[llvm] [InstCombine] Make indexed compare fold GEP source type independent (PR #71663)
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Tue Nov 21 10:02:26 PST 2023
https://github.com/nikic updated https://github.com/llvm/llvm-project/pull/71663
>From c14d7182309c6aed62c6148c922345aeedb2810c Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov at redhat.com>
Date: Wed, 8 Nov 2023 12:03:17 +0100
Subject: [PATCH 1/4] [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 03bc0f16c8938ae..29e29e05dba15f9 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<Value *> &Explored) {
SmallVector<Value *, 16> 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<GEPOperator>(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<Value *, APInt> 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<Value *> &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<Value *, Value *> 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<GEPOperator>(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<Value *, APInt> 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<ConstantInt>(Op) && cast<ConstantInt>(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<PHINode>(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<Instruction>(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<Value *, Value *>
-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<Value *, APInt>
+getAsConstantIndexedAddress(Value *V, const DataLayout &DL) {
+ APInt Offset = APInt(DL.getIndexTypeSizeInBits(V->getType()), 0);
while (GEPOperator *GEP = dyn_cast<GEPOperator>(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<Constant *>(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<Value *> 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 4681fdc59a99693..e34fd032b17d98b 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 at 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 at 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:
@@ -99,16 +101,17 @@ bb2:
define ptr at 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:
@@ -137,14 +140,15 @@ define ptr at 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 }
@@ -181,15 +185,16 @@ define ptr at 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 900d3f142a6ff79..4448a49ad92bf5d 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 9c7db50304baffd066712789fe34b5971a42b6f7 Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov at redhat.com>
Date: Tue, 14 Nov 2023 15:08:20 +0100
Subject: [PATCH 2/4] 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 29e29e05dba15f9..2f08da7951e5fc8 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<Value *, APInt>
-getAsConstantIndexedAddress(Value *V, const DataLayout &DL) {
- APInt Offset = APInt(DL.getIndexTypeSizeInBits(V->getType()), 0);
- while (GEPOperator *GEP = dyn_cast<GEPOperator>(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<Value *> Nodes;
>From 9af67e1b4a3b4259e23af82312ce8d5b37d81ddf Mon Sep 17 00:00:00 2001
From: Nikita Popov <nikita.ppv at gmail.com>
Date: Tue, 21 Nov 2023 18:46:54 +0100
Subject: [PATCH 3/4] 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 2f08da7951e5fc8..211fab59fa24499 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<Value *, Value *> NewInsts;
NewInsts[Base] = ConstantInt::getNullValue(IndexType);
@@ -565,10 +565,6 @@ static Value *rewriteGEPAsOffset(Value *Start, Value *Base,
continue;
if (auto *GEP = dyn_cast<GEPOperator>(Val)) {
- APInt Offset(IndexSize, 0);
- MapVector<Value *, APInt> VarOffsets;
- GEP->collectOffset(DL, IndexSize, VarOffsets, Offset);
-
setInsertionPoint(Builder, GEP);
Value *Op = NewInsts[GEP->getOperand(0)];
Value *OffsetV = emitGEPOffset(&Builder, DL, GEP);
>From e04064e5f5af6bb4aec9f0ac92687b419d719f86 Mon Sep 17 00:00:00 2001
From: Nikita Popov <nikita.ppv at gmail.com>
Date: Tue, 21 Nov 2023 18:49:03 +0100
Subject: [PATCH 4/4] 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 211fab59fa24499..3fcc498467d9b16 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<Value *> &Explored) {
SmallVector<Value *, 16> 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<GEPOperator>(V)) {
// Only allow GEPs with at most one variable offset.
- APInt Offset(IndexSize, 0);
- MapVector<Value *, APInt> VarOffsets;
- if (!GEP->collectOffset(DL, IndexSize, VarOffsets, Offset) ||
- VarOffsets.size() > 1)
+ auto IsNonConst = [](Value *V) { return !isa<ConstantInt>(V); };
+ if (count_if(GEP->indices(), IsNonConst) > 1)
return false;
if (!Explored.contains(GEP->getOperand(0)))
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