Add an optimization that does CSE in a group of similar GEPs.

This optimization merges the common part of a group of GEPs, so we can compute
each pointer address by adding a simple offset to the common part.

The optimization is currently only enabled for the NVPTX backend, where it has
a large payoff on some benchmarks.

Review: http://reviews.llvm.org/D3462

Patch by Jingyue Wu.

llvm-svn: 207783

3 files changed, 8 insertions, 0 deletions

diff --git a/llvm/include/llvm/InitializePasses.h b/llvm/include/llvm/InitializePasses.h
index 232e422de1c..8e536159db1 100644
--- a/llvm/include/llvm/InitializePasses.h
+++ b/llvm/include/llvm/InitializePasses.h
@@ -238,6 +238,7 @@ void initializeSimpleInlinerPass(PassRegistry&);
 void initializeRegisterCoalescerPass(PassRegistry&);
 void initializeSingleLoopExtractorPass(PassRegistry&);
 void initializeSinkingPass(PassRegistry&);
+void initializeSeparateConstOffsetFromGEPPass(PassRegistry &);
 void initializeSlotIndexesPass(PassRegistry&);
 void initializeSpillPlacementPass(PassRegistry&);
 void initializeStackProtectorPass(PassRegistry&);
diff --git a/llvm/include/llvm/LinkAllPasses.h b/llvm/include/llvm/LinkAllPasses.h
index 9cb1c5c8a83..2616ebd1fab 100644
--- a/llvm/include/llvm/LinkAllPasses.h
+++ b/llvm/include/llvm/LinkAllPasses.h
@@ -156,6 +156,7 @@ namespace {
       (void) llvm::createBBVectorizePass();
       (void) llvm::createPartiallyInlineLibCallsPass();
       (void) llvm::createScalarizerPass();
+      (void) llvm::createSeparateConstOffsetFromGEPPass();
 
       (void)new llvm::IntervalPartition();
       (void)new llvm::FindUsedTypes();
diff --git a/llvm/include/llvm/Transforms/Scalar.h b/llvm/include/llvm/Transforms/Scalar.h
index 453de03972d..6aea643c42a 100644
--- a/llvm/include/llvm/Transforms/Scalar.h
+++ b/llvm/include/llvm/Transforms/Scalar.h
@@ -377,6 +377,12 @@ FunctionPass *createScalarizerPass();
 // AddDiscriminators - Add DWARF path discriminators to the IR.
 FunctionPass *createAddDiscriminatorsPass();
 
+//===----------------------------------------------------------------------===//
+//
+// SeparateConstOffsetFromGEP - Split GEPs for better CSE
+//
+FunctionPass *createSeparateConstOffsetFromGEPPass();
+
 } // End llvm namespace
 
 #endif