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

fhahn · 2025-01-29T20:32:41Z

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

Adds a missing fold after
#123518

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

llvmbot · 2025-01-29T20:33:15Z

@llvm/pr-subscribers-llvm-ir
@llvm/pr-subscribers-llvm-analysis

@llvm/pr-subscribers-llvm-transforms

Author: Florian Hahn (fhahn)

Changes

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

Adds a missing fold after
#123518

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

Full diff: https://github.com/llvm/llvm-project/pull/124981.diff

3 Files Affected:

(modified) llvm/lib/Analysis/ConstantFolding.cpp (+5-4)
(modified) llvm/lib/IR/Value.cpp (+19)
(added) llvm/test/Transforms/InstSimplify/constant-fold-inttoptr-add.ll (+84)

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 80c1277e631653..04741c57492ae6 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/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(),
diff --git a/llvm/lib/IR/Value.cpp b/llvm/lib/IR/Value.cpp
index eddb67282fca46..48905609429b19 100644
--- a/llvm/lib/IR/Value.cpp
+++ b/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);
diff --git a/llvm/test/Transforms/InstSimplify/constant-fold-inttoptr-add.ll b/llvm/test/Transforms/InstSimplify/constant-fold-inttoptr-add.ll
new file mode 100644
index 00000000000000..a0a34e2fe73958
--- /dev/null
+++ b/llvm/test/Transforms/InstSimplify/constant-fold-inttoptr-add.ll
@@ -0,0 +1,84 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -p instcombine -S %s | FileCheck %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+
+@glob = external global [314 x i64]
+
+define i1 @known_constexpr_add_eq() {
+; CHECK-LABEL: define i1 @known_constexpr_add_eq() {
+; 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:    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
+}
+
+define i1 @wrap_positive_to_negate() {
+; CHECK-LABEL: define i1 @wrap_positive_to_negate() {
+; CHECK-NEXT:    ret i1 false
+;
+  %cond = icmp eq ptr @glob, inttoptr (i64 add (i64 ptrtoint (ptr getelementptr nuw (i8, ptr @glob, i64 1)to i64), i64 9223372036854775808) to ptr)
+  ret i1 %cond
+}
+
+; 9223372036854775808 = 2^63
+define i1 @wrap_positive_to_zero() {
+; CHECK-LABEL: define i1 @wrap_positive_to_zero() {
+; 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
+}
+
+define i1 @not_known_constexpr_add_sle() {
+; CHECK-LABEL: define i1 @not_known_constexpr_add_sle() {
+; CHECK-NEXT:    [[COND:%.*]] = icmp sle ptr @glob, inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr)
+; CHECK-NEXT:    ret i1 [[COND]]
+;
+  %cond = icmp sle ptr @glob, inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr)
+  ret i1 %cond
+}
+
+define i1 @not_known_constexpr_add_ule() {
+; CHECK-LABEL: define i1 @not_known_constexpr_add_ule() {
+; CHECK-NEXT:    [[COND:%.*]] = icmp ule ptr @glob, inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr)
+; CHECK-NEXT:    ret i1 [[COND]]
+;
+  %cond = icmp ule ptr @glob, inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr)
+  ret i1 %cond
+}
+
+define i1 @not_known_constexpr_add_sge() {
+; CHECK-LABEL: define i1 @not_known_constexpr_add_sge() {
+; CHECK-NEXT:    [[COND:%.*]] = icmp sge ptr @glob, inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr)
+; CHECK-NEXT:    ret i1 [[COND]]
+;
+  %cond = icmp sge ptr @glob, inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr)
+  ret i1 %cond
+}
+
+define i1 @not_known_constexpr_add_uge() {
+; CHECK-LABEL: define i1 @not_known_constexpr_add_uge() {
+; CHECK-NEXT:    [[COND:%.*]] = icmp uge ptr @glob, inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr)
+; CHECK-NEXT:    ret i1 [[COND]]
+;
+  %cond = icmp uge ptr @glob, inttoptr (i64 add (i64 ptrtoint (ptr @glob to i64), i64 -80) to ptr)
+  ret i1 %cond
+}
+
+define i1 @not_known_integer_width_does_not_match_pointer_index_width() {
+; CHECK-LABEL: define i1 @not_known_integer_width_does_not_match_pointer_index_width() {
+; CHECK-NEXT:    [[COND:%.*]] = icmp eq ptr getelementptr inbounds nuw (i8, ptr @glob, i64 80), inttoptr (i32 add (i32 ptrtoint (ptr @glob to i32), i32 -80) to ptr)
+; CHECK-NEXT:    ret i1 [[COND]]
+;
+  %cond = icmp eq ptr getelementptr inbounds nuw (i8, ptr @glob, i64 80), inttoptr (i32 add (i32 ptrtoint (ptr @glob to i32), i32 -80) to ptr)
+  ret i1 %cond
+}

nikic

This is valid for this particular icmp transform, but generally users of stripAndAccumulateConstantOffsets will assume that the result still has the same provenance, which is not the case if you look through inttoptr. This needs to be behind a flag.

llvm/lib/IR/Value.cpp

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

Precommit tests for #124981.

Precommit tests for llvm/llvm-project#124981.

fhahn

I briefly tried to come up with a tests where the result would be used incorrectly, but wasn't able to.

