diff --git a/src/thingdef/thingdef_exp.h b/src/thingdef/thingdef_exp.h index 3353cad46..bf32d02f6 100644 --- a/src/thingdef/thingdef_exp.h +++ b/src/thingdef/thingdef_exp.h @@ -48,6 +48,7 @@ #define RESOLVE(p,c) if (p!=NULL) p = p->Resolve(c) #define ABORT(p) if (!(p)) { delete this; return NULL; } #define SAFE_RESOLVE(p,c) RESOLVE(p,c); ABORT(p) +#define SAFE_RESOLVE_OPT(p,c) if (p!=NULL) { SAFE_RESOLVE(p,c) } class VMFunctionBuilder; class FxJumpStatement; @@ -927,6 +928,24 @@ public: ExpEmit Emit(VMFunctionBuilder *build); }; +//========================================================================== +// +// FxWhileLoop +// +//========================================================================== + +class FxWhileLoop : public FxExpression +{ + FxExpression *Condition; + FxExpression *Code; + +public: + FxWhileLoop(FxExpression *condition, FxExpression *code, const FScriptPosition &pos); + ~FxWhileLoop(); + FxExpression *Resolve(FCompileContext&); + ExpEmit Emit(VMFunctionBuilder *build); +}; + //========================================================================== // // FxJumpStatement diff --git a/src/thingdef/thingdef_expression.cpp b/src/thingdef/thingdef_expression.cpp index 4e13b7beb..b5eabe7d1 100644 --- a/src/thingdef/thingdef_expression.cpp +++ b/src/thingdef/thingdef_expression.cpp @@ -3857,6 +3857,107 @@ ExpEmit FxIfStatement::Emit(VMFunctionBuilder *build) return ExpEmit(); } +//========================================================================== +// +// FxWhileLoop +// +//========================================================================== + +FxWhileLoop::FxWhileLoop(FxExpression *condition, FxExpression *code, const FScriptPosition &pos) +: FxExpression(pos), Condition(condition), Code(code) +{ + ValueType = TypeVoid; +} + +FxWhileLoop::~FxWhileLoop() +{ + SAFE_DELETE(Condition); + SAFE_DELETE(Code); +} + +FxExpression *FxWhileLoop::Resolve(FCompileContext &ctx) +{ + CHECKRESOLVED(); + SAFE_RESOLVE(Condition, ctx); + SAFE_RESOLVE_OPT(Code, ctx); + + ctx.HandleJumps(TK_Break, this); + ctx.HandleJumps(TK_Continue, this); + + if (Condition->ValueType != TypeBool) + { + Condition = new FxBoolCast(Condition); + SAFE_RESOLVE(Condition, ctx); + } + + if (Condition->isConstant()) + { + if (static_cast(Condition)->GetValue().GetBool() == false) + { // Nothing happens + FxExpression *nop = new FxNop(ScriptPosition); + delete this; + return nop; + } + else if (Code == nullptr) + { // "while (true) { }" + // Someone could be using this for testing. + ScriptPosition.Message(MSG_WARNING, "Infinite empty loop"); + } + } + + return this; +} + +ExpEmit FxWhileLoop::Emit(VMFunctionBuilder *build) +{ + assert(Condition->ValueType == TypeBool); + + size_t loopstart, loopend; + size_t jumpspot; + + // Evaluate the condition and execute/break out of the loop. + loopstart = build->GetAddress(); + if (!Condition->isConstant()) + { + ExpEmit cond = Condition->Emit(build); + build->Emit(OP_TEST, cond.RegNum, 0); + jumpspot = build->Emit(OP_JMP, 0); + cond.Free(build); + } + else assert(static_cast(Condition)->GetValue().GetBool() == true); + + // Execute the loop's content. + if (Code != nullptr) + { + ExpEmit code = Code->Emit(build); + code.Free(build); + } + + // Loop back. + build->Backpatch(build->Emit(OP_JMP, 0), loopstart); + loopend = build->GetAddress(); + + if (!Condition->isConstant()) + { + build->Backpatch(jumpspot, loopend); + } + + // Give a proper address to any break/continue statement within this loop. + for (unsigned int i = 0; i < JumpAddresses.Size(); i++) + { + if (JumpAddresses[i]->Token == TK_Break) + { + build->Backpatch(JumpAddresses[i]->Address, loopend); + } + else + { // Continue statement. + build->Backpatch(JumpAddresses[i]->Address, loopstart); + } + } + + return ExpEmit(); +} + //========================================================================== // // FxJumpStatement diff --git a/src/thingdef/thingdef_states.cpp b/src/thingdef/thingdef_states.cpp index 464221714..6e71f628e 100644 --- a/src/thingdef/thingdef_states.cpp +++ b/src/thingdef/thingdef_states.cpp @@ -480,6 +480,27 @@ static FxExpression *ParseIf(FScanner &sc, FState state, FString statestring, Ba return add; } +static FxExpression *ParseWhile(FScanner &sc, FState state, FString statestring, Baggage &bag, + PPrototype *&retproto, bool &lastwasret) +{ + FxExpression *cond, *code; + PPrototype *proto; + bool ret; + + sc.MustGetStringName("("); + cond = ParseExpression(sc, bag.Info); + sc.MustGetStringName(")"); + sc.MustGetStringName("{"); // Enforce braces like for if statements. + + code = ParseActions(sc, state, statestring, bag, proto, ret); + sc.MustGetString(); + + retproto = ReturnCheck(retproto, proto, sc); + lastwasret = false; // A while loop always jumps back. + + return new FxWhileLoop(cond, code, sc); +} + FxExpression *ParseActions(FScanner &sc, FState state, FString statestring, Baggage &bag, PPrototype *&retproto, bool &endswithret) { @@ -505,9 +526,13 @@ FxExpression *ParseActions(FScanner &sc, FState state, FString statestring, Bagg FxExpression *add; lastwasret = false; if (sc.Compare("if")) - { // Hangle an if statement + { // Handle an if statement add = ParseIf(sc, state, statestring, bag, proto, lastwasret); } + else if (sc.Compare("while")) + { // Handle a while loop + add = ParseWhile(sc, state, statestring, bag, proto, lastwasret); + } else if (sc.Compare("return")) { // Handle a return statement lastwasret = true; diff --git a/src/zscript/vmbuilder.cpp b/src/zscript/vmbuilder.cpp index 2a4f6b1a8..eb49ffb14 100644 --- a/src/zscript/vmbuilder.cpp +++ b/src/zscript/vmbuilder.cpp @@ -436,6 +436,17 @@ bool VMFunctionBuilder::RegAvailability::Reuse(int reg) return true; } +//========================================================================== +// +// VMFunctionBuilder :: GetAddress +// +//========================================================================== + +size_t VMFunctionBuilder::GetAddress() +{ + return Code.Size(); +} + //========================================================================== // // VMFunctionBuilder :: Emit diff --git a/src/zscript/vmbuilder.h b/src/zscript/vmbuilder.h index 89b626c18..2d8721acc 100644 --- a/src/zscript/vmbuilder.h +++ b/src/zscript/vmbuilder.h @@ -34,6 +34,9 @@ public: int GetConstantAddress(void *ptr, VM_ATAG tag); int GetConstantString(FString str); + // Returns the address of the next instruction to be emitted. + size_t GetAddress(); + // Returns the address of the newly-emitted instruction. size_t Emit(int opcode, int opa, int opb, int opc); size_t Emit(int opcode, int opa, VM_SHALF opbc);