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From: "cptarse-luke at yahoo dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/111581] New: [arm-none-eabi-gcc] / suboptimal
 optimization /
Date: Mon, 25 Sep 2023 05:16:02 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Version: 9.3.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111581

            Bug ID: 111581
           Summary: [arm-none-eabi-gcc] / suboptimal optimization /
           Product: gcc
           Version: 9.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: cptarse-luke at yahoo dot com
  Target Milestone: ---

it seems like, i should have filed this separately:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111500

i think the uxth/sxth is superfluous here,
since nobody ever looks at the high half word...

> arm-none-eabi-gcc -v
Using built-in specs.
COLLECT_GCC=3Darm-none-eabi-gcc
COLLECT_LTO_WRAPPER=3D/usr/lib/gcc/arm-none-eabi/9.3.0/lto-wrapper
Target: arm-none-eabi
Configured with: ../configure --disable-decimal-float --disable-libffi
--disable-libgomp --disable-libmudflap --disable-libquadmath --disable-libs=
sp
--disable-libstdcxx-pch --disable-libstdc__-v3 --disable-nls --disable-shar=
ed
--disable-threads --disable-tls --disable-werror --enable-__cxa_atexit
--enable-c99 --enable-gnu-indirect-function --enable-interwork
--enable-languages=3Dc,c++ --enable-long-long --enable-multilib --enable-pl=
ugins
--host=3D --libdir=3D/usr/lib --libexecdir=3D/usr/lib --prefix=3D/usr
--target=3Darm-none-eabi --with-gmp --with-gnu-as --with-gnu-ld
--with-headers=3D/usr/arm-none-eabi/include --with-host-libstdcxx=3D'-stati=
c-libgcc
-Wl,-Bstatic,-lstdc++,-Bdynamic -lm' --with-isl --with-libelf --with-mpc
--with-mpfr --with-multilib-list=3Drmprofile
--with-native-system-header-dir=3D/include --with-newlib
--with-python-dir=3Dshare/gcc-arm-none-eabi --with-sysroot=3D/usr/arm-none-=
eabi
--with-system-zlib
Thread model: single
gcc version 9.3.0 (GCC)=20
> arm-none-eabi-gcc -save-temps -S a.c -O3 -g -mcpu=3Dcortex-m0plus -mthumb=
 -Wall --specs=3Dnosys.specs -nostdlib -fdata-sections -ffunction-sections =
-ffreestanding -Winline
> cat a.i
# 1 "a.c"
# 1 "/tmp//"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "a.c"
void artiSXTH(volatile short * a) {
 short b =3D *a;
 *a =3D b;
}
> cat a.s
artiSXTH:
        ldrh    r3, [r0]
        sxth    r3, r3
        strh    r3, [r0]
        bx      lr=