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author | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2021-11-06 09:38:09 -0300 |
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committer | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2021-11-22 14:49:11 -0300 |
commit | aac54dcd378209bbdddbcec749561b1d8f167d11 (patch) | |
tree | 5f3102ec38089693210ca3a9d6a7369a3fa54129 /sysdeps/powerpc/powerpc64/configure | |
parent | bc801b3a40f3a9bc8f24f1d0fdc39413874c3172 (diff) | |
download | glibc-aac54dcd378209bbdddbcec749561b1d8f167d11.tar.gz glibc-aac54dcd378209bbdddbcec749561b1d8f167d11.tar.xz glibc-aac54dcd378209bbdddbcec749561b1d8f167d11.zip |
powerpc: Define USE_PPC64_NOTOC iff compiler supports it
The @notoc usage only yields an advantage on ISA 3.1+ machine (power10) and for ld.bfd also when it sees pcrel relocations used on the code (generated if compiler targets ISA 3.1+). On bfd case ISA 3.1+ instruction on stubs are used iff linker also sees the new pc-relative relocations (for instance R_PPC64_D34), otherwise it generates default stubs (ppc64_elf_check_relocs:4700). This patch also help on linkers that do not implement this optimization, since building for older ISA (such as 3.0 / power9) will also trigger power10 stubs generation in the assembly code uses the NOTOC imacro. Checked on powerpc64le-linux-gnu. Reviewed-by: Fangrui Song <maskray@google.com> Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
Diffstat (limited to 'sysdeps/powerpc/powerpc64/configure')
-rw-r--r-- | sysdeps/powerpc/powerpc64/configure | 42 |
1 files changed, 26 insertions, 16 deletions
diff --git a/sysdeps/powerpc/powerpc64/configure b/sysdeps/powerpc/powerpc64/configure index 5ce77af631..fddea0355a 100644 --- a/sysdeps/powerpc/powerpc64/configure +++ b/sysdeps/powerpc/powerpc64/configure @@ -32,26 +32,36 @@ if test x$libc_cv_overlapping_opd = xyes; then fi -# @notoc started to be supported in GNU Binutils 2.31. - -{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if the assembler supports @notoc" >&5 -$as_echo_n "checking if the assembler supports @notoc... " >&6; } +# We check if compiler supports @notoc generation since there is no +# gain by enabling it if it will be optimized away by the linker. +# It also helps linkers that might not optimize it and end up +# generating stubs with ISA 3.1 instruction even targetting older ISA. +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if the compiler supports @notoc" >&5 +$as_echo_n "checking if the compiler supports @notoc... " >&6; } if ${libc_cv_ppc64_notoc+:} false; then : $as_echo_n "(cached) " >&6 else - - cat confdefs.h - <<_ACEOF >conftest.$ac_ext -/* end confdefs.h. */ - -void foo (void) {asm("b foo@notoc");} - -_ACEOF -if ac_fn_c_try_compile "$LINENO"; then : - libc_cv_ppc64_notoc=yes -else + cat > conftest.c <<EOF +int bar (void); +int foo (void) { return bar () + 1; } +EOF libc_cv_ppc64_notoc=no -fi -rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext + if { ac_try='${CC-cc} $libc_cv_cc_submachine $CFLAGS $CPPFLAGS -S -o conftest.s conftest.c' + { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5 + (eval $ac_try) 2>&5 + ac_status=$? + $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5 + test $ac_status = 0; }; } \ + && { ac_try='grep -q -E 'bar@notoc' conftest.s' + { { eval echo "\"\$as_me\":${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_ppc64_notoc=yes + fi + rm -rf conftest.* fi { $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_ppc64_notoc" >&5 $as_echo "$libc_cv_ppc64_notoc" >&6; } |