[Value] Look through inttoptr (add ..) in accumulateConstantOffsets (#124981)

Look through inttoptr (add (ptrtoint P), C) when accumulating offsets.

Adds a missing fold after
https://github.com/llvm/llvm-project/pull/123518

Alive2 for the tests with changes: https://alive2.llvm.org/ce/z/VvPrzv

PR: https://github.com/llvm/llvm-project/pull/124981

4 files changed, 62 insertions, 19 deletions

diff --git a/llvm/include/llvm/IR/Value.h b/llvm/include/llvm/IR/Value.h
index 011aedec..cfed12e 100644
--- a/llvm/include/llvm/IR/Value.h
+++ b/llvm/include/llvm/IR/Value.h
@@ -710,6 +710,10 @@ public:
   /// For example, for a value \p ExternalAnalysis might try to calculate a
   /// lower bound. If \p ExternalAnalysis is successful, it should return true.
   ///
+  /// If \p LookThroughIntToPtr is true then this method also looks through
+  /// IntToPtr and PtrToInt constant expressions. The returned pointer may not
+  /// have the same provenance as this value.
+  ///
   /// If this is called on a non-pointer value, it returns 'this' and the
   /// \p Offset is not modified.
   ///
@@ -722,17 +726,19 @@ public:
       const DataLayout &DL, APInt &Offset, bool AllowNonInbounds,
       bool AllowInvariantGroup = false,
       function_ref<bool(Value &Value, APInt &Offset)> ExternalAnalysis =
-          nullptr) const;
+          nullptr,
+      bool LookThroughIntToPtr = false) const;
 
   Value *stripAndAccumulateConstantOffsets(
       const DataLayout &DL, APInt &Offset, bool AllowNonInbounds,
       bool AllowInvariantGroup = false,
       function_ref<bool(Value &Value, APInt &Offset)> ExternalAnalysis =
-          nullptr) {
+          nullptr,
+      bool LookThroughIntToPtr = false) {
     return const_cast<Value *>(
         static_cast<const Value *>(this)->stripAndAccumulateConstantOffsets(
-            DL, Offset, AllowNonInbounds, AllowInvariantGroup,
-            ExternalAnalysis));
+            DL, Offset, AllowNonInbounds, AllowInvariantGroup, ExternalAnalysis,
+            LookThroughIntToPtr));
   }
 
   /// This is a wrapper around stripAndAccumulateConstantOffsets with the
diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 80c1277..d645bf8 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1258,11 +1258,16 @@ Constant *llvm::ConstantFoldCompareInstOperands(
     if (Ops0->getType()->isPointerTy() && !ICmpInst::isSigned(Predicate)) {
       unsigned IndexWidth = DL.getIndexTypeSizeInBits(Ops0->getType());
       APInt Offset0(IndexWidth, 0);
-      Value *Stripped0 =
-          Ops0->stripAndAccumulateInBoundsConstantOffsets(DL, Offset0);
+      bool IsEqPred = ICmpInst::isEquality(Predicate);
+      Value *Stripped0 = Ops0->stripAndAccumulateConstantOffsets(
+          DL, Offset0, /*AllowNonInbounds=*/IsEqPred,
+          /*AllowInvariantGroup=*/false, /*ExternalAnalysis=*/nullptr,
+          /*LookThroughIntToPtr=*/IsEqPred);
       APInt Offset1(IndexWidth, 0);
-      Value *Stripped1 =
-          Ops1->stripAndAccumulateInBoundsConstantOffsets(DL, Offset1);
+      Value *Stripped1 = Ops1->stripAndAccumulateConstantOffsets(
+          DL, Offset1, /*AllowNonInbounds=*/IsEqPred,
+          /*AllowInvariantGroup=*/false, /*ExternalAnalysis=*/nullptr,
+          /*LookThroughIntToPtr=*/IsEqPred);
       if (Stripped0 == Stripped1)
         return ConstantInt::getBool(
             Ops0->getContext(),
diff --git a/llvm/lib/IR/Value.cpp b/llvm/lib/IR/Value.cpp
index eddb672..b5a69b9 100644
--- a/llvm/lib/IR/Value.cpp
+++ b/llvm/lib/IR/Value.cpp
@@ -714,7 +714,8 @@ const Value *Value::stripPointerCastsForAliasAnalysis() const {
 const Value *Value::stripAndAccumulateConstantOffsets(
     const DataLayout &DL, APInt &Offset, bool AllowNonInbounds,
     bool AllowInvariantGroup,
-    function_ref<bool(Value &, APInt &)> ExternalAnalysis) const {
+    function_ref<bool(Value &, APInt &)> ExternalAnalysis,
+    bool LookThroughIntToPtr) const {
   if (!getType()->isPtrOrPtrVectorTy())
     return this;
 
