[llvm-branch-commits] [llvm] [InstCombine] Improve inbounds preservation for ADD+GEP -> GEP+GEP (PR #135155)
Björn Pettersson via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Fri Apr 11 04:00:46 PDT 2025
https://github.com/bjope updated https://github.com/llvm/llvm-project/pull/135155
>From 84108e55aa15eeabc634671fdf7b8170d0667912 Mon Sep 17 00:00:00 2001
From: Bjorn Pettersson <bjorn.a.pettersson at ericsson.com>
Date: Fri, 11 Apr 2025 10:39:01 +0200
Subject: [PATCH 1/5] [InstCombine] Improve no-wrap flag preservation for
ADD+GEP -> GEP+GEP
Given that we have a "add nuw" and a "getelementptr inbounds nuw" like
this:
%idx = add nuw i64 %idx1, %idx2
%gep = getelementptr inbounds nuw i32, ptr %ptr, i64 %idx
Then we can preserve the "inbounds nuw" flag when transforming that
into two getelementptr instructions:
%gep1 = getelementptr inbounds nuw i32, ptr %ptr, i64 %idx1
%gep = getelementptr inbounds nuw i32, ptr %ptr, i64 %idx2
Similarly for just having "nuw" or "nusw nuw" instead of "inbounds nuw"
on the getelementptr.
Proof: https://alive2.llvm.org/ce/z/QSweWW
---
.../InstCombine/InstructionCombining.cpp | 43 +++++++++++--------
llvm/test/Transforms/InstCombine/array.ll | 14 +++---
2 files changed, 32 insertions(+), 25 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 856e02c9f1ddb..19a818f4baa30 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -3087,12 +3087,22 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
return nullptr;
if (GEP.getNumIndices() == 1) {
- // We can only preserve inbounds if the original gep is inbounds, the add
- // is nsw, and the add operands are non-negative.
- auto CanPreserveInBounds = [&](bool AddIsNSW, Value *Idx1, Value *Idx2) {
+ auto CanPreserveNoWrapFlags = [&](bool AddIsNSW, bool AddIsNUW, Value *Idx1,
+ Value *Idx2) {
+ // Preserve "inbounds nuw" if the original gep is "inbounds nuw",
+ // and the add is "nuw".
+ if (GEP.isInBounds() && GEP.hasNoUnsignedWrap() && AddIsNUW)
+ return GEPNoWrapFlags::inBounds() | GEPNoWrapFlags::noUnsignedWrap();
+ // Preserve "inbounds" if the original gep is "inbounds", the add
+ // is "nsw", and the add operands are non-negative.
SimplifyQuery Q = SQ.getWithInstruction(&GEP);
- return GEP.isInBounds() && AddIsNSW && isKnownNonNegative(Idx1, Q) &&
- isKnownNonNegative(Idx2, Q);
+ if (GEP.isInBounds() && AddIsNSW && isKnownNonNegative(Idx1, Q) &&
+ isKnownNonNegative(Idx2, Q))
+ return GEPNoWrapFlags::inBounds();
+ // Preserve "nuw" if the original gep is "nuw", and the add is "nuw".
+ if (GEP.hasNoUnsignedWrap() && AddIsNUW)
+ return GEPNoWrapFlags::noUnsignedWrap();
+ return GEPNoWrapFlags::none();
};
// Try to replace ADD + GEP with GEP + GEP.
