* libstdc++ "freestanding" ('--disable-hosted-libstdcxx') with '-fno-rtti', '-fno-exceptions': 'libstdc++-v3/libsupc++/tinfo.cc'
@ 2022-07-14 16:42 Thomas Schwinge
2022-07-14 18:39 ` Jonathan Wakely
0 siblings, 1 reply; 3+ messages in thread
From: Thomas Schwinge @ 2022-07-14 16:42 UTC (permalink / raw)
To: libstdc++, Jonathan Wakely
Hi!
In context of <https://gcc.gnu.org/PR101544> '[OpenMP][AMDGCN][nvptx]
C++ offloading: unresolved _Znwm = "operator new(unsigned long)"'
I'm looking into building GCN, nvptx offloading libstdc++ "freestanding"
('--disable-hosted-libstdcxx') with '-fno-rtti', '-fno-exceptions'.
(I've basically got these things wired up; details to be shared later.)
While there is some experimental/incomplete/not-to-be-relied-on support
for PTX symbol aliases, we're currently generally running into
"error: alias definitions not supported in this configuration"
for certain GCC/C++-front-end-generated code, for example:
"complete object destructor" aliasing "base object destructor"
(<https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling-special-ctor-dtor>
-- per my understanding, at least). ;-)
It'll ultimately be possible to implement more complete symbol aliasing
support for nvptx, but I found that this specific issue actually is due
to a nvptx back end mis-configuration; fixed with adequate
'TARGET_USE_LOCAL_THUNK_ALIAS_P' and/or 'TARGET_SUPPORTS_ALIASES'
definitions (details to be shared later).
However, we then still run into:
[...]/libstdc++-v3/libsupc++/tinfo.cc:55:1: error: alias definitions not supported in this configuration
55 | std::type_info::__equal (const std::type_info& arg) const _GLIBCXX_NOEXCEPT
| ^~~
make[4]: *** [Makefile:777: tinfo.lo] Error 1
That's 'libstdc++-v3/libsupc++/tinfo.cc':
1 // Methods for type_info for -*- C++ -*- Run Time Type Identification.
[...]
39 // We can't rely on common symbols being shared between shared objects.
40 bool std::type_info::
41 operator== (const std::type_info& arg) const _GLIBCXX_NOEXCEPT
42 {
43 #if __GXX_MERGED_TYPEINFO_NAMES
44 return name () == arg.name ();
45 #else
46 /* The name() method will strip any leading '*' prefix. Therefore
47 take care to look at __name rather than name() when looking for
48 the "pointer" prefix. */
49 return (&arg == this)
50 || (__name[0] != '*' && (__builtin_strcmp (name (), arg.name ()) == 0));
51 #endif
52 }
53
54 bool
55 std::type_info::__equal (const std::type_info& arg) const _GLIBCXX_NOEXCEPT
56 __attribute__((alias("_ZNKSt9type_infoeqERKS_")));
57 #endif
[...]
..., so there's a manual alias from the line 55 function to the line 41
function (if I got that right).
Now we may surely address that in some different way, but I do wonder if
we need this whole file at all, given this is
"Methods for type_info for -*- C++ -*- Run Time Type Identification",
RTTI, and we're generally assuming '-fno-rtti'? Do certain things simply
need to be '#if'-conditionalized, or similar, for example? I've not yet
looked into the details; hoping that's maybe easy for you to answer?
Grüße
Thomas
-----------------
Siemens Electronic Design Automation GmbH; Anschrift: Arnulfstraße 201, 80634 München; Gesellschaft mit beschränkter Haftung; Geschäftsführer: Thomas Heurung, Frank Thürauf; Sitz der Gesellschaft: München; Registergericht München, HRB 106955
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: libstdc++ "freestanding" ('--disable-hosted-libstdcxx') with '-fno-rtti', '-fno-exceptions': 'libstdc++-v3/libsupc++/tinfo.cc'
2022-07-14 16:42 libstdc++ "freestanding" ('--disable-hosted-libstdcxx') with '-fno-rtti', '-fno-exceptions': 'libstdc++-v3/libsupc++/tinfo.cc' Thomas Schwinge
@ 2022-07-14 18:39 ` Jonathan Wakely
2023-11-06 14:57 ` nvptx: Use the usual '#define MAKE_DECL_ONE_ONLY(DECL) (DECL_WEAK (DECL) = 1)' (was: libstdc++ "freestanding" ('--disable-hosted-libstdcxx') with '-fno-rtti', '-fno-exceptions': 'libstdc++-v3/libsupc++/tinfo.cc') Thomas Schwinge
0 siblings, 1 reply; 3+ messages in thread
From: Jonathan Wakely @ 2022-07-14 18:39 UTC (permalink / raw)
To: Thomas Schwinge; +Cc: libstdc++
On Thu, 14 Jul 2022 at 19:14, Thomas Schwinge <thomas@codesourcery.com> wrote:
>
> Hi!
