1 files changed, 194 insertions, 0 deletions
diff --git a/contrib/llvm-project/llvm/lib/Transforms/Utils/GlobalStatus.cpp b/contrib/llvm-project/llvm/lib/Transforms/Utils/GlobalStatus.cpp
new file mode 100644
index 000000000000..f782396be7b6
--- /dev/null
+++ b/contrib/llvm-project/llvm/lib/Transforms/Utils/GlobalStatus.cpp
@@ -0,0 +1,194 @@
+//===-- GlobalStatus.cpp - Compute status info for globals -----------------==//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/GlobalStatus.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/IR/BasicBlock.h"
+#include "llvm/IR/Constant.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/GlobalValue.h"
+#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/InstrTypes.h"
+#include "llvm/IR/Instruction.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Use.h"
+#include "llvm/IR/User.h"
+#include "llvm/IR/Value.h"
+#include "llvm/Support/AtomicOrdering.h"
+#include "llvm/Support/Casting.h"
+#include <algorithm>
+#include <cassert>
+
+using namespace llvm;
+
+/// Return the stronger of the two ordering. If the two orderings are acquire
+/// and release, then return AcquireRelease.
+///
+static AtomicOrdering strongerOrdering(AtomicOrdering X, AtomicOrdering Y) {
+  if ((X == AtomicOrdering::Acquire && Y == AtomicOrdering::Release) ||
+      (Y == AtomicOrdering::Acquire && X == AtomicOrdering::Release))
+    return AtomicOrdering::AcquireRelease;
+  return (AtomicOrdering)std::max((unsigned)X, (unsigned)Y);
+}
+
+/// It is safe to destroy a constant iff it is only used by constants itself.
+/// Note that constants cannot be cyclic, so this test is pretty easy to
+/// implement recursively.
+///
+bool llvm::isSafeToDestroyConstant(const Constant *C) {
+  if (isa<GlobalValue>(C))
+    return false;
+
+  if (isa<ConstantData>(C))
+    return false;
+
+  for (const User *U : C->users())
+    if (const Constant *CU = dyn_cast<Constant>(U)) {
+      if (!isSafeToDestroyConstant(CU))
+        return false;
+    } else
+      return false;
+  return true;
+}
+
+static bool analyzeGlobalAux(const Value *V, GlobalStatus &GS,
+                             SmallPtrSetImpl<const Value *> &VisitedUsers) {
+  if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
+    if (GV->isExternallyInitialized())
+      GS.StoredType = GlobalStatus::StoredOnce;
+
+  for (const Use &U : V->uses()) {
+    const User *UR = U.getUser();
+    if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(UR)) {
+      GS.HasNonInstructionUser = true;
+
+      // If the result of the constantexpr isn't pointer type, then we won't
+      // know to expect it in various places.  Just reject early.
+      if (!isa<PointerType>(CE->getType()))
+        return true;
+
+      // FIXME: Do we need to add constexpr selects to VisitedUsers?
+      if (analyzeGlobalAux(CE, GS, VisitedUsers))
+        return true;
+    } else if (const Instruction *I = dyn_cast<Instruction>(UR)) {
+      if (!GS.HasMultipleAccessingFunctions) {
+        const Function *F = I->getParent()->getParent();
+        if (!GS.AccessingFunction)
+          GS.AccessingFunction = F;
+        else if (GS.AccessingFunction != F)
+          GS.HasMultipleAccessingFunctions = true;
+      }
+      if (const LoadInst *LI = dyn_cast<LoadInst>(I)) {
+        GS.IsLoaded = true;
+        // Don't hack on volatile loads.
+        if (LI->isVolatile())
+          return true;
+        GS.Ordering = strongerOrdering(GS.Ordering, LI->getOrdering());
+      } else if (const StoreInst *SI = dyn_cast<StoreInst>(I)) {
+        // Don't allow a store OF the address, only stores TO the address.
+        if (SI->getOperand(0) == V)
+          return true;
+
+        // Don't hack on volatile stores.
