[LLVMbugs] [Bug 6652] New: ARMv4: missed optimization for LDM + return

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Thu Mar 18 15:56:32 PDT 2010


           Summary: ARMv4: missed optimization for LDM + return
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: ARM
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: john at bass-software.com
                CC: llvmbugs at cs.uiuc.edu

Created an attachment (id=4546)
 --> (http://llvm.org/bugs/attachment.cgi?id=4546)
Patch and test case to merge return into ldm for ARMv4 output

Recent ARMv4 support is missing the optimization to merge:

  ldmfd sp!, {..., lr}
  mov pc, lr


  ldmfd sp!, {..., pc}

In ARMv5 mode this was already happening.  Attached a small patch and test case
for ARMLoadStoreOpt::MergeReturnIntoLDM() doing this optimization for ARMv4.

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