May 2015
Intermediate to advanced
296 pages
5h 10m
English
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Eliminating common subexpression from machine code
The aim of the CSE algorithm is to eliminate common subexpressions to make machine code compact and remove unnecessary, duplicate code. Let's look at the code in the LLVM trunk to understand how it is implemented. The detailed code is in the lib/CodeGen/MachineCSE.cpp file.
How to do it…
- The
MachineCSEclass runs on a machine function, and hence it should inherit theMachineFunctionPassclass. It has various members, such asTargetInstructionInfo, which is used to get information about the target instruction (used in performing CSE);TargetRegisterInfo, which is used to get information about the target register (whether it belongs to a reserved register class, or to more such similar classes; and ...
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