From 3748dfe442ac338009aea1ea554cd5f9fbcb9a85 Mon Sep 17 00:00:00 2001 From: Nikita Popov Date: Wed, 8 Nov 2023 12:03:17 +0100 Subject: [PATCH 1/5] [InstCombine] Make indexed compare fold GEP source type independent The indexed compare fold converts comparisons of GEPs with same (indirect) base into comparisons of offset. Currently, it only supports GEPs with the same source element type. This change makes the transform operate on offsets instead, which removes the type dependence. To keep closer to the scope of the original implementation, this keeps the limitation that we should only have at most one variable index per GEP. --- .../InstCombine/InstCombineCompares.cpp | 95 +++++++------------ .../InstCombine/indexed-gep-compares.ll | 45 +++++---- .../test/Transforms/InstCombine/opaque-ptr.ll | 21 ++-- 3 files changed, 72 insertions(+), 89 deletions(-) diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index b6e59f707e782..9a222bda81d85 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -18,6 +18,7 @@ #include "llvm/Analysis/CmpInstAnalysis.h" #include "llvm/Analysis/ConstantFolding.h" #include "llvm/Analysis/InstructionSimplify.h" +#include "llvm/Analysis/Utils/Local.h" #include "llvm/Analysis/VectorUtils.h" #include "llvm/IR/ConstantRange.h" #include "llvm/IR/DataLayout.h" @@ -413,11 +414,12 @@ Instruction *InstCombinerImpl::foldCmpLoadFromIndexedGlobal( /// Returns true if we can rewrite Start as a GEP with pointer Base /// and some integer offset. The nodes that need to be re-written /// for this transformation will be added to Explored. -static bool canRewriteGEPAsOffset(Type *ElemTy, Value *Start, Value *Base, +static bool canRewriteGEPAsOffset(Value *Start, Value *Base, const DataLayout &DL, SetVector &Explored) { SmallVector WorkList(1, Start); Explored.insert(Base); + uint64_t IndexSize = DL.getIndexTypeSizeInBits(Start->getType()); // The following traversal gives us an order which can be used // when doing the final transformation. Since in the final @@ -447,11 +449,11 @@ static bool canRewriteGEPAsOffset(Type *ElemTy, Value *Start, Value *Base, return false; if (auto *GEP = dyn_cast(V)) { - // We're limiting the GEP to having one index. This will preserve - // the original pointer type. We could handle more cases in the - // future. - if (GEP->getNumIndices() != 1 || !GEP->isInBounds() || - GEP->getSourceElementType() != ElemTy) + // Only allow GEPs with at most one variable offset. + APInt Offset(IndexSize, 0); + MapVector VarOffsets; + if (!GEP->collectOffset(DL, IndexSize, VarOffsets, Offset) || + VarOffsets.size() > 1) return false; if (!Explored.contains(GEP->getOperand(0))) @@ -528,7 +530,7 @@ static void setInsertionPoint(IRBuilder<> &Builder, Value *V, /// Returns a re-written