Some compiler/toolchain readings / resources:
The GCC Python Plugin: http://gcc-python-plugin.readthedocs.io/en/latest/index.html - useful tool for exploring GCC without spending too much time in C! :-)
20-part series on Linkers by Ian Lance Taylor: https://lwn.net/Articles/276782/ - covers many aspects of static and dynamic linking, is quite brief on many topics
GCC for new contributors: https://dmalcolm.fedorapeople.org/gcc/newbies-guide/index.html -practical advice for working on GCC
The GCC Internals guide: https://gcc.gnu.org/onlinedocs/gccint/ - very useful reference for looking up, but not a good tutorial starting point
Essential abstractions in GCC course slides, exercises, notes: https://www.cse.iitb.ac.in/grc/gcc-workshop-13/ - a little dated now but still excellent starting point for understanding GCC
RISC-V LLVM patches: https://github.com/lowRISC/riscv-llvm - nice series of patches for understanding how to add a backend to LLVM
Embecosm application notes: http://www.embecosm.com/resources/appnotes/ - in particular EAN 8 on DejaGNU, EAN 10 on implementing LLVM Integrated assembler (note/disclaimer: I work for Embecosm)
... err, that's the ones I can think of off the top of my head. More later if they come to mind.
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