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Teach the load analysis to allow finding available values which require

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inttoptr or ptrtoint cast provided there is datalayout available.
Eventually, the datalayout can just be required but in practice it will
always be there today.

To go with the ability to expose available values requiring a ptrtoint
or inttoptr cast, helpers are added to perform one of these three casts.

These smarts are necessary to finish canonicalizing loads and stores to
the operational type requirements without regressing fundamental
combines.

I've added some test cases. These should actually improve as the load
combining and store combining improves, but they may fundamentally be
highlighting some missing combines for select in addition to exercising
the specific added logic to load analysis.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220277 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth 2014-10-21 09:00:40 +00:00
parent 59e16813d2
commit 9156c5e3ba
7 changed files with 136 additions and 18 deletions
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12
include/llvm/IR/IRBuilder.h
View File

@ -1246,6 +1246,18 @@ public:
return Insert(Folder.CreateIntCast(VC, DestTy, isSigned), Name);
return Insert(CastInst::CreateIntegerCast(V, DestTy, isSigned), Name);
}
Value *CreateBitOrPointerCast(Value *V, Type *DestTy,
const Twine &Name = "") {
if (V->getType() == DestTy)
return V;
if (V->getType()->isPointerTy() && DestTy->isIntegerTy())
return CreatePtrToInt(V, DestTy, Name);
if (V->getType()->isIntegerTy() && DestTy->isPointerTy())
return CreateIntToPtr(V, DestTy, Name);
return CreateBitCast(V, DestTy, Name);
}
private:
// \brief Provided to resolve 'CreateIntCast(Ptr, Ptr, "...")', giving a
// compile time error, instead of converting the string to bool for the

24
include/llvm/IR/InstrTypes.h
View File

@ -490,6 +490,19 @@ public:
Instruction *InsertBefore = 0 ///< Place to insert the instruction
);
/// @brief Create a BitCast, a PtrToInt, or an IntToPTr cast instruction.
///
/// If the value is a pointer type and the destination an integer type,
/// creates a PtrToInt cast. If the value is an integer type and the
/// destination a pointer type, creates an IntToPtr cast. Otherwise, creates
/// a bitcast.
static CastInst *CreateBitOrPointerCast(
Value *S, ///< The pointer value to be casted (operand 0)
Type *Ty, ///< The type to which cast should be made
const Twine &Name = "", ///< Name for the instruction
Instruction *InsertBefore = 0 ///< Place to insert the instruction
);
/// @brief Create a ZExt, BitCast, or Trunc for int -> int casts.
static CastInst *CreateIntegerCast(
Value *S, ///< The pointer value to be casted (operand 0)
@ -552,6 +565,17 @@ public:
Type *DestTy ///< The Type to which the value should be cast.
);
/// @brief Check whether a bitcast, inttoptr, or ptrtoint cast between these
/// types is valid and a no-op.
///
/// This ensures that any pointer<->integer cast has enough bits in the
/// integer and any other cast is a bitcast.
static bool isBitOrNoopPointerCastable(
Type *SrcTy, ///< The Type from which the value should be cast.
Type *DestTy, ///< The Type to which the value should be cast.
const DataLayout *Layout = 0 ///< Optional DataLayout.
);
/// Returns the opcode necessary to cast Val into Ty using usual casting
/// rules.
/// @brief Infer the opcode for cast operand and type

14
lib/Analysis/Loads.cpp
View File

@ -176,8 +176,13 @@ Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
Type *AccessTy = cast<PointerType>(Ptr->getType())->getElementType();
// If we're using alias analysis to disambiguate get the size of *Ptr.
uint64_t AccessSize = AA ? AA->getTypeStoreSize(AccessTy) : 0;
// Try to get the DataLayout for this module. This may be null, in which case
// the optimizations will be limited.
const DataLayout *DL = ScanBB->getDataLayout();
// Try to get the store size for the type.
uint64_t AccessSize = DL ? DL->getTypeStoreSize(AccessTy)
: AA ? AA->getTypeStoreSize(AccessTy) : 0;
Value *StrippedPtr = Ptr->stripPointerCasts();
@ -202,7 +207,7 @@ Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
if (AreEquivalentAddressValues(
LI->getPointerOperand()->stripPointerCasts(), StrippedPtr) &&
CastInst::isBitCastable(LI->getType(), AccessTy)) {
CastInst::isBitOrNoopPointerCastable(LI->getType(), AccessTy, DL)) {
if (AATags)
LI->getAAMetadata(*AATags);
return LI;
@ -214,7 +219,8 @@ Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
// (This is true even if the store is volatile or atomic, although
// those cases are unlikely.)
if (AreEquivalentAddressValues(StorePtr, StrippedPtr) &&
CastInst::isBitCastable(SI->getValueOperand()->getType(), AccessTy)) {
CastInst::isBitOrNoopPointerCastable(SI->getValueOperand()->getType(),
AccessTy, DL)) {
if (AATags)
SI->getAAMetadata(*AATags);
return SI->getOperand(0);

