From aeeefebf3169ccbdab14cfe2bb12c6834d2e2782 Mon Sep 17 00:00:00 2001
From: cracyc <cracyc@users.noreply.github.com>
Date: Mon, 30 Dec 2019 09:56:24 -0600
Subject: [PATCH] i386: fix over/underflow result and zero div (nw)

---
 src/devices/cpu/i386/i386.h     |  2 +-
 src/devices/cpu/i386/x87ops.hxx | 32 ++++++++++++++++++++------------
 2 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/src/devices/cpu/i386/i386.h b/src/devices/cpu/i386/i386.h
index 5f3053f7571..e6fda6278bc 100644
--- a/src/devices/cpu/i386/i386.h
+++ b/src/devices/cpu/i386/i386.h
@@ -1357,7 +1357,7 @@ protected:
 	inline void x87_set_stack_overflow();
 	int x87_inc_stack();
 	int x87_dec_stack();
-	int x87_check_exceptions();
+	int x87_check_exceptions(bool store = false);
 	int x87_mf_fault();
 	inline void x87_write_cw(uint16_t cw);
 	void x87_reset();
diff --git a/src/devices/cpu/i386/x87ops.hxx b/src/devices/cpu/i386/x87ops.hxx
index cce3bc712a2..5ed9fcaf62d 100644
--- a/src/devices/cpu/i386/x87ops.hxx
+++ b/src/devices/cpu/i386/x87ops.hxx
@@ -150,7 +150,7 @@ uint32_t i386_device::Getx87EA(uint8_t modrm, int rwn)
 	return ret;
 }
 
-int i386_device::x87_check_exceptions()
+int i386_device::x87_check_exceptions(bool store)
 {
 	m_x87_cs = m_sreg[CS].selector;
 	if (PROTECTED_MODE && !V8086_MODE)
@@ -179,7 +179,13 @@ int i386_device::x87_check_exceptions()
 		m_x87_sw |= X87_SW_PE;
 		float_exception_flags &= ~float_flag_inexact;
 	}
+	if (float_exception_flags & float_flag_divbyzero)
+	{
+		m_x87_sw |= X87_SW_ZE;
+		float_exception_flags &= ~float_flag_divbyzero;
+	}
 
+	uint16_t unmasked = (m_x87_sw & ~m_x87_cw) & 0x3f;
 	if ((m_x87_sw & ~m_x87_cw) & 0x3f)
 	{
 		// m_device->execute().set_input_line(INPUT_LINE_FERR, RAISE_LINE);
@@ -187,6 +193,8 @@ int i386_device::x87_check_exceptions()
 		// interrupt handler
 		m_x87_sw |= X87_SW_ES;
 		m_ferr_handler(1);
+		if (store || !(unmasked & (X87_SW_OE | X87_SW_UE)))
+			return 0;
 	}
 
 	return 1;
@@ -2935,7 +2943,7 @@ void i386_device::x87_fst_m32real(uint8_t modrm)
 		value = ST(0);
 	}
 
-	if (x87_check_exceptions())
+	if (x87_check_exceptions(true))
 	{
 		uint32_t m32real = floatx80_to_float32(value);
 		WRITE32(ea, m32real);
@@ -2962,7 +2970,7 @@ void i386_device::x87_fst_m64real(uint8_t modrm)
 		value = ST(0);
 	}
 
-	if (x87_check_exceptions())
+	if (x87_check_exceptions(true))
 	{
 		uint64_t m64real = floatx80_to_float64(value);
 		WRITE64(ea, m64real);
@@ -3016,7 +3024,7 @@ void i386_device::x87_fstp_m32real(uint8_t modrm)
 		value = ST(0);
 	}
 
-	if (x87_check_exceptions())
+	if (x87_check_exceptions(true))
 	{
 		uint32_t m32real = floatx80_to_float32(value);
 		WRITE32(ea, m32real);
@@ -3045,7 +3053,7 @@ void i386_device::x87_fstp_m64real(uint8_t modrm)
 
 
 	uint32_t ea = Getx87EA(modrm, 1);
-	if (x87_check_exceptions())
+	if (x87_check_exceptions(true))
 	{
 		uint64_t m64real = floatx80_to_float64(value);
 		WRITE64(ea, m64real);
@@ -3073,7 +3081,7 @@ void i386_device::x87_fstp_m80real(uint8_t modrm)
 	}
 
 	uint32_t ea = Getx87EA(modrm, 1);
-	if (x87_check_exceptions())
+	if (x87_check_exceptions(true))
 	{
 		WRITE80(ea, value);
 		x87_inc_stack();
@@ -3139,7 +3147,7 @@ void i386_device::x87_fist_m16int(uint8_t modrm)
 	}
 
 	uint32_t ea = Getx87EA(modrm, 1);
-	if (x87_check_exceptions())
+	if (x87_check_exceptions(true))
 	{
 		WRITE16(ea, m16int);
 	}
@@ -3174,7 +3182,7 @@ void i386_device::x87_fist_m32int(uint8_t modrm)
 	}
 
 	uint32_t ea = Getx87EA(modrm, 1);
-	if (x87_check_exceptions())
+	if (x87_check_exceptions(true))
 	{
 		WRITE32(ea, m32int);
 	}
@@ -3209,7 +3217,7 @@ if (X87_IS_ST_EMPTY(0))
 	}
 
 	uint32_t ea = Getx87EA(modrm, 1);
-	if (x87_check_exceptions())
+	if (x87_check_exceptions(true))
 	{
 		WRITE16(ea, m16int);
 		x87_inc_stack();
@@ -3245,7 +3253,7 @@ void i386_device::x87_fistp_m32int(uint8_t modrm)
 	}
 
 	uint32_t ea = Getx87EA(modrm, 1);
-	if (x87_check_exceptions())
+	if (x87_check_exceptions(true))
 	{
 		WRITE32(ea, m32int);
 		x87_inc_stack();
@@ -3281,7 +3289,7 @@ void i386_device::x87_fistp_m64int(uint8_t modrm)
 	}
 
 	uint32_t ea = Getx87EA(modrm, 1);
-	if (x87_check_exceptions())
+	if (x87_check_exceptions(true))
 	{
 		WRITE64(ea, m64int);
 		x87_inc_stack();
@@ -3318,7 +3326,7 @@ void i386_device::x87_fbstp(uint8_t modrm)
 	}
 
 	uint32_t ea = Getx87EA(modrm, 1);
-	if (x87_check_exceptions())
+	if (x87_check_exceptions(true))
 	{
 		WRITE80(ea, result);
 		x87_inc_stack();