[Refactor] Remove containsLoop to find innermost loops

Use the fact that if we visit a for node first in pre and next in post order
  we know we did not visit any children, thus we found an innermost loop.

  + Test case for an innermost loop with a conditional inside

llvm-svn: 213870

polly/lib/CodeGen/IslAst.cpp

@@ -84,13 +84,20 @@ IslAstInfo::IslAstUserPayload::~IslAstUserPayload() {
   isl_ast_build_free(Build);
 }
 
-// Temporary information used when building the ast.
+/// @brief Temporary information used when building the ast.
 struct AstBuildUserInfo {
-  // The dependence information.
+  /// @brief Construct and initialize the helper struct for AST creation.
+  AstBuildUserInfo()
+      : Deps(nullptr), InParallelFor(false), LastForNodeId(nullptr) {}
+
+  /// @brief The dependence information used for the parallelism check.
   Dependences *Deps;
 
-  // We are inside a parallel for node.
-  int InParallelFor;
+  /// @brief Flag to indicate that we are inside a parallel for node.
+  bool InParallelFor;
+
+  /// @brief The last iterator id created for the current SCoP.
+  isl_id *LastForNodeId;
 };
 
 // Print a loop annotated with OpenMP or vector pragmas.
@@ -237,52 +244,13 @@ static __isl_give isl_id *astBuildBeforeFor(__isl_keep isl_ast_build *Build,
   IslAstUserPayload *NodeInfo = new IslAstUserPayload();
   isl_id *Id = isl_id_alloc(isl_ast_build_get_ctx(Build), "", NodeInfo);
   Id = isl_id_set_free_user(Id, freeIslAstUserPayload);
+  BuildInfo->LastForNodeId = Id;
 
   markOpenmpParallel(Build, BuildInfo, NodeInfo);
 
   return Id;
 }
 
-// Returns 0 when Node contains loops, otherwise returns -1. This search
-// function uses ISL's way to iterate over lists of isl_ast_nodes with
-// isl_ast_node_list_foreach. Please use the single argument wrapper function
-// that returns a bool instead of using this function directly.
-static int containsLoops(__isl_take isl_ast_node *Node, void *User) {
-  if (!Node)
-    return -1;
-
-  switch (isl_ast_node_get_type(Node)) {
-  case isl_ast_node_for:
-    isl_ast_node_free(Node);
-    return 0;
-  case isl_ast_node_block: {
-    isl_ast_node_list *List = isl_ast_node_block_get_children(Node);
-    int Res = isl_ast_node_list_foreach(List, &containsLoops, nullptr);
-    isl_ast_node_list_free(List);
-    isl_ast_node_free(Node);
-    return Res;
-  }
-  case isl_ast_node_if: {
-    int Res = -1;
-    if (0 == containsLoops(isl_ast_node_if_get_then(Node), nullptr) ||
-        (isl_ast_node_if_has_else(Node) &&
-         0 == containsLoops(isl_ast_node_if_get_else(Node), nullptr)))
-      Res = 0;
-    isl_ast_node_free(Node);
-    return Res;
-  }
-  case isl_ast_node_user:
-  default:
-    isl_ast_node_free(Node);
-    return -1;
-  }
-}
-
-// Returns true when Node contains loops.
-static bool containsLoops(__isl_take isl_ast_node *Node) {
-  return 0 == containsLoops(Node, nullptr);
-}
-
 // This method is executed after the construction of a for node.
 //
 // It performs the following actions:
@@ -299,10 +267,12 @@ astBuildAfterFor(__isl_take isl_ast_node *Node, __isl_keep isl_ast_build *Build,
   IslAstUserPayload *Info = (IslAstUserPayload *)isl_id_get_user(Id);
   AstBuildUserInfo *BuildInfo = (AstBuildUserInfo *)User;
 
+  bool IsInnermost = (Id == BuildInfo->LastForNodeId);
+
   if (Info) {
     if (Info->IsOutermostParallel)
       BuildInfo->InParallelFor = 0;
-    if (!containsLoops(isl_ast_node_for_get_body(Node)))
+    if (IsInnermost)
       if (astScheduleDimIsParallel(Build, BuildInfo->Deps,
                                    Info->IsReductionParallel))
         Info->IsInnermostParallel = 1;

polly/test/Isl/CodeGen/loop_with_condition_2.ll

@@ -1,4 +1,16 @@
-; RUN: opt %loadPolly %defaultOpts -polly-ast -analyze < %s | FileCheck %s
+; RUN: opt %loadPolly %defaultOpts -polly-ast -polly-ast-detect-parallel -analyze < %s | FileCheck %s
+
+; Verify that we actually detect this loop as the innermost loop even though
+; there is a conditional inside.
+
+; CHECK: #pragma simd
+; CHECK: for (int c1 = 0; c1 <= 1023; c1 += 1) {
+; CHECK:   if (c1 >= m + 1025) {
+; CHECK:     Stmt_if_else(c1);
+; CHECK:   } else
+; CHECK:     Stmt_if_then(c1);
+; CHECK:   Stmt_if_end(c1);
+; CHECK: }
 
 target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
 target triple = "x86_64-unknown-linux-gnu"
@@ -127,11 +139,3 @@ return:                                           ; preds = %for.end35, %if.then
 }
 
 declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) nounwind
-
-; CHECK: for (int c1 = 0; c1 <= 1023; c1 += 1) {
-; CHECK:   if (c1 >= m + 1025) {
-; CHECK:     Stmt_if_else(c1);
-; CHECK:   } else
-; CHECK:     Stmt_if_then(c1);
-; CHECK:   Stmt_if_end(c1);
-; CHECK: }