[LLVMbugs] [Bug 4273] New: Top-down list schedulers do not support physreg dependencies

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=4273

           Summary: Top-down list schedulers do not support physreg
                    dependencies
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Common Code Generator Code
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: asl at math.spbu.ru
                CC: llvmbugs at cs.uiuc.edu


Currently when scheduling for latency (and thus - via topdown list schedulers)
I need to always flag comparison to conditional branch since it's impossible to
reuse the status register due to lack of physreg dependencies.

This is quite unfortunate and yields ugly code :(

I think one can easily reproduce the problem with x86 backend codegen'ing
something like select_cc / br_cc and changing default (pre-RA) scheduler to
list-td


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