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/* armsupp.c -- ARMulator support code: ARM6 Instruction Emulator.
Copyright (C) 1994 Advanced RISC Machines Ltd.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
#include "core/arm/skyeye_common/armdefs.h"
// Unsigned sum of absolute difference
u8 ARMul_UnsignedAbsoluteDifference(u8 left, u8 right)
{
if (left > right)
return left - right;
return right - left;
}
// Add with carry, indicates if a carry-out or signed overflow occurred.
u32 AddWithCarry(u32 left, u32 right, u32 carry_in, bool* carry_out_occurred, bool* overflow_occurred)
{
u64 unsigned_sum = (u64)left + (u64)right + (u64)carry_in;
s64 signed_sum = (s64)(s32)left + (s64)(s32)right + (s64)carry_in;
u64 result = (unsigned_sum & 0xFFFFFFFF);
if (carry_out_occurred)
*carry_out_occurred = (result != unsigned_sum);
if (overflow_occurred)
*overflow_occurred = ((s64)(s32)result != signed_sum);
return (u32)result;
}
// Compute whether an addition of A and B, giving RESULT, overflowed.
bool AddOverflow(ARMword a, ARMword b, ARMword result)
{
return ((NEG(a) && NEG(b) && POS(result)) ||
(POS(a) && POS(b) && NEG(result)));
}
// Compute whether a subtraction of A and B, giving RESULT, overflowed.
bool SubOverflow(ARMword a, ARMword b, ARMword result)
{
return ((NEG(a) && POS(b) && POS(result)) ||
(POS(a) && NEG(b) && NEG(result)));
}
// Returns true if the Q flag should be set as a result of overflow.
bool ARMul_AddOverflowQ(ARMword a, ARMword b)
{
u32 result = a + b;
if (((result ^ a) & (u32)0x80000000) && ((a ^ b) & (u32)0x80000000) == 0)
return true;
return false;
}
// 8-bit signed saturated addition
u8 ARMul_SignedSaturatedAdd8(u8 left, u8 right)
{
u8 result = left + right;
if (((result ^ left) & 0x80) && ((left ^ right) & 0x80) == 0) {
if (left & 0x80)
result = 0x80;
else
result = 0x7F;
}
return result;
}
// 8-bit signed saturated subtraction
u8 ARMul_SignedSaturatedSub8(u8 left, u8 right)
{
u8 result = left - right;
if (((result ^ left) & 0x80) && ((left ^ right) & 0x80) != 0) {
if (left & 0x80)
result = 0x80;
else
result = 0x7F;
}
return result;
}
// 16-bit signed saturated addition
u16 ARMul_SignedSaturatedAdd16(u16 left, u16 right)
{
u16 result = left + right;
if (((result ^ left) & 0x8000) && ((left ^ right) & 0x8000) == 0) {
if (left & 0x8000)
result = 0x8000;
else
result = 0x7FFF;
}
return result;
}
// 16-bit signed saturated subtraction
u16 ARMul_SignedSaturatedSub16(u16 left, u16 right)
{
u16 result = left - right;
if (((result ^ left) & 0x8000) && ((left ^ right) & 0x8000) != 0) {
if (left & 0x8000)
result = 0x8000;
else
result = 0x7FFF;
}
return result;
}
// 8-bit unsigned saturated addition
u8 ARMul_UnsignedSaturatedAdd8(u8 left, u8 right)
{
u8 result = left + right;
if (result < left)
result = 0xFF;
return result;
}
// 16-bit unsigned saturated addition
u16 ARMul_UnsignedSaturatedAdd16(u16 left, u16 right)
{
u16 result = left + right;
if (result < left)
result = 0xFFFF;
return result;
}
// 8-bit unsigned saturated subtraction
u8 ARMul_UnsignedSaturatedSub8(u8 left, u8 right)
{
if (left <= right)
return 0;
return left - right;
}
// 16-bit unsigned saturated subtraction
u16 ARMul_UnsignedSaturatedSub16(u16 left, u16 right)
{
if (left <= right)
return 0;
return left - right;
}
// Signed saturation.
u32 ARMul_SignedSatQ(s32 value, u8 shift, bool* saturation_occurred)
{
const u32 max = (1 << shift) - 1;
const s32 top = (value >> shift);
if (top > 0) {
*saturation_occurred = true;
return max;
}
else if (top < -1) {
*saturation_occurred = true;
return ~max;
}
*saturation_occurred = false;
return (u32)value;
}
// Unsigned saturation
u32 ARMul_UnsignedSatQ(s32 value, u8 shift, bool* saturation_occurred)
{
const u32 max = (1 << shift) - 1;
if (value < 0) {
*saturation_occurred = true;
return 0;
} else if ((u32)value > max) {
*saturation_occurred = true;
return max;
}
*saturation_occurred = false;
return (u32)value;
}
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