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[InstCombine] Don't require GEP in indexed compare fold #81614

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[InstCombine] Don't require GEP in indexed compare fold #81614

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39 changes: 20 additions & 19 deletions llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -626,32 +626,34 @@ static Value *rewriteGEPAsOffset(Value *Start, Value *Base, GEPNoWrapFlags NW,
return NewInsts[Start];
}

/// Converts (CMP GEPLHS, RHS) if this change would make RHS a constant.
/// Converts (CMP LHS, 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.
static Instruction *transformToIndexedCompare(GEPOperator *GEPLHS, Value *RHS,
CmpPredicate Cond,
/// between LHS and RHS.
static Instruction *transformToIndexedCompare(Value *LHS, Value *RHS,
ICmpInst::Predicate Cond,
const DataLayout &DL,
InstCombiner &IC) {
// FIXME: Support vector of pointers.
if (GEPLHS->getType()->isVectorTy())
if (ICmpInst::isSigned(Cond))
return nullptr;

if (!GEPLHS->hasAllConstantIndices())
// FIXME: Support vector of pointers.
if (!LHS->getType()->isPointerTy())
return nullptr;

APInt Offset(DL.getIndexTypeSizeInBits(GEPLHS->getType()), 0);
APInt Offset(DL.getIndexTypeSizeInBits(LHS->getType()), 0);
Value *PtrBase =
GEPLHS->stripAndAccumulateConstantOffsets(DL, Offset,
/*AllowNonInbounds*/ false);
LHS->stripAndAccumulateConstantOffsets(DL, Offset,
/*AllowNonInbounds*/ false);

// Bail if we looked through addrspacecast.
if (PtrBase->getType() != GEPLHS->getType())
if (PtrBase->getType() != LHS->getType())
return nullptr;

// The set of nodes that will take part in this transformation.
SetVector<Value *> Nodes;
GEPNoWrapFlags NW = GEPLHS->getNoWrapFlags();
GEPNoWrapFlags NW = GEPNoWrapFlags::all();
if (auto *GEPLHS = dyn_cast<GEPOperator>(LHS))
NW = GEPLHS->getNoWrapFlags();
if (!canRewriteGEPAsOffset(RHS, PtrBase, NW, DL, Nodes))
return nullptr;

Expand Down Expand Up @@ -800,10 +802,7 @@ Instruction *InstCombinerImpl::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
return replaceInstUsesWith(I, Cmp);
}

// Otherwise, the base pointers are different and the indices are
// different. Try convert this to an indexed compare by looking through
// PHIs/casts.
return transformToIndexedCompare(GEPLHS, RHS, Cond, DL, *this);
return nullptr;
}

if (GEPLHS->getNumOperands() == GEPRHS->getNumOperands() &&
Expand Down Expand Up @@ -851,9 +850,7 @@ Instruction *InstCombinerImpl::foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
}
}

// Try convert this to an indexed compare by looking through PHIs/casts as a
// last resort.
return transformToIndexedCompare(GEPLHS, RHS, Cond, DL, *this);
return nullptr;
}

bool InstCombinerImpl::foldAllocaCmp(AllocaInst *Alloca) {
Expand Down Expand Up @@ -7312,6 +7309,10 @@ Instruction *InstCombinerImpl::foldICmpCommutative(CmpPredicate Pred,
if (Instruction *NI = foldGEPICmp(GEP, Op1, Pred, CxtI))
return NI;

if (Instruction *Res =
transformToIndexedCompare(Op0, Op1, Pred, getDataLayout(), *this))
return Res;

