[OpenRISC] [PATCH] or1k: Add mcmodel option to handle large GOTs

[OpenRISC] [PATCH] or1k: Add mcmodel option to handle large GOTs

[Stafford Horne]

When building libgeos we get an error with:

    linux-uclibc/9.3.0/crtbeginS.o: in function `__do_global_dtors_aux':
    crtstuff.c:(.text+0x118): relocation truncated to fit: R_OR1K_GOT16 against symbol `__cxa_finalize' defined in .text section in
    /home/shorne/work/openrisc/3eb9f9d0f6d8274b2d19753c006bd83f7d536e3c/output/host/or1k-buildroot-linux-uclibc/sysroot/lib/libc.so.

This is caused by GOT code having a limit of 64k.  In OpenRISC this
looks to be the only relocation code pattern to be limited to 64k.

This patch allows specifying a new option -mcmodel=large which can be
used to generate 2 more instructions to construct 32-bit addresses for
up to 4G GOTs.

gcc/ChangeLog:

	PR 99783
	* config/or1k/or1k-opts.h: New file.
	* config/or1k/or1k.c (or1k_legitimize_address_1, print_reloc):
	Support generating gotha relocations if -mcmodel=large is
	specified.
	* config/or1k/or1k.h (TARGET_CMODEL_SMALL, TARGET_CMODEL_LARGE):
	New macros.
	* config/or1k/or1k.opt (mcmodel=): New option.
	* doc/invoke.text (OpenRISC Options): Document mcmodel.
---

This depends on the binutils-gdb patch sent here:
 - https://sourceware.org/pipermail/binutils/2021-April/116155.html

 gcc/config/or1k/or1k-opts.h | 30 ++++++++++++++++++++++++++++++
 gcc/config/or1k/or1k.c      | 11 +++++++++--
 gcc/config/or1k/or1k.h      |  7 +++++++
 gcc/config/or1k/or1k.opt    | 19 +++++++++++++++++++
 gcc/doc/invoke.texi         | 12 +++++++++++-
 5 files changed, 76 insertions(+), 3 deletions(-)
 create mode 100644 gcc/config/or1k/or1k-opts.h

diff --git a/gcc/config/or1k/or1k-opts.h b/gcc/config/or1k/or1k-opts.h
new file mode 100644
index 00000000000..f791b894fdd
--- /dev/null
+++ b/gcc/config/or1k/or1k-opts.h
@@ -0,0 +1,30 @@
+/* Definitions for option handling for OpenRISC.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   Contributed by Stafford Horne.
+
+   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.
+
+   You should have received a copy of the GNU General Public License
+   along with GCC; see the file COPYING3.  If not see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef GCC_OR1K_OPTS_H
+#define GCC_OR1K_OPTS_H
+
+/* The OpenRISC code generation models available.  */
+enum or1k_cmodel_type {
+  CMODEL_SMALL,
+  CMODEL_LARGE
+};
+
+#endif /* GCC_OR1K_OPTS_H */
diff --git a/gcc/config/or1k/or1k.c b/gcc/config/or1k/or1k.c
index e772a7addea..27d3fa17995 100644
--- a/gcc/config/or1k/or1k.c
+++ b/gcc/config/or1k/or1k.c
@@ -750,7 +750,14 @@ or1k_legitimize_address_1 (rtx x, rtx scratch)
 	    {
 	      base = gen_sym_unspec (base, UNSPEC_GOT);
 	      crtl->uses_pic_offset_table = 1;
-	      t2 = gen_rtx_LO_SUM (Pmode, pic_offset_table_rtx, base);
+	      if (TARGET_CMODEL_LARGE)
+		{
+	          emit_insn (gen_rtx_SET (t1, gen_rtx_HIGH (Pmode, base)));
+	          emit_insn (gen_add3_insn (t1, t1, pic_offset_table_rtx));
+	          t2 = gen_rtx_LO_SUM (Pmode, t1, base);
+		}
+	      else
+	        t2 = gen_rtx_LO_SUM (Pmode, pic_offset_table_rtx, base);
 	      t2 = gen_const_mem (Pmode, t2);
 	      emit_insn (gen_rtx_SET (t1, t2));
 	      base = t1;
@@ -1089,7 +1096,7 @@ print_reloc (FILE *stream, rtx x, HOST_WIDE_INT add, reloc_kind kind)
      no special markup.  */
   static const char * const relocs[RKIND_MAX][RTYPE_MAX] = {
     { "lo", "got", "gotofflo", "tpofflo", "gottpofflo", "tlsgdlo" },
-    { "ha", NULL,  "gotoffha", "tpoffha", "gottpoffha", "tlsgdhi" },
+    { "ha", "gotha", "gotoffha", "tpoffha", "gottpoffha", "tlsgdhi" },
   };
   reloc_type type = RTYPE_DIRECT;
 
diff --git a/gcc/config/or1k/or1k.h b/gcc/config/or1k/or1k.h
index fe01ab81ead..669907e7e74 100644
--- a/gcc/config/or1k/or1k.h
+++ b/gcc/config/or1k/or1k.h
@@ -21,6 +21,8 @@
 #ifndef GCC_OR1K_H
 #define GCC_OR1K_H
 