value of Start as an indexed GEP using Base as a /// pointer. -static Value *rewriteGEPAsOffset(Type *ElemTy, Value *Start, Value *Base, +static Value *rewriteGEPAsOffset(Value *Start, Value *Base, const DataLayout &DL, SetVector &Explored, InstCombiner &IC) { @@ -539,8 +541,8 @@ static Value *rewriteGEPAsOffset(Type *ElemTy, Value *Start, Value *Base, // 3. Add the edges for the PHI nodes. // 4. Emit GEPs to get the original pointers. // 5. Remove the original instructions. - Type *IndexType = IntegerType::get( - Base->getContext(), DL.getIndexTypeSizeInBits(Start->getType())); + uint64_t IndexSize = DL.getIndexTypeSizeInBits(Start->getType()); + Type *IndexType = IntegerType::get(Base->getContext(), IndexSize); DenseMap NewInsts; NewInsts[Base] = ConstantInt::getNullValue(IndexType); @@ -559,29 +561,22 @@ static Value *rewriteGEPAsOffset(Type *ElemTy, Value *Start, Value *Base, // Create all the other instructions. for (Value *Val : Explored) { - if (NewInsts.contains(Val)) continue; if (auto *GEP = dyn_cast(Val)) { - Value *Index = NewInsts[GEP->getOperand(1)] ? NewInsts[GEP->getOperand(1)] - : GEP->getOperand(1); - setInsertionPoint(Builder, GEP); - // Indices might need to be sign extended. GEPs will magically do - // this, but we need to do it ourselves here. - if (Index->getType()->getScalarSizeInBits() != - NewInsts[GEP->getOperand(0)]->getType()->getScalarSizeInBits()) { - Index = Builder.CreateSExtOrTrunc( - Index, NewInsts[GEP->getOperand(0)]->getType(), - GEP->getOperand(0)->getName() + ".sext"); - } + APInt Offset(IndexSize, 0); + MapVector VarOffsets; + GEP->collectOffset(DL, IndexSize, VarOffsets, Offset); - auto *Op = NewInsts[GEP->getOperand(0)]; + setInsertionPoint(Builder, GEP); + Value *Op = NewInsts[GEP->getOperand(0)]; + Value *OffsetV = emitGEPOffset(&Builder, DL, GEP); if (isa(Op) && cast(Op)->isZero()) - NewInsts[GEP] = Index; + NewInsts[GEP] = OffsetV; else NewInsts[GEP] = Builder.CreateNSWAdd( - Op, Index, GEP->getOperand(0)->getName() + ".add"); + Op, OffsetV, GEP->getOperand(0)->getName() + ".add"); continue; } if (isa(Val)) @@ -609,23 +604,14 @@ static Value *rewriteGEPAsOffset(Type *ElemTy, Value *Start, Value *Base, } } - PointerType *PtrTy = PointerType::get( - Base->getContext(), Start->getType()->getPointerAddressSpace()); for (Value *Val : Explored) { if (Val == Base) continue; - // Depending on the type, for external users we have to emit - // a GEP or a GEP + ptrtoint. setInsertionPoint(Builder, Val, false); - - // Cast base to the expected type. - Value *NewVal = Builder.CreateBitOrPointerCast( - Base, PtrTy, Start->getName() + "to.ptr"); - NewVal = Builder.CreateInBoundsGEP(ElemTy, NewVal, ArrayRef(NewInsts[Val]), - Val->getName() + ".ptr"); - NewVal = Builder.CreateBitOrPointerCast( - NewVal, Val->getType(), Val->getName() + ".conv"); + // Create GEP for external users. + Value *NewVal = Builder.CreateInBoundsGEP( + Builder.getInt8Ty(), Base, NewInsts[Val], Val->getName() + ".ptr"); IC.replaceInstUsesWith(*cast(Val), NewVal); // Add old instruction to worklist for DCE. We don't directly remove it // here because the original compare is one of the users. @@ -637,28 +623,18 @@ static Value *rewriteGEPAsOffset(Type *ElemTy, Value *Start, Value *Base, /// Looks through GEPs in order to express the input Value as a constant /// indexed GEP. Returns a pair containing the GEPs Pointer and Index. -static std::pair -getAsConstantIndexedAddress(Type *ElemTy, Value *V, const DataLayout &DL) { - Type *IndexType = IntegerType::get(V->getContext(), - DL.getIndexTypeSizeInBits(V->getType())); - - Constant *Index = ConstantInt::getNullValue(IndexType); +static std::pair +getAsConstantIndexedAddress(Value *V, const DataLayout &DL) { + APInt Offset = APInt(DL.getIndexTypeSizeInBits(V->getType()), 0); while (GEPOperator *GEP = dyn_cast(V)) { // We accept only inbouds GEPs here to exclude the possibility of // overflow. - if (!GEP->isInBounds()) + if (!GEP->isInBounds() || !GEP->accumulateConstantOffset(DL, Offset)) break; - if (GEP->hasAllConstantIndices() && GEP->getNumIndices() == 1 && - GEP->getSourceElementType() == ElemTy && - GEP->getOperand(1)->getType() == IndexType) { - V = GEP->getOperand(0); - Constant *GEPIndex = static_cast(GEP->getOperand(1)); - Index = ConstantExpr::getAdd(Index, GEPIndex); - continue; - } - break; + + V = GEP->getPointerOperand(); } - return {V, Index}; + return {V, Offset}; } /// Converts (CMP GEPLHS, RHS) if this change would make RHS a constant. @@ -675,14 +651,14 @@ static Instruction *transformToIndexedCompare(GEPOperator *GEPLHS, Value *RHS, if (!GEPLHS->hasAllConstantIndices()) return nullptr; - Type *ElemTy = GEPLHS->getSourceElementType(); - Value *PtrBase, *Index; - std::tie(PtrBase, Index) = getAsConstantIndexedAddress(ElemTy, GEPLHS, DL); + Value *PtrBase; + APInt Offset; + std::tie(PtrBase, Offset) = getAsConstantIndexedAddress(GEPLHS, DL); // The set of nodes that will take part in this transformation. SetVector Nodes; - if (!canRewriteGEPAsOffset(ElemTy, RHS, PtrBase, DL, Nodes)) + if (!canRewriteGEPAsOffset(RHS, PtrBase, DL, Nodes)) return nullptr; // We know we can re-write this as @@ -691,13 +667,14 @@ static Instruction *transformToIndexedCompare(GEPOperator *GEPLHS, Value *RHS, // can't have overflow on either side. We can therefore re-write // this as: // OFFSET1 cmp OFFSET2 - Value *NewRHS = rewriteGEPAsOffset(ElemTy, RHS, PtrBase, DL, Nodes, IC); + Value *NewRHS = rewriteGEPAsOffset(RHS, PtrBase, DL, Nodes, IC); // RewriteGEPAsOffset