I added a new LookThroughIntToPtr flag.

llvm/lib/IR/Value.cpp

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

nikic

LGTM

nikic · 2025-01-30T13:36:37Z

llvm/lib/Analysis/ConstantFolding.cpp

+      Value *Stripped0 = Ops0->stripAndAccumulateConstantOffsets(
+          DL, Offset0, /*AllowNonInbounds=*/IsEqPred,
+          /*AllowInvariantGroup=*/false, /*ExternalAnalysis=*/nullptr,
+          /*LookThroughIntToPtr*/ IsEqPred);


Suggested change

/*LookThroughIntToPtr*/ IsEqPred);

/*LookThroughIntToPtr=*/IsEqPred);

Done thanks

nikic · 2025-01-30T13:36:45Z

llvm/lib/Analysis/ConstantFolding.cpp

+      Value *Stripped1 = Ops1->stripAndAccumulateConstantOffsets(
+          DL, Offset1, /*AllowNonInbounds=*/IsEqPred,
+          /*AllowInvariantGroup=*/false, /*ExternalAnalysis=*/nullptr,
+          /*LookThroughIntToPtr*/ IsEqPred);


Suggested change

/*LookThroughIntToPtr*/ IsEqPred);

/*LookThroughIntToPtr=*/IsEqPred);

Done thanks

nikic · 2025-01-30T13:37:38Z

llvm/lib/IR/Value.cpp

+      const APInt &AddOffset = CI->getValue();
+      Offset += AddOffset;


Suggested change

const APInt &AddOffset = CI->getValue();

Offset += AddOffset;

Offset += CI->getValue();

Done thanks

nikic · 2025-01-30T13:38:11Z

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

This test should either use -p instsimplify or be in the InstCombine directory.

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

nikic · 2025-01-30T13:39:05Z

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

@@ -5,26 +5,23 @@

 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() {


I don't get what the difference between this test and the previous is. What's swapped here?

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

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

…ntOffsets (#124981) Look through inttoptr (add (ptrtoint P), C) when accumulating offsets. Adds a missing fold after llvm/llvm-project#123518 Alive2 for the tests with changes: https://alive2.llvm.org/ce/z/VvPrzv PR: llvm/llvm-project#124981

fhahn requested review from nikic, dtcxzyw, goldsteinn and efriedma-quic January 29, 2025 20:32

llvmbot added llvm:instcombine Covers the InstCombine, InstSimplify and AggressiveInstCombine passes llvm:ir llvm:analysis Includes value tracking, cost tables and constant folding llvm:transforms labels Jan 29, 2025

nikic requested changes Jan 29, 2025

View reviewed changes

nikic reviewed Jan 29, 2025

View reviewed changes

llvm/lib/IR/Value.cpp Outdated Show resolved Hide resolved

llvm/lib/IR/Value.cpp Outdated Show resolved Hide resolved

llvm/lib/IR/Value.cpp Outdated Show resolved Hide resolved

llvm/test/Transforms/InstSimplify/constant-fold-inttoptr-add.ll Outdated Show resolved Hide resolved

fhahn added a commit that referenced this pull request Jan 30, 2025

[InstSimplify] Add tests with inttoptr (add ..) ConstExprs.

56ad542

Precommit tests for #124981.

github-actions bot pushed a commit to arm/arm-toolchain that referenced this pull request Jan 30, 2025

Automerge: [InstSimplify] Add tests with inttoptr (add ..) ConstExprs.

b1689cc

Precommit tests for llvm/llvm-project#124981.

fhahn force-pushed the accumulate-inttoptr-add branch 2 times, most recently from 766ac5d to 96ddc6f Compare January 30, 2025 13:03

fhahn commented Jan 30, 2025

View reviewed changes

llvm/lib/IR/Value.cpp Outdated Show resolved Hide resolved

llvm/lib/IR/Value.cpp Outdated Show resolved Hide resolved

llvm/lib/IR/Value.cpp Outdated Show resolved Hide resolved

llvm/test/Transforms/InstSimplify/constant-fold-inttoptr-add.ll Outdated Show resolved Hide resolved

nikic approved these changes Jan 30, 2025

View reviewed changes

fhahn mentioned this pull request Jan 30, 2025

Task submission dtcxzyw/llvm-opt-benchmark#1312

Open

dtcxzyw mentioned this pull request Jan 30, 2025

pre-commit: PR124981 dtcxzyw/llvm-opt-benchmark#2024

Closed

fhahn added 3 commits January 30, 2025 18:18

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

9f59ca7

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

!fixup add LookThroughIntToPtr flag

d5fb1db

!fixup address comments, thanks

fb338c3

fhahn force-pushed the accumulate-inttoptr-add branch from 96ddc6f to fb338c3 Compare January 30, 2025 18:36

fhahn merged commit 55815b6 into llvm:main Jan 30, 2025
6 of 8 checks passed

fhahn deleted the accumulate-inttoptr-add branch January 30, 2025 21:05

	/LookThroughIntToPtr/ IsEqPred);
	/LookThroughIntToPtr=/IsEqPred);

		const APInt &AddOffset = CI->getValue();
		Offset += AddOffset;

	const APInt &AddOffset = CI->getValue();
	Offset += AddOffset;
	Offset += CI->getValue();

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

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

Uh oh!

Conversation

fhahn commented Jan 29, 2025

Uh oh!

llvmbot commented Jan 29, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

nikic left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

fhahn left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

nikic left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

llvmbot commented Jan 29, 2025 •

edited

Loading