New pass manager for LICM.

Summary: Port LICM to the new pass manager.

Reviewers: davidxl, silvas

Subscribers: silvas, davide, sanjoy, llvm-commits, mehdi_amini

Differential Revision: http://reviews.llvm.org/D21772

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275118 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 49 insertions, 1 deletions

diff --git a/include/llvm/InitializePasses.h b/include/llvm/InitializePasses.h
index b17a216d328..f4db6fe6f91 100644
--- a/include/llvm/InitializePasses.h
+++ b/include/llvm/InitializePasses.h
@@ -159,7 +159,7 @@ void initializeInternalizeLegacyPassPass(PassRegistry&);
 void initializeIntervalPartitionPass(PassRegistry&);
 void initializeJumpThreadingPass(PassRegistry&);
 void initializeLCSSAWrapperPassPass(PassRegistry &);
-void initializeLICMPass(PassRegistry&);
+void initializeLegacyLICMPassPass(PassRegistry&);
 void initializeLazyValueInfoWrapperPassPass(PassRegistry&);
 void initializeLintPass(PassRegistry&);
 void initializeLiveDebugValuesPass(PassRegistry&);
diff --git a/include/llvm/Transforms/Scalar/LICM.h b/include/llvm/Transforms/Scalar/LICM.h
new file mode 100644
index 00000000000..a050a43d617
--- /dev/null
+++ b/include/llvm/Transforms/Scalar/LICM.h
@@ -0,0 +1,48 @@
+//===- LICM.h - Loop Invariant Code Motion Pass -------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass performs loop invariant code motion, attempting to remove as much
+// code from the body of a loop as possible.  It does this by either hoisting
+// code into the preheader block, or by sinking code to the exit blocks if it is
+// safe.  This pass also promotes must-aliased memory locations in the loop to
+// live in registers, thus hoisting and sinking "invariant" loads and stores.
+//
+// This pass uses alias analysis for two purposes:
+//
+//  1. Moving loop invariant loads and calls out of loops.  If we can determine
+//     that a load or call inside of a loop never aliases anything stored to,
+//     we can hoist it or sink it like any other instruction.
+//  2. Scalar Promotion of Memory - If there is a store instruction inside of
+//     the loop, we try to move the store to happen AFTER the loop instead of
+//     inside of the loop.  This can only happen if a few conditions are true:
+//       A. The pointer stored through is loop invariant
+//       B. There are no stores or loads in the loop which _may_ alias the
+//          pointer.  There are no calls in the loop which mod/ref the pointer.
+//     If these conditions are true, we can promote the loads and stores in the
+//     loop of the pointer to use a temporary alloca'd variable.  We then use
+//     the SSAUpdater to construct the appropriate SSA form for the value.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_SCALAR_LICM_H
+#define LLVM_TRANSFORMS_SCALAR_LICM_H
+
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/IR/PassManager.h"
+
+namespace llvm {
+
+/// Performs Loop Invariant Code Motion Pass.
+class LICMPass : public PassInfoMixin<LICMPass> {
+public:
+  PreservedAnalyses run(Loop &L, AnalysisManager<Loop> &AM);
+};
+} // end namespace llvm
+
+#endif // LLVM_TRANSFORMS_SCALAR_LICM_H