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Aug 4, 2023
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[NFC][SYCL] Refactor SpecConstantsPass #10613

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[NFC][SYCL] Refactor SpecConstPass. Part 1
maksimsab Jul 28, 2023
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92 changes: 0 additions & 92 deletions llvm/test/tools/sycl-post-link/spec-constants/composite-default-value.ll
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200 changes: 114 additions & 86 deletions llvm/tools/sycl-post-link/SpecConstants.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -610,6 +610,115 @@ Instruction *emitSpecConstantRecursive(Type *Ty, Instruction *InsertBefore,
DefaultValue);
}

/// Function creates load instruction from the given Buffer by the given Offset.
/// Function returns the value of load instruction.
Value *createLoadFromBuffer(CallInst *InsertBefore, Value *Buffer,
size_t Offset, Type *SCType) {
LLVMContext &C = InsertBefore->getContext();
Type *Int8Ty = Type::getInt8Ty(C);
Type *Int32Ty = Type::getInt32Ty(C);
GetElementPtrInst *GEP = GetElementPtrInst::Create(
Int8Ty, Buffer, {ConstantInt::get(Int32Ty, Offset, false)}, "gep",
InsertBefore);

Instruction *BitCast = nullptr;
if (SCType->isIntegerTy(1)) // No bitcast to i1 before load
BitCast = GEP;
else
BitCast =
new BitCastInst(GEP, PointerType::get(SCType, GEP->getAddressSpace()),
"bc", InsertBefore);

// When we encounter i1 spec constant, we still load the whole byte
Value *Load = new LoadInst(SCType->isIntegerTy(1) ? Int8Ty : SCType, BitCast,
"load", InsertBefore);
if (SCType->isIntegerTy(1)) // trunc back to i1 if necessary
Load = CastInst::CreateIntegerCast(Load, SCType, /* IsSigned */ false,
"tobool", InsertBefore);

return Load;
}

/// Function tries to dig out the initializer from the given CallInst to
/// SpecConst function. ArgIndex is the expected index of the function operand
/// leading to the initializer.
///
/// Examples:
/// 1)
/// %"spec_id" = type { i32 }
/// @value = internal addrspace(1) constant %"spec_id" { i32 123 }, align 4
/// call spir_func i32 @sycl_getScalar2020SpecConst(%1, @value, %2)
///
/// 2)
/// %"spec_id" = type { %A }
/// %A = type { i32 }
/// @value = constant %"spec_id" { %A { i32 1 } }, align 4
/// call spir_func void @getCompositeSpecConst(%1, %2, @value, %3)
Constant *getSpecConstInitializerFromCI(CallInst *CI, unsigned ArgIndex) {
auto *GV =
cast<GlobalVariable>(CI->getArgOperand(ArgIndex)->stripPointerCasts());

// Go through global variable if the argument was not null.
assert(GV->hasInitializer() && "GV is expected to have initializer");
Constant *Initializer = GV->getInitializer();
assert((isa<ConstantAggregate>(Initializer) || Initializer->isZeroValue()) &&
"expected specialization_id instance");
// specialization_id structure contains a single field which is the
// default value of corresponding specialization constant.
return Initializer->getAggregateElement(0u);
}

/// Function replaces last Metadata node in the given vector with new
/// node which contains given Padding.
void updatePaddingInLastMDNode(LLVMContext &Ctx,
MapVector<StringRef, MDNode *> &SCMetadata,
unsigned Padding) {
// The spec constant map can't be empty as the first offset is 0
// and so it can't be misaligned.
assert(!SCMetadata.empty() && "Cannot add padding to first spec constant");

// To communicate the padding to the runtime, update the metadata
// node of the previous spec constant to append a padding node. It
// can't be added in front of the current spec constant, as doing
// so would require the spec constant node to have a non-zero
// CompositeOffset which breaks accessing it in the runtime.
auto Last = SCMetadata.back();

// Emulated spec constants don't use composite so should
// always be formatted as (SymID, ID, Offset, Size), except when
// they include padding, but since padding is added at insertion
// of the next element, the last element of the map can never be
// padded.
assert(Last.second->getNumOperands() == 4 &&
"Incorrect emulated spec constant format");

Type *Int32Ty = Type::getInt32Ty(Ctx);
SmallVector<Metadata *, 16> MDOps;

// Copy the existing metadata.
MDOps.push_back(Last.second->getOperand(0));
MDOps.push_back(Last.second->getOperand(1));
MDOps.push_back(Last.second->getOperand(2));
auto &SizeOp = Last.second->getOperand(3);
MDOps.push_back(SizeOp);

// Extract the size of the previous node to use as CompositeOffset
// for the padding node.
auto PrevSize = mdconst::extract<ConstantInt>(SizeOp)->getValue();

// The max value is a magic value used for padding that the
// runtime knows to skip.
MDOps.push_back(ConstantAsMetadata::get(Constant::getIntegerValue(
Int32Ty, APInt(32, std::numeric_limits<unsigned>::max()))));
MDOps.push_back(
ConstantAsMetadata::get(Constant::getIntegerValue(Int32Ty, PrevSize)));
MDOps.push_back(ConstantAsMetadata::get(
Constant::getIntegerValue(Int32Ty, APInt(32, Padding))));

// Replace the last metadata node with the node including the padding.
SCMetadata[Last.first] = MDNode::get(Ctx, MDOps);
}

} // namespace

PreservedAnalyses SpecConstantsPass::run(Module &M,
Expand All @@ -627,6 +736,7 @@ PreservedAnalyses SpecConstantsPass::run(Module &M,
// setting (see below).
bool IRModified = false;

