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lowerxarch.cpp
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
/*XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XX XX
XX Lowering for AMD64, x86 XX
XX XX
XX This encapsulates all the logic for lowering trees for the AMD64 XX
XX architecture. For a more detailed view of what is lowering, please XX
XX take a look at Lower.cpp XX
XX XX
XX XX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
*/
#include "jitpch.h"
#ifdef _MSC_VER
#pragma hdrstop
#endif
#ifdef TARGET_XARCH // This file is only used for xarch
#include "jit.h"
#include "sideeffects.h"
#include "lower.h"
// xarch supports both ROL and ROR instructions so no lowering is required.
void Lowering::LowerRotate(GenTree* tree)
{
ContainCheckShiftRotate(tree->AsOp());
}
//------------------------------------------------------------------------
// LowerStoreLoc: Lower a store of a lclVar
//
// Arguments:
// storeLoc - the local store (GT_STORE_LCL_FLD or GT_STORE_LCL_VAR)
//
// Notes:
// This involves:
// - Handling of contained immediates.
// - Widening some small stores.
//
void Lowering::LowerStoreLoc(GenTreeLclVarCommon* storeLoc)
{
// Most small locals (the exception is dependently promoted fields) have 4 byte wide stack slots, so
// we can widen the store, if profitable. The widening is only (largely) profitable for 2 byte stores.
// We could widen bytes too but that would only be better when the constant is zero and reused, which
// we presume is not common enough.
//
if (storeLoc->OperIs(GT_STORE_LCL_VAR) && (genTypeSize(storeLoc) == 2) && storeLoc->Data()->IsCnsIntOrI())
{
if (!comp->lvaGetDesc(storeLoc)->lvIsStructField)
{
storeLoc->gtType = TYP_INT;
}
}
if (storeLoc->OperIs(GT_STORE_LCL_FLD))
{
// We should only encounter this for lclVars that are lvDoNotEnregister.
verifyLclFldDoNotEnregister(storeLoc->GetLclNum());
}
ContainCheckStoreLoc(storeLoc);
}
//------------------------------------------------------------------------
// LowerStoreIndir: Determine addressing mode for an indirection, and whether operands are contained.
//
// Arguments:
// node - The indirect store node (GT_STORE_IND) of interest
//
// Return Value:
// None.
//
void Lowering::LowerStoreIndir(GenTreeStoreInd* node)
{
// Mark all GT_STOREIND nodes to indicate that it is not known
// whether it represents a RMW memory op.
node->SetRMWStatusDefault();
if (!varTypeIsFloating(node))
{
// Perform recognition of trees with the following structure:
// StoreInd(addr, BinOp(expr, GT_IND(addr)))
// to be able to fold this into an instruction of the form
// BINOP [addr], register
// where register is the actual place where 'expr' is computed.
//
// SSE2 doesn't support RMW form of instructions.
if (LowerRMWMemOp(node))
{
return;
}
}
// Optimization: do not unnecessarily zero-extend the result of setcc.
if (varTypeIsByte(node) && (node->Data()->OperIsCompare() || node->Data()->OperIs(GT_SETCC)))
{
node->Data()->ChangeType(TYP_BYTE);
}
ContainCheckStoreIndir(node);
}
//----------------------------------------------------------------------------------------------
// Lowering::TryLowerMulWithConstant:
// Lowers a tree MUL(X, CNS) to LSH(X, CNS_SHIFT)
// or
// Lowers a tree MUL(X, CNS) to SUB(LSH(X, CNS_SHIFT), X)
// or
// Lowers a tree MUL(X, CNS) to ADD(LSH(X, CNS_SHIFT), X)
//
// Arguments:
// node - GT_MUL node of integral type
//
// Return Value:
// Returns the replacement node if one is created else nullptr indicating no replacement
//
// Notes:
// Performs containment checks on the replacement node if one is created
GenTree* Lowering::TryLowerMulWithConstant(GenTreeOp* node)
{
assert(node->OperIs(GT_MUL));
// Do not do these optimizations when min-opts enabled.
if (comp->opts.MinOpts())
return nullptr;
if (!varTypeIsIntegral(node))
return nullptr;
if (node->gtOverflow())
return nullptr;
GenTree* op1 = node->gtGetOp1();
GenTree* op2 = node->gtGetOp2();
if (op1->isContained() || op2->isContained())
return nullptr;
if (!op2->IsCnsIntOrI())
return nullptr;
GenTreeIntConCommon* cns = op2->AsIntConCommon();
ssize_t cnsVal = cns->IconValue();
// Use GT_LEA if cnsVal is 3, 5, or 9.
