From cd6ac51aa68a02d538ddcccf600ff0fef20b08aa Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sat, 16 Jan 2021 21:45:44 -0500
Subject: [PATCH] Muddles along to generating functions.

Albeit right now without a body.
---
 InstructionSets/M50740/Executor.cpp    |  7 +++--
 InstructionSets/M50740/Executor.hpp    | 38 +++++++++++++++++++++++++-
 InstructionSets/M50740/Instruction.hpp |  7 +++++
 3 files changed, 48 insertions(+), 4 deletions(-)

diff --git a/InstructionSets/M50740/Executor.cpp b/InstructionSets/M50740/Executor.cpp
index 39e0a38b1..71a39913a 100644
--- a/InstructionSets/M50740/Executor.cpp
+++ b/InstructionSets/M50740/Executor.cpp
@@ -16,8 +16,9 @@ template <Operation operation> void Executor::perform(uint8_t *operand [[maybe_u
 template <Operation operation, AddressingMode addressing_mode> void Executor::perform(Executor *) {
 }
 
-Executor::Action Executor::action_for(Instruction) {
-	Action action;
-	action.perform = &perform<Operation::ADC, AddressingMode::Immediate>;
+Executor::Action Executor::action_for(Instruction instruction) {
+	Action action {
+		.perform = performer_lookup_.performer(instruction.operation, instruction.addressing_mode)
+	};
 	return action;
 }
diff --git a/InstructionSets/M50740/Executor.hpp b/InstructionSets/M50740/Executor.hpp
index c17a5a4cd..b291f1e21 100644
--- a/InstructionSets/M50740/Executor.hpp
+++ b/InstructionSets/M50740/Executor.hpp
@@ -10,6 +10,7 @@
 #define Executor_h
 
 #include "Instruction.hpp"
+#include "Parser.hpp"
 
 namespace InstructionSet {
 namespace M50740 {
@@ -23,7 +24,8 @@ class Executor {
 			so using the Executor to enquire of memory and the program counter is sufficient.
 		*/
 		struct Action {
-			void (* perform)(Executor *) = nullptr;
+			using Performer = void (*)(Executor *);
+			Performer perform = nullptr;
 		};
 
 		Action action_for(Instruction);
@@ -38,6 +40,40 @@ class Executor {
 			Performs @c operation in @c addressing_mode.
 		*/
 		template <Operation operation, AddressingMode addressing_mode> static void perform(Executor *);
+
+		/*!
+			Provides dynamic lookup of @c perform(Executor*).
+		*/
+		class PerformerLookup {
+			public:
+				PerformerLookup() {
+					fill<int(MinOperation), int(MinAddressingMode)>(performers);
+				}
+
+				Action::Performer performer(Operation operation, AddressingMode addressing_mode) {
+					return performers[int(addressing_mode) * (MaxOperation - MinOperation) + int(operation) - MinOperation];
+				}
+
+			private:
+				Action::Performer performers[(MaxAddressingMode - MinAddressingMode) * (MaxOperation - MinOperation)];
+
+				template<int operation, int addressing_mode> void fill_operation(Action::Performer *target) {
+					*target = &Executor::perform<Operation(operation), AddressingMode(addressing_mode)>;
+					if constexpr (addressing_mode+1 < MaxAddressingMode) {
+						fill<operation, addressing_mode+1>(target + 1);
+					}
+				}
+
+				template<int operation, int addressing_mode> void fill(Action::Performer *target) {
+					fill_operation<operation, addressing_mode>(target);
+					target += MaxOperation - MinOperation;
+					if constexpr (operation+1 < MaxOperation) {
+						fill<operation+1, addressing_mode>(target);
+					}
+				}
+		};
+
+		inline static PerformerLookup performer_lookup_;
 };
 
 }
diff --git a/InstructionSets/M50740/Instruction.hpp b/InstructionSets/M50740/Instruction.hpp
index f823c4ee3..93ab2ebe8 100644
--- a/InstructionSets/M50740/Instruction.hpp
+++ b/InstructionSets/M50740/Instruction.hpp
@@ -38,6 +38,9 @@ enum class AddressingMode {
 	Bit4ZeroPageRelative,		Bit5ZeroPageRelative,		Bit6ZeroPageRelative,		Bit7ZeroPageRelative,
 };
 
+static constexpr auto MaxAddressingMode = int(AddressingMode::Bit7ZeroPageRelative);
+static constexpr auto MinAddressingMode = int(AddressingMode::Implied);
+
 constexpr int size(AddressingMode mode) {
 	// This is coupled to the AddressingMode list above; be careful!
 	constexpr int sizes[] = {
@@ -58,6 +61,7 @@ constexpr int size(AddressingMode mode) {
 		2,	2,	2,	2,
 		2,	2,	2,	2,
 	};
+	static_assert(sizeof(sizes)/sizeof(*sizes) == int(MaxAddressingMode) + 1);
 	return sizes[int(mode)];
 }
 
@@ -99,6 +103,9 @@ enum class Operation: uint8_t {
 	STA,	STX,	STY,
 };
 
+static constexpr auto MaxOperation = int(Operation::STY);
+static constexpr auto MinOperation = int(Operation::BBC);
+
 constexpr AccessType access_type(Operation operation) {
 	if(operation < Operation::ADC)	return AccessType::None;
 	if(operation < Operation::ASL)	return AccessType::Read;