Revert "[llvm] Improve llvm.objectsize computation by computing GEP, alloca and malloc parameters bound" (#117020)

Reverts #115522

This caused UBSan errors in multi-stage clang build:

https://lab.llvm.org/buildbot/#/builders/25/builds/4241/steps/10/logs/stdio

Author: fmayer

llvm/include/llvm/IR/Value.h

@@ -723,16 +723,12 @@ class Value {
       bool AllowInvariantGroup = false,
       function_ref<bool(Value &Value, APInt &Offset)> ExternalAnalysis =
           nullptr) const;
-
-  Value *stripAndAccumulateConstantOffsets(
-      const DataLayout &DL, APInt &Offset, bool AllowNonInbounds,
-      bool AllowInvariantGroup = false,
-      function_ref<bool(Value &Value, APInt &Offset)> ExternalAnalysis =
-          nullptr) {
+  Value *stripAndAccumulateConstantOffsets(const DataLayout &DL, APInt &Offset,
+                                           bool AllowNonInbounds,
+                                           bool AllowInvariantGroup = false) {
     return const_cast<Value *>(
         static_cast<const Value *>(this)->stripAndAccumulateConstantOffsets(
-            DL, Offset, AllowNonInbounds, AllowInvariantGroup,
-            ExternalAnalysis));
+            DL, Offset, AllowNonInbounds, AllowInvariantGroup));
   }
 
   /// This is a wrapper around stripAndAccumulateConstantOffsets with the

llvm/lib/Analysis/MemoryBuiltins.cpp

@@ -673,69 +673,6 @@ STATISTIC(ObjectVisitorArgument,
 STATISTIC(ObjectVisitorLoad,
           "Number of load instructions with unsolved size and offset");
 
-static std::optional<APInt>
-combinePossibleConstantValues(std::optional<APInt> LHS,
-                              std::optional<APInt> RHS,
-                              ObjectSizeOpts::Mode EvalMode) {
-  if (!LHS || !RHS)
-    return std::nullopt;
-  if (EvalMode == ObjectSizeOpts::Mode::Max)
-    return LHS->sge(*RHS) ? *LHS : *RHS;
-  else
-    return LHS->sle(*RHS) ? *LHS : *RHS;
-}
-
-static std::optional<APInt> aggregatePossibleConstantValuesImpl(
-    const Value *V, ObjectSizeOpts::Mode EvalMode, unsigned recursionDepth) {
-  constexpr unsigned maxRecursionDepth = 4;
-  if (recursionDepth == maxRecursionDepth)
-    return std::nullopt;
-
-  if (const auto *CI = dyn_cast<ConstantInt>(V)) {
-    return CI->getValue();
-  }
-
-  else if (const auto *SI = dyn_cast<SelectInst>(V)) {
-    return combinePossibleConstantValues(
-        aggregatePossibleConstantValuesImpl(SI->getTrueValue(), EvalMode,
-                                            recursionDepth + 1),
-        aggregatePossibleConstantValuesImpl(SI->getFalseValue(), EvalMode,
-                                            recursionDepth + 1),
-        EvalMode);
-  }
-
-  else if (const auto *PN = dyn_cast<PHINode>(V)) {
-    unsigned Count = PN->getNumIncomingValues();
-    if (Count == 0)
-      return std::nullopt;
-    auto Acc = aggregatePossibleConstantValuesImpl(
-        PN->getIncomingValue(0), EvalMode, recursionDepth + 1);
-    for (unsigned I = 1; Acc && I < Count; ++I) {
-      auto Tmp = aggregatePossibleConstantValuesImpl(
-          PN->getIncomingValue(1), EvalMode, recursionDepth + 1);
-      Acc = combinePossibleConstantValues(Acc, Tmp, EvalMode);
-    }
-    return Acc;
-  }
-
-  return std::nullopt;
-}
-
-static std::optional<APInt>
-aggregatePossibleConstantValues(const Value *V, ObjectSizeOpts::Mode EvalMode) {
-  if (auto *CI = dyn_cast<ConstantInt>(V))
-    return CI->getValue();
-
-  if (EvalMode != ObjectSizeOpts::Mode::Min &&
-      EvalMode != ObjectSizeOpts::Mode::Max)
-    return std::nullopt;
-
-  // Not using computeConstantRange here because we cannot guarantee it's not
-  // doing optimization based on UB which we want to avoid when expanding
-  // __builtin_object_size.
-  return aggregatePossibleConstantValuesImpl(V, EvalMode, 0u);
-}
-
 /// Align \p Size according to \p Alignment. If \p Size is greater than
 /// getSignedMaxValue(), set it as unknown as we can only represent signed value
 /// in OffsetSpan.
@@ -783,36 +720,11 @@ OffsetSpan ObjectSizeOffsetVisitor::computeImpl(Value *V) {
   V = V->stripAndAccumulateConstantOffsets(
       DL, Offset, /* AllowNonInbounds */ true, /* AllowInvariantGroup */ true);
 