// These are handled in codegen.
if (cnsVal == 3 || cnsVal == 5 || cnsVal == 9)
return nullptr;
// Use GT_LSH if cnsVal is a power of two.
if (isPow2(cnsVal))
{
// Use shift for constant multiply when legal
unsigned int shiftAmount = genLog2(static_cast<uint64_t>(static_cast<size_t>(cnsVal)));
cns->SetIconValue(shiftAmount);
node->ChangeOper(GT_LSH);
ContainCheckShiftRotate(node);
return node;
}
// We do not do this optimization in X86 as it is not recommended.
#if TARGET_X86
return nullptr;
#endif // TARGET_X86
ssize_t cnsValPlusOne = cnsVal + 1;
ssize_t cnsValMinusOne = cnsVal - 1;
bool useSub = isPow2(cnsValPlusOne);
if (!useSub && !isPow2(cnsValMinusOne))
return nullptr;
LIR::Use op1Use(BlockRange(), &node->gtOp1, node);
op1 = ReplaceWithLclVar(op1Use);
if (useSub)
{
cnsVal = cnsValPlusOne;
node->ChangeOper(GT_SUB);
}
else
{
cnsVal = cnsValMinusOne;
node->ChangeOper(GT_ADD);
}
unsigned int shiftAmount = genLog2(static_cast<uint64_t>(static_cast<size_t>(cnsVal)));
cns->SetIconValue(shiftAmount);
node->gtOp1 = comp->gtNewOperNode(GT_LSH, node->gtType, op1, cns);
node->gtOp2 = comp->gtClone(op1);
BlockRange().Remove(op1);
BlockRange().Remove(cns);
BlockRange().InsertBefore(node, node->gtGetOp2());
BlockRange().InsertBefore(node, cns);
BlockRange().InsertBefore(node, op1);
BlockRange().InsertBefore(node, node->gtGetOp1());
ContainCheckBinary(node);
ContainCheckShiftRotate(node->gtGetOp1()->AsOp());
return node;
}
//------------------------------------------------------------------------
// LowerMul: Lower a GT_MUL/GT_MULHI/GT_MUL_LONG node.
//
// Currently only performs containment checks.
//
// Arguments:
// mul - The node to lower
//
// Return Value:
// The next node to lower.
//
GenTree* Lowering::LowerMul(GenTreeOp* mul)
{
assert(mul->OperIsMul());
if (mul->OperIs(GT_MUL))
{
GenTree* replacementNode = TryLowerMulWithConstant(mul);
if (replacementNode != nullptr)
{
return replacementNode->gtNext;
}
}
ContainCheckMul(mul);
return mul->gtNext;
}
//------------------------------------------------------------------------
// LowerBinaryArithmetic: lowers the given binary arithmetic node.
//
// Recognizes opportunities for using target-independent "combined" nodes
// Performs containment checks.
//
// Arguments:
// node - the arithmetic node to lower
//
// Returns:
// The next node to lower.
//
GenTree* Lowering::LowerBinaryArithmetic(GenTreeOp* binOp)
{
#ifdef FEATURE_HW_INTRINSICS
if (comp->opts.OptimizationEnabled() && varTypeIsIntegral(binOp))
{
if (binOp->OperIs(GT_AND))
{
GenTree* replacementNode = TryLowerAndOpToAndNot(binOp);
if (replacementNode != nullptr)
{
return replacementNode->gtNext;
}
replacementNode = TryLowerAndOpToResetLowestSetBit(binOp);
if (replacementNode != nullptr)
{
return replacementNode->gtNext;
}
replacementNode = TryLowerAndOpToExtractLowestSetBit(binOp);
if (replacementNode != nullptr)
{
return replacementNode->gtNext;
}
}
else if (binOp->OperIs(GT_XOR))
{
GenTree* replacementNode = TryLowerXorOpToGetMaskUpToLowestSetBit(binOp);
if (replacementNode != nullptr)
{
return replacementNode->gtNext;
}
}
}
#endif
ContainCheckBinary(binOp);
return binOp->gtNext;
}
//------------------------------------------------------------------------
// LowerBlockStore: Lower a block store node
//
// Arguments:
// blkNode - The block store node to lower
//
void Lowering::LowerBlockStore(GenTreeBlk* blkNode)
{
TryCreateAddrMode(blkNode->Addr(), false, blkNode);
GenTree* dstAddr = blkNode->Addr();
GenTree* src = blkNode->Data();
unsigned size = blkNode->Size();
if (blkNode->OperIsInitBlkOp())
{
if (src->OperIs(GT_INIT_VAL))
{
src->SetContained();
src = src->AsUnOp()->gtGetOp1();
}
if (blkNode->OperIs(GT_STORE_OBJ))
{
blkNode->SetOper(GT_STORE_BLK);
}
if (!blkNode->OperIs(GT_STORE_DYN_BLK) && (size <= INITBLK_UNROLL_LIMIT))
{
if (!src->OperIs(GT_CNS_INT))
{
// TODO-CQ: We could unroll even when the initialization value is not a constant
// by inserting a MUL init, 0x01010101 instruction. We need to determine if the
// extra latency that MUL introduces isn't worse that rep stosb. Likely not.
