[Bug rtl-optimization/17576] New: poor optimization of calls to function objects

[sebor at roguewave dot com]

For the program below, the 3.4.0 optimizer generates the following suboptimal
code on SPARC. The specialization of bar() is as much as 10% slower or more
than foo() in my tests.

template <class T>
struct S
{
    bool operator() (const T &a, const T &b) const {
        return a < b;
    }
};

const int* foo (const int *a, const int *b)
{
    const int* c = a;

    for (; !(a == b); ++a)
        if (*c < *a)
            c = a;

    return c;
}

template <class F>
const int* bar (const int *a, const int *b, F f)
{
    const int* c = a;

    for (; !(a == b); ++a)
        if (f (*c, *a))
            c = a;

    return c;
}

template const int* bar (const int *a, const int *b, S<int>);



        .file   "t.cpp"
        .section        ".text"
        .align 4
        .global _Z3fooPKiS0_
        .type   _Z3fooPKiS0_, #function
        .proc   0104
_Z3fooPKiS0_:
.LLFB3:
        !#PROLOGUE# 0
        !#PROLOGUE# 1
        cmp     %o0, %o1
        be      .LL8
        mov     %o0, %o4
        ld      [%o4], %o5
.LL14:
        ld      [%o0], %g1
        cmp     %o5, %g1
        bl,a    .LL4
        mov     %o0, %o4
.LL4:
        add     %o0, 4, %o0
        cmp     %o0, %o1
        bne,a   .LL14
        ld      [%o4], %o5
.LL8:
        retl
        mov     %o4, %o0
.LLFE3:
        .size   _Z3fooPKiS0_, .-_Z3fooPKiS0_
        .section        ".gnu.linkonce.t._Z3barI1SIiEEPKiS3_S3_T_",#alloc,#execinstr
        .align 4
        .weak   _Z3barI1SIiEEPKiS3_S3_T_
        .type   _Z3barI1SIiEEPKiS3_S3_T_, #function
        .proc   0104
_Z3barI1SIiEEPKiS3_S3_T_:
.LLFB5:
        !#PROLOGUE# 0
        !#PROLOGUE# 1
        cmp     %o0, %o1
        be      .LL24
        mov     %o0, %o4
        ld      [%o0], %g1
.LL29:
        ld      [%o4], %o5
        cmp     %o5, %g1
        bl      .LL21
        mov     1, %g1
        mov     0, %g1
.LL21:
        cmp     %g1, 0
        bne,a   .LL18
        mov     %o0, %o4
.LL18:
        add     %o0, 4, %o0
        cmp     %o0, %o1
        bne,a   .LL29
        ld      [%o0], %g1
.LL24:
        retl
        mov     %o4, %o0
.LLFE5:
        .size   _Z3barI1SIiEEPKiS3_S3_T_, .-_Z3barI1SIiEEPKiS3_S3_T_
        .ident  "GCC: (GNU) 3.4.0"

-- 
           Summary: poor optimization of calls to function objects
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: sebor at roguewave dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: sparc-sun-solaris2.7
  GCC host triplet: sparc-sun-solaris2.7
GCC target triplet: sparc-sun-solaris2.7


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17576