Skip to content

[interp] Implement tailcalls #118901

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Aug 22, 2025
Merged

[interp] Implement tailcalls #118901

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
d978828
Add dedicated interpreter opcodes for tailcalls and generate them
kg Aug 19, 2025
977d1bf
Implement tailcalls
kg Aug 19, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
17 changes: 11 additions & 6 deletions src/coreclr/interpreter/compiler.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1241,7 +1241,7 @@ InterpMethod* InterpCompiler::CreateInterpMethod()

bool unmanagedCallersOnly = corJitFlags.IsSet(CORJIT_FLAGS::CORJIT_FLAG_REVERSE_PINVOKE);

InterpMethod *pMethod = new InterpMethod(m_methodHnd, m_totalVarsStackSize, pDataItems, initLocals, unmanagedCallersOnly);
InterpMethod *pMethod = new InterpMethod(m_methodHnd, m_ILLocalsOffset, m_totalVarsStackSize, pDataItems, initLocals, unmanagedCallersOnly);

return pMethod;
}
Expand Down Expand Up @@ -3074,7 +3074,7 @@ void InterpCompiler::EmitCall(CORINFO_RESOLVED_TOKEN* pConstrainedToken, bool re
}
else if (isCalli)
{
AddIns(INTOP_CALLI);
AddIns(tailcall ? INTOP_CALLI_TAIL : INTOP_CALLI);
m_pLastNewIns->data[0] = GetDataItemIndex(calliCookie);
m_pLastNewIns->SetSVars2(CALL_ARGS_SVAR, callIFunctionPointerVar);
}
Expand All @@ -3092,6 +3092,11 @@ void InterpCompiler::EmitCall(CORINFO_RESOLVED_TOKEN* pConstrainedToken, bool re
assert(!isPInvoke && !isMarshaledPInvoke);
AddIns(INTOP_CALLDELEGATE);
}
else if (tailcall)
{
assert(!isPInvoke && !isMarshaledPInvoke);
AddIns(INTOP_CALL_TAIL);
}
else
{
AddIns((isPInvoke && !isMarshaledPInvoke) ? INTOP_CALL_PINVOKE : INTOP_CALL);
Expand Down Expand Up @@ -3128,14 +3133,14 @@ void InterpCompiler::EmitCall(CORINFO_RESOLVED_TOKEN* pConstrainedToken, bool re

calliCookie = m_compHnd->GetCookieForInterpreterCalliSig(&callInfo.sig);

AddIns(INTOP_CALLI);
AddIns(tailcall ? INTOP_CALLI_TAIL : INTOP_CALLI);
m_pLastNewIns->data[0] = GetDataItemIndex(calliCookie);
m_pLastNewIns->SetSVars2(CALL_ARGS_SVAR, codePointerLookupResult);
break;
}
case CORINFO_VIRTUALCALL_VTABLE:
// Traditional virtual call. In theory we could optimize this to using the vtable
AddIns(INTOP_CALLVIRT);
AddIns(tailcall ? INTOP_CALLVIRT_TAIL : INTOP_CALLVIRT);
m_pLastNewIns->data[0] = GetDataItemIndex(callInfo.hMethod);
break;

Expand Down Expand Up @@ -3163,13 +3168,13 @@ void InterpCompiler::EmitCall(CORINFO_RESOLVED_TOKEN* pConstrainedToken, bool re

calliCookie = m_compHnd->GetCookieForInterpreterCalliSig(&callInfo.sig);

AddIns(INTOP_CALLI);
AddIns(tailcall ? INTOP_CALLI_TAIL : INTOP_CALLI);
m_pLastNewIns->data[0] = GetDataItemIndex(calliCookie);
m_pLastNewIns->SetSVars2(CALL_ARGS_SVAR, synthesizedLdvirtftnPtrVar);
}
else
{
AddIns(INTOP_CALLVIRT);
AddIns(tailcall ? INTOP_CALLVIRT_TAIL : INTOP_CALLVIRT);
m_pLastNewIns->data[0] = GetDataItemIndex(callInfo.hMethod);
}
break;
Expand Down
5 changes: 3 additions & 2 deletions src/coreclr/interpreter/interpretershared.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -30,19 +30,20 @@ struct InterpMethod
InterpMethod *self;
#endif
CORINFO_METHOD_HANDLE methodHnd;
int32_t allocaSize;
int32_t argsSize, allocaSize;
void** pDataItems;
// This stub is used for calling the interpreted method from JITted/AOTed code
CallStubHeader *pCallStub;
bool initLocals;
bool unmanagedCallersOnly;