LLVMContext &Ctx = M.getContext();
for (Function &F : M) {
if (!F.isDeclaration())
continue;
Expand Down Expand Up @@ -665,23 +775,7 @@ PreservedAnalyses SpecConstantsPass::run(Module &M,
StringRef SymID = getStringLiteralArg(CI, NameArgNo, DelInsts);
Value *Replacement = nullptr;

Constant *DefaultValue = nullptr;
// There is a mechanism to specify the default value in SYCL 2020.
// It is stored as an initializer of a global variable referenced by
// the second argument of the intrinsic.
auto *GV = dyn_cast<GlobalVariable>(
CI->getArgOperand(NameArgNo + 1)->stripPointerCasts());
// Go through global variable if the second argument was not null.
if (GV) {
assert(GV->hasInitializer() && "expected initializer");
auto *Initializer = GV->getInitializer();
assert((isa<ConstantAggregate>(Initializer) ||
Initializer->isZeroValue()) &&
"expected specialization_id instance");
// specialization_id structure contains a single field which is the
// default value of corresponding specialization constant.
DefaultValue = Initializer->getAggregateElement(0u);
}
Constant *DefaultValue = getSpecConstInitializerFromCI(CI, NameArgNo + 1);

bool IsNewSpecConstant = false;
unsigned Padding = 0;
Expand Down Expand Up @@ -743,54 +837,7 @@ PreservedAnalyses SpecConstantsPass::run(Module &M,
OffsetMap[SymID] = NextOffset;

assert(CurrentOffset % Align == 0 && "Alignment calculation error");

// The spec constant map can't be empty as the first offset is 0
// and so it can't be misaligned.
assert(!SCMetadata.empty() &&
"Cannot add padding to first spec constant");

// To communicate the padding to the runtime, update the metadata
// node of the previous spec constant to append a padding node. It
// can't be added in front of the current spec constant, as doing
// so would require the spec constant node to have a non-zero
// CompositeOffset which breaks accessing it in the runtime.
auto Prev = SCMetadata.back();

// Emulated spec constants don't use composite so should
// always be formatted as (SymID, ID, Offset, Size), except when
// they include padding, but since padding is added at insertion
// of the next element, the last element of the map can never be
// padded.
assert(Prev.second->getNumOperands() == 4 &&
"Incorrect emulated spec constant format");

LLVMContext &Ctx = M.getContext();
auto *Int32Ty = Type::getInt32Ty(Ctx);
SmallVector<Metadata *, 16> MDOps;

// Copy the existing metadata.
MDOps.push_back(Prev.second->getOperand(0));
MDOps.push_back(Prev.second->getOperand(1));
MDOps.push_back(Prev.second->getOperand(2));
auto &SizeOp = Prev.second->getOperand(3);
MDOps.push_back(SizeOp);

// Extract the size of the previous node to use as CompositeOffset
// for the padding node.
auto PrevSize = mdconst::extract<ConstantInt>(SizeOp)->getValue();

// The max value is a magic value used for padding that the
// runtime knows to skip.
MDOps.push_back(ConstantAsMetadata::get(Constant::getIntegerValue(
Int32Ty, APInt(32, std::numeric_limits<unsigned>::max()))));
MDOps.push_back(ConstantAsMetadata::get(
Constant::getIntegerValue(Int32Ty, PrevSize)));
MDOps.push_back(ConstantAsMetadata::get(
Constant::getIntegerValue(Int32Ty, APInt(32, Padding))));

// Replace previous metadata node with the node including the
// padding.
SCMetadata[Prev.first] = MDNode::get(Ctx, MDOps);
updatePaddingInLastMDNode(Ctx, SCMetadata, Padding);
}

SCMetadata[SymID] = generateSpecConstantMetadata(
Expand All @@ -800,31 +847,12 @@ PreservedAnalyses SpecConstantsPass::run(Module &M,
NextOffset += Size;
}

Type *Int8Ty = Type::getInt8Ty(CI->getContext());
Type *Int32Ty = Type::getInt32Ty(CI->getContext());
GetElementPtrInst *GEP = GetElementPtrInst::Create(
Int8Ty, RTBuffer, {ConstantInt::get(Int32Ty, CurrentOffset, false)},
"gep", CI);

Instruction *BitCast = nullptr;
if (SCTy->isIntegerTy(1)) // No bitcast to i1 before load
BitCast = GEP;
else
BitCast = new BitCastInst(
GEP, PointerType::get(SCTy, GEP->getAddressSpace()), "bc", CI);

// When we encounter i1 spec constant, we still load the whole byte
Replacement = new LoadInst(SCTy->isIntegerTy(1) ? Int8Ty : SCTy,
BitCast, "load", CI);
if (SCTy->isIntegerTy(1)) // trunc back to i1 if necessary
Replacement = CastInst::CreateIntegerCast(
Replacement, SCTy, /* IsSigned */ false, "tobool", CI);
Replacement = createLoadFromBuffer(CI, RTBuffer, CurrentOffset, SCTy);
}

if (IsNewSpecConstant && DefaultValue) {
if (IsNewSpecConstant) {
if (Padding != 0) {
// Initialize the padding with null data
LLVMContext &Ctx = DefaultValue->getContext();
auto PadTy = ArrayType::get(Type::getInt8Ty(Ctx), Padding);
DefaultsMetadata.push_back(MDNode::get(
Ctx,
Expand Down