@@ -3104,15 +3114,15 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// as:
// %newptr = getelementptr i32, ptr %ptr, i64 %idx1
// %newgep = getelementptr i32, ptr %newptr, i64 %idx2
- bool IsInBounds = CanPreserveInBounds(
- cast<OverflowingBinaryOperator>(GEP.getOperand(1))->hasNoSignedWrap(),
- Idx1, Idx2);
+ bool NSW = match(GEP.getOperand(1), m_NSWAddLike(m_Value(), m_Value()));
+ bool NUW = match(GEP.getOperand(1), m_NUWAddLike(m_Value(), m_Value()));
+ GEPNoWrapFlags NWFlags = CanPreserveNoWrapFlags(NSW, NUW, Idx1, Idx2);
auto *NewPtr =
Builder.CreateGEP(GEP.getSourceElementType(), GEP.getPointerOperand(),
- Idx1, "", IsInBounds);
- return replaceInstUsesWith(
- GEP, Builder.CreateGEP(GEP.getSourceElementType(), NewPtr, Idx2, "",
- IsInBounds));
+ Idx1, "", NWFlags);
+ return replaceInstUsesWith(GEP,
+ Builder.CreateGEP(GEP.getSourceElementType(),
+ NewPtr, Idx2, "", NWFlags));
}
ConstantInt *C;
if (match(GEP.getOperand(1), m_OneUse(m_SExtLike(m_OneUse(m_NSWAdd(
@@ -3123,17 +3133,16 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// as:
// %newptr = getelementptr i32, ptr %ptr, i32 %idx1
// %newgep = getelementptr i32, ptr %newptr, i32 idx2
- bool IsInBounds = CanPreserveInBounds(
- /*IsNSW=*/true, Idx1, C);
+ GEPNoWrapFlags NWFlags = CanPreserveNoWrapFlags(
+ /*IsNSW=*/true, /*IsNUW=*/false, Idx1, C);
auto *NewPtr = Builder.CreateGEP(
GEP.getSourceElementType(), GEP.getPointerOperand(),
- Builder.CreateSExt(Idx1, GEP.getOperand(1)->getType()), "",
- IsInBounds);
+ Builder.CreateSExt(Idx1, GEP.getOperand(1)->getType()), "", NWFlags);
return replaceInstUsesWith(
GEP,
Builder.CreateGEP(GEP.getSourceElementType(), NewPtr,
Builder.CreateSExt(C, GEP.getOperand(1)->getType()),
- "", IsInBounds));
+ "", NWFlags));
}
}
diff --git a/llvm/test/Transforms/InstCombine/array.ll b/llvm/test/Transforms/InstCombine/array.ll
index a09b66273368c..aa32c094c9e27 100644
--- a/llvm/test/Transforms/InstCombine/array.ll
+++ b/llvm/test/Transforms/InstCombine/array.ll
@@ -122,12 +122,11 @@ define ptr @gep_inbounds_nuwaddlike(ptr %ptr, i64 %a, i64 %b) {
ret ptr %gep
}
-; FIXME: Preserve "inbounds nuw".
define ptr @gep_inbounds_add_nuw(ptr %ptr, i64 %a, i64 %b) {
; CHECK-LABEL: define ptr @gep_inbounds_add_nuw(
; CHECK-SAME: ptr [[PTR:%.*]], i64 [[A:%.*]], i64 [[B:%.*]]) {
-; CHECK-NEXT: [[TMP1:%.*]] = getelementptr i32, ptr [[PTR]], i64 [[A]]
-; CHECK-NEXT: [[GEP:%.*]] = getelementptr i32, ptr [[TMP1]], i64 [[B]]
+; CHECK-NEXT: [[TMP1:%.*]] = getelementptr inbounds nuw i32, ptr [[PTR]], i64 [[A]]
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr inbounds nuw i32, ptr [[TMP1]], i64 [[B]]
; CHECK-NEXT: ret ptr [[GEP]]
;
%add = add nuw i64 %a, %b
@@ -139,8 +138,8 @@ define ptr @gep_inbounds_add_nuw(ptr %ptr, i64 %a, i64 %b) {
define ptr @gep_inbounds_add_nusw_nuw(ptr %ptr, i64 %a, i64 %b) {
; CHECK-LABEL: define ptr @gep_inbounds_add_nusw_nuw(
; CHECK-SAME: ptr [[PTR:%.*]], i64 [[A:%.*]], i64 [[B:%.*]]) {
-; CHECK-NEXT: [[TMP1:%.*]] = getelementptr i32, ptr [[PTR]], i64 [[A]]
-; CHECK-NEXT: [[GEP:%.*]] = getelementptr i32, ptr [[TMP1]], i64 [[B]]
+; CHECK-NEXT: [[TMP1:%.*]] = getelementptr nuw i32, ptr [[PTR]], i64 [[A]]
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr nuw i32, ptr [[TMP1]], i64 [[B]]
; CHECK-NEXT: ret ptr [[GEP]]
;
%add = add nuw i64 %a, %b
@@ -148,12 +147,11 @@ define ptr @gep_inbounds_add_nusw_nuw(ptr %ptr, i64 %a, i64 %b) {
ret ptr %gep
}
-; FIXME: Preserve "nuw".
