This patch implements support for embedding symbols in the array of large constants inside a stackmap/patchpoint.
We (=Pyston project) embed in the LLVM IR we generate a lot of pointers to external constants. I would like to cache the JITed functions and therefore I need to make the embedded constants relocatable -> change the IR to refer to module variables instead which I can replace when loading the cached object.
Currently when a patchpoint has a constant variable as live argument it will materialize it in a register. Which we don't want because the live variables are rarely used (also the regalloc runs out of registers when having to many const variables as argument to the pp?!?... I filled PR23306).
This patch emits a symbol reference inside the array of large constants in the stackmap. The stack map format is untouched by this patch.
Together with http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20150330/269160.html this should make it possible to cache more JITed functions containing patchpoints.