23
lib/IR/Instructions.cpp
View File

@ -2559,6 +2559,17 @@ CastInst *CastInst::CreatePointerBitCastOrAddrSpaceCast(
return Create(Instruction::BitCast, S, Ty, Name, InsertBefore);
}
CastInst *CastInst::CreateBitOrPointerCast(Value *S, Type *Ty,
const Twine &Name,
Instruction *InsertBefore) {
if (S->getType()->isPointerTy() && Ty->isIntegerTy())
return Create(Instruction::PtrToInt, S, Ty, Name, InsertBefore);
if (S->getType()->isIntegerTy() && Ty->isPointerTy())
return Create(Instruction::IntToPtr, S, Ty, Name, InsertBefore);
return Create(Instruction::BitCast, S, Ty, Name, InsertBefore);
}
CastInst *CastInst::CreateIntegerCast(Value *C, Type *Ty,
bool isSigned, const Twine &Name,
Instruction *InsertBefore) {
@ -2716,6 +2727,18 @@ bool CastInst::isBitCastable(Type *SrcTy, Type *DestTy) {
return true;
}
bool CastInst::isBitOrNoopPointerCastable(Type *SrcTy, Type *DestTy,
const DataLayout *DL) {
if (auto *PtrTy = dyn_cast<PointerType>(SrcTy))
if (auto *IntTy = dyn_cast<IntegerType>(DestTy))
return DL && IntTy->getBitWidth() >= DL->getPointerTypeSizeInBits(PtrTy);
if (auto *PtrTy = dyn_cast<PointerType>(DestTy))
if (auto *IntTy = dyn_cast<IntegerType>(SrcTy))
return DL && IntTy->getBitWidth() >= DL->getPointerTypeSizeInBits(PtrTy);
return isBitCastable(SrcTy, DestTy);
}
// Provide a way to get a "cast" where the cast opcode is inferred from the
// types and size of the operand. This, basically, is a parallel of the
// logic in the castIsValid function below. This axiom should hold:

3
lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
View File

@ -417,7 +417,8 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
BasicBlock::iterator BBI = &LI;
if (Value *AvailableVal = FindAvailableLoadedValue(Op, LI.getParent(), BBI,6))
return ReplaceInstUsesWith(
LI, Builder->CreateBitCast(AvailableVal, LI.getType()));
LI, Builder->CreateBitOrPointerCast(AvailableVal, LI.getType(),
LI.getName() + ".cast"));
// load(gep null, ...) -> unreachable
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) {

8
lib/Transforms/Scalar/JumpThreading.cpp
View File

@ -902,8 +902,8 @@ bool JumpThreading::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
// only happen in dead loops.
if (AvailableVal == LI) AvailableVal = UndefValue::get(LI->getType());
if (AvailableVal->getType() != LI->getType())
AvailableVal = CastInst::Create(CastInst::BitCast, AvailableVal,
LI->getType(), "", LI);
AvailableVal =
CastInst::CreateBitOrPointerCast(AvailableVal, LI->getType(), "", LI);
LI->replaceAllUsesWith(AvailableVal);
LI->eraseFromParent();
return true;
@ -1040,8 +1040,8 @@ bool JumpThreading::SimplifyPartiallyRedundantLoad(LoadInst *LI) {
// predecessor use the same bitcast.
Value *&PredV = I->second;
if (PredV->getType() != LI->getType())
PredV = CastInst::Create(CastInst::BitCast, PredV, LI->getType(), "",
P->getTerminator());
PredV = CastInst::CreateBitOrPointerCast(PredV, LI->getType(), "",
P->getTerminator());
PN->addIncoming(PredV, I->first);
}

