Re: [PATCH v8 08/12] LoongArch Port: libgcc

[Andreas Schwab]

On Mär 08 2022, Richard Sandiford via Gcc-patches wrote:

>> +
>> +.section .init,"ax",@progbits
>> +.globl  _init
>> +.type   _init,@function
>> +_init:
>> +addi.d   $r3,$r3,-16
>> +st.d  $r1,$r3,8
>> +addi.d   $r3,$r3,16
>> +jirl$r0,$r1,0
>> +
>> +.section .fini,"ax",@progbits
>> +.globl  _fini
>> +.type   _fini,@function
>> +_fini:
>> +addi.d   $r3,$r3,-16
>> +st.d  $r1,$r3,8
>> +addi.d   $r3,$r3,16
>> +jirl$r0,$r1,0
>
> Are you sure this is right?  It looks like it pushes LR and then
> immediately pops it and returns, which would have the effect of
> bypassing the rest of the .init and .fini code.
>
> The idea instead is that .init starts with the code in crti.S,
> then contains any .init code linked in from .o files, then ends
> with the .init code in crtn.S.  Same for .fini.

New architectures should not use .init/.fini at all.

-- 
Andreas Schwab, sch...@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."

Re: [PATCH v8 08/12] LoongArch Port: libgcc

[Richard Sandiford via Gcc-patches]

xucheng...@loongson.cn writes:
> diff --git a/libgcc/config/loongarch/crti.S b/libgcc/config/loongarch/crti.S
> new file mode 100644
> index 000..27b7eab3626
> --- /dev/null
> +++ b/libgcc/config/loongarch/crti.S
> @@ -0,0 +1,43 @@
> +/* Copyright (C) 2021-2022 Free Software Foundation, Inc.
> +
> +This file is part of GCC.
> +
> +GCC is free software; you can redistribute it and/or modify it under
> +the terms of the GNU General Public License as published by the Free
> +Software Foundation; either version 3, or (at your option) any later
> +version.
> +
> +GCC is distributed in the hope that it will be useful, but WITHOUT ANY
> +WARRANTY; without even the implied warranty of MERCHANTABILITY or
> +FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
> +for more details.
> +
> +Under Section 7 of GPL version 3, you are granted additional
> +permissions described in the GCC Runtime Library Exception, version
> +3.1, as published by the Free Software Foundation.
> +
> +You should have received a copy of the GNU General Public License and
> +a copy of the GCC Runtime Library Exception along with this program;
> +see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
> +.  */
> +
> +/* 4 slots for argument spill area.  1 for cpreturn, 1 for stack.
> +   Return spill offset of 8.  Aligned to 16 bytes for lp64.  */

The comment doesn't apply to the Loongson code.  Probably best
to delete it.

Same for crtn.S.

> +
> + .section .init,"ax",@progbits
> + .globl  _init
> + .type   _init,@function
> +_init:
> + addi.d   $r3,$r3,-16
> + st.d  $r1,$r3,8
> + addi.d   $r3,$r3,16
> + jirl$r0,$r1,0
> +
> + .section .fini,"ax",@progbits
> + .globl  _fini
> + .type   _fini,@function
> +_fini:
> + addi.d   $r3,$r3,-16
> + st.d  $r1,$r3,8
> + addi.d   $r3,$r3,16
> + jirl$r0,$r1,0

Are you sure this is right?  It looks like it pushes LR and then
immediately pops it and returns, which would have the effect of
bypassing the rest of the .init and .fini code.

The idea instead is that .init starts with the code in crti.S,
then contains any .init code linked in from .o files, then ends
with the .init code in crtn.S.  Same for .fini.

Looks good to me otherwise.

Thanks,
Richard

[PATCH v8 08/12] LoongArch Port: libgcc

[xuchenghua]