if (auto *SI = dyn_cast<SelectInst>(Op0))
if (Instruction *NI = foldSelectICmp(Pred, SI, Op1, CxtI))
return NI;
Expand Down
8 changes: 4 additions & 4 deletions llvm/test/Transforms/InstCombine/getelementptr.ll
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Expand Up @@ -686,15 +686,15 @@ define i32 @test28() nounwind {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[ORIENTATIONS:%.*]] = alloca [1 x [1 x %struct.x]], align 8
; CHECK-NEXT: [[T3:%.*]] = call i32 @puts(ptr noundef nonnull dereferenceable(1) @.str) #[[ATTR0]]
; CHECK-NEXT: [[T45:%.*]] = getelementptr inbounds nuw i8, ptr [[ORIENTATIONS]], i64 1
; CHECK-NEXT: br label [[BB10:%.*]]
; CHECK: bb10:
; CHECK-NEXT: [[INDVAR:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[INDVAR_NEXT:%.*]], [[BB10]] ]
; CHECK-NEXT: [[T12_REC:%.*]] = xor i32 [[INDVAR]], -1
; CHECK-NEXT: [[TMP0:%.*]] = sext i32 [[T12_REC]] to i64
; CHECK-NEXT: [[T12:%.*]] = getelementptr inbounds [[STRUCT_X:%.*]], ptr [[T45]], i64 [[TMP0]]
; CHECK-NEXT: [[T16:%.*]] = call i32 (ptr, ...) @printf(ptr noundef nonnull dereferenceable(1) @.str1, ptr nonnull [[T12]]) #[[ATTR0]]
; CHECK-NEXT: [[T84:%.*]] = icmp eq ptr [[T12]], [[ORIENTATIONS]]
; CHECK-NEXT: [[TMP1:%.*]] = getelementptr i8, ptr [[ORIENTATIONS]], i64 [[TMP0]]
; CHECK-NEXT: [[T12_PTR:%.*]] = getelementptr i8, ptr [[TMP1]], i64 1
; CHECK-NEXT: [[T16:%.*]] = call i32 (ptr, ...) @printf(ptr noundef nonnull dereferenceable(1) @.str1, ptr nonnull [[T12_PTR]]) #[[ATTR0]]
; CHECK-NEXT: [[T84:%.*]] = icmp eq i32 [[INDVAR]], 0
; CHECK-NEXT: [[INDVAR_NEXT]] = add i32 [[INDVAR]], 1
; CHECK-NEXT: br i1 [[T84]], label [[BB17:%.*]], label [[BB10]]
; CHECK: bb17:
Expand Down
12 changes: 3 additions & 9 deletions llvm/test/Transforms/InstCombine/pr39908.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -7,9 +7,7 @@ target datalayout = "p:32:32"

