[LLVMbugs] [Bug 9417] New: memset not created out of per-field store instructions

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Sun Mar 6 23:19:37 PST 2011


           Summary: memset not created out of per-field store instructions
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Loop Optimizer
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: nlewycky at google.com
                CC: llvmbugs at cs.uiuc.edu

Created an attachment (id=6287)
 --> (http://llvm.org/bugs/attachment.cgi?id=6287)
testcase .ll

The attached file is a .ll with a simple loop doing 3 stores of 0 to each
member in @glbl. Loop idiom recognizer won't merge it because each store has a
stride larger than the width of the store.

Who's responsible for merging:

  A = gep foo, 0
  B = gep foo, 1
  store 0, A
  store 0, B

into one store/memset instruction?

This is pulled from MultiSource/Benchmarks/Ptrdist/ks which has gcc/llc = 0.46
on x86-64 linux.

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