Destructor loads of struct that do not contains padding in InstCombine.

[deadalnix]

Summary

For non padded structs, we can just proceed and deaggregate them. We don't want ot do this when there is padding in the struct as to not lose information about this padding (the subsequents passes would then try hard to preserve the padding, which is undesirable).

Also update extractvalue.ll and cast.ll so that they use structs with padding.

Remove the FIXME in the extractvalue of laod case as the non padded case is handled when processing the load, and we don't want to do it on the padded case.

[deadalnix]

rebase and ping

[deadalnix]

Do not steal a bit from StructLayout.

Maybe that will make this less controversial. Yet I kind of feel bad over computing this again and again.

[mehdi_amini]

LTGM. We can always revisit the caching later if it shows up on a profile.

lib/IR/DataLayout.cpp

77

Remove the empty line change

[deadalnix]

As per direction on IRC stealing a bit on the element count rather than on the struct size or recomputing.

[mehdi_amini]

include/llvm/IR/DataLayout.h

478–479

I think it needs a description, especially since it does not track padding in nested struct IIUC.

[deadalnix]

Add comment on hasPadding to mention it doesn't include nested padding.

[mehdi_amini]

include/llvm/IR/DataLayout.h

489

no brief
s/wiether/whether/
s/it field/its fields/

[deadalnix]

typos

[mehdi_amini]

LGTM

[mehdi_amini]

r255600

include/llvm/IR/DataLayout.h

inline LLVMTargetDataRef wrap(const DataLayout *P) {
   return reinterpret_cast<LLVMTargetDataRef>(const_cast<DataLayout *>(P));
 }
 
 /// Used to lazily calculate structure layout information for a target machine,
 /// based on the DataLayout structure.
 class StructLayout {
   uint64_t StructSize;
   unsigned StructAlignment;
-  unsigned NumElements;
+  bool IsPadded : 1;
+  unsigned NumElements : 31;
   uint64_t MemberOffsets[1]; // variable sized array!
 public:
   uint64_t getSizeInBytes() const { return StructSize; }
 
   uint64_t getSizeInBits() const { return 8 * StructSize; }
 
   unsigned getAlignment() const { return StructAlignment; }
 
+  /// Returns whether the struct has padding or not between its fields.
+  /// NB: Padding in nested element is not taken into account.
+  bool hasPadding() const { return IsPadded; }
+
   /// \brief Given a valid byte offset into the structure, returns the structure
   /// index that contains it.
   unsigned getElementContainingOffset(uint64_t Offset) const;
 
   uint64_t getElementOffset(unsigned Idx) const {
     assert(Idx < NumElements && "Invalid element idx!");
     return MemberOffsets[Idx];
   }

lib/IR/DataLayout.cpp

 //===----------------------------------------------------------------------===//
 // Support for StructLayout
 //===----------------------------------------------------------------------===//
 
 StructLayout::StructLayout(StructType *ST, const DataLayout &DL) {
   assert(!ST->isOpaque() && "Cannot get layout of opaque structs");
   StructAlignment = 0;
   StructSize = 0;
+  IsPadded = false;
   NumElements = ST->getNumElements();
 
   // Loop over each of the elements, placing them in memory.
   for (unsigned i = 0, e = NumElements; i != e; ++i) {
     Type *Ty = ST->getElementType(i);
     unsigned TyAlign = ST->isPacked() ? 1 : DL.getABITypeAlignment(Ty);
 
     // Add padding if necessary to align the data element properly.
-    if ((StructSize & (TyAlign-1)) != 0)
+    if ((StructSize & (TyAlign-1)) != 0) {
+      IsPadded = true;
       StructSize = RoundUpToAlignment(StructSize, TyAlign);
+    }
 
     // Keep track of maximum alignment constraint.
     StructAlignment = std::max(TyAlign, StructAlignment);
 
     MemberOffsets[i] = StructSize;
     StructSize += DL.getTypeAllocSize(Ty); // Consume space for this data item
   }
 
   // Empty structures have alignment of 1 byte.
   if (StructAlignment == 0) StructAlignment = 1;
 