blkNode->gtBlkOpKind = GenTreeBlk::BlkOpKindRepInstr;
}
else
{
blkNode->gtBlkOpKind = GenTreeBlk::BlkOpKindUnroll;
// The fill value of an initblk is interpreted to hold a
// value of (unsigned int8) however a constant of any size
// may practically reside on the evaluation stack. So extract
// the lower byte out of the initVal constant and replicate
// it to a larger constant whose size is sufficient to support
// the largest width store of the desired inline expansion.
ssize_t fill = src->AsIntCon()->IconValue() & 0xFF;
if (fill == 0)
{
if (size >= XMM_REGSIZE_BYTES)
{
const bool canUse16BytesSimdMov = !blkNode->IsOnHeapAndContainsReferences();
#ifdef TARGET_AMD64
const bool willUseOnlySimdMov = canUse16BytesSimdMov && (size % XMM_REGSIZE_BYTES == 0);
#else
const bool willUseOnlySimdMov = (size % 8 == 0);
#endif
if (willUseOnlySimdMov)
{
src->SetContained();
}
}
}
#ifdef TARGET_AMD64
else if (size >= REGSIZE_BYTES)
{
fill *= 0x0101010101010101LL;
src->gtType = TYP_LONG;
}
#endif
else
{
fill *= 0x01010101;
}
src->AsIntCon()->SetIconValue(fill);
ContainBlockStoreAddress(blkNode, size, dstAddr, nullptr);
}
}
else
{
#ifdef TARGET_AMD64
blkNode->gtBlkOpKind = GenTreeBlk::BlkOpKindHelper;
#else
// TODO-X86-CQ: Investigate whether a helper call would be beneficial on x86
blkNode->gtBlkOpKind = GenTreeBlk::BlkOpKindRepInstr;
#endif
}
}
else
{
assert(src->OperIs(GT_IND, GT_LCL_VAR, GT_LCL_FLD));
src->SetContained();
if (src->OperIs(GT_IND))
{
// TODO-Cleanup: Make sure that GT_IND lowering didn't mark the source address as contained.
// Sometimes the GT_IND type is a non-struct type and then GT_IND lowering may contain the
// address, not knowing that GT_IND is part of a block op that has containment restrictions.
src->AsIndir()->Addr()->ClearContained();
}
else if (src->OperIs(GT_LCL_VAR))
{
// TODO-1stClassStructs: for now we can't work with STORE_BLOCK source in register.
const unsigned srcLclNum = src->AsLclVar()->GetLclNum();
comp->lvaSetVarDoNotEnregister(srcLclNum DEBUGARG(DoNotEnregisterReason::StoreBlkSrc));
}
if (blkNode->OperIs(GT_STORE_OBJ))
{
if (!blkNode->AsObj()->GetLayout()->HasGCPtr())
{
blkNode->SetOper(GT_STORE_BLK);
}
#ifndef JIT32_GCENCODER
else if (dstAddr->OperIsLocalAddr() && (size <= CPBLK_UNROLL_LIMIT))
{
// If the size is small enough to unroll then we need to mark the block as non-interruptible
// to actually allow unrolling. The generated code does not report GC references loaded in the
// temporary register(s) used for copying.
