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

Fangrui Song maskray@google.com
Tue Nov 2 20:29:06 GMT 2021


On 2021-11-02, H.J. Lu wrote:
>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.

Thanks

Reviewed-by: Fangrui Song <maskray@google.com>


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