   // Add padding to the end of the struct so that it could be put in an array
   // and all array elements would be aligned correctly.
-  if ((StructSize & (StructAlignment-1)) != 0)
+  if ((StructSize & (StructAlignment-1)) != 0) {
+    IsPadded = true;
     StructSize = RoundUpToAlignment(StructSize, StructAlignment);
   }
+}
 
 
 /// getElementContainingOffset - Given a valid offset into the structure,
 /// return the structure index that contains it.
 unsigned StructLayout::getElementContainingOffset(uint64_t Offset) const {
   const uint64_t *SI =
     std::upper_bound(&MemberOffsets[0], &MemberOffsets[NumElements], Offset);
   assert(SI != &MemberOffsets[0] && "Offset not in structure type!");
   --SI;
   assert(*SI <= Offset && "upper_bound didn't work");
   assert((SI == &MemberOffsets[0] || *(SI-1) <= Offset) &&

lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp

static Instruction *unpackLoadToAggregate(InstCombiner &IC, LoadInst &LI) {
   Type *T = LI.getType();
   if (!T->isAggregateType())
     return nullptr;
 
   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.
-    if (ST->getNumElements() == 1) {
+    unsigned Count = ST->getNumElements();
+    if (Count == 1) {
       LoadInst *NewLoad = combineLoadToNewType(IC, LI, ST->getTypeAtIndex(0U),
                                                ".unpack");
       return IC.ReplaceInstUsesWith(LI, IC.Builder->CreateInsertValue(
         UndefValue::get(T), NewLoad, 0, LI.getName()));
     }
+
+    // We don't want to break loads with padding here as we'd loose
+    // the knowledge that padding exists for the rest of the pipeline.
+    const DataLayout &DL = IC.getDataLayout();
+    auto *SL = DL.getStructLayout(ST);
+    if (SL->hasPadding())
+      return nullptr;
+
+    auto Name = LI.getName();
+    auto LoadName = LI.getName() + ".unpack";
+    auto EltName = Name + ".elt";
+    auto *Addr = LI.getPointerOperand();
+    Value *V = UndefValue::get(T);
+    auto *IdxType = Type::getInt32Ty(ST->getContext());
+    auto *Zero = ConstantInt::get(IdxType, 0);
+    for (unsigned i = 0; i < Count; i++) {
+      Value *Indices[2] = {
+        Zero,
+        ConstantInt::get(IdxType, i),
+      };
+      auto *Ptr = IC.Builder->CreateInBoundsGEP(ST, Addr, makeArrayRef(Indices), EltName);
+      auto *L = IC.Builder->CreateLoad(ST->getTypeAtIndex(i), Ptr, LoadName);
+      V = IC.Builder->CreateInsertValue(V, L, i);
+    }
+
+    V->setName(Name);
+    return IC.ReplaceInstUsesWith(LI, V);
   }
 
   if (auto *AT = dyn_cast<ArrayType>(T)) {
     // If the array only have one element, we unpack.
     if (AT->getNumElements() == 1) {
       LoadInst *NewLoad = combineLoadToNewType(IC, LI, AT->getElementType(),
                                                ".unpack");
       return IC.ReplaceInstUsesWith(LI, IC.Builder->CreateInsertValue(
static bool unpackStoreToAggregate(InstCombiner &IC, StoreInst &SI) {
   Value *V = SI.getValueOperand();
   Type *T = V->getType();
 
   if (!T->isAggregateType())
     return false;
 
   if (auto *ST = dyn_cast<StructType>(T)) {
     // If the struct only have one element, we unpack.
-    if (ST->getNumElements() == 1) {
+    unsigned Count = ST->getNumElements();
+    if (Count == 1) {
       V = IC.Builder->CreateExtractValue(V, 0);
       combineStoreToNewValue(IC, SI, V);
       return true;
     }
+
+    // We don't want to break loads with padding here as we'd loose
+    // the knowledge that padding exists for the rest of the pipeline.
+    const DataLayout &DL = IC.getDataLayout();
+    auto *SL = DL.getStructLayout(ST);
+    if (SL->hasPadding())
+      return false;
+
+    auto EltName = V->getName() + ".elt";
+    auto *Addr = SI.getPointerOperand();
+    auto AddrName = Addr->getName() + ".repack";
+    auto *IdxType = Type::getInt32Ty(ST->getContext());
+    auto *Zero = ConstantInt::get(IdxType, 0);
+    for (unsigned i = 0; i < Count; i++) {
+      Value *Indices[2] = {
+        Zero,
+        ConstantInt::get(IdxType, i),
+      };
+      auto *Ptr = IC.Builder->CreateInBoundsGEP(ST, Addr, makeArrayRef(Indices), AddrName);
+      auto *Val = IC.Builder->CreateExtractValue(V, i, EltName);
+      IC.Builder->CreateStore(Val, Ptr);
+    }
+
+    return true;
   }
 
