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[InstCombine] Make indexed compare fold opaque ptr compatible

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Rather than relying on pointer type equality (which, for a change,
is silently incorrect with opaque pointers) check that the GEP
source element types match.
This commit is contained in:
Nikita Popov 2021-06-24 22:31:06 +02:00
parent 5cfe2f65b5
commit ab8f422ef7
2 changed files with 66 additions and 14 deletions
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24
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -502,7 +502,7 @@ static Value *evaluateGEPOffsetExpression(User *GEP, InstCombinerImpl &IC,
/// 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(Value *Start, Value *Base,
static bool canRewriteGEPAsOffset(Type *ElemTy, Value *Start, Value *Base,
const DataLayout &DL,
SetVector<Value *> &Explored) {
SmallVector<Value *, 16> WorkList(1, Start);
@ -550,7 +550,7 @@ static bool canRewriteGEPAsOffset(Value *Start, Value *Base,
// the original pointer type. We could handle more cases in the
// future.
if (GEP->getNumIndices() != 1 || !GEP->isInBounds() ||
GEP->getType() != Start->getType())
GEP->getSourceElementType() != ElemTy)
return false;
if (Explored.count(GEP->getOperand(0)) == 0)
@ -626,7 +626,7 @@ 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(Value *Start, Value *Base,
static Value *rewriteGEPAsOffset(Type *ElemTy, Value *Start, Value *Base,
const DataLayout &DL,
SetVector<Value *> &Explored) {
// Perform all the substitutions. This is a bit tricky because we can
@ -728,8 +728,7 @@ static Value *rewriteGEPAsOffset(Value *Start, Value *Base,
Start->getName() + "to.ptr");
Value *GEP = Builder.CreateInBoundsGEP(
Start->getType()->getPointerElementType(), NewBase,
makeArrayRef(NewInsts[Val]), Val->getName() + ".ptr");
ElemTy, NewBase, makeArrayRef(NewInsts[Val]), Val->getName() + ".ptr");
if (!Val->getType()->isPointerTy()) {
Value *Cast = Builder.CreatePointerCast(GEP, Val->getType(),
@ -746,7 +745,7 @@ static Value *rewriteGEPAsOffset(Value *Start, Value *Base,
/// the input Value as a constant indexed GEP. Returns a pair containing
/// the GEPs Pointer and Index.
static std::pair<Value *, Value *>
getAsConstantIndexedAddress(Value *V, const DataLayout &DL) {
getAsConstantIndexedAddress(Type *ElemTy, Value *V, const DataLayout &DL) {
Type *IndexType = IntegerType::get(V->getContext(),
DL.getIndexTypeSizeInBits(V->getType()));
@ -758,7 +757,7 @@ getAsConstantIndexedAddress(Value *V, const DataLayout &DL) {
if (!GEP->isInBounds())
break;
if (GEP->hasAllConstantIndices() && GEP->getNumIndices() == 1 &&
GEP->getType() == V->getType()) {
GEP->getSourceElementType() == ElemTy) {
V = GEP->getOperand(0);
Constant *GEPIndex = static_cast<Constant *>(GEP->getOperand(1));
Index = ConstantExpr::getAdd(
@ -797,17 +796,14 @@ static Instruction *transformToIndexedCompare(GEPOperator *GEPLHS, Value *RHS,
if (!GEPLHS->hasAllConstantIndices())
return nullptr;
// Make sure the pointers have the same type.
if (GEPLHS->getType() != RHS->getType())
return nullptr;
Type *ElemTy = GEPLHS->getSourceElementType();
Value *PtrBase, *Index;
std::tie(PtrBase, Index) = getAsConstantIndexedAddress(GEPLHS, DL);
std::tie(PtrBase, Index) = getAsConstantIndexedAddress(ElemTy, GEPLHS, DL);
// The set of nodes that will take part in this transformation.
SetVector<Value *> Nodes;
if (!canRewriteGEPAsOffset(RHS, PtrBase, DL, Nodes))
if (!canRewriteGEPAsOffset(ElemTy, RHS, PtrBase, DL, Nodes))
return nullptr;
// We know we can re-write this as
@ -816,7 +812,7 @@ 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(RHS, PtrBase, DL, Nodes);
Value *NewRHS = rewriteGEPAsOffset(ElemTy, RHS, PtrBase, DL, Nodes);
// 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

56
test/Transforms/InstCombine/indexed-gep-compares.ll
View File

@ -29,7 +29,63 @@ bb:
bb2:
ret i32* %RHS
}
define ptr @test1_opaque_ptr(ptr %A, i32 %Offset) {
; CHECK-LABEL: @test1_opaque_ptr(
; CHECK-NEXT: entry:
; 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: br i1 [[COND]], label [[BB2:%.*]], label [[BB]]
; CHECK: bb2:
; CHECK-NEXT: [[RHS_PTR:%.*]] = getelementptr inbounds i32, ptr [[A:%.*]], i32 [[RHS_IDX]]
; CHECK-NEXT: ret ptr [[RHS_PTR]]
;
entry:
%tmp = getelementptr inbounds i32, ptr %A, i32 %Offset
br label %bb
bb:
%RHS = phi ptr [ %RHS.next, %bb ], [ %tmp, %entry ]
%LHS = getelementptr inbounds i32, ptr %A, i32 100
%RHS.next = getelementptr inbounds i32, ptr %RHS, i64 1
%cond = icmp ult ptr %LHS, %RHS
br i1 %cond, label %bb2, label %bb
bb2:
ret ptr %RHS
}
define ptr @test_opaque_ptr_different_types(ptr %A, i32 %Offset) {
; CHECK-LABEL: @test_opaque_ptr_different_types(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP:%.*]] = getelementptr inbounds i32, ptr [[A:%.*]], i32 [[OFFSET:%.*]]
; 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]], i32 100
; CHECK-NEXT: [[RHS_NEXT]] = getelementptr inbounds i32, ptr [[RHS]], i32 1
; CHECK-NEXT: [[COND:%.*]] = icmp ult ptr [[LHS]], [[RHS]]
; CHECK-NEXT: br i1 [[COND]], label [[BB2:%.*]], label [[BB]]
; CHECK: bb2:
; CHECK-NEXT: ret ptr [[RHS]]
;
entry:
%tmp = getelementptr inbounds i32, ptr %A, i32 %Offset
br label %bb
bb:
%RHS = phi ptr [ %RHS.next, %bb ], [ %tmp, %entry ]
%LHS = getelementptr inbounds i64, ptr %A, i32 100
%RHS.next = getelementptr inbounds i32, ptr %RHS, i64 1
%cond = icmp ult ptr %LHS, %RHS
br i1 %cond, label %bb2, label %bb
bb2:
ret ptr %RHS
}
define i32 *@test2(i32 %A, i32 %Offset) {