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[MemCpyOpt] Fix a variety of scalable-type crashes

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This patch fixes a variety of crashes resulting from the `MemCpyOptPass`
casting `TypeSize` to a constant integer, whether implicitly or
explicitly.

Since the `MemsetRanges` requires a constant size to work, all but one
of the fixes in this patch simply involve skipping the various
optimizations for scalable types as cleanly as possible.

The optimization of `byval` parameters, however, has been updated to
work on scalable types in theory. In practice, this optimization is only
valid when the length of the `memcpy` is known to be larger than the
scalable type size, which is currently never the case. This could
perhaps be done in the future using the `vscale_range` attribute.

Some implicit casts have been left as they were, under the knowledge
they are only called on aggregate types. These should never be
scalably-sized.

Reviewed By: nikic, tra

Differential Revision: https://reviews.llvm.org/D109329

(cherry-picked from commit 7fb66d4)
This commit is contained in:
Fraser Cormack 2021-09-08 12:19:45 +01:00 committed by Tom Stellard
parent 28d769100d
commit 5e5115bbd0
3 changed files with 130 additions and 13 deletions
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2
include/llvm/Transforms/Scalar/MemCpyOptimizer.h
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@ -65,7 +65,7 @@ private:
bool processMemCpy(MemCpyInst *M, BasicBlock::iterator &BBI);
bool processMemMove(MemMoveInst *M);
bool performCallSlotOptzn(Instruction *cpyLoad, Instruction *cpyStore,
Value *cpyDst, Value *cpySrc, uint64_t cpyLen,
Value *cpyDst, Value *cpySrc, TypeSize cpyLen,
Align cpyAlign, CallInst *C);
bool processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep);
bool processMemSetMemCpyDependence(MemCpyInst *MemCpy, MemSetInst *MemSet);

