[LoopVectorize] Teach Loop Vectorizor about interleaved memory accesses.

Interleaved memory accesses are grouped and vectorized into vector load/store and shufflevector.
E.g. for (i = 0; i < N; i+=2) {
       a = A[i];         // load of even element
       b = A[i+1];       // load of odd element
       ...               // operations on a, b, c, d
       A[i] = c;         // store of even element
       A[i+1] = d;       // store of odd element
     }

  The loads of even and odd elements are identified as an interleave load group, which will be transfered into vectorized IRs like:
     %wide.vec = load <8 x i32>, <8 x i32>* %ptr
     %vec.even = shufflevector <8 x i32> %wide.vec, <8 x i32> undef, <4 x i32> <i32 0, i32 2, i32 4, i32 6>
     %vec.odd = shufflevector <8 x i32> %wide.vec, <8 x i32> undef, <4 x i32> <i32 1, i32 3, i32 5, i32 7>

  The stores of even and odd elements are identified as an interleave store group, which will be transfered into vectorized IRs like:
     %interleaved.vec = shufflevector <4 x i32> %vec.even, %vec.odd, <8 x i32> <i32 0, i32 4, i32 1, i32 5, i32 2, i32 6, i32 3, i32 7> 
     store <8 x i32> %interleaved.vec, <8 x i32>* %ptr

This optimization is currently disabled by defaut. To try it by adding '-enable-interleaved-mem-accesses=true'. 

llvm-svn: 239291

1 files changed, 2 insertions, 7 deletions

diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index 518a55dd5b3..18ace6b2cdd 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -289,11 +289,6 @@ static bool hasComputableBounds(ScalarEvolution *SE,
   return AR->isAffine();
 }
 
-/// \brief Check the stride of the pointer and ensure that it does not wrap in
-/// the address space.
-static int isStridedPtr(ScalarEvolution *SE, Value *Ptr, const Loop *Lp,
-                        const ValueToValueMap &StridesMap);
-
 bool AccessAnalysis::canCheckPtrAtRT(
     LoopAccessInfo::RuntimePointerCheck &RtCheck, unsigned &NumComparisons,
     ScalarEvolution *SE, Loop *TheLoop, const ValueToValueMap &StridesMap,
@@ -510,8 +505,8 @@ static bool isInBoundsGep(Value *Ptr) {
 }
 
 /// \brief Check whether the access through \p Ptr has a constant stride.
-static int isStridedPtr(ScalarEvolution *SE, Value *Ptr, const Loop *Lp,
-                        const ValueToValueMap &StridesMap) {
+int llvm::isStridedPtr(ScalarEvolution *SE, Value *Ptr, const Loop *Lp,
+                       const ValueToValueMap &StridesMap) {
   const Type *Ty = Ptr->getType();
   assert(Ty->isPointerTy() && "Unexpected non-ptr");