+#include "config/or1k/or1k-opts.h"
+
 /* Names to predefine in the preprocessor for this target machine.  */
 #define TARGET_CPU_CPP_BUILTINS()		\
   do						\
@@ -37,6 +39,11 @@
     }						\
   while (0)
 
+#define TARGET_CMODEL_SMALL \
+  (or1k_code_model == CMODEL_SMALL)
+#define TARGET_CMODEL_LARGE \
+  (or1k_code_model == CMODEL_LARGE)
+
 /* Storage layout.  */
 
 #define DEFAULT_SIGNED_CHAR 1
diff --git a/gcc/config/or1k/or1k.opt b/gcc/config/or1k/or1k.opt
index 6bd0f3eee6d..cc23e3b8856 100644
--- a/gcc/config/or1k/or1k.opt
+++ b/gcc/config/or1k/or1k.opt
@@ -21,6 +21,9 @@
 ; See the GCC internals manual (options.texi) for a description of
 ; this file's format.
 
+HeaderInclude
+config/or1k/or1k-opts.h
+
 mhard-div
 Target RejectNegative InverseMask(SOFT_DIV)
 Enable generation of hardware divide (l.div, l.divu) instructions.  This is the
@@ -63,6 +66,22 @@ When -mhard-float is selected, enables generation of unordered floating point
 compare and set flag (lf.sfun*) instructions.  By default functions from libgcc
 are used to perform unordered floating point compare and set flag operations.
 
+mcmodel=
+Target RejectNegative Joined Enum(or1k_cmodel_type) Var(or1k_code_model) Init(CMODEL_SMALL)
+Specify the code model used for accessing memory addresses.  Specifying large
+enables generating binaries with large global offset tables.  By default the
+value is small.
+
+Enum
+Name(or1k_cmodel_type) Type(enum or1k_cmodel_type)
+Known code model types (for use with the -mcmodel= option):
+
+EnumValue
+Enum(or1k_cmodel_type) String(small) Value(CMODEL_SMALL)
+
+EnumValue
+Enum(or1k_cmodel_type) String(large) Value(CMODEL_LARGE)
+
 mcmov
 Target RejectNegative Mask(CMOV)
 Enable generation of conditional move (l.cmov) instructions.  By default the
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 096cebc8562..63cc4ec97db 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1135,7 +1135,8 @@ Objective-C and Objective-C++ Dialects}.
 @gccoptlist{-mboard=@var{name}  -mnewlib  -mhard-mul  -mhard-div @gol
 -msoft-mul  -msoft-div @gol
 -msoft-float  -mhard-float  -mdouble-float -munordered-float @gol
--mcmov  -mror  -mrori  -msext  -msfimm  -mshftimm}
+-mcmov  -mror  -mrori  -msext  -msfimm  -mshftimm @gol
+-mcmodel=@var{code-model}}
 
 @emph{PDP-11 Options}
 @gccoptlist{-mfpu  -msoft-float  -mac0  -mno-ac0  -m40  -m45  -m10 @gol
@@ -26406,6 +26407,15 @@ Enable generation of shift with immediate (@code{l.srai}, @code{l.srli},
 @code{l.slli}) instructions.  By default extra instructions will be generated
 to store the immediate to a register first.
 
+ at item -mcmodel=small
+ at opindex mcmodel=small
+Generate OpenRISC code for the small model: The GOT is limited to 64k. This is
+the default model.
+
+ at item -mcmodel=large
+ at opindex mcmodel=large
+Generate OpenRISC code for the large model: The GOT may grow up to 4G in size.
+
 
 @end table
 
-- 
2.26.2

[OpenRISC] [PATCH] or1k: Add mcmodel option to handle large GOTs

[Jeff Law]

On 4/18/2021 6:10 PM, Stafford Horne via Gcc-patches wrote:
> When building libgeos we get an error with:
>
>      linux-uclibc/9.3.0/crtbeginS.o: in function `__do_global_dtors_aux':
>      crtstuff.c:(.text+0x118): relocation truncated to fit: R_OR1K_GOT16 against symbol `__cxa_finalize' defined in .text section in
>      /home/shorne/work/openrisc/3eb9f9d0f6d8274b2d19753c006bd83f7d536e3c/output/host/or1k-buildroot-linux-uclibc/sysroot/lib/libc.so.
>
> This is caused by GOT code having a limit of 64k.  In OpenRISC this
> looks to be the only relocation code pattern to be limited to 64k.
>
> This patch allows specifying a new option -mcmodel=large which can be
> used to generate 2 more instructions to construct 32-bit addresses for
> up to 4G GOTs.
>
> gcc/ChangeLog:
>
> 	PR 99783
> 	* config/or1k/or1k-opts.h: New file.
> 	* config/or1k/or1k.c (or1k_legitimize_address_1, print_reloc):
> 	Support generating gotha relocations if -mcmodel=large is
> 	specified.
> 	* config/or1k/or1k.h (TARGET_CMODEL_SMALL, TARGET_CMODEL_LARGE):
> 	New macros.
> 	* config/or1k/or1k.opt (mcmodel=): New option.
> 	* doc/invoke.text (OpenRISC Options): Document mcmodel.