40
lib/Transforms/Scalar/MemCpyOptimizer.cpp
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@ -178,9 +178,9 @@ public:
}
void addStore(int64_t OffsetFromFirst, StoreInst *SI) {
int64_t StoreSize = DL.getTypeStoreSize(SI->getOperand(0)->getType());
addRange(OffsetFromFirst, StoreSize, SI->getPointerOperand(),
TypeSize StoreSize = DL.getTypeStoreSize(SI->getOperand(0)->getType());
assert(!StoreSize.isScalable() && "Can't track scalable-typed stores");
addRange(OffsetFromFirst, StoreSize.getFixedSize(), SI->getPointerOperand(),
SI->getAlign().value(), SI);
}
@ -371,6 +371,11 @@ Instruction *MemCpyOptPass::tryMergingIntoMemset(Instruction *StartInst,
Value *ByteVal) {
const DataLayout &DL = StartInst->getModule()->getDataLayout();
// We can't track scalable types
if (StoreInst *SI = dyn_cast<StoreInst>(StartInst))
if (DL.getTypeStoreSize(SI->getOperand(0)->getType()).isScalable())
return nullptr;
// Okay, so we now have a single store that can be splatable. Scan to find
// all subsequent stores of the same value to offset from the same pointer.
// Join these together into ranges, so we can decide whether contiguous blocks
@ -426,6 +431,10 @@ Instruction *MemCpyOptPass::tryMergingIntoMemset(Instruction *StartInst,
if (DL.isNonIntegralPointerType(StoredVal->getType()->getScalarType()))
break;
// We can't track ranges involving scalable types.
if (DL.getTypeStoreSize(StoredVal->getType()).isScalable())
break;
// Check to see if this stored value is of the same byte-splattable value.
Value *StoredByte = isBytewiseValue(StoredVal, DL);
if (isa<UndefValue>(ByteVal) && StoredByte)
@ -859,7 +868,7 @@ bool MemCpyOptPass::processMemSet(MemSetInst *MSI, BasicBlock::iterator &BBI) {
/// the call write its result directly into the destination of the memcpy.
bool MemCpyOptPass::performCallSlotOptzn(Instruction *cpyLoad,
Instruction *cpyStore, Value *cpyDest,
Value *cpySrc, uint64_t cpyLen,
Value *cpySrc, TypeSize cpySize,
Align cpyAlign, CallInst *C) {
// The general transformation to keep in mind is
//
@ -875,6 +884,10 @@ bool MemCpyOptPass::performCallSlotOptzn(Instruction *cpyLoad,
// src only holds uninitialized values at the moment of the call, meaning that
// the memcpy can be discarded rather than moved.
// We can't optimize scalable types.
if (cpySize.isScalable())
return false;
// Lifetime marks shouldn't be operated on.
if (Function *F = C->getCalledFunction())
if (F->isIntrinsic() && F->getIntrinsicID() == Intrinsic::lifetime_start)
@ -893,13 +906,13 @@ bool MemCpyOptPass::performCallSlotOptzn(Instruction *cpyLoad,
uint64_t srcSize = DL.getTypeAllocSize(srcAlloca->getAllocatedType()) *
srcArraySize->getZExtValue();
if (cpyLen < srcSize)
if (cpySize < srcSize)
return false;
// Check that accessing the first srcSize bytes of dest will not cause a
// trap. Otherwise the transform is invalid since it might cause a trap
// to occur earlier than it otherwise would.
if (!isDereferenceableAndAlignedPointer(cpyDest, Align(1), APInt(64, cpyLen),
if (!isDereferenceableAndAlignedPointer(cpyDest, Align(1), APInt(64, cpySize),
DL, C, DT))
return false;
@ -1452,9 +1465,10 @@ bool MemCpyOptPass::processMemCpy(MemCpyInst *M, BasicBlock::iterator &BBI) {
// of conservatively taking the minimum?
Align Alignment = std::min(M->getDestAlign().valueOrOne(),
M->getSourceAlign().valueOrOne());
if (performCallSlotOptzn(M, M, M->getDest(), M->getSource(),
CopySize->getZExtValue(), Alignment,
C)) {
if (performCallSlotOptzn(
M, M, M->getDest(), M->getSource(),
TypeSize::getFixed(CopySize->getZExtValue()), Alignment,
C)) {
LLVM_DEBUG(dbgs() << "Performed call slot optimization:\n"
<< " call: " << *C << "\n"
<< " memcpy: " << *M << "\n");
@ -1509,7 +1523,8 @@ bool MemCpyOptPass::processMemCpy(MemCpyInst *M, BasicBlock::iterator &BBI) {
Align Alignment = std::min(M->getDestAlign().valueOrOne(),
M->getSourceAlign().valueOrOne());
if (performCallSlotOptzn(M, M, M->getDest(), M->getSource(),
CopySize->getZExtValue(), Alignment, C)) {
TypeSize::getFixed(CopySize->getZExtValue()),
Alignment, C)) {
eraseInstruction(M);
++NumMemCpyInstr;
return true;
@ -1584,7 +1599,7 @@ bool MemCpyOptPass::processByValArgument(CallBase &CB, unsigned ArgNo) {
// Find out what feeds this byval argument.
Value *ByValArg = CB.getArgOperand(ArgNo);
Type *ByValTy = CB.getParamByValType(ArgNo);
uint64_t ByValSize = DL.getTypeAllocSize(ByValTy);
TypeSize ByValSize = DL.getTypeAllocSize(ByValTy);
MemoryLocation Loc(ByValArg, LocationSize::precise(ByValSize));
MemCpyInst *MDep = nullptr;
if (EnableMemorySSA) {
@ -1612,7 +1627,8 @@ bool MemCpyOptPass::processByValArgument(CallBase &CB, unsigned ArgNo) {
// The length of the memcpy must be larger or equal to the size of the byval.
ConstantInt *C1 = dyn_cast<ConstantInt>(MDep->getLength());
if (!C1 || C1->getValue().getZExtValue() < ByValSize)
if (!C1 || !TypeSize::isKnownGE(
TypeSize::getFixed(C1->getValue().getZExtValue()), ByValSize))
return false;
// Get the alignment of the byval. If the call doesn't specify the alignment,

