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JIT: Support FIELD_LIST for returns #112308

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Feb 18, 2025
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2 changes: 1 addition & 1 deletion src/coreclr/jit/codegen.h
Original file line number Diff line number Diff line change
Expand Up @@ -1358,7 +1358,7 @@ class CodeGen final : public CodeGenInterface
// Codegen for multi-register struct returns.
bool isStructReturn(GenTree* treeNode);
#ifdef FEATURE_SIMD
void genSIMDSplitReturn(GenTree* src, ReturnTypeDesc* retTypeDesc);
void genSIMDSplitReturn(GenTree* src, const ReturnTypeDesc* retTypeDesc);
#endif
void genStructReturn(GenTree* treeNode);

Expand Down
2 changes: 1 addition & 1 deletion src/coreclr/jit/codegenarmarch.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -4528,7 +4528,7 @@ void CodeGen::genLeaInstruction(GenTreeAddrMode* lea)
// src - The source of the return
// retTypeDesc - The return type descriptor.
//
void CodeGen::genSIMDSplitReturn(GenTree* src, ReturnTypeDesc* retTypeDesc)
void CodeGen::genSIMDSplitReturn(GenTree* src, const ReturnTypeDesc* retTypeDesc)
{
assert(varTypeIsSIMD(src));
assert(src->isUsedFromReg());
Expand Down
31 changes: 28 additions & 3 deletions src/coreclr/jit/codegencommon.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -7320,6 +7320,11 @@ bool CodeGen::isStructReturn(GenTree* treeNode)
return false;
}

if (!treeNode->TypeIs(TYP_VOID) && treeNode->AsOp()->GetReturnValue()->OperIsFieldList())
{
return true;
}

#if defined(TARGET_AMD64) && !defined(UNIX_AMD64_ABI)
assert(!varTypeIsStruct(treeNode));
return false;
Expand Down Expand Up @@ -7347,12 +7352,32 @@ void CodeGen::genStructReturn(GenTree* treeNode)
GenTree* op1 = treeNode->AsOp()->GetReturnValue();
GenTree* actualOp1 = op1->gtSkipReloadOrCopy();

genConsumeRegs(op1);
const ReturnTypeDesc& retTypeDesc = compiler->compRetTypeDesc;
const unsigned regCount = retTypeDesc.GetReturnRegCount();

ReturnTypeDesc retTypeDesc = compiler->compRetTypeDesc;
const unsigned regCount = retTypeDesc.GetReturnRegCount();
assert(regCount <= MAX_RET_REG_COUNT);

if (op1->OperIsFieldList())
{
unsigned regIndex = 0;
for (GenTreeFieldList::Use& use : op1->AsFieldList()->Uses())
{
GenTree* fieldNode = use.GetNode();
regNumber sourceReg = genConsumeReg(fieldNode);
regNumber destReg = retTypeDesc.GetABIReturnReg(regIndex, compiler->info.compCallConv);
var_types type = retTypeDesc.GetReturnRegType(regIndex);

// We have constrained the reg in LSRA, but due to def-use
// conflicts we may still need a move here.
inst_Mov(type, destReg, sourceReg, /* canSkip */ true, emitActualTypeSize(type));
regIndex++;
}

return;
}

genConsumeRegs(op1);

#if FEATURE_MULTIREG_RET
// Right now the only enregisterable structs supported are SIMD vector types.
if (genIsRegCandidateLocal(actualOp1))
Expand Down
2 changes: 1 addition & 1 deletion src/coreclr/jit/codegenxarch.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -1352,7 +1352,7 @@ void CodeGen::genCodeForMul(GenTreeOp* treeNode)
// src - The source of the return
// retTypeDesc - The return type descriptor.
//
void CodeGen::genSIMDSplitReturn(GenTree* src, ReturnTypeDesc* retTypeDesc)
void CodeGen::genSIMDSplitReturn(GenTree* src, const ReturnTypeDesc* retTypeDesc)
{
assert(varTypeIsSIMD(src));
assert(src->isUsedFromReg());
Expand Down
2 changes: 2 additions & 0 deletions src/coreclr/jit/compiler.h
Original file line number Diff line number Diff line change
Expand Up @@ -3234,6 +3234,8 @@ class Compiler
GenTreeConditional* gtNewConditionalNode(
genTreeOps oper, GenTree* cond, GenTree* op1, GenTree* op2, var_types type);

