Implement missing Short8 assignment operators

Bug b/129356087

Change-Id: Iab3325d74e783fd158b49ca8f6512641bf7f89ec
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/28008
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>

src/Reactor/Reactor.cpp

diff --git a/src/Reactor/Reactor.cpp b/src/Reactor/Reactor.cpp
index 185184d..559cb4f 100644
--- a/src/Reactor/Reactor.cpp
+++ b/src/Reactor/Reactor.cpp
@@ -1960,6 +1960,29 @@
 		storeValue(packed);
 	}
 
+	RValue<Short8> Short8::operator=(RValue<Short8> rhs)
+	{
+		storeValue(rhs.value);
+
+		return rhs;
+	}
+
+	RValue<Short8> Short8::operator=(const Short8 &rhs)
+	{
+		Value *value = rhs.loadValue();
+		storeValue(value);
+
+		return RValue<Short8>(value);
+	}
+
+	RValue<Short8> Short8::operator=(const Reference<Short8> &rhs)
+	{
+		Value *value = rhs.loadValue();
+		storeValue(value);
+
+		return RValue<Short8>(value);
+	}
+
 	RValue<Short8> operator+(RValue<Short8> lhs, RValue<Short8> rhs)
 	{
 		return RValue<Short8>(Nucleus::createAdd(lhs.value, rhs.value));