armemu: Fix underflows in USAD8/USADA8

Initially reported by xdec.

1 files changed, 9 insertions, 0 deletions

diff --git a/src/core/arm/interpreter/armsupp.cpp b/src/core/arm/interpreter/armsupp.cpp
index 6774f8a74..61639d156 100644
--- a/src/core/arm/interpreter/armsupp.cpp
+++ b/src/core/arm/interpreter/armsupp.cpp
@@ -392,6 +392,15 @@ ARMul_NthReg (ARMword instr, unsigned number)
     return (bit - 1);
 }
 
+/* Unsigned sum of absolute difference */
+u8 ARMul_UnsignedAbsoluteDifference(u8 left, u8 right)
+{
+        if (left > right)
+                return left - right;
+
+        return right - left;
+}
+
 /* Assigns the N and Z flags depending on the value of result.  */
 
 void