define ptr @gep_add_nuw(ptr %ptr, i64 %a, i64 %b) {
; CHECK-LABEL: define ptr @gep_add_nuw(
; CHECK-SAME: ptr [[PTR:%.*]], i64 [[A:%.*]], i64 [[B:%.*]]) {
-; CHECK-NEXT: [[TMP1:%.*]] = getelementptr i32, ptr [[PTR]], i64 [[A]]
-; CHECK-NEXT: [[GEP:%.*]] = getelementptr i32, ptr [[TMP1]], i64 [[B]]
+; CHECK-NEXT: [[TMP1:%.*]] = getelementptr nuw i32, ptr [[PTR]], i64 [[A]]
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr nuw i32, ptr [[TMP1]], i64 [[B]]
; CHECK-NEXT: ret ptr [[GEP]]
;
%add = add nuw i64 %a, %b
>From 9b57d63a57843ca5f0ab7c8466eb5e33b0788b89 Mon Sep 17 00:00:00 2001
From: Bjorn Pettersson <bjorn.a.pettersson at ericsson.com>
Date: Thu, 10 Apr 2025 15:00:34 +0200
Subject: [PATCH 2/5] Fixups after review feedback:
- Make sure we try to derive inbound + nuw before doing the
ADD+GEP->GEP+GEP rewrites. This to make it possible to rely
on "nuw" being present when trying to preserve flags.
- Make sure the special ADDNSW+SEXTLIKE+GEP->GEP+GEP case is checking
for ADDNUW+ZEXTNNEG+GEP->GEP+GEP when preserving flags.
This way we do not need to check for non-negative operands.
---
.../InstCombine/InstructionCombining.cpp | 99 +++++++++----------
1 file changed, 48 insertions(+), 51 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 19a818f4baa30..b5e085be9b084 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -3086,23 +3086,51 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
if (GEPType->isVectorTy())
return nullptr;
+ if (!GEP.isInBounds()) {
+ unsigned IdxWidth =
+ DL.getIndexSizeInBits(PtrOp->getType()->getPointerAddressSpace());
+ APInt BasePtrOffset(IdxWidth, 0);
+ Value *UnderlyingPtrOp =
+ PtrOp->stripAndAccumulateInBoundsConstantOffsets(DL,
+ BasePtrOffset);
+ bool CanBeNull, CanBeFreed;
+ uint64_t DerefBytes = UnderlyingPtrOp->getPointerDereferenceableBytes(
+ DL, CanBeNull, CanBeFreed);
+ if (!CanBeNull && !CanBeFreed && DerefBytes != 0) {
+ if (GEP.accumulateConstantOffset(DL, BasePtrOffset) &&
+ BasePtrOffset.isNonNegative()) {
+ APInt AllocSize(IdxWidth, DerefBytes);
+ if (BasePtrOffset.ule(AllocSize)) {
+ return GetElementPtrInst::CreateInBounds(
+ GEP.getSourceElementType(), PtrOp, Indices, GEP.getName());
+ }
+ }
+ }
+ }
+
+ // nusw + nneg -> nuw
+ if (GEP.hasNoUnsignedSignedWrap() && !GEP.hasNoUnsignedWrap() &&
+ all_of(GEP.indices(), [&](Value *Idx) {
+ return isKnownNonNegative(Idx, SQ.getWithInstruction(&GEP));
+ })) {
+ GEP.setNoWrapFlags(GEP.getNoWrapFlags() | GEPNoWrapFlags::noUnsignedWrap());
+ return &GEP;
+ }
+
+ // These rewrites is trying to preserve inbounds/nuw attributes. So we want to
+ // do this after having tried to derive "nuw" above.
if (GEP.getNumIndices() == 1) {
- auto CanPreserveNoWrapFlags = [&](bool AddIsNSW, bool AddIsNUW, Value *Idx1,
- Value *Idx2) {
- // Preserve "inbounds nuw" if the original gep is "inbounds nuw",
- // and the add is "nuw".
- if (GEP.isInBounds() && GEP.hasNoUnsignedWrap() && AddIsNUW)
- return GEPNoWrapFlags::inBounds() | GEPNoWrapFlags::noUnsignedWrap();
- // Preserve "inbounds" if the original gep is "inbounds", the add
- // is "nsw", and the add operands are non-negative.
