Commits on Aug 10, 2015

1. Remove morestack support …

   This commit removes all morestack support from the compiler which entails:
   
   * Segmented stacks are no longer emitted in codegen.
   * We no longer build or distribute libmorestack.a
   * The `stack_exhausted` lang item is no longer required
   
   The only current use of the segmented stack support in LLVM is to detect stack
   overflow. This is no longer really required, however, because we already have
   guard pages for all threads and registered signal handlers watching for a
   segfault on those pages (to print out a stack overflow message). Additionally,
   major platforms (aka Windows) already don't use morestack.
   
   This means that Rust is by default less likely to catch stack overflows because
   if a function takes up more than one page of stack space it won't hit the guard
   page. This is what the purpose of morestack was (to catch this case), but it's
   better served with stack probes which have more cross platform support and no
   runtime support necessary. Until LLVM supports this for all platform it looks
   like morestack isn't really buying us much.
   
   cc rust-lang#16012 (still need stack probes)
   Closes rust-lang#26458 (a drive-by fix to help diagnostics on stack overflow)

   

   alexcrichton committed Aug 10, 2015
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