December 2015
Beginner to intermediate
166 pages
3h 8m
English
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Legalizing SelectionDAG
In the preceding topic, we saw how an IR is converted to SelectionDAG. The whole process didn't involve any knowledge of target architecture for which we are trying to generate code. A DAG node might be illegal for the given target architecture. For example, the X86 architecture doesn't support the sdiv instruction. Instead, it supports sdivrem instruction. This target specific information is conveyed to the SelectionDAG phase by the TargetLowering interface. Targets implement this interface to describe how LLVM IR instructions should be lowered to legal SelectionDAG operations.
In our IR case, we need to 'expand' the sdiv instruction to 'sdivrem' instruction. In the function void SelectionDAGLegalize::LegalizeOp(SDNode ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.