Re: [PATCH] riscv: Build with -mno-relax if linker does not support R_RISCV_ALIGN

["H.J. Lu" <hjl.tools@gmail.com>]

On Tue, Nov 2, 2021 at 12:57 PM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
> It allows build both glibc and tests with lld (Since lld does not
> support R_RISCV_ALIGN linker relaxation).
>
> Checked with a build for riscv32-linux-gnu-rv32imafdc-ilp32d and
> riscv64-linux-gnu-rv64imafdc-lp64d.
> ---
>  sysdeps/riscv/Makefile     |  6 ++++++
>  sysdeps/riscv/configure    | 30 ++++++++++++++++++++++++++++++
>  sysdeps/riscv/configure.ac | 16 ++++++++++++++++
>  3 files changed, 52 insertions(+)
>
> diff --git a/sysdeps/riscv/Makefile b/sysdeps/riscv/Makefile
> index 20a9968106..8fb10b164f 100644
> --- a/sysdeps/riscv/Makefile
> +++ b/sysdeps/riscv/Makefile
> @@ -5,3 +5,9 @@ endif
>  # RISC-V's assembler also needs to know about PIC as it changes the definition
>  # of some assembler macros.
>  ASFLAGS-.os += $(pic-ccflag)
> +
> +ifeq (no,$(riscv-r-align))
> +ASFLAGS-.os += -Wa,-mno-relax
> +ASFLAGS-.o += -Wa,-mno-relax
> +sysdep-CFLAGS += -mno-relax
> +endif
> diff --git a/sysdeps/riscv/configure b/sysdeps/riscv/configure
> index 53f5f1b5f1..4a56fca94b 100644
> --- a/sysdeps/riscv/configure
> +++ b/sysdeps/riscv/configure
> @@ -2,3 +2,33 @@
>   # Local configure fragment for sysdeps/riscv/elf.
>
>  $as_echo "#define PI_STATIC_AND_HIDDEN 1" >>confdefs.h
> +
> +
> +# Check if static linker supports R_RISCV_ALIGN
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for R_RISCV_ALIGN linker relaxation support" >&5
> +$as_echo_n "checking for R_RISCV_ALIGN linker relaxation support... " >&6; }
> +if ${libc_cv_riscv_r_align+:} false; then :
> +  $as_echo_n "(cached) " >&6
> +else
> +    cat > conftest.S <<EOF
> +.align 3
> +foo:
> +  li a0,42
> +  ret
> +EOF
> +  libc_cv_riscv_r_align=no
> +  if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -nostdlib -nostartfiles $no_ssp -shared -fPIC -o contests.o conftest.S'
> +  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
> +  (eval $ac_try) 2>&5
> +  ac_status=$?
> +  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
> +  test $ac_status = 0; }; }
> +  then
> +    libc_cv_riscv_r_align=yes
> +  fi
> +  rm -rf conftest.*
> +fi
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_riscv_r_align" >&5
> +$as_echo "$libc_cv_riscv_r_align" >&6; }
> +config_vars="$config_vars
> +riscv-r-align = $libc_cv_riscv_r_align"
> diff --git a/sysdeps/riscv/configure.ac b/sysdeps/riscv/configure.ac
> index 34f62d4b4b..44a5279903 100644
> --- a/sysdeps/riscv/configure.ac
> +++ b/sysdeps/riscv/configure.ac
> @@ -2,3 +2,19 @@ GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
>  # Local configure fragment for sysdeps/riscv/elf.
>
>  AC_DEFINE(PI_STATIC_AND_HIDDEN)
> +
> +# Check if static linker supports R_RISCV_ALIGN
> +AC_CACHE_CHECK([for R_RISCV_ALIGN linker relaxation support], [libc_cv_riscv_r_align],[dnl
> +  cat > conftest.S <<EOF
> +.align 3
> +foo:
> +  li a0,42
> +  ret
> +EOF
> +  libc_cv_riscv_r_align=no
> +  if AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -nostdlib -nostartfiles $no_ssp -shared -fPIC -o contests.o conftest.S])
> +  then
> +    libc_cv_riscv_r_align=yes
> +  fi
> +  rm -rf conftest.*])
> +LIBC_CONFIG_VAR([riscv-r-align], [$libc_cv_riscv_r_align])
> --
> 2.32.0
>

LGTM.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

Thanks.

-- 
H.J.