@@ -775,6 +776,24 @@ const Value *Value::stripAndAccumulateConstantOffsets(
           V = RV;
         if (AllowInvariantGroup && Call->isLaunderOrStripInvariantGroup())
           V = Call->getArgOperand(0);
+    } else if (auto *Int2Ptr = dyn_cast<Operator>(V)) {
+      // Try to accumulate across (inttoptr (add (ptrtoint p), off)).
+      if (!AllowNonInbounds || !LookThroughIntToPtr || !Int2Ptr ||
+          Int2Ptr->getOpcode() != Instruction::IntToPtr ||
+          Int2Ptr->getOperand(0)->getType()->getScalarSizeInBits() != BitWidth)
+        return V;
+
+      auto *Add = dyn_cast<AddOperator>(Int2Ptr->getOperand(0));
+      if (!Add)
+        return V;
+
+      auto *Ptr2Int = dyn_cast<PtrToIntOperator>(Add->getOperand(0));
+      auto *CI = dyn_cast<ConstantInt>(Add->getOperand(1));
+      if (!Ptr2Int || !CI)
+        return V;
+
+      Offset += CI->getValue();
+      V = Ptr2Int->getOperand(0);
     }
     assert(V->getType()->isPtrOrPtrVectorTy() && "Unexpected operand type!");
   } while (Visited.insert(V).second);
diff --git a/llvm/test/Transforms/InstSimplify/constant-fold-inttoptr-add.ll b/llvm/test/Transforms/InstSimplify/constant-fold-inttoptr-add.ll
index 59b4157..34dee39 100644
--- a/llvm/test/Transforms/InstSimplify/constant-fold-inttoptr-add.ll
+++ b/llvm/test/Transforms/InstSimplify/constant-fold-inttoptr-add.ll
@@ -1,12 +1,11 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
-; RUN: opt -p instcombine -S %s | FileCheck %s
+; RUN: opt -p instsimplify -S %s | FileCheck %s
 
 @glob = external global [314 x i64]
 
 define i1 @known_constexpr_add_eq() {
 ; CHECK-LABEL: define i1 @known_constexpr_add_eq() {
-; CHECK-NEXT:    [[COND:%.*]] = icmp eq ptr getelementptr inbounds nuw (i8, ptr @glob, i64 80), inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr)
-; CHECK-NEXT:    ret i1 [[COND]]
+; CHECK-NEXT:    ret i1 false
 ;
   %cond = icmp eq ptr getelementptr inbounds nuw (i8, ptr @glob, i64 80), inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr)
   ret i1 %cond
@@ -14,17 +13,15 @@ define i1 @known_constexpr_add_eq() {
 
 define i1 @known_constexpr_add_eq_ops_swapped() {
 ; CHECK-LABEL: define i1 @known_constexpr_add_eq_ops_swapped() {
-; CHECK-NEXT:    [[COND:%.*]] = icmp eq ptr getelementptr inbounds nuw (i8, ptr @glob, i64 80), inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr)
-; CHECK-NEXT:    ret i1 [[COND]]
+; CHECK-NEXT:    ret i1 false
 ;
-  %cond = icmp eq ptr getelementptr inbounds nuw (i8, ptr @glob, i64 80), inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr)
+  %cond = icmp eq ptr inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr), getelementptr inbounds nuw (i8, ptr @glob, i64 80)
   ret i1 %cond
 }
 
 define i1 @known_constexpr_add_ne() {
 ; CHECK-LABEL: define i1 @known_constexpr_add_ne() {
-; CHECK-NEXT:    [[COND:%.*]] = icmp ne ptr getelementptr inbounds nuw (i8, ptr @glob, i64 80), inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr)
-; CHECK-NEXT:    ret i1 [[COND]]
+; CHECK-NEXT:    ret i1 true
 ;
   %cond = icmp ne ptr getelementptr inbounds nuw (i8, ptr @glob, i64 80), inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr)
   ret i1 %cond
@@ -41,8 +38,7 @@ define i1 @wrap_positive_to_negate() {
 ; 9223372036854775808 = 2^63
 define i1 @wrap_positive_to_zero() {
 ; CHECK-LABEL: define i1 @wrap_positive_to_zero() {
-; CHECK-NEXT:    [[COND:%.*]] = icmp eq ptr @glob, inttoptr (i64 add (i64 ptrtoint (ptr getelementptr nuw (i8, ptr @glob, i64 -9223372036854775808) to i64), i64 -9223372036854775808) to ptr)
-; CHECK-NEXT:    ret i1 [[COND]]
+; CHECK-NEXT:    ret i1 true
 ;
   %cond = icmp eq ptr @glob, inttoptr (i64 add (i64 ptrtoint (ptr getelementptr nuw (i8, ptr @glob, i64 9223372036854775808)to i64), i64 9223372036854775808) to ptr)
   ret i1 %cond
@@ -99,3 +95,20 @@ define ptr @return_inttoptr() {
 ;
   ret ptr inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 8) to ptr)
 }
+
+define i1 @known_constexpr_add_nested_1() {
+; CHECK-LABEL: define i1 @known_constexpr_add_nested_1() {
+; CHECK-NEXT:    ret i1 true
+;
+  %cond = icmp eq ptr @glob, inttoptr (i64 add (i64 ptrtoint (ptr getelementptr inbounds nuw (i8, ptr @glob, i64 80) to i64), i64 -80) to ptr)
+  ret i1 %cond
+}
+
+define i1 @known_constexpr_add_nested_2() {
+; CHECK-LABEL: define i1 @known_constexpr_add_nested_2() {
+; CHECK-NEXT:    ret i1 true
+;
+  ;%cond = icmp eq ptr @glob, ptr getelementptr inbounds nuw (i8, ptr inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr), i64 80)
+  %cond = icmp eq ptr @glob, getelementptr inbounds nuw (i8, ptr inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr), i64 80)
+  ret i1 %cond
+}