// This is not supported for the JIT32_GCENCODER.
blkNode->SetOper(GT_STORE_BLK);
blkNode->gtBlkOpGcUnsafe = true;
}
#endif
}
if (blkNode->OperIs(GT_STORE_OBJ))
{
assert((dstAddr->TypeGet() == TYP_BYREF) || (dstAddr->TypeGet() == TYP_I_IMPL));
// If we have a long enough sequence of slots that do not require write barriers then
// we can use REP MOVSD/Q instead of a sequence of MOVSD/Q instructions. According to the
// Intel Manual, the sweet spot for small structs is between 4 to 12 slots of size where
// the entire operation takes 20 cycles and encodes in 5 bytes (loading RCX and REP MOVSD/Q).
unsigned nonGCSlots = 0;
if (dstAddr->OperIsLocalAddr())
{
// If the destination is on the stack then no write barriers are needed.
nonGCSlots = blkNode->GetLayout()->GetSlotCount();
}
else
{
// Otherwise a write barrier is needed for every GC pointer in the layout
// so we need to check if there's a long enough sequence of non-GC slots.
ClassLayout* layout = blkNode->GetLayout();
unsigned slots = layout->GetSlotCount();
for (unsigned i = 0; i < slots; i++)
{
if (layout->IsGCPtr(i))
{
nonGCSlots = 0;
}
else
{
nonGCSlots++;
if (nonGCSlots >= CPOBJ_NONGC_SLOTS_LIMIT)
{
break;
}
}
}
}
if (nonGCSlots >= CPOBJ_NONGC_SLOTS_LIMIT)
{
blkNode->gtBlkOpKind = GenTreeBlk::BlkOpKindRepInstr;
}
else
{
blkNode->gtBlkOpKind = GenTreeBlk::BlkOpKindUnroll;
}
}
else if (blkNode->OperIs(GT_STORE_BLK) && (size <= CPBLK_UNROLL_LIMIT))
{
blkNode->gtBlkOpKind = GenTreeBlk::BlkOpKindUnroll;
if (src->OperIs(GT_IND))
{
ContainBlockStoreAddress(blkNode, size, src->AsIndir()->Addr(), src->AsIndir());
}
ContainBlockStoreAddress(blkNode, size, dstAddr, nullptr);
}
else
{
assert(blkNode->OperIs(GT_STORE_BLK, GT_STORE_DYN_BLK));
#ifdef TARGET_AMD64
blkNode->gtBlkOpKind = GenTreeBlk::BlkOpKindHelper;
#else
// TODO-X86-CQ: Investigate whether a helper call would be beneficial on x86
blkNode->gtBlkOpKind = GenTreeBlk::BlkOpKindRepInstr;
#endif
}
}
}
//------------------------------------------------------------------------
// ContainBlockStoreAddress: Attempt to contain an address used by an unrolled block store.
//
// Arguments:
// blkNode - the block store node
// size - the block size
// addr - the address node to try to contain
// addrParent - the parent of addr, in case this is checking containment of the source address.
//
void Lowering::ContainBlockStoreAddress(GenTreeBlk* blkNode, unsigned size, GenTree* addr, GenTree* addrParent)
{
assert(blkNode->OperIs(GT_STORE_BLK) && (blkNode->gtBlkOpKind == GenTreeBlk::BlkOpKindUnroll));
assert(size < INT32_MAX);
if (addr->OperIsLocalAddr())
{
addr->SetContained();
return;
}
if (!addr->OperIsAddrMode() && !TryCreateAddrMode(addr, true, blkNode))
{
return;
}
GenTreeAddrMode* addrMode = addr->AsAddrMode();
// On x64 the address mode displacement is signed so it must not exceed INT32_MAX. This check is
// an approximation since the last displacement we generate in an unrolled block operation can be
// up to 16 bytes lower than offset + size. But offsets large enough to hit this case are likely
// to be extremely rare for this to ever be a CQ issue.
// On x86 this shouldn't be needed but then again, offsets large enough to hit this are rare.
if (addrMode->Offset() > (INT32_MAX - static_cast<int>(size)))
{
return;
}
// Note that the parentNode is always the block node, even if we're dealing with the source address.
// The source address is not directly used by the block node but by an IND node and that IND node is
// always contained.
if (!IsInvariantInRange(addrMode, blkNode, addrParent))
{
return;
}
addrMode->SetContained();
}
//------------------------------------------------------------------------
// LowerPutArgStkOrSplit: Lower a GT_PUTARG_STK/GT_PUTARG_SPLIT.