101
test/Transforms/MemCpyOpt/vscale-crashes.ll Normal file
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@ -0,0 +1,101 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -memcpyopt -S -verify-memoryssa | FileCheck %s
; Check that a call featuring a scalable-vector byval argument fed by a memcpy
; doesn't crash the compiler. It previously assumed the byval type's size could
; be represented as a known constant amount.
define void @byval_caller(i8 *%P) {
; CHECK-LABEL: @byval_caller(
; CHECK-NEXT: [[A:%.*]] = alloca i8, align 1
; CHECK-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 4 [[A]], i8* align 4 [[P:%.*]], i64 8, i1 false)
; CHECK-NEXT: [[VA:%.*]] = bitcast i8* [[A]] to <vscale x 1 x i8>*
; CHECK-NEXT: call void @byval_callee(<vscale x 1 x i8>* byval(<vscale x 1 x i8>) align 1 [[VA]])
; CHECK-NEXT: ret void
;
%a = alloca i8
call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 4 %a, i8* align 4 %P, i64 8, i1 false)
%va = bitcast i8* %a to <vscale x 1 x i8>*
call void @byval_callee(<vscale x 1 x i8>* align 1 byval(<vscale x 1 x i8>) %va)
ret void
}
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* align 4, i8* align 4, i64, i1)
declare void @byval_callee(<vscale x 1 x i8>* align 1 byval(<vscale x 1 x i8>))
; Check that two scalable-vector stores (overlapping, with a constant offset)
; do not crash the compiler when checked whether or not they can be merged into
; a single memset. There was previously an assumption that the stored values'
; sizes could be represented by a known constant amount.
define void @merge_stores_both_scalable(<vscale x 1 x i8>* %ptr) {
; CHECK-LABEL: @merge_stores_both_scalable(
; CHECK-NEXT: store <vscale x 1 x i8> zeroinitializer, <vscale x 1 x i8>* [[PTR:%.*]], align 1
; CHECK-NEXT: [[PTRI8:%.*]] = bitcast <vscale x 1 x i8>* [[PTR]] to i8*
; CHECK-NEXT: [[PTR_NEXT:%.*]] = getelementptr i8, i8* [[PTRI8]], i64 1
; CHECK-NEXT: [[PTR_NEXT_2:%.*]] = bitcast i8* [[PTR_NEXT]] to <vscale x 1 x i8>*
; CHECK-NEXT: store <vscale x 1 x i8> zeroinitializer, <vscale x 1 x i8>* [[PTR_NEXT_2]], align 1
; CHECK-NEXT: ret void
;
store <vscale x 1 x i8> zeroinitializer, <vscale x 1 x i8>* %ptr
%ptri8 = bitcast <vscale x 1 x i8>* %ptr to i8*
%ptr.next = getelementptr i8, i8* %ptri8, i64 1
%ptr.next.2 = bitcast i8* %ptr.next to <vscale x 1 x i8>*
store <vscale x 1 x i8> zeroinitializer, <vscale x 1 x i8>* %ptr.next.2
ret void
}
; As above, but where the base is scalable but the subsequent store(s) are not.
define void @merge_stores_first_scalable(<vscale x 1 x i8>* %ptr) {
; CHECK-LABEL: @merge_stores_first_scalable(
; CHECK-NEXT: store <vscale x 1 x i8> zeroinitializer, <vscale x 1 x i8>* [[PTR:%.*]], align 1
; CHECK-NEXT: [[PTRI8:%.*]] = bitcast <vscale x 1 x i8>* [[PTR]] to i8*
; CHECK-NEXT: [[PTR_NEXT:%.*]] = getelementptr i8, i8* [[PTRI8]], i64 1
; CHECK-NEXT: store i8 0, i8* [[PTR_NEXT]], align 1
; CHECK-NEXT: ret void
;
store <vscale x 1 x i8> zeroinitializer, <vscale x 1 x i8>* %ptr
