From 57bfec285fc682b4b85a49e26c9c2194ff488501 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sat, 26 Aug 2017 23:08:57 -0400
Subject: [PATCH] Makes it optional whether the Z80 supports the wait line. If
 the wait line isn't in use, runtime costs are decreased because the optional
 wait cycles need not be iterated over.

---
 Machines/AmstradCPC/AmstradCPC.cpp |  2 +-
 Machines/ZX8081/ZX8081.cpp         |  2 +-
 Processors/Z80/Z80.hpp             | 19 +++++++++++++++++--
 3 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/Machines/AmstradCPC/AmstradCPC.cpp b/Machines/AmstradCPC/AmstradCPC.cpp
index 1d6ff8458..0244ddb41 100644
--- a/Machines/AmstradCPC/AmstradCPC.cpp
+++ b/Machines/AmstradCPC/AmstradCPC.cpp
@@ -998,7 +998,7 @@ class ConcreteMachine:
 			}
 		}
 
-		CPU::Z80::Processor<ConcreteMachine, false> z80_;
+		CPU::Z80::Processor<ConcreteMachine, false, true> z80_;
 
 		CRTCBusHandler crtc_bus_handler_;
 		Motorola::CRTC::CRTC6845<CRTCBusHandler> crtc_;
diff --git a/Machines/ZX8081/ZX8081.cpp b/Machines/ZX8081/ZX8081.cpp
index fab9c8986..2737d3cf9 100644
--- a/Machines/ZX8081/ZX8081.cpp
+++ b/Machines/ZX8081/ZX8081.cpp
@@ -332,7 +332,7 @@ class ConcreteMachine:
 		HalfCycles get_typer_frequency() override final { return Cycles(390000); }
 
 	private:
-		CPU::Z80::Processor<ConcreteMachine, false> z80_;
+		CPU::Z80::Processor<ConcreteMachine, false, true> z80_;
 
 		std::shared_ptr<Video> video_;
 		std::vector<uint8_t> zx81_rom_, zx80_rom_;
diff --git a/Processors/Z80/Z80.hpp b/Processors/Z80/Z80.hpp
index 913105a2b..f616b9d1c 100644
--- a/Processors/Z80/Z80.hpp
+++ b/Processors/Z80/Z80.hpp
@@ -193,7 +193,7 @@ class BusHandler {
 	order to provide the bus on which the Z80 operates and @c flush(), which is called upon completion of a continuous run
 	of cycles to allow a subclass to bring any on-demand activities up to date.
 */
-template <class T, bool uses_bus_request> class Processor {
+template <class T, bool uses_bus_request, bool uses_wait_line> class Processor {
 	private:
 		T &bus_handler_;
 
@@ -451,6 +451,7 @@ template <class T, bool uses_bus_request> class Processor {
 
 			// Allocate a landing area.
 			std::vector<size_t> operation_indices;
+			target.all_operations.reserve(number_of_micro_ops);
 			target.instructions.resize(256, nullptr);
 
 			// Copy in all programs, recording where they go.
@@ -464,6 +465,12 @@ template <class T, bool uses_bus_request> class Processor {
 						continue;
 					}
 
+					// Skip optional waits if this instance doesn't use the wait line.
+					if(table[c][t].machine_cycle.was_requested && !uses_wait_line) {
+						t++;
+						continue;
+					}
+
 					// If an index placeholder is hit then drop it, and if offsets aren't being added,
 					// then also drop the indexing that follows, which is assumed to be everything
 					// up to and including the next ::CalculateIndexAddress. Coupled to the INDEX() macro.
@@ -795,6 +802,13 @@ template <class T, bool uses_bus_request> class Processor {
 			while(!isTerminal(source[length].type)) length++;
 			size_t pointer = 0;
 			while(true) {
+				// TODO: This test is duplicated from assemble_page; can a better factoring be found?
+				// Skip optional waits if this instance doesn't use the wait line.
+				if(source[pointer].machine_cycle.was_requested && !uses_wait_line) {
+					pointer++;
+					continue;
+				}
+
 				destination.emplace_back(source[pointer]);
 				if(isTerminal(source[pointer].type)) break;
 				pointer++;
@@ -955,7 +969,7 @@ template <class T, bool uses_bus_request> class Processor {
 								bus_handler_.flush();
 								return;
 							}
-							if(operation->machine_cycle.was_requested) {
+							if(uses_wait_line && operation->machine_cycle.was_requested) {
 								if(wait_line_) {
 									scheduled_program_counter_--;
 								} else {
@@ -2002,6 +2016,7 @@ template <class T, bool uses_bus_request> class Processor {
 			Sets the logical value of the wait line.
 		*/
 		inline void set_wait_line(bool value) {
+			assert(uses_wait_line);
 			wait_line_ = value;
 		}