private SourceType getMostTrustedParameterSource(Function func) {
		SourceType highestSource = func.getSignatureSource();
		Parameter[] parameters = func.getParameters();
		for (Parameter parameter : parameters) {
			SourceType paramSource = parameter.getSource();
			if (paramSource.isHigherPriorityThan(highestSource)) {
				highestSource = paramSource;
			}
		}
		return highestSource;
	}
Get the instruction directly before this address, makeing sure it is the
head instruction in a delayslot

@param address to get instruction before
@return instruction if found, null otherwise
Ghidra/Features/Base/src/main/java/ghidra/app/cmd/function/ApplyFunctionDataTypesCmd.java