70
test/Transforms/InstCombine/select.ll
View File

@ -1256,7 +1256,7 @@ define i32 @test76(i1 %flag, i32* %x) {
ret i32 %v
}
declare void @scribble_on_memory(i32*)
declare void @scribble_on_i32(i32*)
define i32 @test77(i1 %flag, i32* %x) {
; The load here must not be speculated around the select. One side of the
@ -1264,13 +1264,13 @@ define i32 @test77(i1 %flag, i32* %x) {
; load does.
; CHECK-LABEL: @test77(
; CHECK: %[[A:.*]] = alloca i32, align 1
; CHECK: call void @scribble_on_memory(i32* %[[A]])
; CHECK: call void @scribble_on_i32(i32* %[[A]])
; CHECK: store i32 0, i32* %x
; CHECK: %[[P:.*]] = select i1 %flag, i32* %[[A]], i32* %x
; CHECK: load i32* %[[P]]
%under_aligned = alloca i32, align 1
call void @scribble_on_memory(i32* %under_aligned)
call void @scribble_on_i32(i32* %under_aligned)
store i32 0, i32* %x
%p = select i1 %flag, i32* %under_aligned, i32* %x
%v = load i32* %p
@ -1327,8 +1327,8 @@ define i32 @test80(i1 %flag) {
entry:
%x = alloca i32
%y = alloca i32
call void @scribble_on_memory(i32* %x)
call void @scribble_on_memory(i32* %y)
call void @scribble_on_i32(i32* %x)
call void @scribble_on_i32(i32* %y)
%tmp = load i32* %x
store i32 %tmp, i32* %y
%p = select i1 %flag, i32* %x, i32* %y
@ -1351,8 +1351,8 @@ entry:
%y = alloca i32
%x1 = bitcast float* %x to i32*
%y1 = bitcast i32* %y to float*
call void @scribble_on_memory(i32* %x1)
call void @scribble_on_memory(i32* %y)
call void @scribble_on_i32(i32* %x1)
call void @scribble_on_i32(i32* %y)
%tmp = load i32* %x1
store i32 %tmp, i32* %y
%p = select i1 %flag, float* %x, float* %y1
@ -1377,11 +1377,63 @@ entry:
%y = alloca i32
%x1 = bitcast float* %x to i32*
%y1 = bitcast i32* %y to float*
call void @scribble_on_memory(i32* %x1)
call void @scribble_on_memory(i32* %y)
call void @scribble_on_i32(i32* %x1)
call void @scribble_on_i32(i32* %y)
%tmp = load float* %x
store float %tmp, float* %y1
%p = select i1 %flag, i32* %x1, i32* %y
%v = load i32* %p
ret i32 %v
}
declare void @scribble_on_i64(i64*)
define i8* @test83(i1 %flag) {
; Test that we can speculate the load around the select even though they use
; differently typed pointers and requires inttoptr casts.
; CHECK-LABEL: @test83(
; CHECK: %[[X:.*]] = alloca i8*
; CHECK-NEXT: %[[Y:.*]] = alloca i8*
; CHECK: %[[V:.*]] = load i64* %[[X]]
; CHECK-NEXT: %[[C1:.*]] = inttoptr i64 %[[V]] to i8*
; CHECK-NEXT: store i8* %[[C1]], i8** %[[Y]]
; CHECK-NEXT: %[[C2:.*]] = inttoptr i64 %[[V]] to i8*
; CHECK-NEXT: %[[S:.*]] = select i1 %flag, i8* %[[C2]], i8* %[[C1]]
; CHECK-NEXT: ret i8* %[[S]]
entry:
%x = alloca i8*
%y = alloca i64
%x1 = bitcast i8** %x to i64*
%y1 = bitcast i64* %y to i8**
call void @scribble_on_i64(i64* %x1)
call void @scribble_on_i64(i64* %y)
%tmp = load i64* %x1
store i64 %tmp, i64* %y
%p = select i1 %flag, i8** %x, i8** %y1
%v = load i8** %p
ret i8* %v
}
define i64 @test84(i1 %flag) {
; Test that we can speculate the load around the select even though they use
; differently typed pointers and requires a ptrtoint cast.
; CHECK-LABEL: @test84(
; CHECK: %[[X:.*]] = alloca i8*
; CHECK-NEXT: %[[Y:.*]] = alloca i8*
; CHECK: %[[V:.*]] = load i8** %[[X]]
; CHECK-NEXT: store i8* %[[V]], i8** %[[Y]]
; CHECK-NEXT: %[[C:.*]] = ptrtoint i8* %[[V]] to i64
; CHECK-NEXT: ret i64 %[[C]]
entry:
%x = alloca i8*
%y = alloca i64
%x1 = bitcast i8** %x to i64*
%y1 = bitcast i64* %y to i8**
call void @scribble_on_i64(i64* %x1)
call void @scribble_on_i64(i64* %y)
%tmp = load i8** %x
store i8* %tmp, i8** %y1
%p = select i1 %flag, i64* %x1, i64* %y
%v = load i64* %p
ret i64 %v
}