+        if (SI->isVolatile())
+          return true;
+
+        GS.Ordering = strongerOrdering(GS.Ordering, SI->getOrdering());
+
+        // If this is a direct store to the global (i.e., the global is a scalar
+        // value, not an aggregate), keep more specific information about
+        // stores.
+        if (GS.StoredType != GlobalStatus::Stored) {
+          if (const GlobalVariable *GV =
+                  dyn_cast<GlobalVariable>(SI->getOperand(1))) {
+            Value *StoredVal = SI->getOperand(0);
+
+            if (Constant *C = dyn_cast<Constant>(StoredVal)) {
+              if (C->isThreadDependent()) {
+                // The stored value changes between threads; don't track it.
+                return true;
+              }
+            }
+
+            if (GV->hasInitializer() && StoredVal == GV->getInitializer()) {
+              if (GS.StoredType < GlobalStatus::InitializerStored)
+                GS.StoredType = GlobalStatus::InitializerStored;
+            } else if (isa<LoadInst>(StoredVal) &&
+                       cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
+              if (GS.StoredType < GlobalStatus::InitializerStored)
+                GS.StoredType = GlobalStatus::InitializerStored;
+            } else if (GS.StoredType < GlobalStatus::StoredOnce) {
+              GS.StoredType = GlobalStatus::StoredOnce;
+              GS.StoredOnceValue = StoredVal;
+            } else if (GS.StoredType == GlobalStatus::StoredOnce &&
+                       GS.StoredOnceValue == StoredVal) {
+              // noop.
+            } else {
+              GS.StoredType = GlobalStatus::Stored;
+            }
+          } else {
+            GS.StoredType = GlobalStatus::Stored;
+          }
+        }
+      } else if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I) ||
+                 isa<AddrSpaceCastInst>(I)) {
+        // Skip over bitcasts and GEPs; we don't care about the type or offset
+        // of the pointer.
+        if (analyzeGlobalAux(I, GS, VisitedUsers))
+          return true;
+      } else if (isa<SelectInst>(I) || isa<PHINode>(I)) {
+        // Look through selects and PHIs to find if the pointer is
+        // conditionally accessed. Make sure we only visit an instruction
+        // once; otherwise, we can get infinite recursion or exponential
+        // compile time.
+        if (VisitedUsers.insert(I).second)
+          if (analyzeGlobalAux(I, GS, VisitedUsers))
+            return true;
+      } else if (isa<CmpInst>(I)) {
+        GS.IsCompared = true;
+      } else if (const MemTransferInst *MTI = dyn_cast<MemTransferInst>(I)) {
+        if (MTI->isVolatile())
+          return true;
+        if (MTI->getArgOperand(0) == V)
+          GS.StoredType = GlobalStatus::Stored;
+        if (MTI->getArgOperand(1) == V)
+          GS.IsLoaded = true;
+      } else if (const MemSetInst *MSI = dyn_cast<MemSetInst>(I)) {
+        assert(MSI->getArgOperand(0) == V && "Memset only takes one pointer!");
+        if (MSI->isVolatile())
+          return true;
+        GS.StoredType = GlobalStatus::Stored;
+      } else if (const auto *CB = dyn_cast<CallBase>(I)) {
+        if (!CB->isCallee(&U))
+          return true;
+        GS.IsLoaded = true;
+      } else {
+        return true; // Any other non-load instruction might take address!
+      }
+    } else if (const Constant *C = dyn_cast<Constant>(UR)) {
+      GS.HasNonInstructionUser = true;
+      // We might have a dead and dangling constant hanging off of here.
+      if (!isSafeToDestroyConstant(C))
+        return true;
+    } else {
+      GS.HasNonInstructionUser = true;
+      // Otherwise must be some other user.
+      return true;
+    }
+  }
+
+  return false;
+}
+
+GlobalStatus::GlobalStatus() = default;
+
+bool GlobalStatus::analyzeGlobal(const Value *V, GlobalStatus &GS) {
+  SmallPtrSet<const Value *, 16> VisitedUsers;
+  return analyzeGlobalAux(V, GS, VisitedUsers);
+}