[NFC] [Polly] Move PPCGCodeGeneration::pollyBuildAstExprForStmt to isl++.

[bollu]

@grosser I'm not entirely sure if this makes it cleaner due to the interfacing with PPCG. I think it's easier to see the transforms that are going on.

[grosser]

I am fine with moving more to the C++ interface.

Two comments;

1. Use isl::manage(isl_ast_build_copy(Build)) and drop the "Build.release()" line

2. I really dislike the Build_ variable name. Can you call it Build_C?

[grosser]

LGTM, assuming you agree with the previously mentioned changes.

[bollu]

• [NFC wrt patch] copy the isl_multi_pw_aff object rather than acquiring and releasing it.

[grosser]

Nice. That looks better.

[bollu]

This was closed by r308869. Unfortunately, the commit was mis-labeled, and wound up closing D35771

lib/CodeGen/PPCGCodeGeneration.cpp

static MustKillsInfo computeMustKillsInfo(const Scop &S) {
   return Info;
 }
 
 /// Create the ast expressions for a ScopStmt.
 ///
 /// This function is a callback for to generate the ast expressions for each
 /// of the scheduled ScopStmts.
 static __isl_give isl_id_to_ast_expr *pollyBuildAstExprForStmt(
-    void *StmtT, isl_ast_build *Build,
+    void *StmtT, __isl_take isl_ast_build *Build_C,
     isl_multi_pw_aff *(*FunctionIndex)(__isl_take isl_multi_pw_aff *MPA,
                                        isl_id *Id, void *User),
     void *UserIndex,
     isl_ast_expr *(*FunctionExpr)(isl_ast_expr *Expr, isl_id *Id, void *User),
     void *UserExpr) {
 
   ScopStmt *Stmt = (ScopStmt *)StmtT;
 
-  isl_ctx *Ctx;
-
-  if (!Stmt || !Build)
+  if (!Stmt || !Build_C)
     return NULL;
 
-  Ctx = isl_ast_build_get_ctx(Build);
-  isl_id_to_ast_expr *RefToExpr = isl_id_to_ast_expr_alloc(Ctx, 0);
+  isl::ast_build Build = isl::manage(isl_ast_build_copy(Build_C));
+  isl::ctx Ctx = Build.get_ctx();
+  isl::id_to_ast_expr RefToExpr = isl::id_to_ast_expr::alloc(Ctx, 0);
 
   for (MemoryAccess *Acc : *Stmt) {
-    isl_map *AddrFunc = Acc->getAddressFunction().release();
-    AddrFunc = isl_map_intersect_domain(AddrFunc, Stmt->getDomain());
-    isl_id *RefId = Acc->getId().release();
-    isl_pw_multi_aff *PMA = isl_pw_multi_aff_from_map(AddrFunc);
-    isl_multi_pw_aff *MPA = isl_multi_pw_aff_from_pw_multi_aff(PMA);
-    MPA = isl_multi_pw_aff_coalesce(MPA);
-    MPA = FunctionIndex(MPA, RefId, UserIndex);
-    isl_ast_expr *Access = isl_ast_build_access_from_multi_pw_aff(Build, MPA);
-    Access = FunctionExpr(Access, RefId, UserExpr);
-    RefToExpr = isl_id_to_ast_expr_set(RefToExpr, RefId, Access);
+    isl::map AddrFunc = Acc->getAddressFunction();
+    AddrFunc = AddrFunc.intersect_domain(isl::manage(Stmt->getDomain()));
+
+    isl::id RefId = Acc->getId();
+    isl::pw_multi_aff PMA = isl::pw_multi_aff::from_map(AddrFunc);
+
+    isl::multi_pw_aff MPA = isl::multi_pw_aff(PMA);
+    MPA = MPA.coalesce();
+    MPA = isl::manage(FunctionIndex(MPA.release(), RefId.get(), UserIndex));
+
+    isl::ast_expr Access = Build.access_from(MPA);
+    Access = isl::manage(FunctionExpr(Access.release(), RefId.get(), UserExpr));
+    RefToExpr = RefToExpr.set(RefId, Access);
   }
 
-  return RefToExpr;
+  return RefToExpr.release();
 }
 
 /// Given a LLVM Type, compute its size in bytes,
 static int computeSizeInBytes(const Type *T) {
   int bytes = T->getPrimitiveSizeInBits() / 8;
   if (bytes == 0)
     bytes = T->getScalarSizeInBits() / 8;
   return bytes;