[LLVMbugs] [Bug 2218] New: memcpyopt fails to eliminate pointless memcpy's

bugzilla-daemon at cs.uiuc.edu bugzilla-daemon at cs.uiuc.edu
Fri Apr 11 08:24:11 PDT 2008


           Summary: memcpyopt fails to eliminate pointless memcpy's
           Product: new-bugs
           Version: unspecified
          Platform: Other
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: baldrick at free.fr
                CC: resistor at mac.com, llvmbugs at cs.uiuc.edu

Created an attachment (id=1590)
 --> (http://llvm.org/bugs/attachment.cgi?id=1590)
testcase .ll

Here's the testcase (also attached).  %pointless could be
eliminated since no use is ever made of it except as a
memcpy target.  %temporary could also be eliminated in
favour of passing %result directly to the @initialize call.

define void @f(i8* noalias sret  %result) {
        %temporary = alloca i8          ; <i8*> [#uses=3]
        %pointless = alloca i8          ; <i8*> [#uses=1]
        call void @initialize( i8* noalias sret  %temporary )
        call void @llvm.memcpy.i32( i8* %pointless, i8* %temporary, i32 1, i32
4 )
        call void @llvm.memcpy.i32( i8* %result, i8* %temporary, i32 1, i32 4 )
        ret void

declare void @initialize(i8* noalias sret )
declare void @llvm.memcpy.i32(i8*, i8*, i32, i32) nounwind

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