GenTreeFieldList* gtNewFieldList();

#ifdef FEATURE_SIMD
void SetOpLclRelatedToSIMDIntrinsic(GenTree* op);
#endif
Expand Down
29 changes: 29 additions & 0 deletions src/coreclr/jit/gentree.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -8556,6 +8556,11 @@ GenTreeConditional* Compiler::gtNewConditionalNode(
return node;
}

GenTreeFieldList* Compiler::gtNewFieldList()
{
return new (this, GT_FIELD_LIST) GenTreeFieldList();
}

GenTreeLclFld* Compiler::gtNewLclFldNode(unsigned lnum, var_types type, unsigned offset, ClassLayout* layout)
{
GenTreeLclFld* node = new (this, GT_LCL_FLD) GenTreeLclFld(GT_LCL_FLD, type, lnum, offset, layout);
Expand Down Expand Up @@ -30497,6 +30502,30 @@ void ReturnTypeDesc::InitializeReturnType(Compiler* comp,
}
}

//-------------------------------------------------------------------
// GetReturnFieldOffset:
// For the N'th returned register, identified by "index", returns the
// starting offset in the struct return type of the data being returned.
//
// Arguments:
// index - The register whose offset to get
//
// Return Value:
// Starting offset of data returned in that register.
//
unsigned ReturnTypeDesc::GetReturnFieldOffset(unsigned index) const
{
assert(m_regType[index] != TYP_UNKNOWN);
#if defined(TARGET_RISCV64) || defined(TARGET_LOONGARCH64)
return m_fieldOffset[index];
#else
unsigned offset = 0;
for (unsigned i = 0; i < index; i++)
offset += genTypeSize(m_regType[i]);
return offset;
#endif
}

//-------------------------------------------------------------------
// GetABIReturnReg: Return i'th return register as per target ABI
//
Expand Down
8 changes: 1 addition & 7 deletions src/coreclr/jit/gentree.h
Original file line number Diff line number Diff line change
Expand Up @@ -4464,13 +4464,7 @@ struct ReturnTypeDesc
#endif
}

#if defined(TARGET_RISCV64) || defined(TARGET_LOONGARCH64)
unsigned GetReturnFieldOffset(unsigned index) const
{
assert(m_regType[index] != TYP_UNKNOWN);
return m_fieldOffset[index];
}
#endif
unsigned GetReturnFieldOffset(unsigned index) const;

// Get i'th ABI return register
regNumber GetABIReturnReg(unsigned idx, CorInfoCallConvExtension callConv) const;
Expand Down
16 changes: 16 additions & 0 deletions src/coreclr/jit/lclvars.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -95,6 +95,22 @@ void Compiler::lvaInitTypeRef()
info.compRetNativeType = hasRetBuffArg ? TYP_STRUCT : TYP_VOID;
}

#ifdef DEBUG
if (verbose)
{
CORINFO_CLASS_HANDLE retClass = info.compMethodInfo->args.retTypeClass;
printf("%u return registers for return type %s %s\n", returnRegCount, varTypeName(info.compRetType),
varTypeIsStruct(info.compRetType) ? eeGetClassName(retClass) : "");
for (unsigned i = 0; i < returnRegCount; i++)
{
unsigned offset = compRetTypeDesc.GetReturnFieldOffset(i);
unsigned size = genTypeSize(compRetTypeDesc.GetReturnRegType(i));
printf(" [%02u..%02u) reg %s\n", offset, offset + size,
getRegName(compRetTypeDesc.GetABIReturnReg(i, info.compCallConv)));
}
}
#endif

