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34786a3ad7
Reserved registers don't have proper live ranges, their LiveInterval simply has a snippet of liveness for each def. Virtual registers with a single value that is a copy of a reserved register (typically %esp) can be coalesced with the reserved register if the live range doesn't overlap any reserved register defs. When coalescing with a reserved register, don't modify the reserved register live range. Just leave it as a bunch of dead defs. This eliminates quadratic coalescer behavior in i386 functions with many function calls. PR11699 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@147726 91177308-0d34-0410-b5e6-96231b3b80d8