[LICM] Refactor to expose functionality as utility functions

This refactors the core functionality of LICM: HoistRegion, SinkRegion and
PromoteAliasSet (renamed to promoteLoopAccessesToScalars) as utility functions
in LoopUtils. This will enable other transformations to make use of them
directly.

Patch by Ashutosh Nema.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230178 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Transforms/Utils/LoopUtils.h

@@ -24,6 +24,19 @@ class Loop;
 class LoopInfo;
 class Pass;
 class ScalarEvolution;
+class AliasSetTracker;
+class AliasSet;
+class PredIteratorCache;
+
+/// \brief Captures loop safety information.
+/// It keep information for loop & its header may throw exception.
+struct LICMSafetyInfo {
+  bool MayThrow;           // The current loop contains an instruction which
+                           // may throw.
+  bool HeaderMayThrow;     // Same as previous, but specific to loop header
+  LICMSafetyInfo() : MayThrow(false), HeaderMayThrow(false)
+  {}
+};
 
 BasicBlock *InsertPreheaderForLoop(Loop *L, Pass *P);
 
@@ -63,6 +76,49 @@ bool formLCSSA(Loop &L, DominatorTree &DT, LoopInfo *LI,
 /// Returns true if any modifications are made to the loop.
 bool formLCSSARecursively(Loop &L, DominatorTree &DT, LoopInfo *LI,
                           ScalarEvolution *SE = nullptr);
+
+/// \brief Walk the specified region of the CFG (defined by all blocks
+/// dominated by the specified block, and that are in the current loop) in
+/// reverse depth first order w.r.t the DominatorTree. This allows us to visit
+/// uses before definitions, allowing us to sink a loop body in one pass without
+/// iteration. Takes DomTreeNode, AliasAnalysis, LoopInfo, DominatorTree, 
+/// DataLayout, TargetLibraryInfo, Loop, AliasSet information for all 
+/// instructions of the loop and loop safety information as arguments. 
+/// It returns changed status. 
+bool sinkRegion(DomTreeNode *, AliasAnalysis *, LoopInfo *, DominatorTree *,
+                const DataLayout *, TargetLibraryInfo *, Loop *,
+                AliasSetTracker *, LICMSafetyInfo *);
+
+/// \brief Walk the specified region of the CFG (defined by all blocks
+/// dominated by the specified block, and that are in the current loop) in depth
+/// first order w.r.t the DominatorTree.  This allows us to visit definitions
+/// before uses, allowing us to hoist a loop body in one pass without iteration.
+/// Takes DomTreeNode, AliasAnalysis, LoopInfo, DominatorTree, DataLayout,
+/// TargetLibraryInfo, Loop, AliasSet information for all instructions of the 
+/// loop and loop safety information as arguments. It returns changed status.
+bool hoistRegion(DomTreeNode *, AliasAnalysis *, LoopInfo *, DominatorTree *,
+                 const DataLayout *, TargetLibraryInfo *, Loop *,
+                 AliasSetTracker *, LICMSafetyInfo *);
+
+/// \brief Try to promote memory values to scalars by sinking stores out of 
+/// the loop and moving loads to before the loop.  We do this by looping over
+/// the stores in the loop, looking for stores to Must pointers which are 
+/// loop invariant. It takes AliasSet, Loop exit blocks vector, loop exit blocks
+/// insertion point vector, PredIteratorCache, LoopInfo, DominatorTree, Loop,
+/// AliasSet information for all instructions of the loop and loop safety 
+/// information as arguments. It returns changed status.
+bool promoteLoopAccessesToScalars(AliasSet &, SmallVectorImpl<BasicBlock*> &,
+                                  SmallVectorImpl<Instruction*> &,
+                                  PredIteratorCache &, LoopInfo *,
+                                  DominatorTree *, Loop *, AliasSetTracker *,
+                                  LICMSafetyInfo *);
+
+/// \brief Computes safety information for a loop
+/// checks loop body & header for the possiblity of may throw
+/// exception, it takes LICMSafetyInfo and loop as argument.
+/// Updates safety information in LICMSafetyInfo argument.
+void computeLICMSafetyInfo(LICMSafetyInfo *, Loop *);
+
 }
 
 #endif