly/lib/Analysis/ScopInfo.cpp
@@ -2042,6 +2042,22 @@ void ScopStmt::removeSingleMemoryAccess(MemoryAccess *MA) {
   }
 }
 
+MemoryAccess *ScopStmt::ensureValueRead(Value *V) {
+  MemoryAccess *Access = lookupInputAccessOf(V);
+  if (Access)
+    return Access;
+
+  ScopArrayInfo *SAI =
+      Parent.getOrCreateScopArrayInfo(V, V->getType(), {}, MemoryKind::Value);
+  Access = new MemoryAccess(this, nullptr, MemoryAccess::READ, V, V->getType(),
+                            true, {}, {}, V, MemoryKind::Value);
+  Parent.addAccessFunction(Access);
+  Access->buildAccessRelation(SAI);
+  addAccess(Access);
+  Parent.addAccessData(Access);
+  return Access;
+}
+
 raw_ostream &polly::operator<<(raw_ostream &O, const ScopStmt &S) {
   S.print(O, PollyPrintInstructions);
   return O;