Note you're the port maintainer, so you don't need approval to commit 
this to GCC.

Jeff

[OpenRISC] [PATCH] or1k: Add mcmodel option to handle large GOTs

[Stafford Horne]

On Tue, Apr 20, 2021 at 05:20:39PM -0600, Jeff Law wrote:
> 
> On 4/18/2021 6:10 PM, Stafford Horne via Gcc-patches wrote:
> > When building libgeos we get an error with:
> > 
> >      linux-uclibc/9.3.0/crtbeginS.o: in function `__do_global_dtors_aux':
> >      crtstuff.c:(.text+0x118): relocation truncated to fit: R_OR1K_GOT16 against symbol `__cxa_finalize' defined in .text section in
> >      /home/shorne/work/openrisc/3eb9f9d0f6d8274b2d19753c006bd83f7d536e3c/output/host/or1k-buildroot-linux-uclibc/sysroot/lib/libc.so.
> > 
> > This is caused by GOT code having a limit of 64k.  In OpenRISC this
> > looks to be the only relocation code pattern to be limited to 64k.
> > 
> > This patch allows specifying a new option -mcmodel=large which can be
> > used to generate 2 more instructions to construct 32-bit addresses for
> > up to 4G GOTs.
> > 
> > gcc/ChangeLog:
> > 
> > 	PR 99783
> > 	* config/or1k/or1k-opts.h: New file.
> > 	* config/or1k/or1k.c (or1k_legitimize_address_1, print_reloc):
> > 	Support generating gotha relocations if -mcmodel=large is
> > 	specified.
> > 	* config/or1k/or1k.h (TARGET_CMODEL_SMALL, TARGET_CMODEL_LARGE):
> > 	New macros.
> > 	* config/or1k/or1k.opt (mcmodel=): New option.
> > 	* doc/invoke.text (OpenRISC Options): Document mcmodel.
> 
> Note you're the port maintainer, so you don't need approval to commit this
> to GCC.

Thanks for confirming, I know that after Segher told me with some previous
patches. :)

For this series Giulio picked it up and tested it.  We found some issues and I
am going to fix with a V2.  I should commit that version, after the binutils
changes are in.

-Stafford

[OpenRISC] [PATCH] or1k: Add mcmodel option to handle large GOTs

[Jeff Law]

On 4/20/2021 6:12 PM, Stafford Horne wrote:
> On Tue, Apr 20, 2021 at 05:20:39PM -0600, Jeff Law wrote:
>> On 4/18/2021 6:10 PM, Stafford Horne via Gcc-patches wrote:
>>> When building libgeos we get an error with:
>>>
>>>       linux-uclibc/9.3.0/crtbeginS.o: in function `__do_global_dtors_aux':
>>>       crtstuff.c:(.text+0x118): relocation truncated to fit: R_OR1K_GOT16 against symbol `__cxa_finalize' defined in .text section in
>>>       /home/shorne/work/openrisc/3eb9f9d0f6d8274b2d19753c006bd83f7d536e3c/output/host/or1k-buildroot-linux-uclibc/sysroot/lib/libc.so.
>>>
>>> This is caused by GOT code having a limit of 64k.  In OpenRISC this
>>> looks to be the only relocation code pattern to be limited to 64k.
>>>
>>> This patch allows specifying a new option -mcmodel=large which can be
>>> used to generate 2 more instructions to construct 32-bit addresses for
>>> up to 4G GOTs.
>>>
>>> gcc/ChangeLog:
>>>
>>> 	PR 99783
>>> 	* config/or1k/or1k-opts.h: New file.
>>> 	* config/or1k/or1k.c (or1k_legitimize_address_1, print_reloc):
>>> 	Support generating gotha relocations if -mcmodel=large is
>>> 	specified.
>>> 	* config/or1k/or1k.h (TARGET_CMODEL_SMALL, TARGET_CMODEL_LARGE):
>>> 	New macros.
>>> 	* config/or1k/or1k.opt (mcmodel=): New option.
>>> 	* doc/invoke.text (OpenRISC Options): Document mcmodel.
>> Note you're the port maintainer, so you don't need approval to commit this
>> to GCC.
> Thanks for confirming, I know that after Segher told me with some previous
> patches. :)
>
> For this series Giulio picked it up and tested it.  We found some issues and I
> am going to fix with a V2.  I should commit that version, after the binutils
> changes are in.

Sounds good.  Thanks.  Given we're making gcc-11 RCs you'll have to 
decide if its worth the risk of introducing those changes this late in 
the cycle is safe or not.

jeff