   if (auto *AT = dyn_cast<ArrayType>(T)) {
     // If the array only have one element, we unpack.
     if (AT->getNumElements() == 1) {
       V = IC.Builder->CreateExtractValue(V, 0);
       combineStoreToNewValue(IC, SI, V);
       return true;

lib/Transforms/InstCombine/InstructionCombining.cpp

if (II->hasOneUse()) {
         break;
       default:
         break;
       }
     }
   }
   if (LoadInst *L = dyn_cast<LoadInst>(Agg))
     // If the (non-volatile) load only has one use, we can rewrite this to a
-    // load from a GEP. This reduces the size of the load.
-    // FIXME: If a load is used only by extractvalue instructions then this
-    //        could be done regardless of having multiple uses.
+    // load from a GEP. This reduces the size of the load. If a load is used
+    // only by extractvalue instructions then this either must have been
+    // optimized before, or it is a struct with padding, in which case we
+    // don't want to do the transformation as it loses padding knowledge.
     if (L->isSimple() && L->hasOneUse()) {
       // extractvalue has integer indices, getelementptr has Value*s. Convert.
       SmallVector<Value*, 4> Indices;
       // Prefix an i32 0 since we need the first element.
       Indices.push_back(Builder->getInt32(0));
       for (ExtractValueInst::idx_iterator I = EV.idx_begin(), E = EV.idx_end();
             I != E; ++I)
         Indices.push_back(Builder->getInt32(*I));

test/Transforms/InstCombine/cast.ll

define i1 @test67(i1 %a, i32 %b) {
   %conv.i.i = ashr exact i32 %neg.i, 24
   %trunc = trunc i32 %conv.i.i to i8
   %tobool.i = icmp eq i8 %trunc, 0
   ret i1 %tobool.i
 ; CHECK-LABEL: @test67(
 ; CHECK: ret i1 false
 }
 
-%s = type { i32, i32, i32 }
+%s = type { i32, i32, i16 }
 
 define %s @test68(%s *%p, i64 %i) {
 ; CHECK-LABEL: @test68(
   %o = mul i64 %i, 12
   %q = bitcast %s* %p to i8*
   %pp = getelementptr inbounds i8, i8* %q, i64 %o
 ; CHECK-NEXT: getelementptr %s, %s*
   %r = bitcast i8* %pp to %s*

test/Transforms/InstCombine/extractvalue.ll

 ; CHECK-NEXT: [[GEP:%[a-z0-9]+]] = getelementptr inbounds {{.*}}, {{.*}}* %pair, i64 0, i32 1
 ; CHECK-NEXT: [[LOAD:%[A-Za-z0-9]+]] = load i32, i32* [[GEP]]
 ; CHECK-NEXT: store
 ; CHECK-NEXT: br label %loop
 ; CHECK-NOT: extractvalue
 ; CHECK: call {{.*}}(i32 [[LOAD]])
 ; CHECK-NOT: extractvalue
 ; CHECK: ret i32 [[LOAD]]
-define i32 @extract2gep({i32, i32}* %pair, i32* %P) {
+define i32 @extract2gep({i16, i32}* %pair, i32* %P) {
         ; The load + extractvalue should be converted
         ; to an inbounds gep + smaller load.
         ; The new load should be in the same spot as the old load.
-        %L = load {i32, i32}, {i32, i32}* %pair
+        %L = load {i16, i32}, {i16, i32}* %pair
         store i32 0, i32* %P
         br label %loop
 