- SimplifyQuery Q = SQ.getWithInstruction(&GEP);
- if (GEP.isInBounds() && AddIsNSW && isKnownNonNegative(Idx1, Q) &&
- isKnownNonNegative(Idx2, Q))
- return GEPNoWrapFlags::inBounds();
- // Preserve "nuw" if the original gep is "nuw", and the add is "nuw".
- if (GEP.hasNoUnsignedWrap() && AddIsNUW)
- return GEPNoWrapFlags::noUnsignedWrap();
- return GEPNoWrapFlags::none();
+ auto GetPreservedNoWrapFlags = [&](bool AddIsNUW, Value *Idx1, Value *Idx2) {
+ // Preserve "inbounds nuw" if the original gep is "inbounds nuw", and the
+ // add is "nuw". Preserve "nuw" if the original gep is "nuw", and the add
+ // is "nuw".
+ GEPNoWrapFlags Flags = GEPNoWrapFlags::none();
+ if (GEP.hasNoUnsignedWrap() && AddIsNUW) {
+ Flags |= GEPNoWrapFlags::noUnsignedWrap();
+ if (GEP.isInBounds())
+ Flags |= GEPNoWrapFlags::inBounds();
+ }
+ return Flags;
};
// Try to replace ADD + GEP with GEP + GEP.
@@ -3114,9 +3142,8 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// as:
// %newptr = getelementptr i32, ptr %ptr, i64 %idx1
// %newgep = getelementptr i32, ptr %newptr, i64 %idx2
- bool NSW = match(GEP.getOperand(1), m_NSWAddLike(m_Value(), m_Value()));
bool NUW = match(GEP.getOperand(1), m_NUWAddLike(m_Value(), m_Value()));
- GEPNoWrapFlags NWFlags = CanPreserveNoWrapFlags(NSW, NUW, Idx1, Idx2);
+ GEPNoWrapFlags NWFlags = GetPreservedNoWrapFlags(NUW, Idx1, Idx2);
auto *NewPtr =
Builder.CreateGEP(GEP.getSourceElementType(), GEP.getPointerOperand(),
Idx1, "", NWFlags);
@@ -3133,8 +3160,9 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// as:
// %newptr = getelementptr i32, ptr %ptr, i32 %idx1
// %newgep = getelementptr i32, ptr %newptr, i32 idx2
- GEPNoWrapFlags NWFlags = CanPreserveNoWrapFlags(
- /*IsNSW=*/true, /*IsNUW=*/false, Idx1, C);
+ bool NUW = match(GEP.getOperand(1), m_NNegZExt(m_NUWAddLike(m_Value(),
+ m_Value())));
+ GEPNoWrapFlags NWFlags = GetPreservedNoWrapFlags(NUW, Idx1, C);
auto *NewPtr = Builder.CreateGEP(
GEP.getSourceElementType(), GEP.getPointerOperand(),
Builder.CreateSExt(Idx1, GEP.getOperand(1)->getType()), "", NWFlags);
@@ -3146,37 +3174,6 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
}
}
- if (!GEP.isInBounds()) {
- unsigned IdxWidth =
- DL.getIndexSizeInBits(PtrOp->getType()->getPointerAddressSpace());
- APInt BasePtrOffset(IdxWidth, 0);
- Value *UnderlyingPtrOp =
- PtrOp->stripAndAccumulateInBoundsConstantOffsets(DL,
- BasePtrOffset);
- bool CanBeNull, CanBeFreed;
- uint64_t DerefBytes = UnderlyingPtrOp->getPointerDereferenceableBytes(
- DL, CanBeNull, CanBeFreed);
- if (!CanBeNull && !CanBeFreed && DerefBytes != 0) {
- if (GEP.accumulateConstantOffset(DL, BasePtrOffset) &&
- BasePtrOffset.isNonNegative()) {
- APInt AllocSize(IdxWidth, DerefBytes);
- if (BasePtrOffset.ule(AllocSize)) {
- return GetElementPtrInst::CreateInBounds(
- GEP.getSourceElementType(), PtrOp, Indices, GEP.getName());
- }
- }
- }
- }
-
- // nusw + nneg -> nuw
- if (GEP.hasNoUnsignedSignedWrap() && !GEP.hasNoUnsignedWrap() &&
- all_of(GEP.indices(), [&](Value *Idx) {
- return isKnownNonNegative(Idx, SQ.getWithInstruction(&GEP));