has replaced RHS and all of its uses with a re-written // GEP having PtrBase as the pointer base, and has returned in NewRHS the // offset. Since Index is the offset of LHS to the base pointer, we will now // compare the offsets instead of comparing the pointers. - return new ICmpInst(ICmpInst::getSignedPredicate(Cond), Index, NewRHS); + return new ICmpInst(ICmpInst::getSignedPredicate(Cond), + IC.Builder.getInt(Offset), NewRHS); } /// Fold comparisons between a GEP instruction and something else. At this point diff --git a/llvm/test/Transforms/InstCombine/indexed-gep-compares.ll b/llvm/test/Transforms/InstCombine/indexed-gep-compares.ll index 80b61b19a2c19..61cf727fb6c8c 100644 --- a/llvm/test/Transforms/InstCombine/indexed-gep-compares.ll +++ b/llvm/test/Transforms/InstCombine/indexed-gep-compares.ll @@ -6,14 +6,15 @@ target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:32-f3 define ptr@test1(ptr %A, i32 %Offset) { ; CHECK-LABEL: @test1( ; CHECK-NEXT: entry: +; CHECK-NEXT: [[TMP_IDX:%.*]] = shl nsw i32 [[OFFSET:%.*]], 2 ; CHECK-NEXT: br label [[BB:%.*]] ; CHECK: bb: -; CHECK-NEXT: [[RHS_IDX:%.*]] = phi i32 [ [[RHS_ADD:%.*]], [[BB]] ], [ [[OFFSET:%.*]], [[ENTRY:%.*]] ] -; CHECK-NEXT: [[RHS_ADD]] = add nsw i32 [[RHS_IDX]], 1 -; CHECK-NEXT: [[COND:%.*]] = icmp sgt i32 [[RHS_IDX]], 100 +; CHECK-NEXT: [[RHS_IDX:%.*]] = phi i32 [ [[RHS_ADD:%.*]], [[BB]] ], [ [[TMP_IDX]], [[ENTRY:%.*]] ] +; CHECK-NEXT: [[RHS_ADD]] = add nsw i32 [[RHS_IDX]], 4 +; CHECK-NEXT: [[COND:%.*]] = icmp sgt i32 [[RHS_IDX]], 400 ; CHECK-NEXT: br i1 [[COND]], label [[BB2:%.*]], label [[BB]] ; CHECK: bb2: -; CHECK-NEXT: [[RHS_PTR:%.*]] = getelementptr inbounds i32, ptr [[A:%.*]], i32 [[RHS_IDX]] +; CHECK-NEXT: [[RHS_PTR:%.*]] = getelementptr inbounds i8, ptr [[A:%.*]], i32 [[RHS_IDX]] ; CHECK-NEXT: ret ptr [[RHS_PTR]] ; entry: @@ -34,15 +35,16 @@ bb2: define ptr@test2(i32 %A, i32 %Offset) { ; CHECK-LABEL: @test2( ; CHECK-NEXT: entry: +; CHECK-NEXT: [[TMP_IDX:%.*]] = shl nsw i32 [[OFFSET:%.*]], 2 ; CHECK-NEXT: br label [[BB:%.*]] ; CHECK: bb: -; CHECK-NEXT: [[RHS_IDX:%.*]] = phi i32 [ [[RHS_ADD:%.*]], [[BB]] ], [ [[OFFSET:%.*]], [[ENTRY:%.*]] ] -; CHECK-NEXT: [[RHS_ADD]] = add nsw i32 [[RHS_IDX]], 1 -; CHECK-NEXT: [[COND:%.*]] = icmp sgt i32 [[RHS_IDX]], 100 +; CHECK-NEXT: [[RHS_IDX:%.*]] = phi i32 [ [[RHS_ADD:%.*]], [[BB]] ], [ [[TMP_IDX]], [[ENTRY:%.*]] ] +; CHECK-NEXT: [[RHS_ADD]] = add nsw i32 [[RHS_IDX]], 4 +; CHECK-NEXT: [[COND:%.*]] = icmp sgt i32 [[RHS_IDX]], 400 ; CHECK-NEXT: br i1 [[COND]], label [[BB2:%.*]], label [[BB]] ; CHECK: bb2: ; CHECK-NEXT: [[A_PTR:%.*]] = inttoptr i32 [[A:%.*]] to ptr -; CHECK-NEXT: [[RHS_PTR:%.*]] = getelementptr inbounds i32, ptr [[A_PTR]], i32 [[RHS_IDX]] +; CHECK-NEXT: [[RHS_PTR:%.