From 78886f11f7a2e6c4af41ad6bc06623267da3b1c5 Mon Sep 17 00:00:00 2001
From: drmortalwombat <90205530+drmortalwombat@users.noreply.github.com>
Date: Mon, 20 Sep 2021 13:02:38 +0200
Subject: [PATCH] Native code peephole optimisation for commutative
 instructions

---
 oscar64/NativeCodeGenerator.cpp | 17 ++++++++++++++++-
 oscar64/NativeCodeGenerator.h   |  1 +
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/oscar64/NativeCodeGenerator.cpp b/oscar64/NativeCodeGenerator.cpp
index f54faeb..a1b2dd3 100644
--- a/oscar64/NativeCodeGenerator.cpp
+++ b/oscar64/NativeCodeGenerator.cpp
@@ -71,7 +71,7 @@ bool NativeCodeInstruction::IsUsedResultInstructions(NumberSet& requiredTemps)
 		mLive |= LIVE_CPU_REG_Z;
 	if (requiredTemps[CPU_REG_C])
 		mLive |= LIVE_CPU_REG_C;
-	if (mMode == ASMIM_ZERO_PAGE)
+	if (mMode == ASMIM_ZERO_PAGE && requiredTemps[mAddress])
 		mLive |= LIVE_MEM;
 
 	if (mType == ASMIT_JSR)
@@ -446,6 +446,11 @@ bool NativeCodeInstruction::ChangesAddress(void) const
 		return false;
 }
 
+bool NativeCodeInstruction::IsCommutative(void) const
+{
+	return mType == ASMIT_ADC || mType == ASMIT_AND || mType == ASMIT_ORA || mType == ASMIT_EOR;
+}
+
 
 bool NativeCodeInstruction::SameEffectiveAddress(const NativeCodeInstruction& ins) const
 {
@@ -4080,6 +4085,16 @@ bool NativeCodeBasicBlock::PeepHoleOptimizer(void)
 						mIns[i + 2].mType = ASMIT_STA;
 						progress = true;
 					}
+					else if (mIns[i + 0].mType == ASMIT_STA && mIns[i + 0].mMode == ASMIM_ZERO_PAGE &&
+						mIns[i + 1].mType == ASMIT_LDA && mIns[i + 1].mMode != ASMIM_ZERO_PAGE &&
+						mIns[i + 2].mMode == ASMIM_ZERO_PAGE && mIns[i + 0].mAddress == mIns[i + 2].mAddress &&
+						mIns[i + 2].IsCommutative() && HasAsmInstructionMode(mIns[i + 2].mType, mIns[i + 1].mMode) &&
+						(mIns[i + 2].mLive & LIVE_MEM) == 0)
+					{
+						mIns[i + 1].mType = mIns[i + 2].mType;
+						mIns[i + 0].mType = ASMIT_NOP;
+						mIns[i + 2].mType = ASMIT_NOP;
+					}
 				}
 
 				if (i + 3 < mIns.Size())
diff --git a/oscar64/NativeCodeGenerator.h b/oscar64/NativeCodeGenerator.h
index e898a57..2681049 100644
--- a/oscar64/NativeCodeGenerator.h
+++ b/oscar64/NativeCodeGenerator.h
@@ -47,6 +47,7 @@ public:
 	bool LoadsAccu(void) const;
 	bool ChangesAddress(void) const;
 	bool SameEffectiveAddress(const NativeCodeInstruction& ins) const;
+	bool IsCommutative(void) const;
 };
 
 class NativeCodeBasicBlock