[delinearize] Extract array dimensions from alloca and global declarations

This implements an alternative to extract multi-dimensional array information
directly from alloca instructions and global variable declarations instead of
relying on parsing the information from GEP instructions.

The functionality for GEP delinearization remains in this patch such that we can
evaluate regressions of the array_info extraction.

Next patch removes the code for GEP delinearization.

Author: sebpop

llvm/include/llvm/Analysis/Delinearization.h

@@ -112,6 +112,13 @@ void delinearize(ScalarEvolution &SE, const SCEV *Expr,
                  SmallVectorImpl<const SCEV *> &Subscripts,
                  SmallVectorImpl<const SCEV *> &Sizes, const SCEV *ElementSize);
 
+/// Same as delinearize.  TODO: only use delinearize() instead of other internal
+/// functions.
+bool delinearizeUsingArrayInfo(ScalarEvolution &SE, const SCEV *AccessFn,
+                               SmallVectorImpl<const SCEV *> &Subscripts,
+                               SmallVectorImpl<const SCEV *> &Sizes,
+                               const SCEV *ElementSize);
+
 /// Compute the dimensions of fixed size array from \Expr and save the results
 /// in \p Sizes.
 bool findFixedSizeArrayDimensions(ScalarEvolution &SE, const SCEV *Expr,
@@ -155,6 +162,17 @@ bool getIndexExpressionsFromGEP(ScalarEvolution &SE,
                                 SmallVectorImpl<const SCEV *> &Subscripts,
                                 SmallVectorImpl<int> &Sizes);
 
+/// Compute access functions for each subscript in a delinearized array access.
+void computeAccessFunctions(ScalarEvolution &SE, const SCEV *Expr,
+                            SmallVectorImpl<const SCEV *> &Subscripts,
+                            SmallVectorImpl<const SCEV *> &Sizes,
+                            const SCEV *ElementSize);
+
+/// Backward compatibility wrapper for computeAccessFunctions.
+void computeAccessFunctions(ScalarEvolution &SE, const SCEV *Expr,
+                            SmallVectorImpl<const SCEV *> &Subscripts,
+                            SmallVectorImpl<const SCEV *> &Sizes);
+
 /// Implementation of fixed size array delinearization. Try to delinearize
 /// access function for a fixed size multi-dimensional array, by deriving
 /// subscripts from GEP instructions. Returns true upon success and false