*]] = getelementptr inbounds i8, ptr [[A_PTR]], i32 [[RHS_IDX]] ; CHECK-NEXT: ret ptr [[RHS_PTR]] ; entry: @@ -157,16 +159,17 @@ bb2: define ptr@test4(i16 %A, i32 %Offset) { ; CHECK-LABEL: @test4( ; CHECK-NEXT: entry: +; CHECK-NEXT: [[TMP_IDX:%.*]] = shl nsw i32 [[OFFSET:%.*]], 2 ; CHECK-NEXT: br label [[BB:%.*]] ; CHECK: bb: -; CHECK-NEXT: [[RHS_IDX:%.*]] = phi i32 [ [[RHS_ADD:%.*]], [[BB]] ], [ [[OFFSET:%.*]], [[ENTRY:%.*]] ] -; CHECK-NEXT: [[RHS_ADD]] = add nsw i32 [[RHS_IDX]], 1 -; CHECK-NEXT: [[COND:%.*]] = icmp sgt i32 [[RHS_IDX]], 100 +; CHECK-NEXT: [[RHS_IDX:%.*]] = phi i32 [ [[RHS_ADD:%.*]], [[BB]] ], [ [[TMP_IDX]], [[ENTRY:%.*]] ] +; CHECK-NEXT: [[RHS_ADD]] = add nsw i32 [[RHS_IDX]], 4 +; CHECK-NEXT: [[COND:%.*]] = icmp sgt i32 [[RHS_IDX]], 400 ; CHECK-NEXT: br i1 [[COND]], label [[BB2:%.*]], label [[BB]] ; CHECK: bb2: ; CHECK-NEXT: [[TMP0:%.*]] = zext i16 [[A:%.*]] to i32 ; CHECK-NEXT: [[A_PTR:%.*]] = inttoptr i32 [[TMP0]] to ptr -; CHECK-NEXT: [[RHS_PTR:%.*]] = getelementptr inbounds i32, ptr [[A_PTR]], i32 [[RHS_IDX]] +; CHECK-NEXT: [[RHS_PTR:%.*]] = getelementptr inbounds i8, ptr [[A_PTR]], i32 [[RHS_IDX]] ; CHECK-NEXT: ret ptr [[RHS_PTR]] ; entry: @@ -195,14 +198,15 @@ define ptr@test5(i32 %Offset) personality ptr @__gxx_personality_v0 { ; CHECK-NEXT: [[A:%.*]] = invoke ptr @fun_ptr() ; CHECK-NEXT: to label [[CONT:%.*]] unwind label [[LPAD:%.*]] ; CHECK: cont: +; CHECK-NEXT: [[TMP_IDX:%.*]] = shl nsw i32 [[OFFSET:%.*]], 2 ; CHECK-NEXT: br label [[BB:%.*]] ; CHECK: bb: -; CHECK-NEXT: [[RHS_IDX:%.*]] = phi i32 [ [[RHS_ADD:%.*]], [[BB]] ], [ [[OFFSET:%.*]], [[CONT]] ] -; CHECK-NEXT: [[RHS_ADD]] = add nsw i32 [[RHS_IDX]], 1 -; CHECK-NEXT: [[COND:%.*]] = icmp sgt i32 [[RHS_IDX]], 100 +; CHECK-NEXT: [[RHS_IDX:%.*]] = phi i32 [ [[RHS_ADD:%.*]], [[BB]] ], [ [[TMP_IDX]], [[CONT]] ] +; CHECK-NEXT: [[RHS_ADD]] = add nsw i32 [[RHS_IDX]], 4 +; CHECK-NEXT: [[COND:%.*]] = icmp sgt i32 [[RHS_IDX]], 400 ; CHECK-NEXT: br i1 [[COND]], label [[BB2:%.*]], label [[BB]] ; CHECK: bb2: -; CHECK-NEXT: [[RHS_PTR:%.*]] = getelementptr inbounds i32, ptr [[A]], i32 [[RHS_IDX]] +; CHECK-NEXT: [[RHS_PTR:%.*]] = getelementptr inbounds i8, ptr [[A]], i32 [[RHS_IDX]] ; CHECK-NEXT: ret ptr [[RHS_PTR]] ; CHECK: lpad: ; CHECK-NEXT: [[L:%.*]] = landingpad { ptr, i32 } @@ -239,15 +243,16 @@ define ptr@test6(i32 %Offset) personality ptr @__gxx_personality_v0 { ; CHECK-NEXT: [[A:%.*]] = invoke i32 @fun_i32() ; CHECK-NEXT: to label [[CONT:%.*]] unwind label [[LPAD:%.*]] ; CHECK: cont: +; CHECK-NEXT: [[TMP_IDX:%.*]] = shl nsw i32 [[OFFSET:%.*]], 2 ; CHECK-NEXT: br label [[BB:%.*]] ; CHECK: bb: -; CHECK-NEXT: [[RHS_IDX:%.*]] = phi i32 [ [[RHS_ADD:%.*]], [[BB]] ], [ [[OFFSET:%.*]], [[CONT]] ] -; CHECK-NEXT: [[RHS_ADD]] = add nsw i32 [[RHS_IDX]], 1 -; CHECK-NEXT: [[COND:%.