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  • Delay slot filler. Is that legal instruction to have ??

    From Umesh Kalappa@21:1/5 to All on Thu Oct 25 15:50:30 2018
    Hi All,

    For the below C code

    Test.u32pt = u32PtLen;
    Test.u32pn = u32PtCnt;
    Test.pstpk = pstPt;
    Test.psteo = pstEgrInfo;
    Test.e = 1;
    Test.pstfi = pstFi ;

    return foo(&Test, AclAction);

    where "Test" is the struct type .

    the generated code for mips (with -fno-delayed-branch) :

    Test.u32pt = u32PtLen;
    370: afb50084 sw s5,132(sp)
    Test.u32pn = u32PtCnt;
    374: afb60080 sw s6,128(sp)
    Test.pstpk = pstPt;
    Test.psteo = pstEgrInfo;
    Test.e = 1;
    Test.pstfi = pstFi ;

    return foo(&Test, AclAction)
    378: 0c000000 jal 0 <FSVC_Egr_L4ACLfoo>
    37c: 00000000 nop

    with -fdelayed-branch(gcc 4.8.1) the generated code is

    Test.u32pt = u32PtLen;
    370: afb50084 sw s5,132(sp)
    Test.pstpk = pstPt;
    Test.psteo = pstEgrInfo;
    Test.e = 1;
    Test.pstfi = pstFi ;

    return foo(&Test, AclAction)
    378: 0c000000 jal 0 <FSVC_Egr_L4ACLfoo>
    Test.u32pn = u32PtCnt;
    374: afb60080 sw s6,128(sp)

    can filler place the "sw s6,128(sp)" in the delay slot ,is
    that legal and if not why it so ?

    Thank you
    ~Umesh

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