Reapply "[MachineCopyPropagation] Reimplement CopyTracker in terms of register units"
Recommits r342942, which was reverted in r343189, with a fix for an
issue where we would propagate unsafely if we defined only the upper
part of a register.
Original message:
Change the copy tracker to keep a single map of register units
instead of 3 maps of registers. This gives a very significant
compile time performance improvement to the pass. I measured a
30-40% decrease in time spent in MCP on x86 and AArch64 and much
more significant improvements on out of tree targets with more
registers.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@344942
91177308-0d34-0410-b5e6-
96231b3b80d8
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