1 Commits

Author	SHA1	Message	Date
Evan Cheng	8f90b6eb2f	The coalescer does not coalesce a virtual register to a physical register if any of the physical register's sub-register live intervals overlaps with the virtual register. This is overly conservative. It prevents a extract_subreg from being coalesced away: ... v1024 = EDI // not killed = = EDI One possible solution is for the coalescer to examine the sub-register live intervals in the same manner as the physical register. Another possibility is to examine defs and uses (when needed) of sub-registers. Both solutions are too expensive. For now, look for "short virtual intervals" and scan instructions to look for conflict instead. This is a small win on x86-64. e.g. It shaves 403.gcc by ~80 instructions. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61847 91177308-0d34-0410-b5e6-96231b3b80d8	2009-01-07 02:08:57 +00:00