//
// Arguments:
// putArgNode - The node of interest
//
void Lowering::LowerPutArgStkOrSplit(GenTreePutArgStk* putArgNode)
{
assert(putArgNode->OperIs(GT_PUTARG_STK)); // No split args on XArch.
LowerPutArgStk(putArgNode);
}
//------------------------------------------------------------------------
// LowerPutArgStk: Lower a GT_PUTARG_STK.
//
// Arguments:
// putArgStk - The node of interest
//
void Lowering::LowerPutArgStk(GenTreePutArgStk* putArgStk)
{
GenTree* src = putArgStk->Data();
bool srcIsLocal = src->OperIsLocalRead();
if (src->OperIs(GT_FIELD_LIST))
{
#ifdef TARGET_X86
GenTreeFieldList* fieldList = src->AsFieldList();
// The code generator will push these fields in reverse order by offset. Reorder the list here s.t. the order
// of uses is visible to LSRA.
assert(fieldList->Uses().IsSorted());
fieldList->Uses().Reverse();
// Containment checks.
for (GenTreeFieldList::Use& use : fieldList->Uses())
{
GenTree* const fieldNode = use.GetNode();
const var_types fieldType = use.GetType();
assert(!fieldNode->TypeIs(TYP_LONG));
// For x86 we must mark all integral fields as contained or reg-optional, and handle them
// accordingly in code generation, since we may have up to 8 fields, which cannot all be in
// registers to be consumed atomically by the call.
if (varTypeIsIntegralOrI(fieldNode))
{
if (IsContainableImmed(putArgStk, fieldNode))
{
MakeSrcContained(putArgStk, fieldNode);
}
else if (IsContainableMemoryOp(fieldNode) && IsSafeToContainMem(putArgStk, fieldNode))
{
MakeSrcContained(putArgStk, fieldNode);
}
else
{
// For the case where we cannot directly push the value, if we run out of registers,
// it would be better to defer computation until we are pushing the arguments rather
// than spilling, but this situation is not all that common, as most cases of FIELD_LIST
// are promoted structs, which do not not have a large number of fields, and of those
// most are lclVars or copy-propagated constants.
fieldNode->SetRegOptional();
}
}
}
// Set the copy kind.
// TODO-X86-CQ: Even if we are using push, if there are contiguous floating point fields, we should
// adjust the stack once for those fields. The latter is really best done in code generation, but
// this tuning should probably be undertaken as a whole.
// Also, if there are floating point fields, it may be better to use the "Unroll" mode
// of copying the struct as a whole, if the fields are not register candidates.
putArgStk->gtPutArgStkKind = GenTreePutArgStk::Kind::Push;
#endif // TARGET_X86
return;
}
#ifdef FEATURE_PUT_STRUCT_ARG_STK
if (src->TypeIs(TYP_STRUCT))
{
assert(src->OperIs(GT_OBJ) || src->OperIsLocalRead());
ClassLayout* layout = src->GetLayout(comp);
var_types regType = layout->GetRegisterType();
if (regType == TYP_UNDEF)
{
// In case of a CpBlk we could use a helper call. In case of putarg_stk we
// can't do that since the helper call could kill some already set up outgoing args.
// TODO-Amd64-Unix: converge the code for putarg_stk with cpyblk/cpyobj.
// The cpyXXXX code is rather complex and this could cause it to be more complex, but
// it might be the right thing to do.
// If possible, widen the load, this results in more compact code.
unsigned loadSize = srcIsLocal ? roundUp(layout->GetSize(), TARGET_POINTER_SIZE) : layout->GetSize();
putArgStk->SetArgLoadSize(loadSize);
// TODO-X86-CQ: The helper call either is not supported on x86 or required more work
// (I don't know which).
if (!layout->HasGCPtr())
{
#ifdef TARGET_X86
// Codegen for "Kind::Push" will always load bytes in TARGET_POINTER_SIZE
// chunks. As such, we'll only use this path for correctly-sized sources.
if ((loadSize < XMM_REGSIZE_BYTES) && ((loadSize % TARGET_POINTER_SIZE) == 0))
{
putArgStk->gtPutArgStkKind = GenTreePutArgStk::Kind::Push;
}
else
#endif // TARGET_X86
if (loadSize <= CPBLK_UNROLL_LIMIT)
{
putArgStk->gtPutArgStkKind = GenTreePutArgStk::Kind::Unroll;
}
else
{
putArgStk->gtPutArgStkKind = GenTreePutArgStk::Kind::RepInstr;
}
}
else // There are GC pointers.