define i1 @test(ptr %p, i32 %n) {
; CHECK-LABEL: @test(
; CHECK-NEXT: [[END:%.*]] = getelementptr inbounds [0 x %S], ptr [[P:%.*]], i32 0, i32 [[N:%.*]], i32 0, i32 0
; CHECK-NEXT: [[LAST:%.*]] = getelementptr inbounds i8, ptr [[END]], i32 -8
; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[LAST]], [[P]]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[N:%.*]], 1
; CHECK-NEXT: ret i1 [[CMP]]
;
%end = getelementptr inbounds [0 x %S], ptr %p, i32 0, i32 %n, i32 0, i32 0
Expand All @@ -22,9 +20,7 @@ define i1 @test(ptr %p, i32 %n) {
define i1 @test64(ptr %p, i64 %n) {
; CHECK-LABEL: @test64(
; CHECK-NEXT: [[TMP1:%.*]] = trunc i64 [[N:%.*]] to i32
; CHECK-NEXT: [[END:%.*]] = getelementptr inbounds [0 x %S], ptr [[P:%.*]], i32 0, i32 [[TMP1]], i32 0, i32 0
; CHECK-NEXT: [[LAST:%.*]] = getelementptr inbounds i8, ptr [[END]], i32 -8
; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[LAST]], [[P]]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[TMP1]], 1
; CHECK-NEXT: ret i1 [[CMP]]
;
%end = getelementptr inbounds [0 x %S], ptr %p, i64 0, i64 %n, i32 0, i64 0
Expand All @@ -37,9 +33,7 @@ define i1 @test64(ptr %p, i64 %n) {
define i1 @test64_overflow(ptr %p, i64 %n) {
; CHECK-LABEL: @test64_overflow(
; CHECK-NEXT: [[TMP1:%.*]] = trunc i64 [[N:%.*]] to i32
; CHECK-NEXT: [[END:%.*]] = getelementptr inbounds [0 x %S], ptr [[P:%.*]], i32 0, i32 [[TMP1]], i32 0, i32 0
; CHECK-NEXT: [[LAST:%.*]] = getelementptr inbounds i8, ptr [[END]], i32 -8
; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[LAST]], [[P]]
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[TMP1]], 1
; CHECK-NEXT: ret i1 [[CMP]]
;
%end = getelementptr inbounds [0 x %S], ptr %p, i64 0, i64 %n, i32 0, i64 8589934592
Expand Down
11 changes: 6 additions & 5 deletions llvm/test/Transforms/PhaseOrdering/loop-access-checks.ll
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Expand Up @@ -24,7 +24,7 @@ define void @test_fill_with_foreach([2 x i64] %elems.coerce) {
; CHECK-NEXT: [[ELEMS_COERCE_FCA_0_EXTRACT:%.*]] = extractvalue [2 x i64] [[ELEMS_COERCE]], 0
; CHECK-NEXT: [[TMP0:%.*]] = inttoptr i64 [[ELEMS_COERCE_FCA_0_EXTRACT]] to ptr
; CHECK-NEXT: [[ELEMS_COERCE_FCA_1_EXTRACT:%.*]] = extractvalue [2 x i64] [[ELEMS_COERCE]], 1
; CHECK-NEXT: [[ADD_PTR_I:%.*]] = getelementptr inbounds i32, ptr [[TMP0]], i64 [[ELEMS_COERCE_FCA_1_EXTRACT]]
; CHECK-NEXT: [[ADD_PTR_I_IDX:%.*]] = shl nsw i64 [[ELEMS_COERCE_FCA_1_EXTRACT]], 2
; CHECK-NEXT: [[CMP_NOT_I_I_I_I:%.*]] = icmp slt i64 [[ELEMS_COERCE_FCA_1_EXTRACT]], 0
; CHECK-NEXT: br i1 [[CMP_NOT_I_I_I_I]], label [[ERROR:%.*]], label [[FOR_COND_PREHEADER_SPLIT:%.*]]
; CHECK: for.cond.preheader.split:
Expand All @@ -36,10 +36,11 @@ define void @test_fill_with_foreach([2 x i64] %elems.coerce) {
; CHECK-NEXT: tail call void @error()
; CHECK-NEXT: br label [[COMMON_RET]]
; CHECK: for.body:
; CHECK-NEXT: [[__BEGIN1_SROA_0_03:%.*]] = phi ptr [ [[INCDEC_PTR_I:%.*]], [[FOR_BODY]] ], [ [[TMP0]], [[FOR_COND_PREHEADER_SPLIT]] ]
; CHECK-NEXT: tail call void @use(ptr noundef nonnull align 4 dereferenceable(4) [[__BEGIN1_SROA_0_03]])
; CHECK-NEXT: [[INCDEC_PTR_I]] = getelementptr inbounds nuw i8, ptr [[__BEGIN1_SROA_0_03]], i64 4
; CHECK-NEXT: [[CMP_I_NOT:%.*]] = icmp eq ptr [[INCDEC_PTR_I]], [[ADD_PTR_I]]
; CHECK-NEXT: [[__BEGIN1_SROA_0_0_IDX3:%.*]] = phi i64 [ [[__BEGIN1_SROA_0_0_ADD:%.*]], [[FOR_BODY]] ], [ 0, [[FOR_COND_PREHEADER_SPLIT]] ]
; CHECK-NEXT: [[__BEGIN1_SROA_0_0_PTR4:%.*]] = getelementptr inbounds nuw i8, ptr [[TMP0]], i64 [[__BEGIN1_SROA_0_0_IDX3]]
; CHECK-NEXT: tail call void @use(ptr noundef nonnull align 4 dereferenceable(4) [[__BEGIN1_SROA_0_0_PTR4]])
; CHECK-NEXT: [[__BEGIN1_SROA_0_0_ADD]] = add nuw nsw i64 [[__BEGIN1_SROA_0_0_IDX3]], 4
; CHECK-NEXT: [[CMP_I_NOT:%.*]] = icmp eq i64 [[__BEGIN1_SROA_0_0_ADD]], [[ADD_PTR_I_IDX]]
; CHECK-NEXT: br i1 [[CMP_I_NOT]], label [[COMMON_RET]], label [[FOR_BODY]]
;
entry:
Expand Down
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