InterpMethod(CORINFO_METHOD_HANDLE methodHnd, int32_t allocaSize, void** pDataItems, bool initLocals, bool unmanagedCallersOnly)
InterpMethod(CORINFO_METHOD_HANDLE methodHnd, int32_t argsSize, int32_t allocaSize, void** pDataItems, bool initLocals, bool unmanagedCallersOnly)
{
#if DEBUG
this->self = this;
#endif
this->methodHnd = methodHnd;
this->argsSize = argsSize;
this->allocaSize = allocaSize;
this->pDataItems = pDataItems;
this->initLocals = initLocals;
Expand Down
5 changes: 5 additions & 0 deletions src/coreclr/interpreter/intops.def
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -365,6 +365,11 @@ OPDEF(INTOP_NEWOBJ, "newobj", 5, 1, 1, InterpOpMethodHandle)
OPDEF(INTOP_NEWOBJ_GENERIC, "newobj.generic", 6, 1, 2, InterpOpMethodHandle)
OPDEF(INTOP_NEWOBJ_VT, "newobj.vt", 5, 1, 1, InterpOpMethodHandle)

// Tail calls
OPDEF(INTOP_CALL_TAIL, "call.tail", 4, 1, 1, InterpOpMethodHandle)
OPDEF(INTOP_CALLI_TAIL, "calli", 5, 1, 2, InterpOpLdPtr)
OPDEF(INTOP_CALLVIRT_TAIL, "callvirt.tail", 4, 1, 1, InterpOpMethodHandle)

// The following helper call instructions exist in 2 variants, one for normal methods, and one for cases where a shared generic lookup is needed.
// In the case where a shared generic lookup is needed an extra argument is passed as an svar, which is a pointer to the generic context.
// If there is a generic context argument it is always the first SVar to the instruction.
Expand Down
51 changes: 42 additions & 9 deletions src/coreclr/vm/interpexec.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -543,6 +543,7 @@ void InterpExecMethod(InterpreterFrame *pInterpreterFrame, InterpMethodContextFr
}

int32_t returnOffset, callArgsOffset, methodSlot;
bool isTailcall = false;
MethodDesc* targetMethod;

MAIN_LOOP:
Expand Down Expand Up @@ -1895,8 +1896,10 @@ void InterpExecMethod(InterpreterFrame *pInterpreterFrame, InterpMethodContextFr
break;
}

case INTOP_CALLVIRT_TAIL:
case INTOP_CALLVIRT:
{
isTailcall = (*ip == INTOP_CALLVIRT_TAIL);
returnOffset = ip[1];
callArgsOffset = ip[2];
methodSlot = ip[3];
Expand All @@ -1914,8 +1917,10 @@ void InterpExecMethod(InterpreterFrame *pInterpreterFrame, InterpMethodContextFr
goto CALL_INTERP_METHOD;
}

case INTOP_CALLI_TAIL:
case INTOP_CALLI:
{
isTailcall = (*ip == INTOP_CALLI_TAIL);
returnOffset = ip[1];
callArgsOffset = ip[2];
int32_t calliFunctionPointerVar = ip[3];
Expand All @@ -1927,6 +1932,7 @@ void InterpExecMethod(InterpreterFrame *pInterpreterFrame, InterpMethodContextFr
// Save current execution state for when we return from called method
pFrame->ip = ip;

// Interpreter-FIXME: isTailcall
InvokeCalliStub(LOCAL_VAR(calliFunctionPointerVar, PCODE), pCallStub, stack + callArgsOffset, stack + returnOffset);
break;
}
Expand All @@ -1936,6 +1942,7 @@ void InterpExecMethod(InterpreterFrame *pInterpreterFrame, InterpMethodContextFr
// This opcode handles p/invokes that don't use a managed wrapper for marshaling. These
// calls are special in that they need an InlinedCallFrame in order for proper EH to happen

isTailcall = false;
returnOffset = ip[1];
callArgsOffset = ip[2];
methodSlot = ip[3];
Expand Down Expand Up @@ -1971,6 +1978,7 @@ void InterpExecMethod(InterpreterFrame *pInterpreterFrame, InterpMethodContextFr