{
#ifdef TARGET_X86
// On x86, we must use `push` to store GC references to the stack in order for the emitter to
// properly update the function's GC info. These `putargstk` nodes will generate a sequence of
// `push` instructions.
putArgStk->gtPutArgStkKind = GenTreePutArgStk::Kind::Push;
#else // !TARGET_X86
putArgStk->gtPutArgStkKind = GenTreePutArgStk::Kind::PartialRepInstr;
#endif // !TARGET_X86
}
if (src->OperIs(GT_LCL_VAR))
{
comp->lvaSetVarDoNotEnregister(src->AsLclVar()->GetLclNum()
DEBUGARG(DoNotEnregisterReason::IsStructArg));
}
// Always mark the OBJ/LCL_VAR/LCL_FLD as contained trees.
MakeSrcContained(putArgStk, src);
}
else
{
// The ABI allows upper bits of small struct args to remain undefined,
// so if possible, widen the load to avoid the sign/zero-extension.
if (varTypeIsSmall(regType) && srcIsLocal)
{
assert(genTypeSize(TYP_INT) <= putArgStk->GetStackByteSize());
regType = TYP_INT;
}
src->ChangeType(regType);
if (src->OperIs(GT_OBJ))
{
src->SetOper(GT_IND);
LowerIndir(src->AsIndir());
}
}
}
if (src->TypeIs(TYP_STRUCT))
{
return;
}
#endif // FEATURE_PUT_STRUCT_ARG_STK
assert(!src->TypeIs(TYP_STRUCT));
// If the child of GT_PUTARG_STK is a constant, we don't need a register to
// move it to memory (stack location).
//
// On AMD64, we don't want to make 0 contained, because we can generate smaller code
// by zeroing a register and then storing it. E.g.:
// xor rdx, rdx
// mov gword ptr [rsp+28H], rdx
// is 2 bytes smaller than:
// mov gword ptr [rsp+28H], 0
//
// On x86, we push stack arguments; we don't use 'mov'. So:
// push 0
// is 1 byte smaller than:
// xor rdx, rdx
// push rdx
if (IsContainableImmed(putArgStk, src)
#if defined(TARGET_AMD64)
&& !src->IsIntegralConst(0)
#endif // TARGET_AMD64
)
{
MakeSrcContained(putArgStk, src);
}
#ifdef TARGET_X86
else if (genTypeSize(src) == TARGET_POINTER_SIZE)
{
// We can use "src" directly from memory with "push [mem]".
TryMakeSrcContainedOrRegOptional(putArgStk, src);
}
#endif // TARGET_X86
}
/* Lower GT_CAST(srcType, DstType) nodes.
*
* Casts from small int type to float/double are transformed as follows:
* GT_CAST(byte, float/double) = GT_CAST(GT_CAST(byte, int32), float/double)
* GT_CAST(sbyte, float/double) = GT_CAST(GT_CAST(sbyte, int32), float/double)
* GT_CAST(int16, float/double) = GT_CAST(GT_CAST(int16, int32), float/double)
* GT_CAST(uint16, float/double) = GT_CAST(GT_CAST(uint16, int32), float/double)
*
* SSE2 conversion instructions operate on signed integers. casts from Uint32/Uint64
* are morphed as follows by front-end and hence should not be seen here.
* GT_CAST(uint32, float/double) = GT_CAST(GT_CAST(uint32, long), float/double)
* GT_CAST(uint64, float) = GT_CAST(GT_CAST(uint64, double), float)
*
*
* Similarly casts from float/double to a smaller int type are transformed as follows:
* GT_CAST(float/double, byte) = GT_CAST(GT_CAST(float/double, int32), byte)
* GT_CAST(float/double, sbyte) = GT_CAST(GT_CAST(float/double, int32), sbyte)
* GT_CAST(float/double, int16) = GT_CAST(GT_CAST(double/double, int32), int16)
* GT_CAST(float/double, uint16) = GT_CAST(GT_CAST(double/double, int32), uint16)
*
* SSE2 has instructions to convert a float/double vlaue into a signed 32/64-bit
* integer. The above transformations help us to leverage those instructions.
*
* Note that for the following conversions we still depend on helper calls and
* don't expect to see them here.
