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

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Jan 30, 2025
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[Value] Look through inttoptr (add ..) in accumulateConstantOffsets #124981

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9f59ca7
[Value] Look through inttoptr (add ..) in accumulateConstantOffsets
fhahn Jan 29, 2025
d5fb1db
!fixup add LookThroughIntToPtr flag
fhahn Jan 30, 2025
fb338c3
!fixup address comments, thanks
fhahn Jan 30, 2025
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14 changes: 10 additions & 4 deletions llvm/include/llvm/IR/Value.h
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Original file line number Diff line number Diff line change
Expand Up @@ -710,6 +710,10 @@ class Value {
/// 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.
///
Expand All @@ -722,17 +726,19 @@ class Value {
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
Expand Down
13 changes: 9 additions & 4 deletions llvm/lib/Analysis/ConstantFolding.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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(),
Expand Down
21 changes: 20 additions & 1 deletion llvm/lib/IR/Value.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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;

Expand Down Expand Up @@ -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);
Expand Down
33 changes: 23 additions & 10 deletions llvm/test/Transforms/InstSimplify/constant-fold-inttoptr-add.ll
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This test should either use -p instsimplify or be in the InstCombine directory.

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Originally I had it in instcombine, then moved but. not updated the run-line should be fixed now thanks

Original file line number Diff line number Diff line change
@@ -1,30 +1,27 @@
; 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
}

define i1 @known_constexpr_add_eq_ops_swapped() {
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I don't get what the difference between this test and the previous is. What's swapped here?

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Adjusted the name but not the code... fixed now, thanks

; 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
Expand All @@ -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
Expand Down Expand Up @@ -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
}