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Fix load alignement when unpacking aggregates structs 

Summary: Store and loads unpacked by instcombine do not always have the right alignement. This explicitely compute the alignement and set it.

Reviewers: dblaikie, majnemer, reames, hfinkel, joker.eph

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D17326

llvm-svn: 261139
This commit is contained in:
Amaury Sechet 2016-02-17 19:21:28 +00:00
parent f48bcb2bd9
commit 61a7d629ec
2 changed files with 53 additions and 12 deletions
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38
llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
View File

@ -523,16 +523,17 @@ static Instruction *unpackLoadToAggregate(InstCombiner &IC, LoadInst &LI) {
if (!T->isAggregateType())
return nullptr;
auto Name = LI.getName();
assert(LI.getAlignment() && "Alignment must be set at this point");
if (auto *ST = dyn_cast<StructType>(T)) {
// If the struct only have one element, we unpack.
unsigned Count = ST->getNumElements();
if (Count == 1) {
auto NumElements = ST->getNumElements();
if (NumElements == 1) {
LoadInst *NewLoad = combineLoadToNewType(IC, LI, ST->getTypeAtIndex(0U),
".unpack");
return IC.replaceInstUsesWith(LI, IC.Builder->CreateInsertValue(
UndefValue::get(T), NewLoad, 0, LI.getName()));
UndefValue::get(T), NewLoad, 0, Name));
}
// We don't want to break loads with padding here as we'd loose
@ -542,23 +543,29 @@ static Instruction *unpackLoadToAggregate(InstCombiner &IC, LoadInst &LI) {
if (SL->hasPadding())
return nullptr;
auto Name = LI.getName();
auto Align = LI.getAlignment();
if (!Align)
Align = DL.getABITypeAlignment(ST);
SmallString<16> LoadName = Name;
LoadName += ".unpack";
SmallString<16> EltName = Name;
EltName += ".elt";
auto *Addr = LI.getPointerOperand();
Value *V = UndefValue::get(T);
auto *IdxType = Type::getInt32Ty(ST->getContext());
auto *IdxType = Type::getInt32Ty(T->getContext());
auto *Zero = ConstantInt::get(IdxType, 0);
for (unsigned i = 0; i < Count; i++) {
Value *V = UndefValue::get(T);
for (unsigned i = 0; i < NumElements; i++) {
Value *Indices[2] = {
Zero,
ConstantInt::get(IdxType, i),
};
auto *Ptr = IC.Builder->CreateInBoundsGEP(ST, Addr, makeArrayRef(Indices), EltName);
auto *L = IC.Builder->CreateAlignedLoad(Ptr, LI.getAlignment(),
LoadName);
auto *Ptr = IC.Builder->CreateInBoundsGEP(ST, Addr,
makeArrayRef(Indices), EltName);
auto EltAlign = MinAlign(Align, SL->getElementOffset(i));
auto *L = IC.Builder->CreateAlignedLoad(Ptr, EltAlign, LoadName);
V = IC.Builder->CreateInsertValue(V, L, i);
}
@ -948,11 +955,16 @@ static bool unpackStoreToAggregate(InstCombiner &IC, StoreInst &SI) {
if (SL->hasPadding())
return false;
auto Align = SI.getAlignment();
if (!Align)
Align = DL.getABITypeAlignment(ST);
SmallString<16> EltName = V->getName();
EltName += ".elt";
auto *Addr = SI.getPointerOperand();
SmallString<16> AddrName = Addr->getName();
AddrName += ".repack";
auto *IdxType = Type::getInt32Ty(ST->getContext());
auto *Zero = ConstantInt::get(IdxType, 0);
for (unsigned i = 0; i < Count; i++) {
@ -960,9 +972,11 @@ static bool unpackStoreToAggregate(InstCombiner &IC, StoreInst &SI) {
Zero,
ConstantInt::get(IdxType, i),
};
auto *Ptr = IC.Builder->CreateInBoundsGEP(ST, Addr, makeArrayRef(Indices), AddrName);
auto *Ptr = IC.Builder->CreateInBoundsGEP(ST, Addr,
makeArrayRef(Indices), AddrName);
auto *Val = IC.Builder->CreateExtractValue(V, i, EltName);
IC.Builder->CreateStore(Val, Ptr);
auto EltAlign = MinAlign(Align, SL->getElementOffset(i));
IC.Builder->CreateAlignedStore(Val, Ptr, EltAlign);
}
return true;

27
llvm/test/Transforms/InstCombine/unpack-fca.ll
View File

@ -151,3 +151,30 @@ define i32 @packed_alignment(%struct.S* dereferenceable(9) %s) {
%v = extractvalue %struct.T %tv, 1
ret i32 %v
}
%struct.U = type {i8, i8, i8, i8, i8, i8, i8, i8, i64}
define void @check_alignment(%struct.U* %u, %struct.U* %v) {
; CHECK-LABEL: check_alignment
; CHECK: load i8, i8* {{.*}}, align 8
; CHECK: load i8, i8* {{.*}}, align 1
; CHECK: load i8, i8* {{.*}}, align 2
; CHECK: load i8, i8* {{.*}}, align 1
; CHECK: load i8, i8* {{.*}}, align 4
; CHECK: load i8, i8* {{.*}}, align 1
; CHECK: load i8, i8* {{.*}}, align 2
; CHECK: load i8, i8* {{.*}}, align 1
; CHECK: load i64, i64* {{.*}}, align 8
; CHECK: store i8 {{.*}}, i8* {{.*}}, align 8
; CHECK: store i8 {{.*}}, i8* {{.*}}, align 1
; CHECK: store i8 {{.*}}, i8* {{.*}}, align 2
; CHECK: store i8 {{.*}}, i8* {{.*}}, align 1
; CHECK: store i8 {{.*}}, i8* {{.*}}, align 4
; CHECK: store i8 {{.*}}, i8* {{.*}}, align 1
; CHECK: store i8 {{.*}}, i8* {{.*}}, align 2
; CHECK: store i8 {{.*}}, i8* {{.*}}, align 1
; CHECK: store i64 {{.*}}, i64* {{.*}}, align 8
%1 = load %struct.U, %struct.U* %u
store %struct.U %1, %struct.U* %v
ret void
}