[LLVM] Fix stack overflow in SCEV

Break recursion in createNodeFromSelectLikePHI.

Author: mmerecki

external/llvm/releases/14.0.0/patches_external/0003-ScalarEvolutionStackOverflowWindows.patch

@@ -0,0 +1,58 @@
+/*========================== 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"	2023-12-19 12:51:55.043965800 +0100
++++ "b/llvm/include/llvm/Analysis/ScalarEvolution.h"	2023-12-19 12:28:39.120139600 +0100
+@@ -1295,6 +1295,9 @@
+   /// Set of Phis processed in createSCEVIter.
+   SmallPtrSet<const PHINode*, 6> PendingPhiSCEVIter;
+ 
++  /// Set of Phis processed in createPhiNodeFromSelectLikePHI.
++  SmallPtrSet<const PHINode*, 6> PendingPhiNodeFromSelectLikePHI;
++
+   /// 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"	2023-12-19 12:52:55.207074600 +0100
++++ "b/llvm/lib/Analysis/ScalarEvolution.cpp"	2023-12-19 12:37:39.188525900 +0100
+@@ -5836,11 +5836,18 @@
+     auto *BI = dyn_cast<BranchInst>(IDom->getTerminator());
+     Value *Cond = nullptr, *LHS = nullptr, *RHS = nullptr;
+ 
+-    if (BI && BI->isConditional() &&
+-        BrPHIToSelect(DT, BI, PN, Cond, LHS, RHS) &&
+-        IsAvailableOnEntry(L, DT, getSCEV(LHS), PN->getParent()) &&
+-        IsAvailableOnEntry(L, DT, getSCEV(RHS), PN->getParent()))
+-      return createNodeForSelectOrPHI(PN, Cond, LHS, RHS);
++    // do not run over cycled PHIs while processing createNodeFromSelectLikePHI
++    if (PendingPhiNodeFromSelectLikePHI.insert(PN).second) {
++      const SCEV* S = nullptr;
++      if (BI && BI->isConditional() &&
++         BrPHIToSelect(DT, BI, PN, Cond, LHS, RHS) &&
++         IsAvailableOnEntry(L, DT, getSCEV(LHS), PN->getParent()) &&
++         IsAvailableOnEntry(L, DT, getSCEV(RHS), PN->getParent())) {
++          S = createNodeForSelectOrPHI(PN, Cond, LHS, RHS);
++      }
++      PendingPhiNodeFromSelectLikePHI.erase(PN);
++      return S;
++    }
+   }
+ 
+   return nullptr;