 loop:
-        %E = extractvalue {i32, i32} %L, 1
+        %E = extractvalue {i16, i32} %L, 1
         %C = call i32 @baz(i32 %E)
         store i32 %C, i32* %P
         %cond = icmp eq i32 %C, 0
         br i1 %cond, label %end, label %loop
 
 end:
         ret i32 %E
 }
 
-; CHECK-LABEL: define i32 @doubleextract2gep(
+; CHECK-LABEL: define i16 @doubleextract2gep(
 ; CHECK-NEXT: [[GEP:%[a-z0-9]+]] = getelementptr inbounds {{.*}}, {{.*}}* %arg, i64 0, i32 1, i32 1
-; CHECK-NEXT: [[LOAD:%[A-Za-z0-9]+]] = load i32, i32* [[GEP]]
-; CHECK-NEXT: ret i32 [[LOAD]]
-define i32 @doubleextract2gep({i32, {i32, i32}}* %arg) {
+; CHECK-NEXT: [[LOAD:%[A-Za-z0-9]+]] = load i16, i16* [[GEP]]
+; CHECK-NEXT: ret i16 [[LOAD]]
+define i16 @doubleextract2gep({i16, {i32, i16}}* %arg) {
         ; The load + extractvalues should be converted
         ; to a 3-index inbounds gep + smaller load.
-        %L = load {i32, {i32, i32}}, {i32, {i32, i32}}* %arg
-        %E1 = extractvalue {i32, {i32, i32}} %L, 1
-        %E2 = extractvalue {i32, i32} %E1, 1
-        ret i32 %E2
+        %L = load {i16, {i32, i16}}, {i16, {i32, i16}}* %arg
+        %E1 = extractvalue {i16, {i32, i16}} %L, 1
+        %E2 = extractvalue {i32, i16} %E1, 1
+        ret i16 %E2
 }
 
 ; CHECK: define i32 @nogep-multiuse
 ; CHECK-NEXT: load {{.*}} %pair
 ; CHECK-NEXT: extractvalue
 ; CHECK-NEXT: extractvalue
 ; CHECK-NEXT: add
 ; CHECK-NEXT: ret

test/Transforms/InstCombine/unpack-fca.ll

 ; RUN: opt -instcombine -S < %s | FileCheck %s
 
 target datalayout = "e-i64:64-f80:128-n8:16:32:64"
 target triple = "x86_64-unknown-linux-gnu"
 
 %A__vtbl = type { i8*, i32 (%A*)* }
 %A = type { %A__vtbl* }
+%B = type { i8*, i64 }
 
 @A__vtblZ = constant %A__vtbl { i8* null, i32 (%A*)* @A.foo }
 
 declare i32 @A.foo(%A* nocapture %this)
 
-declare i8* @allocmemory(i64)
-
-define void @storeA() {
-body:
-  %0 = tail call i8* @allocmemory(i64 32)
-  %1 = bitcast i8* %0 to %A*
+define void @storeA(%A* %a.ptr) {
 ; CHECK-LABEL: storeA
-; CHECK: store %A__vtbl* @A__vtblZ
-  store %A { %A__vtbl* @A__vtblZ }, %A* %1, align 8
+; CHECK-NEXT: [[GEP:%[a-z0-9\.]+]] = getelementptr inbounds %A, %A* %a.ptr, i64 0, i32 0
+; CHECK-NEXT: store %A__vtbl* @A__vtblZ, %A__vtbl** [[GEP]], align 8
+; CHECK-NEXT: ret void
+  store %A { %A__vtbl* @A__vtblZ }, %A* %a.ptr, align 8
+  ret void
+}
+
+define void @storeB(%B* %b.ptr) {
+; CHECK-LABEL: storeB
+; CHECK-NEXT: [[GEP1:%[a-z0-9\.]+]] = getelementptr inbounds %B, %B* %b.ptr, i64 0, i32 0
+; CHECK-NEXT: store i8* null, i8** [[GEP1]], align 8
+; CHECK-NEXT: [[GEP2:%[a-z0-9\.]+]] = getelementptr inbounds %B, %B* %b.ptr, i64 0, i32 1
+; CHECK-NEXT: store i64 42, i64* [[GEP2]], align 8
+; CHECK-NEXT: ret void
+  store %B { i8* null, i64 42 }, %B* %b.ptr, align 8
   ret void
 }
 
