From 48ec7fc0e059e069ef17e0f69291ea52503c4946 Mon Sep 17 00:00:00 2001
From: Toni Wilen <twilen@winuae.net>
Date: Mon, 2 Sep 2019 20:04:15 +0300
Subject: [PATCH] CHK2/CMP2 undefined N and V flags emulated.

---
 gencpu.cpp        |  18 ++++----
 include/newcpu.h  |   2 +-
 newcpu_common.cpp | 105 +++++++++++++++++++++++++++++++++++++++-------
 3 files changed, 101 insertions(+), 24 deletions(-)

diff --git a/gencpu.cpp b/gencpu.cpp
index 4b68b632..d1770636 100644
--- a/gencpu.cpp
+++ b/gencpu.cpp
@@ -5017,7 +5017,7 @@ bccl_not68020:
 		genamode (curi, curi->smode, "srcreg", curi->size, "extra", 1, 0, 0);
 		genamode (curi, curi->dmode, "dstreg", curi->size, "dst", 2, 0, 0);
 		fill_prefetch_0 ();
-		printf ("\t{uae_u32 upper,lower,reg = regs.regs[(extra >> 12) & 15];\n");
+		printf ("\t{uae_s32 upper,lower,reg = regs.regs[(extra >> 12) & 15];\n");
 		switch (curi->size) {
 		case sz_byte:
 			printf ("\tlower = (uae_s32)(uae_s8)%s (dsta); upper = (uae_s32)(uae_s8)%s (dsta + 1);\n", srcb, srcb);
@@ -5033,12 +5033,16 @@ bccl_not68020:
 		default:
 			term ();
 		}
-		printf("\tsetchk2undefinedflags(lower, upper, reg, (extra & 0x8000) ? %d : 2);\n", curi->size);
-		printf("\tupper -= lower;\n");
-		printf("\treg -= lower;\n");
-		printf("\tSET_ZFLG (upper == reg || 0 == reg);\n");
-		printf("\tSET_CFLG_ALWAYS (reg > upper);\n");
-		printf("\tif ((extra & 0x800) && GET_CFLG ()) { Exception_cpu(6); goto %s; }\n}\n", endlabelstr);
+		printf("\tSET_CFLG(0);\n");
+		printf("\tSET_ZFLG(0);\n");
+		printf("\tsetchk2undefinedflags(lower, upper, reg, (extra & 0x8000) ? 2 : %d);\n", curi->size);
+		printf("\tif(upper == reg || lower == reg) {\n");
+		printf("\t\tSET_ZFLG(1);\n");
+		printf("\t}else{\n");
+		printf("\t\tif (lower <= upper && (reg < lower || reg > upper)) SET_CFLG(1);\n");
+		printf("\t\tif (lower > upper && reg > upper && reg < lower) SET_CFLG(1);\n");
+		printf("\t}\n");
+		printf("\tif ((extra & 0x800) && GET_CFLG()) { Exception_cpu(6); goto %s; }\n}\n", endlabelstr);
 		need_endlabel = 1;
 		break;
 
diff --git a/include/newcpu.h b/include/newcpu.h
index 83d823c5..b672e3c1 100644
--- a/include/newcpu.h
+++ b/include/newcpu.h
@@ -682,7 +682,7 @@ extern void divbyzero_special(bool issigned, uae_s32 dst);
 extern void setdivuflags(bool overflow, uae_u32 dividend, uae_u16 divisor);
 extern void setdivsflags(bool overflow, uae_s32 dividend, uae_s16 divisor);
 extern void setchkundefinedflags(uae_s32 src, uae_s32 dst, int size);
-extern void setchk2undefinedflags(uae_u32 lower, uae_u32 upper, uae_u32 val, int size);
+extern void setchk2undefinedflags(uae_s32 lower, uae_s32 upper, uae_s32 val, int size);
 extern void protect_roms (bool);
 extern void unprotect_maprom (void);
 extern bool is_hardreset(void);
diff --git a/newcpu_common.cpp b/newcpu_common.cpp
index 02753998..7561d5f1 100644
--- a/newcpu_common.cpp
+++ b/newcpu_common.cpp
@@ -924,25 +924,98 @@ void setchkundefinedflags(uae_s32 src, uae_s32 dst, int size)
 	}
 }
 
-void setchk2undefinedflags(uae_u32 lower, uae_u32 upper, uae_u32 val, int size)
-{
-	uae_u32 nmask;
-	if (size == sz_byte)
-		nmask = 0x80;
-	else if (size == sz_word)
-		nmask = 0x8000;
-	else
-		nmask = 0x80000000;
+/*
+ * CHK2/CMP2 undefined flags
+ *
+ * 68020-68030: See below..
+ * 68040: N: val<0 V=0
+ *
+ */
 
+// This is the complex one.
+// Someone else can attempt to simplify this..
+void setchk2undefinedflags(uae_s32 lower, uae_s32 upper, uae_s32 val, int size)
+{
 	SET_NFLG(0);
-	if ((upper & nmask) && val > upper) {
-		SET_NFLG(1);
-	} else if (!(upper & nmask) && val > upper && val < nmask) {
-		SET_NFLG(1);
-	} else if (val < lower) {
-		SET_NFLG(1);
-	}
 	SET_VFLG(0);
+
+	if (currprefs.cpu_model >= 68040) {
+		SET_NFLG(val < 0);
+		return;
+	}
+
+	if (val == lower || val == upper)
+		return;
+
+	if (lower < 0 && upper >= 0) {
+		if (val < lower) {
+			SET_NFLG(1);
+		}
+		if (val >= 0 && val < upper) {
+			SET_NFLG(1);
+		}
+		if (val >= 0 && lower - val >= 0) {
+			SET_VFLG(1);
+			SET_NFLG(0);
+			if (val > upper) {
+				SET_NFLG(1);
+			}
+		}
+	} else if (lower >= 0 && upper < 0) {
+		if (val >= 0) {
+			SET_NFLG(1);
+		}
+		if (val > upper) {
+			SET_NFLG(1);
+		}
+		if (val > lower && upper - val >= 0) {
+			SET_VFLG(1);
+			SET_NFLG(0);
+		}
+	} else if (lower >= 0 && upper >= 0 && lower > upper) {
+		if (val > upper && val < lower) {
+			SET_NFLG(1);
+		}
+		if (val < 0 && lower - val < 0) {
+			SET_VFLG(1);
+		}
+		if (val < 0 && lower - val >= 0) {
+			SET_NFLG(1);
+		}
+	} else if (lower >= 0 && upper >= 0 && lower <= upper) {
+		if (val >= 0 && val < lower) {
+			SET_NFLG(1);
+		}
+		if (val > upper) {
+			SET_NFLG(1);
+		}
+		if (val < 0 && upper - val < 0) {
+			SET_VFLG(1);
+			SET_NFLG(1);
+		}
+	} else if (lower < 0 && upper < 0 && lower > upper) {
+		if (val >= 0) {
+			SET_NFLG(1);
+		}
+		if (val > upper && val < lower) {
+			SET_NFLG(1);
+		}
+		if (val >= 0 && val - lower < 0) {
+			SET_NFLG(0);
+			SET_VFLG(1);
+		}
+	} else if (lower < 0 && upper < 0 && lower <= upper) {
+		if (val < lower) {
+			SET_NFLG(1);
+		}
+		if (val < 0 && val > upper) {
+			SET_NFLG(1);
+		}
+		if (val >= 0 && val - lower < 0) {
+			SET_NFLG(1);
+			SET_VFLG(1);
+		}
+	}
 }
 
 #ifndef CPUEMU_68000_ONLY
-- 
2.47.3