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

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

Adds a missing fold after
llvm#123518

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

Author: fhahn

llvm/lib/Analysis/ConstantFolding.cpp

@@ -1258,11 +1258,12 @@ 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 AllowNonInbounds = ICmpInst::isEquality(Predicate);
+      Value *Stripped0 = Ops0->stripAndAccumulateConstantOffsets(
+          DL, Offset0, AllowNonInbounds);
       APInt Offset1(IndexWidth, 0);
-      Value *Stripped1 =
-          Ops1->stripAndAccumulateInBoundsConstantOffsets(DL, Offset1);
+      Value *Stripped1 = Ops1->stripAndAccumulateConstantOffsets(
+          DL, Offset1, AllowNonInbounds);
       if (Stripped0 == Stripped1)
         return ConstantInt::getBool(
             Ops0->getContext(),

llvm/lib/IR/Value.cpp

@@ -775,6 +775,25 @@ 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 (!Int2Ptr || Int2Ptr->getOpcode() != Instruction::IntToPtr ||
+          Int2Ptr->getOperand(0)->getType()->getScalarSizeInBits() != BitWidth)
+        return V;
+      auto *Add = dyn_cast<AddOperator>(Int2Ptr->getOperand(0));
+      if (!AllowNonInbounds || !Add)
+        return V;
+      auto *Ptr2Int = dyn_cast<PtrToIntOperator>(Add->getOperand(0));
+      auto *CI = dyn_cast<ConstantInt>(Add->getOperand(1));
+      if (!Ptr2Int || !CI)
+        return V;
+
+      APInt AddOffset = CI->getValue();
+      if (AddOffset.getSignificantBits() > BitWidth)
+        return V;
+
+      Offset = AddOffset.sextOrTrunc(BitWidth);
+      V = Ptr2Int->getOperand(0);
     }
     assert(V->getType()->isPtrOrPtrVectorTy() && "Unexpected operand type!");
   } while (Visited.insert(V).second);

llvm/test/Transforms/InstSimplify/constant-fold-inttoptr-add.ll

@@ -7,17 +7,15 @@ target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:
 
 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
 }
 
 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
@@ -34,8 +32,7 @@ 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