Revert "Temporarily Revert "Add basic loop fusion pass.""

The reversion apparently deleted the test/Transforms directory.

Will be re-reverting again.

llvm-svn: 358552

Author: echristo

llvm/include/llvm/InitializePasses.h

@@ -219,6 +219,7 @@ void initializeLoopDeletionLegacyPassPass(PassRegistry&);
 void initializeLoopDistributeLegacyPass(PassRegistry&);
 void initializeLoopExtractorPass(PassRegistry&);
 void initializeLoopGuardWideningLegacyPassPass(PassRegistry&);
+void initializeLoopFuseLegacyPass(PassRegistry&);
 void initializeLoopIdiomRecognizeLegacyPassPass(PassRegistry&);
 void initializeLoopInfoWrapperPassPass(PassRegistry&);
 void initializeLoopInstSimplifyLegacyPassPass(PassRegistry&);

llvm/include/llvm/Transforms/Scalar.h

@@ -458,6 +458,12 @@ FunctionPass *createNaryReassociatePass();
 //
 FunctionPass *createLoopDistributePass();
 
+//===----------------------------------------------------------------------===//
+//
+// LoopFuse - Fuse loops.
+//
+FunctionPass *createLoopFusePass();
+
 //===----------------------------------------------------------------------===//
 //
 // LoopLoadElimination - Perform loop-aware load elimination.

llvm/include/llvm/Transforms/Scalar/LoopFuse.h

@@ -0,0 +1,30 @@
+//===- LoopFuse.h - Loop Fusion Pass ----------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file implements the Loop Fusion pass.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_SCALAR_LOOPFUSE_H
+#define LLVM_TRANSFORMS_SCALAR_LOOPFUSE_H
+
+#include "llvm/IR/PassManager.h"
+
+namespace llvm {
+
+class Function;
+
+class LoopFusePass : public PassInfoMixin<LoopFusePass> {
+public:
+  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
+};
+
+} // end namespace llvm
+
+#endif // LLVM_TRANSFORMS_SCALAR_LOOPFUSE_H

llvm/lib/Passes/PassBuilder.cpp

@@ -122,6 +122,7 @@
 #include "llvm/Transforms/Scalar/LoopDataPrefetch.h"
 #include "llvm/Transforms/Scalar/LoopDeletion.h"
 #include "llvm/Transforms/Scalar/LoopDistribute.h"
+#include "llvm/Transforms/Scalar/LoopFuse.h"
 #include "llvm/Transforms/Scalar/LoopIdiomRecognize.h"
 #include "llvm/Transforms/Scalar/LoopInstSimplify.h"
 #include "llvm/Transforms/Scalar/LoopLoadElimination.h"

llvm/lib/Passes/PassRegistry.def

@@ -197,6 +197,7 @@ FUNCTION_PASS("partially-inline-libcalls", PartiallyInlineLibCallsPass())
 FUNCTION_PASS("lcssa", LCSSAPass())
 FUNCTION_PASS("loop-data-prefetch", LoopDataPrefetchPass())
 FUNCTION_PASS("loop-load-elim", LoopLoadEliminationPass())
+FUNCTION_PASS("loop-fuse", LoopFusePass())
 FUNCTION_PASS("loop-distribute", LoopDistributePass())
 FUNCTION_PASS("loop-vectorize", LoopVectorizePass())
 FUNCTION_PASS("pgo-memop-opt", PGOMemOPSizeOpt())

llvm/lib/Transforms/Scalar/CMakeLists.txt

@@ -28,6 +28,7 @@ add_llvm_library(LLVMScalarOpts
   LoopDeletion.cpp
   LoopDataPrefetch.cpp
   LoopDistribute.cpp
+  LoopFuse.cpp
   LoopIdiomRecognize.cpp
   LoopInstSimplify.cpp
   LoopInterchange.cpp