[Bug target/52898] New: SH Target: Inefficient comparison of DImode and immediate constant

olegendo at gcc dot gnu.org gcc-bugzilla@gcc.gnu.org
Sat Apr 7 11:18:00 GMT 2012


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52898

             Bug #: 52898
           Summary: SH Target: Inefficient comparison of DImode and
                    immediate constant
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: olegendo@gcc.gnu.org
            Target: sh*-*-*


The following ...

int test (long long a)
{
  return a == 40;
}

compiled with -O2, -O3, -Os:

        mov     #0,r2
        cmp/eq  r2,r4
        bf/s   .L38
        mov     #40,r3
        cmp/eq  r3,r5
.L38:
        rts
        movt    r0


would be better as:

    mov     #40,r3
    tst     r4,r4   ! use tst to compare against zero
    bf      .L38    ! use zero-displacement branch
    cmp/eq  r3,r5
.L38:
    rts
    movt    r0




Using built-in specs.
COLLECT_GCC=sh-elf-gcc
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/sh-elf/4.8.0/lto-wrapper
Target: sh-elf
Configured with: ../gcc-trunk/configure --target=sh-elf --prefix=/usr/local
--enable-languages=c,c++ --enable-multilib --disable-libssp --disable-nls
--disable-werror --enable-lto --with-newlib --with-gnu-as --with-gnu-ld
--with-system-zlib
Thread model: single
gcc version 4.8.0 20120406 (experimental) (GCC)



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