-define void @storeStructOfA() {
-body:
-  %0 = tail call i8* @allocmemory(i64 32)
-  %1 = bitcast i8* %0 to { %A }*
+define void @storeStructOfA({ %A }* %sa.ptr) {
 ; CHECK-LABEL: storeStructOfA
-; CHECK: store %A__vtbl* @A__vtblZ
-  store { %A } { %A { %A__vtbl* @A__vtblZ } }, { %A }* %1, align 8
+; CHECK-NEXT: [[GEP:%[a-z0-9\.]+]] = getelementptr inbounds { %A }, { %A }* %sa.ptr, i64 0, i32 0, i32 0
+; CHECK-NEXT: store %A__vtbl* @A__vtblZ, %A__vtbl** [[GEP]], align 8
+; CHECK-NEXT: ret void
+  store { %A } { %A { %A__vtbl* @A__vtblZ } }, { %A }* %sa.ptr, align 8
   ret void
 }
 
-define void @storeArrayOfA() {
-body:
-  %0 = tail call i8* @allocmemory(i64 32)
-  %1 = bitcast i8* %0 to [1 x %A]*
+define void @storeArrayOfA([1 x %A]* %aa.ptr) {
 ; CHECK-LABEL: storeArrayOfA
-; CHECK: store %A__vtbl* @A__vtblZ
-  store [1 x %A] [%A { %A__vtbl* @A__vtblZ }], [1 x %A]* %1, align 8
+; CHECK-NEXT: [[GEP:%[a-z0-9\.]+]] = getelementptr inbounds [1 x %A], [1 x %A]* %aa.ptr, i64 0, i64 0, i32 0
+; CHECK-NEXT: store %A__vtbl* @A__vtblZ, %A__vtbl** [[GEP]], align 8
+; CHECK-NEXT: ret void
+  store [1 x %A] [%A { %A__vtbl* @A__vtblZ }], [1 x %A]* %aa.ptr, align 8
   ret void
 }
 
-define void @storeStructOfArrayOfA() {
-body:
-  %0 = tail call i8* @allocmemory(i64 32)
-  %1 = bitcast i8* %0 to { [1 x %A] }*
+define void @storeStructOfArrayOfA({ [1 x %A] }* %saa.ptr) {
 ; CHECK-LABEL: storeStructOfArrayOfA
-; CHECK: store %A__vtbl* @A__vtblZ
-  store { [1 x %A] } { [1 x %A] [%A { %A__vtbl* @A__vtblZ }] }, { [1 x %A] }* %1, align 8
+; CHECK-NEXT: [[GEP:%[a-z0-9\.]+]] = getelementptr inbounds { [1 x %A] }, { [1 x %A] }* %saa.ptr, i64 0, i32 0, i64 0, i32 0
+; CHECK-NEXT: store %A__vtbl* @A__vtblZ, %A__vtbl** [[GEP]], align 8
+; CHECK-NEXT: ret void
+  store { [1 x %A] } { [1 x %A] [%A { %A__vtbl* @A__vtblZ }] }, { [1 x %A] }* %saa.ptr, align 8
   ret void
 }
 