From: chenglulu 

2022-03-04  Chenghua Xu  
Lulu Cheng  

libgcc/

* config/loongarch/crtfastmath.c: New file.
* config/loongarch/crti.S: Like wise.
* config/loongarch/crtn.S: Like wise.
* config/loongarch/linux-unwind.h: Like wise.
* config/loongarch/sfp-machine.h: Like wise.
* config/loongarch/t-crtstuff: Like wise.
* config/loongarch/t-loongarch: Like wise.
* config/loongarch/t-loongarch64: Like wise.
* config/loongarch/t-softfp-tf: Like wise.
* config.host: Add LoongArch tuples.
* configure.ac: Add LoongArch support.
---
 libgcc/config.host |  28 -
 libgcc/config/loongarch/crtfastmath.c  |  52 +
 libgcc/config/loongarch/crti.S |  43 +++
 libgcc/config/loongarch/crtn.S |  39 +++
 libgcc/config/loongarch/linux-unwind.h |  80 +
 libgcc/config/loongarch/sfp-machine.h  | 152 +
 libgcc/config/loongarch/t-crtstuff |   5 +
 libgcc/config/loongarch/t-loongarch|   7 ++
 libgcc/config/loongarch/t-loongarch64  |   1 +
 libgcc/config/loongarch/t-softfp-tf|   3 +
 libgcc/configure.ac|   2 +-
 11 files changed, 410 insertions(+), 2 deletions(-)
 create mode 100644 libgcc/config/loongarch/crtfastmath.c
 create mode 100644 libgcc/config/loongarch/crti.S
 create mode 100644 libgcc/config/loongarch/crtn.S
 create mode 100644 libgcc/config/loongarch/linux-unwind.h
 create mode 100644 libgcc/config/loongarch/sfp-machine.h
 create mode 100644 libgcc/config/loongarch/t-crtstuff
 create mode 100644 libgcc/config/loongarch/t-loongarch
 create mode 100644 libgcc/config/loongarch/t-loongarch64
 create mode 100644 libgcc/config/loongarch/t-softfp-tf

diff --git a/libgcc/config.host b/libgcc/config.host
index 094fd3ad254..8c56fcae5d2 100644
--- a/libgcc/config.host
+++ b/libgcc/config.host
@@ -138,6 +138,22 @@ hppa*-*-*)
 lm32*-*-*)
cpu_type=lm32
;;
+loongarch*-*-*)
+   cpu_type=loongarch
+   tmake_file="loongarch/t-loongarch"
+   if test "${libgcc_cv_loongarch_hard_float}" = yes; then
+   tmake_file="${tmake_file} t-hardfp-sfdf t-hardfp"
+   else
+   tmake_file="${tmake_file} t-softfp-sfdf"
+   fi
+   if test "${ac_cv_sizeof_long_double}" = 16; then
+   tmake_file="${tmake_file} loongarch/t-softfp-tf"
+   fi
+   if test "${host_address}" = 64; then
+   tmake_file="${tmake_file} loongarch/t-loongarch64"
+   fi
+   tmake_file="${tmake_file} t-softfp"
+   ;;
 m32r*-*-*)
 cpu_type=m32r
 ;;
@@ -925,7 +941,17 @@ lm32-*-rtems*)
 lm32-*-uclinux*)
 extra_parts="$extra_parts crtbegin.o crtendS.o crtbeginT.o"
 tmake_file="lm32/t-lm32 lm32/t-uclinux t-libgcc-pic t-softfp-sfdf 
t-softfp"
-   ;;  
+   ;;
+loongarch*-*-linux*)
+   extra_parts="$extra_parts crtfastmath.o"
+   tmake_file="${tmake_file} t-crtfm loongarch/t-crtstuff"
+   case ${host} in
+ *)
+   tmake_file="${tmake_file} t-slibgcc-libgcc"
+   ;;
+   esac
+   md_unwind_header=loongarch/linux-unwind.h
+   ;;
 m32r-*-elf*)
tmake_file="$tmake_file m32r/t-m32r t-fdpbit"
extra_parts="$extra_parts crtinit.o crtfini.o"
diff --git a/libgcc/config/loongarch/crtfastmath.c 
b/libgcc/config/loongarch/crtfastmath.c
new file mode 100644
index 000..52b0d6da087
--- /dev/null
+++ b/libgcc/config/loongarch/crtfastmath.c
@@ -0,0 +1,52 @@
+/* Copyright (C) 2021-2022 Free Software Foundation, Inc.
+   Contributed by Loongson Ltd.
+   Based on MIPS target for GNU compiler.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+License for more details.
+
+Under Section 7 of GPL version 3, you are granted additional
+permissions described in the GCC Runtime Library Exception, version
+3.1, as published by the Free Software Foundation.
+
+You should have received a copy of the GNU General Public License
+and a copy of the GCC Runtime Library Exception along with this
+program; see the files COPYING3 and COPYING.RUNTIME respectively.
+If not, see .  */
+
+#ifdef __loongarch_hard_float
+
+/* Rounding control.  */
+#define _FPU_RC_NEAREST 0x000 /* RECOMMENDED.  */
+#define _FPU_RC_ZERO0x100
+#define _FPU_RC_UP  0x200
+#define _FPU_RC_DOWN0x300
+
+/* Enable interrupts for IEEE exceptions.  */
+#define _FPU_IEEE 0x001F
+
+/* Macros for accessing the hardware control word.  */
+#define _FPU_GETCW(cw) __asm__ volatile