>
> In context of <https://gcc.gnu.org/PR101544> '[OpenMP][AMDGCN][nvptx]
> C++ offloading: unresolved _Znwm = "operator new(unsigned long)"'
> I'm looking into building GCN, nvptx offloading libstdc++ "freestanding"
> ('--disable-hosted-libstdcxx') with '-fno-rtti', '-fno-exceptions'.
> (I've basically got these things wired up; details to be shared later.)
>
> While there is some experimental/incomplete/not-to-be-relied-on support
> for PTX symbol aliases, we're currently generally running into
> "error: alias definitions not supported in this configuration"
> for certain GCC/C++-front-end-generated code, for example:
> "complete object destructor" aliasing "base object destructor"
> (<https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling-special-ctor-dtor>
> -- per my understanding, at least). ;-)
>
> It'll ultimately be possible to implement more complete symbol aliasing
> support for nvptx, but I found that this specific issue actually is due
> to a nvptx back end mis-configuration; fixed with adequate
> 'TARGET_USE_LOCAL_THUNK_ALIAS_P' and/or 'TARGET_SUPPORTS_ALIASES'
> definitions (details to be shared later).
>
> However, we then still run into:
>
> [...]/libstdc++-v3/libsupc++/tinfo.cc:55:1: error: alias definitions not supported in this configuration
> 55 | std::type_info::__equal (const std::type_info& arg) const _GLIBCXX_NOEXCEPT
> | ^~~
> make[4]: *** [Makefile:777: tinfo.lo] Error 1
>
> That's 'libstdc++-v3/libsupc++/tinfo.cc':
>
> 1 // Methods for type_info for -*- C++ -*- Run Time Type Identification.
> [...]
> 39 // We can't rely on common symbols being shared between shared objects.
> 40 bool std::type_info::
> 41 operator== (const std::type_info& arg) const _GLIBCXX_NOEXCEPT
> 42 {
> 43 #if __GXX_MERGED_TYPEINFO_NAMES
> 44 return name () == arg.name ();
> 45 #else
> 46 /* The name() method will strip any leading '*' prefix. Therefore
> 47 take care to look at __name rather than name() when looking for
> 48 the "pointer" prefix. */
> 49 return (&arg == this)
> 50 || (__name[0] != '*' && (__builtin_strcmp (name (), arg.name ()) == 0));
> 51 #endif
> 52 }
> 53
> 54 bool
> 55 std::type_info::__equal (const std::type_info& arg) const _GLIBCXX_NOEXCEPT
> 56 __attribute__((alias("_ZNKSt9type_infoeqERKS_")));
> 57 #endif
> [...]
>
> ..., so there's a manual alias from the line 55 function to the line 41
> function (if I got that right).
That's only there for backwards compatibility on ARM EABI and other
targets that don't define __GXX_TYPEINFO_EQUALITY_INLINE==1.
My suggestion would be to define that macro for the target.
>
> Now we may surely address that in some different way, but I do wonder if
> we need this whole file at all, given this is
> "Methods for type_info for -*- C++ -*- Run Time Type Identification",
> RTTI, and we're generally assuming '-fno-rtti'? Do certain things simply
> need to be '#if'-conditionalized, or similar, for example? I've not yet
> looked into the details; hoping that's maybe easy for you to answer?
Again, is -fno-rtti globally true for all code for this target? Not
just while building libstdc++?
If the answer is yes, then you don't need the symbols in this file.
^ permalink raw reply [flat|nested] 3+ messages in thread
* nvptx: Use the usual '#define MAKE_DECL_ONE_ONLY(DECL) (DECL_WEAK (DECL) = 1)' (was: libstdc++ "freestanding" ('--disable-hosted-libstdcxx') with '-fno-rtti', '-fno-exceptions': 'libstdc++-v3/libsupc++/tinfo.cc')
2022-07-14 18:39 ` Jonathan Wakely
@ 2023-11-06 14:57 ` Thomas Schwinge
0 siblings, 0 replies; 3+ messages in thread
From: Thomas Schwinge @ 2023-11-06 14:57 UTC (permalink / raw)
To: gcc-patches; +Cc: Jonathan Wakely, libstdc++, Tom de Vries
[-- Attachment #1: Type: text/plain, Size: 2624 bytes --]
Hi!