case INTOP_CALLDELEGATE:
{
isTailcall = false;
returnOffset = ip[1];
callArgsOffset = ip[2];
methodSlot = ip[3];
Expand All @@ -1996,8 +2004,10 @@ void InterpExecMethod(InterpreterFrame *pInterpreterFrame, InterpMethodContextFr
break;
}

case INTOP_CALL_TAIL:
case INTOP_CALL:
{
isTailcall = (*ip == INTOP_CALL_TAIL);
returnOffset = ip[1];
callArgsOffset = ip[2];
methodSlot = ip[3];
Expand Down Expand Up @@ -2032,24 +2042,44 @@ void InterpExecMethod(InterpreterFrame *pInterpreterFrame, InterpMethodContextFr
if (targetIp == NULL)
{
// If we didn't get the interpreter code pointer setup, then this is a method we need to invoke as a compiled method.
// Interpreter-FIXME: Implement tailcall via helpers, see https://github.com/dotnet/runtime/blob/main/docs/design/features/tailcalls-with-helpers.md
InvokeCompiledMethod(targetMethod, stack + callArgsOffset, stack + returnOffset, targetMethod->GetMultiCallableAddrOfCode(CORINFO_ACCESS_ANY));
break;
}
}

// Allocate child frame.
if (isTailcall)
{
InterpMethodContextFrame *pChildFrame = pFrame->pNext;
if (!pChildFrame)
// Move args from callArgsOffset to start of stack frame.
InterpMethod* pTargetMethod = targetIp->Method;
assert(pTargetMethod->CheckIntegrity());
// It is safe to use memcpy because the source and destination are both on the interp stack, not in the GC heap.
// We need to use the target method's argsSize, not our argsSize, because tail calls (unlike CEE_JMP) can have a
// different signature from the caller.
memcpy(pFrame->pStack, stack + callArgsOffset, pTargetMethod->argsSize);
// Reuse current stack frame. We discard the call insn's returnOffset because it's not important and tail calls are
// required to be followed by a ret, so we know nothing is going to read from stack[returnOffset] after the call.
pFrame->ReInit(pFrame->pParent, targetIp, pFrame->pRetVal, pFrame->pStack);
}
else
{
// Save current execution state for when we return from called method
pFrame->ip = ip;

// Allocate child frame.
{
pChildFrame = (InterpMethodContextFrame*)alloca(sizeof(InterpMethodContextFrame));
pChildFrame->pNext = NULL;
pFrame->pNext = pChildFrame;
InterpMethodContextFrame *pChildFrame = pFrame->pNext;
if (!pChildFrame)
{
pChildFrame = (InterpMethodContextFrame*)alloca(sizeof(InterpMethodContextFrame));
pChildFrame->pNext = NULL;
pFrame->pNext = pChildFrame;
}
pChildFrame->ReInit(pFrame, targetIp, stack + returnOffset, stack + callArgsOffset);
pFrame = pChildFrame;
}
pChildFrame->ReInit(pFrame, targetIp, stack + returnOffset, stack + callArgsOffset);
pFrame = pChildFrame;
assert (((size_t)pFrame->pStack % INTERP_STACK_ALIGNMENT) == 0);
}
assert (((size_t)pFrame->pStack % INTERP_STACK_ALIGNMENT) == 0);

// Set execution state for the new frame
pMethod = pFrame->startIp->Method;
Expand All @@ -2061,6 +2091,7 @@ void InterpExecMethod(InterpreterFrame *pInterpreterFrame, InterpMethodContextFr
}
case INTOP_NEWOBJ_GENERIC:
{
isTailcall = false;
returnOffset = ip[1];
callArgsOffset = ip[2];
methodSlot = ip[4];
Expand All @@ -2079,6 +2110,7 @@ void InterpExecMethod(InterpreterFrame *pInterpreterFrame, InterpMethodContextFr
}
case INTOP_NEWOBJ:
{
isTailcall = false;
returnOffset = ip[1];
callArgsOffset = ip[2];
methodSlot = ip[3];
Expand Down Expand Up @@ -2110,6 +2142,7 @@ void InterpExecMethod(InterpreterFrame *pInterpreterFrame, InterpMethodContextFr
}
case INTOP_NEWOBJ_VT:
{
isTailcall = false;
returnOffset = ip[1];
callArgsOffset = ip[2];
methodSlot = ip[3];
Expand Down
Loading