- })) {
- GEP.setNoWrapFlags(GEP.getNoWrapFlags() | GEPNoWrapFlags::noUnsignedWrap());
- return &GEP;
- }
-
if (Instruction *R = foldSelectGEP(GEP, Builder))
return R;
>From 6f9a251e5fa149fc9d7d262c7aac077e4651aa4e Mon Sep 17 00:00:00 2001
From: Bjorn Pettersson <bjorn.a.pettersson at ericsson.com>
Date: Thu, 10 Apr 2025 16:34:51 +0200
Subject: [PATCH 3/5] Fix clang-format
---
.../Transforms/InstCombine/InstructionCombining.cpp | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index b5e085be9b084..09b6f4880fa16 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -3091,8 +3091,7 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
DL.getIndexSizeInBits(PtrOp->getType()->getPointerAddressSpace());
APInt BasePtrOffset(IdxWidth, 0);
Value *UnderlyingPtrOp =
- PtrOp->stripAndAccumulateInBoundsConstantOffsets(DL,
- BasePtrOffset);
+ PtrOp->stripAndAccumulateInBoundsConstantOffsets(DL, BasePtrOffset);
bool CanBeNull, CanBeFreed;
uint64_t DerefBytes = UnderlyingPtrOp->getPointerDereferenceableBytes(
DL, CanBeNull, CanBeFreed);
@@ -3120,7 +3119,8 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// These rewrites is trying to preserve inbounds/nuw attributes. So we want to
// do this after having tried to derive "nuw" above.
if (GEP.getNumIndices() == 1) {
- auto GetPreservedNoWrapFlags = [&](bool AddIsNUW, Value *Idx1, Value *Idx2) {
+ auto GetPreservedNoWrapFlags = [&](bool AddIsNUW, Value *Idx1,
+ Value *Idx2) {
// Preserve "inbounds nuw" if the original gep is "inbounds nuw", and the
// add is "nuw". Preserve "nuw" if the original gep is "nuw", and the add
// is "nuw".
@@ -3160,8 +3160,8 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// as:
// %newptr = getelementptr i32, ptr %ptr, i32 %idx1
// %newgep = getelementptr i32, ptr %newptr, i32 idx2
- bool NUW = match(GEP.getOperand(1), m_NNegZExt(m_NUWAddLike(m_Value(),
- m_Value())));
+ bool NUW = match(GEP.getOperand(1),
+ m_NNegZExt(m_NUWAddLike(m_Value(), m_Value())));
GEPNoWrapFlags NWFlags = GetPreservedNoWrapFlags(NUW, Idx1, C);
auto *NewPtr = Builder.CreateGEP(
GEP.getSourceElementType(), GEP.getPointerOperand(),
>From cc91c585be1681f4eb6b0f91382bf343139a88d1 Mon Sep 17 00:00:00 2001
From: Bjorn Pettersson <bjorn.a.pettersson at ericsson.com>
Date: Fri, 11 Apr 2025 10:07:20 +0200
Subject: [PATCH 4/5] Fixup
---
llvm/lib/Transforms/InstCombine/InstructionCombining.cpp | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 09b6f4880fa16..14fecc1f090c0 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -3119,8 +3119,7 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// These rewrites is trying to preserve inbounds/nuw attributes. So we want to
// do this after having tried to derive "nuw" above.
if (GEP.getNumIndices() == 1) {
- auto GetPreservedNoWrapFlags = [&](bool AddIsNUW, Value *Idx1,
- Value *Idx2) {
+ auto GetPreservedNoWrapFlags = [&](bool AddIsNUW) {
// Preserve "inbounds nuw" if the original gep is "inbounds nuw", and the
// add is "nuw". Preserve "nuw" if the original gep is "nuw", and the add
// is "nuw".