*]] = icmp sgt i32 [[RHS_IDX]], 100 +; CHECK-NEXT: [[RHS_IDX:%.*]] = phi i32 [ [[RHS_ADD:%.*]], [[BB]] ], [ [[TMP_IDX]], [[CONT]] ] +; CHECK-NEXT: [[RHS_ADD]] = add nsw i32 [[RHS_IDX]], 4 +; CHECK-NEXT: [[COND:%.*]] = icmp sgt i32 [[RHS_IDX]], 400 ; CHECK-NEXT: br i1 [[COND]], label [[BB2:%.*]], label [[BB]] ; CHECK: bb2: ; CHECK-NEXT: [[A_PTR:%.*]] = inttoptr i32 [[A]] to ptr -; CHECK-NEXT: [[RHS_PTR:%.*]] = getelementptr inbounds i32, ptr [[A_PTR]], i32 [[RHS_IDX]] +; CHECK-NEXT: [[RHS_PTR:%.*]] = getelementptr inbounds i8, ptr [[A_PTR]], i32 [[RHS_IDX]] ; CHECK-NEXT: ret ptr [[RHS_PTR]] ; CHECK: lpad: ; CHECK-NEXT: [[L:%.*]] = landingpad { ptr, i32 } diff --git a/llvm/test/Transforms/InstCombine/opaque-ptr.ll b/llvm/test/Transforms/InstCombine/opaque-ptr.ll index 900d3f142a6ff..4448a49ad92bf 100644 --- a/llvm/test/Transforms/InstCombine/opaque-ptr.ll +++ b/llvm/test/Transforms/InstCombine/opaque-ptr.ll @@ -382,14 +382,15 @@ define <4 x i1> @compare_geps_same_indices_scalar_vector_base_mismatch(ptr %ptr, define ptr @indexed_compare(ptr %A, i64 %offset) { ; CHECK-LABEL: @indexed_compare( ; CHECK-NEXT: entry: +; CHECK-NEXT: [[TMP_IDX:%.*]] = shl nsw i64 [[OFFSET:%.*]], 2 ; CHECK-NEXT: br label [[BB:%.*]] ; CHECK: bb: -; CHECK-NEXT: [[RHS_IDX:%.*]] = phi i64 [ [[RHS_ADD:%.*]], [[BB]] ], [ [[OFFSET:%.*]], [[ENTRY:%.*]] ] -; CHECK-NEXT: [[RHS_ADD]] = add nsw i64 [[RHS_IDX]], 1 -; CHECK-NEXT: [[COND:%.*]] = icmp sgt i64 [[RHS_IDX]], 100 +; CHECK-NEXT: [[RHS_IDX:%.*]] = phi i64 [ [[RHS_ADD:%.*]], [[BB]] ], [ [[TMP_IDX]], [[ENTRY:%.*]] ] +; CHECK-NEXT: [[RHS_ADD]] = add nsw i64 [[RHS_IDX]], 4 +; CHECK-NEXT: [[COND:%.*]] = icmp sgt i64 [[RHS_IDX]], 400 ; CHECK-NEXT: br i1 [[COND]], label [[BB2:%.*]], label [[BB]] ; CHECK: bb2: -; CHECK-NEXT: [[RHS_PTR:%.*]] = getelementptr inbounds i32, ptr [[A:%.*]], i64 [[RHS_IDX]] +; CHECK-NEXT: [[RHS_PTR:%.*]] = getelementptr inbounds i8, ptr [[A:%.*]], i64 [[RHS_IDX]] ; CHECK-NEXT: ret ptr [[RHS_PTR]] ; entry: @@ -410,16 +411,16 @@ bb2: define ptr @indexed_compare_different_types(ptr %A, i64 %offset) { ; CHECK-LABEL: @indexed_compare_different_types( ; CHECK-NEXT: entry: -; CHECK-NEXT: [[TMP:%.*]] = getelementptr inbounds i32, ptr [[A:%.*]], i64 [[OFFSET:%.*]] +; CHECK-NEXT: [[TMP_IDX:%.*]] = shl nsw i64 [[OFFSET:%.*]], 2 ; CHECK-NEXT: br label [[BB:%.*]] ; CHECK: bb: -; CHECK-NEXT: [[RHS:%.*]] = phi ptr [ [[RHS_NEXT:%.*]], [[BB]] ], [ [[TMP]], [[ENTRY:%.*]] ] -; CHECK-NEXT: [[LHS:%.*]] = getelementptr inbounds i64, ptr [[A]], i64 100 -; CHECK-NEXT: [[RHS_NEXT]] = getelementptr inbounds i32, ptr [[RHS]], i64 1 -; CHECK-NEXT: [[COND:%.*]] = icmp ult ptr [[LHS]], [[RHS]] +; CHECK-NEXT: [[RHS_IDX:%.*]] = phi i64 [ [[RHS_ADD:%.