Re: [PATCH 1/1] LoongArch: Fix ptr mangling/demangling features.

[Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>]

On 29/08/22 04:08, Xi Ruoyao wrote:
> I'm OK with either this or the simplified version w/o ac check.
> 
> Not sure about Glibc policy about committing a change (does a port
> maintainer needs approval to commit a change within this port?)

Afaik as long the arch-maintainer is ok with the change and there is
no blocker it should be ok to push.  I stil prefer to just use la.pcrel,
since it way simpler and I am really sceptical that using pcalau12i will
yield any real performance difference, but it is not a blocker from my
part.

> 
> On Fri, 2022-08-26 at 16:03 +0800, caiyinyu wrote:
>> Co-authored-by: Xi Ruoyao <xry111@xry111.site>
>> ---
>>  config.h.in                                |  3 ++
>>  sysdeps/loongarch/__longjmp.S              |  2 +-
>>  sysdeps/loongarch/configure                | 26 ++++++++++++++
>>  sysdeps/loongarch/configure.ac             | 14 ++++++++
>>  sysdeps/loongarch/setjmp.S                 |  2 +-
>>  sysdeps/unix/sysv/linux/loongarch/sysdep.h | 40 +++++++++++++--------
>> -
>>  6 files changed, 68 insertions(+), 19 deletions(-)
>>
>> diff --git a/config.h.in b/config.h.in
>> index 43d32518ab..b182de0e91 100644
>> --- a/config.h.in
>> +++ b/config.h.in
>> @@ -138,6 +138,9 @@
>>  /* LOONGARCH floating-point ABI for ld.so.  */
>>  #undef LOONGARCH_ABI_FRLEN
>>  
>> +/* To Indicate whether we can use explicit relocs or not.  */
>> +#undef HAVE_LOONGARCH_EXPLICIT_RELOCS
>> +
>>  /* Linux specific: minimum supported kernel version.  */
>>  #undef __LINUX_KERNEL_VERSION
>>  
>> diff --git a/sysdeps/loongarch/__longjmp.S
>> b/sysdeps/loongarch/__longjmp.S
>> index c2c5b56a80..4207376f5e 100644
>> --- a/sysdeps/loongarch/__longjmp.S
>> +++ b/sysdeps/loongarch/__longjmp.S
>> @@ -22,7 +22,7 @@
>>  ENTRY (__longjmp)
>>  #ifdef PTR_MANGLE
>>         REG_L t0, a0, 0*SZREG
>> -       PTR_DEMANGLE (ra, t0, t1, t2)
>> +       PTR_DEMANGLE (ra, t0, t1)
>>         REG_L t0, a0, 1*SZREG
>>         PTR_DEMANGLE2 (sp, t0, t1)
>>  #else
>> diff --git a/sysdeps/loongarch/configure b/sysdeps/loongarch/configure
>> index 43b54d4965..54385786d2 100644
>> --- a/sysdeps/loongarch/configure
>> +++ b/sysdeps/loongarch/configure
>> @@ -3,3 +3,29 @@
>>  
>>  $as_echo "#define HIDDEN_VAR_NEEDS_DYNAMIC_RELOC 1" >>confdefs.h
>>  
>> +
>> +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether explicit
>> relocs can be used" >&5
>> +$as_echo_n "checking whether explicit relocs can be used... " >&6; }
>> +if ${libc_cv_loongarch_explicit_relocs+:} false; then :
>> +  $as_echo_n "(cached) " >&6
>> +else
>> +  cat > conftest.s << EOF
>> +x: pcalau12i \$t0, %pc_hi20(x)
>> +EOF
>> +libc_cv_loongarch_explicit_relocs=no
>> +if { ac_try='${CC-cc} -c $CFLAGS conftest.s -o conftest.o 1>&5'
>> +  { { eval echo "\"\$as_me\":${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_loongarch_explicit_relocs=yes
>> +fi
>> +rm -f conftest*
>> +fi
>> +{ $as_echo "$as_me:${as_lineno-$LINENO}: result:
>> $libc_cv_loongarch_explicit_relocs" >&5
>> +$as_echo "$libc_cv_loongarch_explicit_relocs" >&6; }
>> +if test $libc_cv_loongarch_explicit_relocs = yes; then
>> +  $as_echo "#define HAVE_LOONGARCH_EXPLICIT_RELOCS 1" >>confdefs.h
>> +
>> +fi
>> diff --git a/sysdeps/loongarch/configure.ac
>> b/sysdeps/loongarch/configure.ac
>> index f744367bf3..c5d3cb5ead 100644
>> --- a/sysdeps/loongarch/configure.ac
>> +++ b/sysdeps/loongarch/configure.ac
>> @@ -4,3 +4,17 @@ GLIBC_PROVIDES dnl See aclocal.m4 in the top level
>> source directory.
>>  dnl It is always possible to access static and hidden symbols in an
>>  dnl position independent way.
>>  AC_DEFINE(HIDDEN_VAR_NEEDS_DYNAMIC_RELOC)
>> +
>> +AC_CACHE_CHECK(whether explicit relocs can be used,
