[PGO] Resubmit "MST based PGO instrumentation infrastructure" (r254021)

Description

[PGO] Resubmit "MST based PGO instrumentation infrastructure" (r254021)

This new patch fixes a few bugs that exposed in last submit. It also improves
the test cases.
--Original Commit Message--
This patch implements a minimum spanning tree (MST) based instrumentation for
PGO. The use of MST guarantees minimum number of CFG edges getting
instrumented. An addition optimization is to instrument the less executed
edges to further reduce the instrumentation overhead. The patch contains both the
instrumentation and the use of the profile to set the branch weights.

Differential Revision: http://reviews.llvm.org/D12781

Details

Committed
xurDec 9 2015, 10:08 AM
Differential Revision
D12781: PGO IR-level instrumentation infrastructure
Parents
rL255131: create 3 issues for testbots: FAIL, ERROR (exceptional), and TIMEOUT
Branches
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