[LLVM] Fix stack overflow in SCEV

Break recursion in getSCEVIter.

Author: mmerecki

external/llvm/releases/14.0.0/patches_external/ScalarEvolutionStackOverflowWindows.patch renamed to external/llvm/releases/14.0.0/patches_external/0001-ScalarEvolutionStackOverflowWindows.patch

@@ -0,0 +1,84 @@
+/*========================== begin_copyright_notice ============================
+
+Copyright (C) 2023 Intel Corporation
+
+SPDX-License-Identifier: MIT
+
+============================= end_copyright_notice ===========================*/
+
+/*========================== begin_copyright_notice ============================
+
+Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+See https://llvm.org/LICENSE.txt for license information.
+SPDX-License-Identifier: Apache-2.0 with LLVM-exception
+
+============================= end_copyright_notice ===========================*/
+
+# TODO: Once upstreamed, update with LLORG revision & adjust per community review
+
+diff -Naur "a/llvm/include/llvm/Analysis/ScalarEvolution.h" "b/llvm/include/llvm/Analysis/ScalarEvolution.h"
+--- "a/llvm/include/llvm/Analysis/ScalarEvolution.h"	2023-09-27 19:27:08.174510600 +0200
++++ "b/llvm/include/llvm/Analysis/ScalarEvolution.h"	2023-09-27 18:41:11.301171800 +0200
+@@ -1292,6 +1292,9 @@
+   /// Mark predicate values currently being processed by isImpliedCond.
+   SmallPtrSet<const Value *, 6> PendingLoopPredicates;
+ 
++  /// Set of Phis processed in createSCEVIter.
++  SmallPtrSet<const PHINode*, 6> PendingPhiSCEVIter;
++
+   /// Mark SCEVUnknown Phis currently being processed by getRangeRef.
+   SmallPtrSet<const PHINode *, 6> PendingPhiRanges;
+ 
+diff -Naur "a/llvm/lib/Analysis/ScalarEvolution.cpp" "b/llvm/lib/Analysis/ScalarEvolution.cpp"
+--- "a/llvm/lib/Analysis/ScalarEvolution.cpp"	2023-09-27 19:27:08.189098000 +0200
++++ "b/llvm/lib/Analysis/ScalarEvolution.cpp"	2023-09-27 19:05:40.601713600 +0200
+@@ -7076,6 +7076,13 @@
+ 
+   Stack.emplace_back(V, true);
+   Stack.emplace_back(V, false);
++
++  if (isa<PHINode>(V) &&
++      !PendingPhiSCEVIter.insert(cast<PHINode>(V)).second) {
++    // cycled back to createSCEVIter while processing this Phi, bail
++    return getUnknown(V);
++  }
++
+   while (!Stack.empty()) {
+     auto E = Stack.pop_back_val();
+     Value *CurV = E.getPointer();
+@@ -7088,6 +7095,12 @@
+     // If all operands have been visited already, create the SCEV.
+     if (E.getInt()) {
+       CreatedSCEV = createSCEV(CurV);
++      if (isa<PHINode>(CurV))
++        PendingPhiSCEVIter.erase(cast<PHINode>(CurV));
++    } else if (isa<PHINode>(CurV) && 
++      PendingPhiSCEVIter.count(cast<PHINode>(CurV)) > 0) {
++      // cycled Phi, try to get its SCEV
++      CreatedSCEV = createSCEV(CurV);
+     } else {
+       // Otherwise get the operands we need to create SCEV's for before creating
+       // the SCEV for CurV. If the SCEV for CurV can be constructed trivially,
+@@ -7101,8 +7114,11 @@
+       // Queue CurV for SCEV creation, followed by its's operands which need to
+       // be constructed first.
+       Stack.emplace_back(CurV, true);
+-      for (Value *Op : Ops)
++      if (isa<PHINode>(CurV))
++          PendingPhiSCEVIter.insert(cast<PHINode>(CurV));
++      for (Value *Op : Ops) {
+         Stack.emplace_back(Op, false);
++      }
+     }
+   }
+ 
+@@ -7225,7 +7241,8 @@
+     return getUnknown(V);
+ 
+   case Instruction::PHI:
+-    // Keep constructing SCEVs' for phis recursively for now.
++    for (auto& Op : cast<PHINode>(U)->operands())
++      Ops.push_back(Op);
+     return nullptr;
+ 
+   case Instruction::Select: {