* i) GT_CAST(float/double, uint64)
* ii) GT_CAST(float/double, int type with overflow detection)
*
* TODO-XArch-CQ: (Low-pri): Jit64 generates in-line code of 8 instructions for (i) above.
* There are hardly any occurrences of this conversion operation in platform
* assemblies or in CQ perf benchmarks (1 occurrence in corelib, microsoft.jscript,
* 1 occurrence in Roslyn and no occurrences in system, system.core, system.numerics
* system.windows.forms, scimark, fractals, bio mums). If we ever find evidence that
* doing this optimization is a win, should consider generating in-lined code.
*/
void Lowering::LowerCast(GenTree* tree)
{
assert(tree->OperGet() == GT_CAST);
GenTree* castOp = tree->AsCast()->CastOp();
var_types castToType = tree->CastToType();
var_types srcType = castOp->TypeGet();
var_types tmpType = TYP_UNDEF;
// force the srcType to unsigned if GT_UNSIGNED flag is set
if (tree->gtFlags & GTF_UNSIGNED)
{
srcType = varTypeToUnsigned(srcType);
}
// We should never see the following casts as they are expected to be lowered
// appropriately or converted into helper calls by front-end.
// srcType = float/double castToType = * and overflow detecting cast
// Reason: must be converted to a helper call
// srcType = float/double, castToType = ulong
// Reason: must be converted to a helper call
// srcType = uint castToType = float/double
// Reason: uint -> float/double = uint -> long -> float/double
// srcType = ulong castToType = float
// Reason: ulong -> float = ulong -> double -> float
if (varTypeIsFloating(srcType))
{
noway_assert(!tree->gtOverflow());
noway_assert(castToType != TYP_ULONG);
}
else if (srcType == TYP_UINT)
{
noway_assert(!varTypeIsFloating(castToType));
}
else if (srcType == TYP_ULONG)
{
noway_assert(castToType != TYP_FLOAT);
}
// Case of src is a small type and dst is a floating point type.
if (varTypeIsSmall(srcType) && varTypeIsFloating(castToType))
{
// These conversions can never be overflow detecting ones.
noway_assert(!tree->gtOverflow());
tmpType = TYP_INT;
}
// case of src is a floating point type and dst is a small type.
else if (varTypeIsFloating(srcType) && varTypeIsSmall(castToType))
{
tmpType = TYP_INT;
}
if (tmpType != TYP_UNDEF)
{
GenTree* tmp = comp->gtNewCastNode(tmpType, castOp, tree->IsUnsigned(), tmpType);
tmp->gtFlags |= (tree->gtFlags & (GTF_OVERFLOW | GTF_EXCEPT));
tree->gtFlags &= ~GTF_UNSIGNED;
tree->AsOp()->gtOp1 = tmp;
BlockRange().InsertAfter(castOp, tmp);
ContainCheckCast(tmp->AsCast());
}
// Now determine if we have operands that should be contained.
ContainCheckCast(tree->AsCast());
}
#ifdef FEATURE_HW_INTRINSICS
//----------------------------------------------------------------------------------------------
// LowerHWIntrinsicCC: Lowers a hardware intrinsic node that produces a boolean value by
// setting the condition flags.
//
// Arguments:
// node - The hardware intrinsic node
// newIntrinsicId - The intrinsic id of the lowered intrinsic node
// condition - The condition code of the generated SETCC/JCC node
//
void Lowering::LowerHWIntrinsicCC(GenTreeHWIntrinsic* node, NamedIntrinsic newIntrinsicId, GenCondition condition)
{
GenTreeCC* cc = LowerNodeCC(node, condition);
assert(HWIntrinsicInfo::lookupNumArgs(newIntrinsicId) == 2);
node->ChangeHWIntrinsicId(newIntrinsicId);
node->gtType = TYP_VOID;
node->ClearUnusedValue();
bool swapOperands = false;
bool canSwapOperands = false;
switch (newIntrinsicId)
{
case NI_SSE_COMISS:
case NI_SSE_UCOMISS:
case NI_SSE2_COMISD:
case NI_SSE2_UCOMISD:
// In some cases we can generate better code if we swap the operands:
// - If the condition is not one of the "preferred" floating point conditions we can swap
// the operands and change the condition to avoid generating an extra JP/JNP branch.
// - If the first operand can be contained but the second cannot, we can swap operands in
// order to be able to contain the first operand and avoid the need for a temp reg.
