Adds support for Atom Silvermont (SLM) - -march=slm

Implements Instruction scheduler latencies for Silvermont,
using latencies from the Intel Silvermont Optimization Guide.

Auto detects SLM.

Turns on post RA scheduler when generating code for SLM.




git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190717 91177308-0d34-0410-b5e6-96231b3b80d8
Add missing break statement in PPCISelLowering

As it turns out, not a problem in practice, but it should be there.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190720 91177308-0d34-0410-b5e6-96231b3b80d8
Make PrettyStackTraceEntry use ManagedStatic for its ThreadLocal.

This was somewhat tricky because ~PrettyStackTraceEntry() may run after 
llvm_shutdown() has been called. This is rare and only happens for a common idiom 
used in the main() functions of command-line tools. This works around the idiom by 
skipping the stack clean-up if the PrettyStackTraceHead ManagedStatic is not 
constructed (i.e. llvm_shutdown() has been called).



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190730 91177308-0d34-0410-b5e6-96231b3b80d8