%ptri8 = bitcast <vscale x 1 x i8>* %ptr to i8*
%ptr.next = getelementptr i8, i8* %ptri8, i64 1
store i8 zeroinitializer, i8* %ptr.next
ret void
}
; As above, but where the base is not scalable but the subsequent store(s) are.
define void @merge_stores_second_scalable(i8* %ptr) {
; CHECK-LABEL: @merge_stores_second_scalable(
; CHECK-NEXT: store i8 0, i8* [[PTR:%.*]], align 1
; CHECK-NEXT: [[PTR_NEXT:%.*]] = getelementptr i8, i8* [[PTR]], i64 1
; CHECK-NEXT: [[PTR_NEXT_2:%.*]] = bitcast i8* [[PTR_NEXT]] to <vscale x 1 x i8>*
; CHECK-NEXT: store <vscale x 1 x i8> zeroinitializer, <vscale x 1 x i8>* [[PTR_NEXT_2]], align 1
; CHECK-NEXT: ret void
;
store i8 zeroinitializer, i8* %ptr
%ptr.next = getelementptr i8, i8* %ptr, i64 1
%ptr.next.2 = bitcast i8* %ptr.next to <vscale x 1 x i8>*
store <vscale x 1 x i8> zeroinitializer, <vscale x 1 x i8>* %ptr.next.2
ret void
}
; Check that the call-slot optimization doesn't crash when encountering scalable types.
define void @callslotoptzn(<vscale x 4 x float> %val, <vscale x 4 x float>* %out) {
; CHECK-LABEL: @callslotoptzn(
; CHECK-NEXT: [[ALLOC:%.*]] = alloca <vscale x 4 x float>, align 16
; CHECK-NEXT: [[IDX:%.*]] = tail call <vscale x 4 x i32> @llvm.experimental.stepvector.nxv4i32()
; CHECK-NEXT: [[BALLOC:%.*]] = getelementptr inbounds <vscale x 4 x float>, <vscale x 4 x float>* [[ALLOC]], i64 0, i64 0
; CHECK-NEXT: [[STRIDE:%.*]] = getelementptr inbounds float, float* [[BALLOC]], <vscale x 4 x i32> [[IDX]]
; CHECK-NEXT: call void @llvm.masked.scatter.nxv4f32.nxv4p0f32(<vscale x 4 x float> [[VAL:%.*]], <vscale x 4 x float*> [[STRIDE]], i32 4, <vscale x 4 x i1> shufflevector (<vscale x 4 x i1> insertelement (<vscale x 4 x i1> poison, i1 true, i32 0), <vscale x 4 x i1> poison, <vscale x 4 x i32> zeroinitializer))
; CHECK-NEXT: [[LI:%.*]] = load <vscale x 4 x float>, <vscale x 4 x float>* [[ALLOC]], align 4
; CHECK-NEXT: store <vscale x 4 x float> [[LI]], <vscale x 4 x float>* [[OUT:%.*]], align 4
; CHECK-NEXT: ret void
;
%alloc = alloca <vscale x 4 x float>, align 16
%idx = tail call <vscale x 4 x i32> @llvm.experimental.stepvector.nxv4i32()
%balloc = getelementptr inbounds <vscale x 4 x float>, <vscale x 4 x float>* %alloc, i64 0, i64 0
%stride = getelementptr inbounds float, float* %balloc, <vscale x 4 x i32> %idx
call void @llvm.masked.scatter.nxv4f32.nxv4p0f32(<vscale x 4 x float> %val, <vscale x 4 x float*> %stride, i32 4, <vscale x 4 x i1> shufflevector (<vscale x 4 x i1> insertelement (<vscale x 4 x i1> poison, i1 true, i32 0), <vscale x 4 x i1> poison, <vscale x 4 x i32> zeroinitializer))
%li = load <vscale x 4 x float>, <vscale x 4 x float>* %alloc, align 4
store <vscale x 4 x float> %li, <vscale x 4 x float>* %out, align 4
ret void
}
declare <vscale x 4 x i32> @llvm.experimental.stepvector.nxv4i32()
declare void @llvm.masked.scatter.nxv4f32.nxv4p0f32(<vscale x 4 x float> , <vscale x 4 x float*> , i32, <vscale x 4 x i1>)