*]], [[BB]] ], [ [[TMP_IDX]], [[ENTRY:%.*]] ] +; CHECK-NEXT: [[RHS_ADD]] = add nsw i64 [[RHS_IDX]], 4 +; CHECK-NEXT: [[COND:%.*]] = icmp sgt i64 [[RHS_IDX]], 800 ; CHECK-NEXT: br i1 [[COND]], label [[BB2:%.*]], label [[BB]] ; CHECK: bb2: -; CHECK-NEXT: ret ptr [[RHS]] +; CHECK-NEXT: [[RHS_PTR:%.*]] = getelementptr inbounds i8, ptr [[A:%.*]], i64 [[RHS_IDX]] +; CHECK-NEXT: ret ptr [[RHS_PTR]] ; entry: %tmp = getelementptr inbounds i32, ptr %A, i64 %offset From a2b4bb779a41fb3ac7fb49e294f045dd41a3637b Mon Sep 17 00:00:00 2001 From: Nikita Popov Date: Tue, 14 Nov 2023 15:08:20 +0100 Subject: [PATCH 2/5] Use stripAndAccumulateConstantOffsets() --- .../InstCombine/InstCombineCompares.cpp | 27 ++++++------------- 1 file changed, 8 insertions(+), 19 deletions(-) diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index 9a222bda81d85..bcd7dfc37a43d 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -621,22 +621,6 @@ static Value *rewriteGEPAsOffset(Value *Start, Value *Base, return NewInsts[Start]; } -/// Looks through GEPs in order to express the input Value as a constant -/// indexed GEP. Returns a pair containing the GEPs Pointer and Index. -static std::pair -getAsConstantIndexedAddress(Value *V, const DataLayout &DL) { - APInt Offset = APInt(DL.getIndexTypeSizeInBits(V->getType()), 0); - while (GEPOperator *GEP = dyn_cast(V)) { - // We accept only inbouds GEPs here to exclude the possibility of - // overflow. - if (!GEP->isInBounds() || !GEP->accumulateConstantOffset(DL, Offset)) - break; - - V = GEP->getPointerOperand(); - } - return {V, Offset}; -} - /// Converts (CMP GEPLHS, RHS) if this change would make RHS a constant. /// We can look through PHIs, GEPs and casts in order to determine a common base /// between GEPLHS and RHS. @@ -651,9 +635,14 @@ static Instruction *transformToIndexedCompare(GEPOperator *GEPLHS, Value *RHS, if (!GEPLHS->hasAllConstantIndices()) return nullptr; - Value *PtrBase; - APInt Offset; - std::tie(PtrBase, Offset) = getAsConstantIndexedAddress(GEPLHS, DL); + APInt Offset(DL.getIndexTypeSizeInBits(GEPLHS->getType()), 0); + Value *PtrBase = + GEPLHS->stripAndAccumulateConstantOffsets(DL, Offset, + /*AllowNonInbounds*/ false); + + // Bail if we looked through addrspacecast. + if (PtrBase->getType() != GEPLHS->getType()) + return nullptr; // The set of nodes that will take part in this transformation. SetVector Nodes; From 79c3ce20b2abc2a4cf71c159eba8c9b784de78f2 Mon Sep 17 00:00:00 2001 From: Nikita Popov Date: Tue, 21 Nov 2023 18:46:54 +0100 Subject: [PATCH 3/5] remove dead code --- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index bcd7dfc37a43d..f7cb5aa26e0fe 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -541,8 +541,8 @@ static Value *rewriteGEPAsOffset(Value *Start, Value *Base, // 3. Add the edges for the PHI nodes. // 4. Emit GEPs to get the original pointers. // 5. Remove the original instructions. - uint64_t IndexSize = DL.getIndexTypeSizeInBits(Start->getType()); - Type *IndexType = IntegerType::get(Base->getContext(), IndexSize); + Type *IndexType = IntegerType::get( + Base->getContext(), DL.getIndexTypeSizeInBits(Start->getType())); DenseMap NewInsts; NewInsts[Base] = ConstantInt::getNullValue(IndexType); @@ -565,10 +565,6 @@ static Value *rewriteGEPAsOffset(Value *Start, Value *Base, continue; if (auto *GEP = dyn_cast(Val)) { - APInt Offset(IndexSize, 0); - MapVector VarOffsets; - GEP->collectOffset(DL, IndexSize, VarOffsets, Offset); - setInsertionPoint(Builder, GEP); Value *Op = NewInsts[GEP->getOperand(0)]; Value *OffsetV = emitGEPOffset(&Builder, DL, GEP); From d3f9de6f1cd8a59b59f83dcbf352da69936939a0 Mon Sep 17 00:00:00 2001 From: Nikita Popov Date: Tue, 21 Nov 2023 18:49:03 +0100 Subject: [PATCH 4/5] Simplify check for at most one variable index --- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index f7cb5aa26e0fe..37f18fb622e9a 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -419,7 +419,6 @@ static bool canRewriteGEPAsOffset(Value *Start, Value *Base, SetVector &Explored) { SmallVector WorkList(1, Start); Explored.insert(Base); - uint64_t IndexSize = DL.getIndexTypeSizeInBits(Start->getType()); // The following traversal gives us an order which can be used // when doing the final transformation. Since in the final @@ -450,10 +449,8 @@ static bool canRewriteGEPAsOffset(Value *Start, Value *Base, if (auto *GEP = dyn_cast(V)) { // Only allow GEPs with at most one variable offset. - APInt Offset(IndexSize, 0); - MapVector VarOffsets; - if (!GEP->collectOffset(DL, IndexSize, VarOffsets, Offset) || - VarOffsets.size() > 1) + auto IsNonConst = [](Value *V) { return !isa(V); }; + if (count_if(GEP->indices(), IsNonConst) > 1) return false; if (!Explored.contains(GEP->getOperand(0))) From af6cc8fadbdcef614b55d18ac6167bf150eac93c Mon Sep 17 00:00:00 2001 From: Nikita Popov Date: Mon, 27 Nov 2023 09:45:58 +0100 Subject: [PATCH 5/5] Restore inbounds check --- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index 37f18fb622e9a..69b96445c76e9 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -448,9 +448,9 @@ static bool canRewriteGEPAsOffset(Value *Start, Value *Base, return false; if (auto *GEP = dyn_cast(V)) { - // Only allow GEPs with at most one variable offset. + // Only allow inbounds GEPs with at most one variable offset. auto IsNonConst = [](Value *V) { return !isa(V); }; - if (count_if(GEP->indices(), IsNonConst) > 1) + if (!GEP->isInBounds() || count_if(GEP->indices(), IsNonConst) > 1) return false; if (!Explored.contains(GEP->getOperand(0)))