From e1736c8214e5b4e35f2f437da95a1a011fcc3048 Mon Sep 17 00:00:00 2001
From: drmortalwombat <90205530+drmortalwombat@users.noreply.github.com>
Date: Thu, 21 Nov 2024 22:02:25 +0100
Subject: [PATCH] Reverse shift with negated distance

---
 oscar64/InterCode.cpp | 71 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 70 insertions(+), 1 deletion(-)

diff --git a/oscar64/InterCode.cpp b/oscar64/InterCode.cpp
index 34ec8d7..ee20015 100644
--- a/oscar64/InterCode.cpp
+++ b/oscar64/InterCode.cpp
@@ -6358,6 +6358,20 @@ static bool ispow2(int64 v)
 	return 0;
 }
 
+static int binlog(int64 n)
+{
+	int	k = -1;
+
+	while (n)
+	{
+		n >>= 1;
+		k++;
+	}
+
+	return k;
+}
+
+
 void InterCodeBasicBlock::CheckValueUsage(InterInstruction * ins, const GrowingInstructionPtrArray& tvalue, const GrowingVariableArray& staticVars, const GrowingInterCodeProcedurePtrArray& staticProcs, FastNumberSet& fsingle)
 {
 	switch (ins->mCode)
@@ -20552,6 +20566,61 @@ bool InterCodeBasicBlock::PeepholeReplaceOptimization(const GrowingVariableArray
 				}
 			}
 		}
+#endif
+#if 1
+		if (i + 1 < mInstructions.Size())
+		{
+			if (mInstructions[i + 0]->mCode == IC_BINARY_OPERATOR && mInstructions[i + 0]->mOperator == IA_SUB &&
+				mInstructions[i + 1]->mCode == IC_BINARY_OPERATOR && mInstructions[i + 1]->mOperator == IA_SHL &&
+				mInstructions[i + 1]->mSrc[0].mTemp == mInstructions[i + 0]->mDst.mTemp && mInstructions[i + 1]->mSrc[0].mFinal && mInstructions[i + 1]->mSrc[0].IsUByte() &&
+				mInstructions[i + 1]->mSrc[1].mTemp < 0 && ispow2(mInstructions[i + 1]->mSrc[1].mIntConst))
+			{
+				int64 k = binlog(mInstructions[i + 1]->mSrc[1].mIntConst);
+				
+				if (mInstructions[i + 0]->mSrc[0].mTemp >= 0 && mInstructions[i + 0]->mSrc[1].mTemp < 0)
+				{
+					int64 s = mInstructions[i + 0]->mSrc[1].mIntConst;
+					mInstructions[i + 0]->mSrc[1] = mInstructions[i + 0]->mSrc[0];
+					mInstructions[i + 0]->mSrc[0].mTemp = -1;
+					mInstructions[i + 0]->mSrc[0].mIntConst = mInstructions[i + 0]->mSrc[1].mRange.mMinValue;
+					mInstructions[i + 0]->mDst.mRange.SetLimit(0, mInstructions[i + 0]->mSrc[1].mRange.mMaxValue - mInstructions[i + 0]->mSrc[0].mIntConst);
+					mInstructions[i + 1]->mOperator = IA_SHR;
+					mInstructions[i + 1]->mSrc[0] = mInstructions[i + 0]->mDst;
+					int64 d = s - mInstructions[i + 0]->mSrc[0].mIntConst;
+					if (d < 0)
+						mInstructions[i + 1]->mSrc[1].mIntConst >>= -d;
+					else
+						mInstructions[i + 1]->mSrc[1].mIntConst <<= d;
+					changed = true;
+				}
+			}
+			if (mInstructions[i + 0]->mCode == IC_BINARY_OPERATOR && mInstructions[i + 0]->mOperator == IA_SUB &&
+				mInstructions[i + 1]->mCode == IC_BINARY_OPERATOR && mInstructions[i + 1]->mOperator == IA_SHR &&
+				mInstructions[i + 1]->mSrc[0].mTemp == mInstructions[i + 0]->mDst.mTemp && mInstructions[i + 1]->mSrc[0].mFinal && mInstructions[i + 1]->mSrc[0].IsUByte() &&
+				mInstructions[i + 1]->mSrc[1].mTemp < 0 && ispow2(mInstructions[i + 1]->mSrc[1].mIntConst))
+			{
+				int64 k = binlog(mInstructions[i + 1]->mSrc[1].mIntConst);
+
+				if (mInstructions[i + 0]->mSrc[0].mTemp >= 0 && mInstructions[i + 0]->mSrc[1].mTemp < 0)
+				{
+					int64 s = mInstructions[i + 0]->mSrc[1].mIntConst;
+					mInstructions[i + 0]->mSrc[1] = mInstructions[i + 0]->mSrc[0];
+					mInstructions[i + 0]->mSrc[0].mTemp = -1;
+					mInstructions[i + 0]->mSrc[0].mIntConst = mInstructions[i + 0]->mSrc[1].mRange.mMinValue;
+					mInstructions[i + 0]->mDst.mRange.SetLimit(0, mInstructions[i + 0]->mSrc[1].mRange.mMaxValue - mInstructions[i + 0]->mSrc[0].mIntConst);
+					mInstructions[i + 1]->mOperator = IA_SHL;
+					mInstructions[i + 1]->mSrc[0] = mInstructions[i + 0]->mDst;
+					int64 d = s - mInstructions[i + 0]->mSrc[0].mIntConst;
+					if (d < 0)
+						mInstructions[i + 1]->mSrc[1].mIntConst <<= -d;
+					else
+						mInstructions[i + 1]->mSrc[1].mIntConst >>= d;
+					changed = true;
+				}
+			}
+		}
+
+
 #endif
 	}
 
@@ -22927,7 +22996,7 @@ void InterCodeProcedure::Close(void)
 {
 	GrowingTypeArray	tstack(IT_NONE);
 
-	CheckFunc = !strcmp(mIdent->mString, "main");
+	CheckFunc = !strcmp(mIdent->mString, "test");
 	CheckCase = false;
 
 	mEntryBlock = mBlocks[0];