// Do we have a RetBuffArg?
if (hasRetBuffArg)
{
Expand Down
134 changes: 130 additions & 4 deletions src/coreclr/jit/lower.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -4885,7 +4885,7 @@ void Lowering::LowerRet(GenTreeOp* ret)
// - We're returning a floating type as an integral type or vice-versa, or
// - If we're returning a struct as a primitive type, we change the type of
// 'retval' in 'LowerRetStructLclVar()'
bool needBitcast = (ret->TypeGet() != TYP_VOID) && !varTypeUsesSameRegType(ret, retVal);
bool needBitcast = !ret->TypeIs(TYP_VOID) && !varTypeUsesSameRegType(ret, retVal);
bool doPrimitiveBitcast = false;
if (needBitcast)
{
Expand All @@ -4905,7 +4905,7 @@ void Lowering::LowerRet(GenTreeOp* ret)
BlockRange().InsertBefore(ret, bitcast);
ContainCheckBitCast(bitcast);
}
else if (ret->TypeGet() != TYP_VOID)
else if (!ret->TypeIs(TYP_VOID))
{
#if FEATURE_MULTIREG_RET
if (comp->compMethodReturnsMultiRegRetType() && retVal->OperIs(GT_LCL_VAR))
Expand Down Expand Up @@ -4934,7 +4934,11 @@ void Lowering::LowerRet(GenTreeOp* ret)
}
#endif // DEBUG

if (varTypeIsStruct(ret))
if (retVal->OperIsFieldList())
{
LowerRetFieldList(ret, retVal->AsFieldList());
}
else if (varTypeIsStruct(ret))
{
LowerRetStruct(ret);
}
Expand All @@ -4946,14 +4950,136 @@ void Lowering::LowerRet(GenTreeOp* ret)
}
}

// Method doing PInvokes has exactly one return block unless it has tail calls.
if (comp->compMethodRequiresPInvokeFrame())
{
InsertPInvokeMethodEpilog(comp->compCurBB DEBUGARG(ret));
}
ContainCheckRet(ret);
}

//----------------------------------------------------------------------------------------------
// LowerRetFieldList:
// Lower a returned FIELD_LIST node.
//
// Arguments:
// ret - The return node
// fieldList - The field list
//
void Lowering::LowerRetFieldList(GenTreeOp* ret, GenTreeFieldList* fieldList)
{
const ReturnTypeDesc& retDesc = comp->compRetTypeDesc;
unsigned numRegs = retDesc.GetReturnRegCount();

bool isCompatible = IsFieldListCompatibleWithReturn(fieldList);
if (!isCompatible)
{
JITDUMP("Spilling field list [%06u] to stack\n", Compiler::dspTreeID(fieldList));
unsigned lclNum = comp->lvaGrabTemp(true DEBUGARG("Spilled local for return value"));
LclVarDsc* varDsc = comp->lvaGetDesc(lclNum);
comp->lvaSetStruct(lclNum, comp->info.compMethodInfo->args.retTypeClass, false);
comp->lvaSetVarDoNotEnregister(lclNum DEBUGARG(DoNotEnregisterReason::BlockOpRet));

for (GenTreeFieldList::Use& use : fieldList->Uses())
{
GenTree* store = comp->gtNewStoreLclFldNode(lclNum, use.GetType(), use.GetOffset(), use.GetNode());
BlockRange().InsertAfter(use.GetNode(), store);
LowerNode(store);
}

GenTree* retValue = comp->gtNewLclvNode(lclNum, varDsc->TypeGet());
ret->SetReturnValue(retValue);
BlockRange().InsertBefore(ret, retValue);
LowerNode(retValue);

