[LLVMbugs] [Bug 16882] New: unnecessary push/pop in small function

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=16882

            Bug ID: 16882
           Summary: unnecessary push/pop in small function
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: ARM
          Assignee: unassignedbugs at nondot.org
          Reporter: jay.foad at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 11034
  --> http://llvm.org/bugs/attachment.cgi?id=11034&action=edit
C source for testcase

On the attached test case I get:

$ clang -target armv6 -O2 -fomit-frame-pointer -S mul.c -o -
...
mul:
    push    {lr}
    smull    r0, r1, r1, r0
    teq    r1, r0, asr #31
    popeq    {lr}
    bxeq    lr
    bl    overflow

The push and popeq instructions are completely unnecessary.

I'm using LLVM and Clang built from svn r188366.

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