[Polly] Fully-Indexed static expansion

This commit implements the initial version of fully-indexed static
expansion.

```
 for(int i = 0; i<Ni; i++)
   for(int j = 0; j<Ni; j++)
S:     B[j] = j;
T: A[i] = B[i]
```

After the pass, we want this :
```
 for(int i = 0; i<Ni; i++)
   for(int j = 0; j<Ni; j++)
S:     B[i][j] = j;
T: A[i] = B[i][i]
```

For now we bail (fail) in the following cases:
  - Scalar access
  - Multiple writes per SAI
  - MayWrite Access
  - Expansion that leads to an access to the original array

Furthermore: We still miss checks for escaping references to the array
base pointers. A future commit will add the missing escape-checks to
stay correct in those cases. The expansion is still locked behind a
CLI-Option and should not yet be used.

Patch contributed by: Nicholas Bonfante <bonfante.nicolas@gmail.com>

Reviewers: simbuerg, Meinersbur, bollu

Reviewed By: Meinersbur

Subscribers: mgorny, llvm-commits, pollydev

Differential Revision: https://reviews.llvm.org/D34982

llvm-svn: 310304

polly/include/polly/LinkAllPasses.h

@@ -55,6 +55,7 @@ llvm::Pass *createPPCGCodeGenerationPass(GPUArch Arch = GPUArch::NVPTX64,
 llvm::Pass *createIslScheduleOptimizerPass();
 llvm::Pass *createFlattenSchedulePass();
 llvm::Pass *createDeLICMPass();
+llvm::Pass *createMaximalStaticExpansionPass();
 
 extern char &CodePreparationID;
 } // namespace polly
@@ -88,6 +89,7 @@ struct PollyForcePassLinking {
     polly::createPPCGCodeGenerationPass();
 #endif
     polly::createIslScheduleOptimizerPass();
+    polly::createMaximalStaticExpansionPass();
     polly::createFlattenSchedulePass();
     polly::createDeLICMPass();
     polly::createDumpModulePass("", true);
@@ -109,6 +111,7 @@ void initializeCodeGenerationPass(llvm::PassRegistry &);
 void initializePPCGCodeGenerationPass(llvm::PassRegistry &);
 #endif
 void initializeIslScheduleOptimizerPass(llvm::PassRegistry &);
+void initializeMaximalStaticExpanderPass(llvm::PassRegistry &);
 void initializePollyCanonicalizePass(llvm::PassRegistry &);
 void initializeFlattenSchedulePass(llvm::PassRegistry &);
 void initializeDeLICMPass(llvm::PassRegistry &);

polly/lib/CMakeLists.txt

@@ -62,6 +62,7 @@ add_library(PollyCore OBJECT
   Transform/DeLICM.cpp
   Transform/ZoneAlgo.cpp
   Transform/Simplify.cpp
+  Transform/MaximalStaticExpansion.cpp
   ${POLLY_HEADER_FILES}
   )
 set_target_properties(PollyCore PROPERTIES FOLDER "Polly")

polly/lib/Support/RegisterPasses.cpp

@@ -149,6 +149,11 @@ static cl::opt<bool> ImportJScop(
     cl::desc("Import the polyhedral description of the detected Scops"),
     cl::Hidden, cl::init(false), cl::ZeroOrMore, cl::cat(PollyCategory));
 
+static cl::opt<bool> FullyIndexedStaticExpansion(
+    "polly-enable-mse",
+    cl::desc("Fully expand the memory accesses of the detected Scops"),
+    cl::Hidden, cl::init(false), cl::ZeroOrMore, cl::cat(PollyCategory));
+
 static cl::opt<bool> ExportJScop(
     "polly-export",
     cl::desc("Export the polyhedral description of the detected Scops"),
@@ -251,6 +256,7 @@ void initializePollyPasses(PassRegistry &Registry) {
   initializeDependenceInfoWrapperPassPass(Registry);
   initializeJSONExporterPass(Registry);
   initializeJSONImporterPass(Registry);
+  initializeMaximalStaticExpanderPass(Registry);
   initializeIslAstInfoWrapperPassPass(Registry);
   initializeIslScheduleOptimizerPass(Registry);
   initializePollyCanonicalizePass(Registry);
@@ -330,6 +336,9 @@ void registerPollyPasses(llvm::legacy::PassManagerBase &PM) {
   if (DeadCodeElim)
     PM.add(polly::createDeadCodeElimPass());
 
+  if (FullyIndexedStaticExpansion)
+    PM.add(polly::createMaximalStaticExpansionPass());
+
   if (EnablePruneUnprofitable)
     PM.add(polly::createPruneUnprofitablePass());