-define %A @loadA() {
-body:
-  %0 = tail call i8* @allocmemory(i64 32)
-  %1 = bitcast i8* %0 to %A*
+define %A @loadA(%A* %a.ptr) {
 ; CHECK-LABEL: loadA
-; CHECK: load %A__vtbl*,
-; CHECK: insertvalue %A undef, %A__vtbl* {{.*}}, 0
-  %2 = load %A, %A* %1, align 8
-  ret %A %2
+; CHECK-NEXT: [[GEP:%[a-z0-9\.]+]] = getelementptr inbounds %A, %A* %a.ptr, i64 0, i32 0
+; CHECK-NEXT: [[LOAD:%[a-z0-9\.]+]] = load %A__vtbl*, %A__vtbl** [[GEP]], align 8
+; CHECK-NEXT: [[IV:%[a-z0-9\.]+]] = insertvalue %A undef, %A__vtbl* [[LOAD]], 0
+; CHECK-NEXT: ret %A [[IV]]
+  %1 = load %A, %A* %a.ptr, align 8
+  ret %A %1
+}
+
+define %B @loadB(%B* %b.ptr) {
+; CHECK-LABEL: loadB
+; CHECK-NEXT: [[GEP1:%[a-z0-9\.]+]] = getelementptr inbounds %B, %B* %b.ptr, i64 0, i32 0
+; CHECK-NEXT: [[LOAD1:%[a-z0-9\.]+]] = load i8*, i8** [[GEP1]], align 8
+; CHECK-NEXT: [[IV1:%[a-z0-9\.]+]] = insertvalue %B undef, i8* [[LOAD1]], 0
+; CHECK-NEXT: [[GEP2:%[a-z0-9\.]+]] = getelementptr inbounds %B, %B* %b.ptr, i64 0, i32 1
+; CHECK-NEXT: [[LOAD2:%[a-z0-9\.]+]] = load i64, i64* [[GEP2]], align 8
+; CHECK-NEXT: [[IV2:%[a-z0-9\.]+]] = insertvalue %B [[IV1]], i64 [[LOAD2]], 1
+; CHECK-NEXT: ret %B [[IV2]]
+  %1 = load %B, %B* %b.ptr, align 8
+  ret %B %1
 }
 
-define { %A } @loadStructOfA() {
-body:
-  %0 = tail call i8* @allocmemory(i64 32)
-  %1 = bitcast i8* %0 to { %A }*
+define { %A } @loadStructOfA({ %A }* %sa.ptr) {
 ; CHECK-LABEL: loadStructOfA
-; CHECK: load %A__vtbl*,
-; CHECK: insertvalue %A undef, %A__vtbl* {{.*}}, 0
-; CHECK: insertvalue { %A } undef, %A {{.*}}, 0
-  %2 = load { %A }, { %A }* %1, align 8
-  ret { %A } %2
+; CHECK-NEXT: [[GEP:%[a-z0-9\.]+]] = getelementptr inbounds { %A }, { %A }* %sa.ptr, i64 0, i32 0, i32 0
+; CHECK-NEXT: [[LOAD:%[a-z0-9\.]+]] = load %A__vtbl*, %A__vtbl** [[GEP]], align 8
+; CHECK-NEXT: [[IV1:%[a-z0-9\.]+]] = insertvalue %A undef, %A__vtbl* [[LOAD]], 0
+; CHECK-NEXT: [[IV2:%[a-z0-9\.]+]] = insertvalue { %A } undef, %A [[IV1]], 0
+; CHECK-NEXT: ret { %A } [[IV2]]
+  %1 = load { %A }, { %A }* %sa.ptr, align 8
+  ret { %A } %1
 }
 
-define [1 x %A] @loadArrayOfA() {
-body:
-  %0 = tail call i8* @allocmemory(i64 32)
-  %1 = bitcast i8* %0 to [1 x %A]*
+define [1 x %A] @loadArrayOfA([1 x %A]* %aa.ptr) {
 ; CHECK-LABEL: loadArrayOfA
-; CHECK: load %A__vtbl*,
-; CHECK: insertvalue %A undef, %A__vtbl* {{.*}}, 0
-; CHECK: insertvalue [1 x %A] undef, %A {{.*}}, 0
-  %2 = load [1 x %A], [1 x %A]* %1, align 8
-  ret [1 x %A] %2
+; CHECK-NEXT: [[GEP:%[a-z0-9\.]+]] = getelementptr inbounds [1 x %A], [1 x %A]* %aa.ptr, i64 0, i64 0, i32 0
+; CHECK-NEXT: [[LOAD:%[a-z0-9\.]+]] = load %A__vtbl*, %A__vtbl** [[GEP]], align 8
+; CHECK-NEXT: [[IV1:%[a-z0-9\.]+]] = insertvalue %A undef, %A__vtbl* [[LOAD]], 0
+; CHECK-NEXT: [[IV2:%[a-z0-9\.]+]] = insertvalue [1 x %A] undef, %A [[IV1]], 0
+; CHECK-NEXT: ret [1 x %A] [[IV2]]
+  %1 = load [1 x %A], [1 x %A]* %aa.ptr, align 8
+  ret [1 x %A] %1
 }
 