// We can't handle both situations at the same time and since an extra branch is likely to
// be worse than an extra temp reg (x64 has a reasonable number of XMM registers) we'll favor
// the branch case:
// - If the condition is not preferred then swap, even if doing this will later prevent
// containment.
// - Allow swapping for containment purposes only if this doesn't result in a non-"preferred"
// condition being generated.
if ((cc != nullptr) && cc->gtCondition.PreferSwap())
{
swapOperands = true;
}
else
{
canSwapOperands = (cc == nullptr) || !GenCondition::Swap(cc->gtCondition).PreferSwap();
}
break;
case NI_SSE41_PTEST:
case NI_AVX_PTEST:
// If we need the Carry flag then we can't swap operands.
canSwapOperands = (cc == nullptr) || cc->gtCondition.Is(GenCondition::EQ, GenCondition::NE);
break;
default:
unreached();
}
if (canSwapOperands)
{
bool op1SupportsRegOptional = false;
bool op2SupportsRegOptional = false;
if (!IsContainableHWIntrinsicOp(node, node->Op(2), &op2SupportsRegOptional) &&
IsContainableHWIntrinsicOp(node, node->Op(1), &op1SupportsRegOptional))
{
// Swap operands if op2 cannot be contained but op1 can.
swapOperands = true;
}
}
if (swapOperands)
{
std::swap(node->Op(1), node->Op(2));
if (cc != nullptr)
{
cc->gtCondition = GenCondition::Swap(cc->gtCondition);
}
}
}
//----------------------------------------------------------------------------------------------
// LowerFusedMultiplyAdd: Changes NI_FMA_MultiplyAddScalar produced by Math(F).FusedMultiplyAdd
// to a better FMA intrinsics if there are GT_NEG around in order to eliminate them.
//
// Arguments:
// node - The hardware intrinsic node
//
// Notes:
// Math(F).FusedMultiplyAdd is expanded into NI_FMA_MultiplyAddScalar and
// depending on additional GT_NEG nodes around it can be:
//
// x * y + z -> NI_FMA_MultiplyAddScalar
// x * -y + z -> NI_FMA_MultiplyAddNegatedScalar
// -x * y + z -> NI_FMA_MultiplyAddNegatedScalar
// -x * -y + z -> NI_FMA_MultiplyAddScalar
// x * y - z -> NI_FMA_MultiplySubtractScalar
// x * -y - z -> NI_FMA_MultiplySubtractNegatedScalar
// -x * y - z -> NI_FMA_MultiplySubtractNegatedScalar
// -x * -y - z -> NI_FMA_MultiplySubtractScalar
//
void Lowering::LowerFusedMultiplyAdd(GenTreeHWIntrinsic* node)
{
assert(node->GetHWIntrinsicId() == NI_FMA_MultiplyAddScalar);
GenTreeHWIntrinsic* createScalarOps[3];
for (size_t i = 1; i <= 3; i++)
{
GenTree* arg = node->Op(i);
if (!arg->OperIsHWIntrinsic() || (arg->AsHWIntrinsic()->GetHWIntrinsicId() != NI_Vector128_CreateScalarUnsafe))
{
return;
}
createScalarOps[i - 1] = arg->AsHWIntrinsic();
}
GenTree* argX = createScalarOps[0]->Op(1);
GenTree* argY = createScalarOps[1]->Op(1);
GenTree* argZ = createScalarOps[2]->Op(1);
const bool negMul = argX->OperIs(GT_NEG) != argY->OperIs(GT_NEG);
if (argX->OperIs(GT_NEG))
{
createScalarOps[0]->Op(1) = argX->gtGetOp1();
BlockRange().Remove(argX);
createScalarOps[0]->Op(1)->ClearContained();
ContainCheckHWIntrinsic(createScalarOps[0]);
}
if (argY->OperIs(GT_NEG))
{
createScalarOps[1]->Op(1) = argY->gtGetOp1();
BlockRange().Remove(argY);
createScalarOps[1]->Op(1)->ClearContained();
ContainCheckHWIntrinsic(createScalarOps[1]);
}
if (argZ->OperIs(GT_NEG))
{
createScalarOps[2]->Op(1) = argZ->gtGetOp1();
BlockRange().Remove(argZ);
createScalarOps[2]->Op(1)->ClearContained();
ContainCheckHWIntrinsic(createScalarOps[2]);