@@ -3143,7 +3142,7 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// %newptr = getelementptr i32, ptr %ptr, i64 %idx1
// %newgep = getelementptr i32, ptr %newptr, i64 %idx2
bool NUW = match(GEP.getOperand(1), m_NUWAddLike(m_Value(), m_Value()));
- GEPNoWrapFlags NWFlags = GetPreservedNoWrapFlags(NUW, Idx1, Idx2);
+ GEPNoWrapFlags NWFlags = GetPreservedNoWrapFlags(NUW);
auto *NewPtr =
Builder.CreateGEP(GEP.getSourceElementType(), GEP.getPointerOperand(),
Idx1, "", NWFlags);
@@ -3162,7 +3161,7 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// %newgep = getelementptr i32, ptr %newptr, i32 idx2
bool NUW = match(GEP.getOperand(1),
m_NNegZExt(m_NUWAddLike(m_Value(), m_Value())));
- GEPNoWrapFlags NWFlags = GetPreservedNoWrapFlags(NUW, Idx1, C);
+ GEPNoWrapFlags NWFlags = GetPreservedNoWrapFlags(NUW);
auto *NewPtr = Builder.CreateGEP(
GEP.getSourceElementType(), GEP.getPointerOperand(),
Builder.CreateSExt(Idx1, GEP.getOperand(1)->getType()), "", NWFlags);
>From 51ec9b0ab4799faad383e8b32c006cf1f49cf9e1 Mon Sep 17 00:00:00 2001
From: Bjorn Pettersson <bjorn.a.pettersson at ericsson.com>
Date: Fri, 11 Apr 2025 12:52:44 +0200
Subject: [PATCH 5/5] Fixup: Also handle "nusw nuw"
---
.../InstCombine/InstructionCombining.cpp | 17 +++++++----------
llvm/test/Transforms/InstCombine/array.ll | 5 ++---
2 files changed, 9 insertions(+), 13 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 14fecc1f090c0..39ea5e111ec18 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -3119,17 +3119,14 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// These rewrites is trying to preserve inbounds/nuw attributes. So we want to
// do this after having tried to derive "nuw" above.
if (GEP.getNumIndices() == 1) {
+ // Given (gep p, x+y) we want to determine the common nowrap flags for both
+ // gep if transforming into (gep (gep p, x), y).
auto GetPreservedNoWrapFlags = [&](bool AddIsNUW) {
- // Preserve "inbounds nuw" if the original gep is "inbounds nuw", and the
- // add is "nuw". Preserve "nuw" if the original gep is "nuw", and the add
- // is "nuw".
- GEPNoWrapFlags Flags = GEPNoWrapFlags::none();
- if (GEP.hasNoUnsignedWrap() && AddIsNUW) {
- Flags |= GEPNoWrapFlags::noUnsignedWrap();
- if (GEP.isInBounds())
- Flags |= GEPNoWrapFlags::inBounds();
- }
- return Flags;
+ // We can preserve both "inbounds nuw", "nusw nuw" and "nuw" if we know
+ // that x + y does not have unsigned wrap.
+ if (GEP.hasNoUnsignedWrap() && AddIsNUW)
+ return GEP.getNoWrapFlags();
+ return GEPNoWrapFlags::none();
};
// Try to replace ADD + GEP with GEP + GEP.
diff --git a/llvm/test/Transforms/InstCombine/array.ll b/llvm/test/Transforms/InstCombine/array.ll
index aa32c094c9e27..dd4725cfb1db3 100644
--- a/llvm/test/Transforms/InstCombine/array.ll
+++ b/llvm/test/Transforms/InstCombine/array.ll
@@ -134,12 +134,11 @@ define ptr @gep_inbounds_add_nuw(ptr %ptr, i64 %a, i64 %b) {
ret ptr %gep
}
-; FIXME: Preserve "nusw nuw".
define ptr @gep_inbounds_add_nusw_nuw(ptr %ptr, i64 %a, i64 %b) {
; CHECK-LABEL: define ptr @gep_inbounds_add_nusw_nuw(
; CHECK-SAME: ptr [[PTR:%.*]], i64 [[A:%.*]], i64 [[B:%.*]]) {
-; CHECK-NEXT: [[TMP1:%.*]] = getelementptr nuw i32, ptr [[PTR]], i64 [[A]]
-; CHECK-NEXT: [[GEP:%.*]] = getelementptr nuw i32, ptr [[TMP1]], i64 [[B]]
+; CHECK-NEXT: [[TMP1:%.*]] = getelementptr nusw nuw i32, ptr [[PTR]], i64 [[A]]
+; CHECK-NEXT: [[GEP:%.*]] = getelementptr nusw nuw i32, ptr [[TMP1]], i64 [[B]]
; CHECK-NEXT: ret ptr [[GEP]]
;
%add = add nuw i64 %a, %b
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