>> +               libc_cv_loongarch_explicit_relocs, [dnl
>> +cat > conftest.s << EOF
>> +x: pcalau12i \$t0, %pc_hi20(x)
>> +EOF
>> +libc_cv_loongarch_explicit_relocs=no
>> +if AC_TRY_COMMAND(${CC-cc} -c $CFLAGS conftest.s -o conftest.o
>> 1>&AS_MESSAGE_LOG_FD); then
>> +  libc_cv_loongarch_explicit_relocs=yes
>> +fi
>> +rm -f conftest*])
>> +if test $libc_cv_loongarch_explicit_relocs = yes; then
>> +  AC_DEFINE(HAVE_LOONGARCH_EXPLICIT_RELOCS)
>> +fi
>> diff --git a/sysdeps/loongarch/setjmp.S b/sysdeps/loongarch/setjmp.S
>> index ec4ddc72da..298bb02a82 100644
>> --- a/sysdeps/loongarch/setjmp.S
>> +++ b/sysdeps/loongarch/setjmp.S
>> @@ -30,7 +30,7 @@ END (setjmp)
>>  
>>  ENTRY (__sigsetjmp)
>>  #ifdef PTR_MANGLE
>> -       PTR_MANGLE (t0, ra, t1, t2)
>> +       PTR_MANGLE (t0, ra, t1)
>>         REG_S t0, a0, 0*SZREG
>>         PTR_MANGLE2 (t0, sp, t1)
>>         REG_S t0, a0, 1*SZREG
>> diff --git a/sysdeps/unix/sysv/linux/loongarch/sysdep.h
>> b/sysdeps/unix/sysv/linux/loongarch/sysdep.h
>> index 157cbd6c6b..0a8773c38d 100644
>> --- a/sysdeps/unix/sysv/linux/loongarch/sysdep.h
>> +++ b/sysdeps/unix/sysv/linux/loongarch/sysdep.h
>> @@ -316,29 +316,35 @@ extern long int __syscall_error (long int
>> neg_errno);
>>  
>>  /* Pointer mangling is supported for LoongArch.  */
>>  
>> -/* Load or store to/from a got-relative EXPR into/from G, using T.
>> +/* Load a got-relative EXPR into G, using T.
>>     Note G and T are register names.  */
>> -#define LDST_GLOBAL(OP, G, T,  EXPR) \
>> -  pcalau12i T, %got_pc_hi20(EXPR); \
>> -  OP       T, T, %got_pc_lo12(EXPR); \
>> -  OP       G, T, 0;
>> +#define LD_GLOBAL(G, EXPR) \
>> +  la.global G, EXPR; \
>> +  REG_L            G,  G,  0;
>>  
>> -/* Load or store to/from a pc-relative EXPR into/from G, using T.
>> +/* Load a pc-relative EXPR into G, using T.
>>     Note G and T are register names.  */
>> -#define LDST_PCREL(OP, G, T,  EXPR) \
>> -  pcalau12i T, %pc_hi20(EXPR); \
>> -  OP       G, T, %pc_lo12(EXPR);
>> +
>> +#ifdef HAVE_LOONGARCH_EXPLICIT_RELOCS
>> +#define LD_PCREL(G, EXPR) \
>> +  pcalau12i G, %pc_hi20(EXPR); \
>> +  REG_L            G,  G,  %pc_lo12(EXPR);
>> +#else
>> +#define LD_PCREL(G, EXPR) \
>> +  la.pcrel  G, EXPR; \
>> +  REG_L            G,  G,  0;
>> +#endif
>>  
>>  #if (IS_IN (rtld) \
>>       || (!defined SHARED && (IS_IN (libc) \
>>       || IS_IN (libpthread))))
>>  
>>  #ifdef __ASSEMBLER__
>> -#define PTR_MANGLE(dst, src, guard, tmp) \
>> -  LDST_PCREL (REG_L, guard, tmp, __pointer_chk_guard_local); \
>> +#define PTR_MANGLE(dst, src, guard) \
>> +  LD_PCREL (guard, __pointer_chk_guard_local); \
>>    PTR_MANGLE2 (dst, src, guard);
>> -#define PTR_DEMANGLE(dst, src, guard, tmp) \
>> -  LDST_PCREL (REG_L, guard, tmp, __pointer_chk_guard_local); \
>> +#define PTR_DEMANGLE(dst, src, guard) \
>> +  LD_PCREL (guard, __pointer_chk_guard_local); \
>>    PTR_DEMANGLE2 (dst, src, guard);
>>  /* Use PTR_MANGLE2 for efficiency if guard is already loaded.  */
>>  #define PTR_MANGLE2(dst, src, guard) \
>> @@ -355,11 +361,11 @@ extern uintptr_t __pointer_chk_guard_local
>> attribute_relro attribute_hidden;
>>  #else
>>  
>>  #ifdef __ASSEMBLER__
>> -#define PTR_MANGLE(dst, src, guard, tmp) \
>> -  LDST_GLOBAL (REG_L, guard, tmp, __pointer_chk_guard); \
>> +#define PTR_MANGLE(dst, src, guard) \
>> +  LD_GLOBAL (guard, __pointer_chk_guard); \
>>    PTR_MANGLE2 (dst, src, guard);
>> -#define PTR_DEMANGLE(dst, src, guard, tmp) \
>> -  LDST_GLOBAL (REG_L, guard, tmp, __pointer_chk_guard); \
>> +#define PTR_DEMANGLE(dst, src, guard) \
>> +  LD_GLOBAL (guard, __pointer_chk_guard); \
>>    PTR_DEMANGLE2 (dst, src, guard);
>>  /* Use PTR_MANGLE2 for efficiency if guard is already loaded.  */
>>  #define PTR_MANGLE2(dst, src, guard) \
>