BlockRange().Remove(fieldList);

if (numRegs == 1)
{
var_types nativeReturnType = comp->info.compRetNativeType;
ret->ChangeType(genActualType(nativeReturnType));
LowerRetSingleRegStructLclVar(ret);
}
else
{
varDsc->lvIsMultiRegRet = true;
}

return;
}

unsigned regIndex = 0;
for (GenTreeFieldList::Use& use : fieldList->Uses())
{
var_types regType = retDesc.GetReturnRegType(regIndex);
if (varTypeUsesIntReg(regType) != varTypeUsesIntReg(use.GetNode()))
{
GenTree* bitcast = comp->gtNewOperNode(GT_BITCAST, regType, use.GetNode());
BlockRange().InsertBefore(fieldList, bitcast);
use.SetNode(bitcast);
LowerNode(bitcast);
}

regIndex++;
}
}

//----------------------------------------------------------------------------------------------
// IsFieldListCompatibleWithReturn:
// Check if the fields of a FIELD_LIST are compatible with the registers
// being returned.
//
// Arguments:
// fieldList - The FIELD_LIST node
//
// Returns:
// True if the fields of the FIELD_LIST map cleanly to the ABI returned
// registers. Insertions of bitcasts may still be required.
//
bool Lowering::IsFieldListCompatibleWithReturn(GenTreeFieldList* fieldList)
{
JITDUMP("Checking if field list [%06u] is compatible with return ABI: ", Compiler::dspTreeID(fieldList));
const ReturnTypeDesc& retDesc = comp->compRetTypeDesc;
unsigned numRetRegs = retDesc.GetReturnRegCount();
unsigned regIndex = 0;

for (const GenTreeFieldList::Use& use : fieldList->Uses())
{
if (regIndex >= numRetRegs)
{
JITDUMP("it is not; too many fields\n");
return false;
}

unsigned offset = retDesc.GetReturnFieldOffset(regIndex);
if (offset != use.GetOffset())
{
JITDUMP("it is not; field %u register starts at offset %u, but field starts at offset %u\n", regIndex,
offset, use.GetOffset());
return false;
}

var_types fieldType = genActualType(use.GetNode());
var_types regType = genActualType(retDesc.GetReturnRegType(regIndex));
if (genTypeSize(fieldType) != genTypeSize(regType))
{
JITDUMP("it is not; field %u register has type %s but field has type %s\n", regIndex, varTypeName(regType),
varTypeName(fieldType));
return false;
}

regIndex++;
}

if (regIndex != numRetRegs)
{
JITDUMP("it is not; too few fields\n");
return false;
}

JITDUMP("it is\n");
return true;
}

//----------------------------------------------------------------------------------------------
// LowerStoreLocCommon: platform independent part of local var or field store lowering.
//
Expand Down
2 changes: 2 additions & 0 deletions src/coreclr/jit/lower.h
Original file line number Diff line number Diff line change
Expand Up @@ -168,6 +168,8 @@ class Lowering final : public Phase
GenTree* LowerStoreLocCommon(GenTreeLclVarCommon* lclVar);
void LowerRetStruct(GenTreeUnOp* ret);
void LowerRetSingleRegStructLclVar(GenTreeUnOp* ret);
void LowerRetFieldList(GenTreeOp* ret, GenTreeFieldList* fieldList);
bool IsFieldListCompatibleWithReturn(GenTreeFieldList* fieldList);
void LowerCallStruct(GenTreeCall* call);
void LowerStoreSingleRegCallStruct(GenTreeBlk* store);
#if !defined(WINDOWS_AMD64_ABI)
Expand Down
16 changes: 16 additions & 0 deletions src/coreclr/jit/lsrabuild.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -4387,6 +4387,22 @@ int LinearScan::BuildReturn(GenTree* tree)
return 1;
}
}
else if (!tree->TypeIs(TYP_VOID) && op1->OperIsFieldList())
{
const ReturnTypeDesc& retDesc = compiler->compRetTypeDesc;

unsigned regIndex = 0;
for (const GenTreeFieldList::Use& use : op1->AsFieldList()->Uses())
{
GenTree* tree = use.GetNode();
regNumber retReg = retDesc.GetABIReturnReg(regIndex, compiler->info.compCallConv);
BuildUse(tree, genSingleTypeRegMask(retReg));

regIndex++;
}

return regIndex;
}
else
{
// In other cases we require the incoming operand to be in the
Expand Down
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