-define { [1 x %A] } @loadStructOfArrayOfA() {
-body:
-  %0 = tail call i8* @allocmemory(i64 32)
-  %1 = bitcast i8* %0 to { [1 x %A] }*
+define { [1 x %A] } @loadStructOfArrayOfA({ [1 x %A] }* %saa.ptr) {
 ; CHECK-LABEL: loadStructOfArrayOfA
-; CHECK: load %A__vtbl*,
-; CHECK: insertvalue %A undef, %A__vtbl* {{.*}}, 0
-; CHECK: insertvalue [1 x %A] undef, %A {{.*}}, 0
-; CHECK: insertvalue { [1 x %A] } undef, [1 x %A] {{.*}}, 0
-  %2 = load { [1 x %A] }, { [1 x %A] }* %1, align 8
-  ret { [1 x %A] } %2
+; CHECK-NEXT: [[GEP:%[a-z0-9\.]+]] = getelementptr inbounds { [1 x %A] }, { [1 x %A] }* %saa.ptr, i64 0, i32 0, i64 0, i32 0
+; CHECK-NEXT: [[LOAD:%[a-z0-9\.]+]] = load %A__vtbl*, %A__vtbl** [[GEP]], align 8
+; CHECK-NEXT: [[IV1:%[a-z0-9\.]+]] = insertvalue %A undef, %A__vtbl* [[LOAD]], 0
+; CHECK-NEXT: [[IV2:%[a-z0-9\.]+]] = insertvalue [1 x %A] undef, %A [[IV1]], 0
+; CHECK-NEXT: [[IV3:%[a-z0-9\.]+]] = insertvalue { [1 x %A] } undef, [1 x %A] [[IV2]], 0
+; CHECK-NEXT: ret { [1 x %A] } [[IV3]]
+  %1 = load { [1 x %A] }, { [1 x %A] }* %saa.ptr, align 8
+  ret { [1 x %A] } %1
 }
 
-define { %A } @structOfA() {
-body:
-  %0 = tail call i8* @allocmemory(i64 32)
-  %1 = bitcast i8* %0 to { %A }*
+define { %A } @structOfA({ %A }* %sa.ptr) {
 ; CHECK-LABEL: structOfA
-; CHECK: store %A__vtbl* @A__vtblZ
-  store { %A } { %A { %A__vtbl* @A__vtblZ } }, { %A }* %1, align 8
-  %2 = load { %A }, { %A }* %1, align 8
-; CHECK-NOT: load
-; CHECK: ret { %A } { %A { %A__vtbl* @A__vtblZ } }
-  ret { %A } %2
+; CHECK-NEXT: [[GEP:%[a-z0-9\.]+]] = getelementptr inbounds { %A }, { %A }* %sa.ptr, i64 0, i32 0, i32 0
+; CHECK-NEXT: store %A__vtbl* @A__vtblZ, %A__vtbl** [[GEP]], align 8
+; CHECK-NEXT: ret { %A } { %A { %A__vtbl* @A__vtblZ } }
+  store { %A } { %A { %A__vtbl* @A__vtblZ } }, { %A }* %sa.ptr, align 8
+  %1 = load { %A }, { %A }* %sa.ptr, align 8
+  ret { %A } %1
+}
+
+define %B @structB(%B* %b.ptr) {
+; CHECK-LABEL: structB
+; CHECK-NEXT: [[GEP1:%[a-z0-9\.]+]] = getelementptr inbounds %B, %B* %b.ptr, i64 0, i32 0
+; CHECK-NEXT: store i8* null, i8** [[GEP1]], align 8
+; CHECK-NEXT: [[GEP2:%[a-z0-9\.]+]] = getelementptr inbounds %B, %B* %b.ptr, i64 0, i32 1
+; CHECK-NEXT: store i64 42, i64* [[GEP2]], align 8
+; CHECK-NEXT: ret %B { i8* null, i64 42 }
+  store %B { i8* null, i64 42 }, %B* %b.ptr, align 8
+  %1 = load %B, %B* %b.ptr, align 8
+  ret %B %1
 }