-  // Give it another try with approximated analysis. We don't start with this
-  // one because stripAndAccumulateConstantOffsets behaves differently wrt.
-  // overflows if we provide an external Analysis.
-  if ((Options.EvalMode == ObjectSizeOpts::Mode::Min ||
-       Options.EvalMode == ObjectSizeOpts::Mode::Max) &&
-      isa<GEPOperator>(V)) {
-    // External Analysis used to compute the Min/Max value of individual Offsets
-    // within a GEP.
-    ObjectSizeOpts::Mode EvalMode =
-        Options.EvalMode == ObjectSizeOpts::Mode::Min
-            ? ObjectSizeOpts::Mode::Max
-            : ObjectSizeOpts::Mode::Min;
-    auto OffsetRangeAnalysis = [EvalMode](Value &VOffset, APInt &Offset) {
-      if (auto PossibleOffset =
-              aggregatePossibleConstantValues(&VOffset, EvalMode)) {
-        Offset = *PossibleOffset;
-        return true;
-      }
-      return false;
-    };
-
-    V = V->stripAndAccumulateConstantOffsets(
-        DL, Offset, /* AllowNonInbounds */ true, /* AllowInvariantGroup */ true,
-        /*ExternalAnalysis=*/OffsetRangeAnalysis);
-  }
-
   // Later we use the index type size and zero but it will match the type of the
   // value that is passed to computeImpl.
   IntTyBits = DL.getIndexTypeSizeInBits(V->getType());
   Zero = APInt::getZero(IntTyBits);
+
   OffsetSpan ORT = computeValue(V);
 
   bool IndexTypeSizeChanged = InitialIntTyBits != IntTyBits;
@@ -900,9 +812,8 @@ OffsetSpan ObjectSizeOffsetVisitor::visitAllocaInst(AllocaInst &I) {
     return OffsetSpan(Zero, align(Size, I.getAlign()));
 
   Value *ArraySize = I.getArraySize();
-  if (auto PossibleSize =
-          aggregatePossibleConstantValues(ArraySize, Options.EvalMode)) {
-    APInt NumElems = *PossibleSize;
+  if (const ConstantInt *C = dyn_cast<ConstantInt>(ArraySize)) {
+    APInt NumElems = C->getValue();
     if (!CheckedZextOrTrunc(NumElems))
       return ObjectSizeOffsetVisitor::unknown();
 
@@ -928,18 +839,7 @@ OffsetSpan ObjectSizeOffsetVisitor::visitArgument(Argument &A) {
 }
 
 OffsetSpan ObjectSizeOffsetVisitor::visitCallBase(CallBase &CB) {
-  auto Mapper = [this](const Value *V) -> const Value * {
-    if (!V->getType()->isIntegerTy())
-      return V;
-
-    if (auto PossibleBound =
-            aggregatePossibleConstantValues(V, Options.EvalMode))
-      return ConstantInt::get(V->getType(), *PossibleBound);
-
-    return V;
-  };
-
-  if (std::optional<APInt> Size = getAllocSize(&CB, TLI, Mapper)) {
+  if (std::optional<APInt> Size = getAllocSize(&CB, TLI)) {
     // Very large unsigned value cannot be represented as OffsetSpan.
     if (Size->isNegative())
       return ObjectSizeOffsetVisitor::unknown();