From 754058e2e509298f70107fc1648099251ba5fa47 Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Mon, 1 Aug 2022 23:40:11 +0200
Subject: [PATCH] AAM and AAD instruction fixes, fixes #2551.

---
 src/cpu/386_common.c  | 6 ++++++
 src/cpu/cpu.c         | 8 +++++---
 src/cpu/cpu.h         | 1 +
 src/cpu/x86.h         | 5 +++--
 src/cpu/x86_ops_bcd.h | 9 ++++++++-
 src/cpu/x86seg.c      | 8 ++++++++
 6 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/src/cpu/386_common.c b/src/cpu/386_common.c
index 6c09e588a..92360a248 100644
--- a/src/cpu/386_common.c
+++ b/src/cpu/386_common.c
@@ -1481,10 +1481,16 @@ checkio(uint32_t port)
 }
 
 
+#ifdef OLD_DIVEXCP
 #define divexcp() { \
 	x386_common_log("Divide exception at %04X(%06X):%04X\n",CS,cs,cpu_state.pc); \
 	x86_int(0); \
 }
+#else
+#define divexcp() { \
+	x86de(NULL, 0); \
+}
+#endif
 
 
 int
diff --git a/src/cpu/cpu.c b/src/cpu/cpu.c
index 68cf6c38f..36d92605f 100644
--- a/src/cpu/cpu.c
+++ b/src/cpu/cpu.c
@@ -382,10 +382,10 @@ cpu_set(void)
     is_am486     = (cpu_s->cpu_type == CPU_ENH_Am486DX);
     is_am486dxl  = (cpu_s->cpu_type == CPU_Am486DXL);
 
-    is6117      = !strcmp(cpu_f->manufacturer, "ALi");
+    is6117       = !strcmp(cpu_f->manufacturer, "ALi");
 
-    cpu_isintel = !strcmp(cpu_f->manufacturer, "Intel");
-    cpu_iscyrix = !strcmp(cpu_f->manufacturer, "Cyrix") || !strcmp(cpu_f->manufacturer, "ST");
+    cpu_isintel  = !strcmp(cpu_f->manufacturer, "Intel");
+    cpu_iscyrix  = !strcmp(cpu_f->manufacturer, "Cyrix") || !strcmp(cpu_f->manufacturer, "ST");
 
     /* SL-Enhanced Intel 486s have the same SMM save state table layout as Pentiums,
        and the WinChip datasheet claims those are Pentium-compatible as well. AMD Am486DXL/DXL2 also has compatible SMM, or would if not for it's different SMBase*/
@@ -398,6 +398,8 @@ cpu_set(void)
     is_cxsmm     = (!strcmp(cpu_f->manufacturer, "Cyrix") || !strcmp(cpu_f->manufacturer, "ST")) &&
 		   (cpu_s->cpu_type >= CPU_Cx486S);
 
+    cpu_isintel  = cpu_isintel || !strcmp(cpu_f->manufacturer, "AMD");
+
     hasfpu       = (fpu_type != FPU_NONE);
     hascache     = (cpu_s->cpu_type >= CPU_486SLC) || (cpu_s->cpu_type == CPU_IBM386SLC) ||
 		   (cpu_s->cpu_type == CPU_IBM486SLC) || (cpu_s->cpu_type == CPU_IBM486BL);
diff --git a/src/cpu/cpu.h b/src/cpu/cpu.h
index b6998162f..964c456eb 100644
--- a/src/cpu/cpu.h
+++ b/src/cpu/cpu.h
@@ -669,6 +669,7 @@ extern void	hardresetx86(void);
 extern void	x86_int(int num);
 extern void	x86_int_sw(int num);
 extern int	x86_int_sw_rm(int num);
+extern void	x86de(char *s, uint16_t error);
 extern void	x86gpf(char *s, uint16_t error);
 extern void	x86np(char *s, uint16_t error);
 extern void	x86ss(char *s, uint16_t error);
diff --git a/src/cpu/x86.h b/src/cpu/x86.h
index b9726dc57..32a3317ea 100644
--- a/src/cpu/x86.h
+++ b/src/cpu/x86.h
@@ -1,4 +1,4 @@
-#define ABRT_MASK 0x7f
+#define ABRT_MASK 0x3f
 /*An 'expected' exception is one that would be expected to occur on every execution
   of this code path; eg a GPF due to being in v86 mode. An 'unexpected' exception is
   one that would be unlikely to occur on the next exception, eg a page fault may be
@@ -71,7 +71,8 @@ enum
         ABRT_NP  = 0xB,
         ABRT_SS  = 0xC,
         ABRT_GPF = 0xD,
-        ABRT_PF  = 0xE
+        ABRT_PF  = 0xE,
+        ABRT_DE  = 0x40     /* INT 0, but we have to distinguish it from ABRT_NONE. */
 };
 
 
diff --git a/src/cpu/x86_ops_bcd.h b/src/cpu/x86_ops_bcd.h
index 385d63cd7..b37b6a6df 100644
--- a/src/cpu/x86_ops_bcd.h
+++ b/src/cpu/x86_ops_bcd.h
@@ -31,7 +31,14 @@ static int opAAD(uint32_t fetchdat)
 static int opAAM(uint32_t fetchdat)
 {
         int base = getbytef();
-        if (!base || !cpu_isintel) base = 10;
+
+	if (base == 0) {
+		x86de(NULL, 0);
+		return 1;
+	}
+
+        if (!cpu_isintel) base = 10;
+
         AH = AL / base;
         AL %= base;
         setznp16(AX);
diff --git a/src/cpu/x86seg.c b/src/cpu/x86seg.c
index e103f0247..c9398dd69 100644
--- a/src/cpu/x86seg.c
+++ b/src/cpu/x86seg.c
@@ -165,6 +165,14 @@ x86_doabrt(int x86_abrt)
 }
 
 
+void
+x86de(char *s, uint16_t error)
+{
+    cpu_state.abrt = ABRT_DE;
+    abrt_error = error;
+}
+
+
 void
 x86gpf(char *s, uint16_t error)
 {