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- removed OP_TAIL.

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The amount of support code for this minor optimization was quite large and this stood in the way of streamlining the VM's calling convention, so it was preferable to remove it before moving on.
This commit is contained in:
Christoph Oelckers 2018-11-18 07:43:03 +01:00
commit 629d329f22
9 changed files with 12 additions and 219 deletions
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56
src/scripting/vm/jit_call.cpp
View file

@ -132,18 +132,6 @@ void JitCompiler::EmitCALL_K()
EmitDoCall(ptr);
}
void JitCompiler::EmitTAIL()
{
EmitDoTail(regA[A]);
}
void JitCompiler::EmitTAIL_K()
{
auto ptr = newTempIntPtr();
cc.mov(ptr, asmjit::imm_ptr(konsta[A].o));
EmitDoTail(ptr);
}
void JitCompiler::EmitDoCall(asmjit::X86Gp vmfunc)
{
using namespace asmjit;
@ -185,50 +173,6 @@ void JitCompiler::EmitScriptCall(asmjit::X86Gp vmfunc, asmjit::X86Gp paramsptr)
call->setArg(4, Imm(C));
}
void JitCompiler::EmitDoTail(asmjit::X86Gp vmfunc)
{
// Whereas the CALL instruction uses its third operand to specify how many return values
// it expects, TAIL ignores its third operand and uses whatever was passed to this Exec call.
// Note: this is not a true tail call, but then again, it isn't in the vmexec implementation either..
using namespace asmjit;
if (NumParam < B)
I_FatalError("OP_TAIL parameter count does not match the number of preceding OP_PARAM instructions");
StoreInOuts(B); // Is REGT_ADDROF even allowed for (true) tail calls?
X86Gp paramsptr = newTempIntPtr();
cc.lea(paramsptr, x86::ptr(vmframe, offsetParams + (int)((NumParam - B) * sizeof(VMValue))));
auto result = newResultInt32();
EmitScriptTailCall(vmfunc, result, paramsptr);
EmitPopFrame();
cc.ret(result);
NumParam -= B;
ParamOpcodes.Resize(ParamOpcodes.Size() - B);
}
void JitCompiler::EmitScriptTailCall(asmjit::X86Gp vmfunc, asmjit::X86Gp result, asmjit::X86Gp paramsptr)
{
using namespace asmjit;
auto scriptcall = newTempIntPtr();
cc.mov(scriptcall, x86::ptr(vmfunc, offsetof(VMScriptFunction, ScriptCall)));
auto call = cc.call(scriptcall, FuncSignature5<int, VMFunction *, VMValue*, int, VMReturn*, int>());
call->setRet(0, result);
call->setArg(0, vmfunc);
call->setArg(1, paramsptr);
call->setArg(2, Imm(B));
call->setArg(3, ret);
call->setArg(4, numret);
}
void JitCompiler::StoreInOuts(int b)
{
using namespace asmjit;

3
src/scripting/vm/jitintern.h
View file

@ -55,9 +55,6 @@ private:
void EmitDoCall(asmjit::X86Gp ptr);
void EmitScriptCall(asmjit::X86Gp vmfunc, asmjit::X86Gp paramsptr);
void EmitDoTail(asmjit::X86Gp ptr);
void EmitScriptTailCall(asmjit::X86Gp vmfunc, asmjit::X86Gp result, asmjit::X86Gp paramsptr);
void StoreInOuts(int b);
void LoadInOuts(int b);
void LoadReturns(const VMOP *retval, int numret);

39
src/scripting/vm/vmexec.h
View file

@ -718,45 +718,6 @@ static int ExecScriptFunc(VMFrameStack *stack, VMReturn *ret, int numret)
pc += C; // Skip RESULTs
}
NEXTOP;
OP(TAIL_K):
ASSERTKA(a);
ptr = konsta[a].o;
goto Do_TAILCALL;
OP(TAIL):
ASSERTA(a);
ptr = reg.a[a];
Do_TAILCALL:
// Whereas the CALL instruction uses its third operand to specify how many return values
// it expects, TAIL ignores its third operand and uses whatever was passed to this Exec call.
assert(B <= f->NumParam);
assert(C <= MAX_RETURNS);
{
VMFunction *call = (VMFunction *)ptr;
if (call->VarFlags & VARF_Native)
{
try
{
VMCycles[0].Unclock();
auto r = static_cast<VMNativeFunction *>(call)->NativeCall(reg.param + f->NumParam - B, B, ret, numret);
VMCycles[0].Clock();
return r;
}
catch (CVMAbortException &err)
{
err.MaybePrintMessage();
err.stacktrace.AppendFormat("Called from %s\n", call->PrintableName.GetChars());
// PrintParameters(reg.param + f->NumParam - B, B);
throw;
}
}
else
{ // FIXME: Not a true tail call
auto sfunc = static_cast<VMScriptFunction *>(call);
return sfunc->ScriptCall(sfunc, reg.param + f->NumParam - B, B, ret, numret);
}
}
NEXTOP;
OP(RET):
if (B == REGT_NIL)
{ // No return values

2
src/scripting/vm/vmops.h
View file

@ -105,8 +105,6 @@ xx(CALL, call, RPI8I8, NOP, 0, 0) // Call function pkA with parameter count B a
xx(CALL_K, call, KPI8I8, CALL, 1, REGT_POINTER)
xx(VTBL, vtbl, RPRPI8, NOP, 0, 0) // dereferences a virtual method table.
xx(SCOPE, scope, RPI8, NOP, 0, 0) // Scope check at runtime.
xx(TAIL, tail, RPI8, NOP, 0, 0) // Call+Ret in a single instruction
xx(TAIL_K, tail, KPI8, TAIL, 1, REGT_POINTER)
xx(RESULT, result, __BCP, NOP, 0, 0) // Result should go in register encoded in BC (in caller, after CALL)
xx(RET, ret, I8BCP, NOP, 0, 0) // Copy value from register encoded in BC to return value A, possibly returning
xx(RETI, reti, I8I16, NOP, 0, 0) // Copy immediate from BC to return value A, possibly returning