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Honored Contributor
Honored ContributorUnnecessary instructions
Hello, it's my first post. I have question about GCC generated code. We can find several unnecessary instructions. --- sample code --- unsigned short uh; uh = IORD_16DIRECT(base,ofst)...
Altera_ForumHonored Contributor
Honored ContributorDear marm,
This is on our list of things to try to improve over the long term (i.e. not Nios II 1.1). The issue that James is referring to is unrelated and has to do with volatile accesses of bitfields. The reason it is lower priority is that the optimization does not affect the normal use of these operations. I think the confusion here comes from the definition of the __builtin_ldXio family of functions. They all return values of type "int". Therefore when you assign it to a short or byte data type, the compiler needs to safely truncate it to that value. Therefore, the correct thing to do is store the returned value in an int and operate with it in that mode. It is almost always better to use int as the data type because it is the fastest data type to operate on. Does that make sense? Jonah