On 2022-07-14T19:39:40+0100, Jonathan Wakely <jwakely@redhat.com> wrote:
> On Thu, 14 Jul 2022 at 19:14, Thomas Schwinge <thomas@codesourcery.com> wrote:
>> I'm looking into building GCN, nvptx offloading libstdc++ [...]
>> While there is some experimental/incomplete/not-to-be-relied-on support
>> for PTX symbol aliases, we're currently generally running into
>> "error: alias definitions not supported in this configuration"
>> [...]/libstdc++-v3/libsupc++/tinfo.cc:55:1: error: alias definitions not supported in this configuration
>> 55 | std::type_info::__equal (const std::type_info& arg) const _GLIBCXX_NOEXCEPT
>> | ^~~
>> make[4]: *** [Makefile:777: tinfo.lo] Error 1
>>
>> That's 'libstdc++-v3/libsupc++/tinfo.cc':
>>
>> 1 // Methods for type_info for -*- C++ -*- Run Time Type Identification.
>> [...]
>> 39 // We can't rely on common symbols being shared between shared objects.
>> 40 bool std::type_info::
>> 41 operator== (const std::type_info& arg) const _GLIBCXX_NOEXCEPT
>> 42 {
>> 43 #if __GXX_MERGED_TYPEINFO_NAMES
>> 44 return name () == arg.name ();
>> 45 #else
>> 46 /* The name() method will strip any leading '*' prefix. Therefore
>> 47 take care to look at __name rather than name() when looking for
>> 48 the "pointer" prefix. */
>> 49 return (&arg == this)
>> 50 || (__name[0] != '*' && (__builtin_strcmp (name (), arg.name ()) == 0));
>> 51 #endif
>> 52 }
>> 53
>> 54 bool
>> 55 std::type_info::__equal (const std::type_info& arg) const _GLIBCXX_NOEXCEPT
>> 56 __attribute__((alias("_ZNKSt9type_infoeqERKS_")));
>> 57 #endif
>> [...]
>>
>> ..., so there's a manual alias from the line 55 function to the line 41
>> function (if I got that right).
>
> That's only there for backwards compatibility on ARM EABI and other
> targets that don't define __GXX_TYPEINFO_EQUALITY_INLINE==1.
>
> My suggestion would be to define that macro for the target.
Thanks, that did put me on the right track -- we shall define it this
way; indirectly.
Pushed to master branch commit 9837f62f066db532c9db6df38ccf2653d0c3a960
"nvptx: Use the usual '#define MAKE_DECL_ONE_ONLY(DECL) (DECL_WEAK (DECL) = 1)'",
see attached.
Grüße
Thomas
-----------------
Siemens Electronic Design Automation GmbH; Anschrift: Arnulfstraße 201, 80634 München; Gesellschaft mit beschränkter Haftung; Geschäftsführer: Thomas Heurung, Frank Thürauf; Sitz der Gesellschaft: München; Registergericht München, HRB 106955
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: 0001-nvptx-Use-the-usual-define-MAKE_DECL_ONE_ONLY-DECL-D.patch --]
[-- Type: text/x-diff, Size: 2765 bytes --]
From 9837f62f066db532c9db6df38ccf2653d0c3a960 Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <thomas@codesourcery.com>
Date: Thu, 14 Jul 2022 23:22:35 +0200
Subject: [PATCH] nvptx: Use the usual '#define MAKE_DECL_ONE_ONLY(DECL)
(DECL_WEAK (DECL) = 1)'
With this 'MAKE_DECL_ONE_ONLY' definition, we get 'SUPPORTS_ONE_ONLY', and thus
'__GXX_WEAK__', and thus '__GXX_TYPEINFO_EQUALITY_INLINE'. This unblocks build
of 'libstdc++-v3/libsupc++/tinfo.cc', which otherwise depends on symbol alias
support, which GCC/nvptx doesn't generally provide. Also, this gets us a
number of FAIL -> PASS progressions in the test suite.
Given that GCC/nvptx support for weak symbols isn't complete, we also get a few
more of the already-known
'error: PTX does not support weak declarations (only weak definitions)':
[-PASS:-]{+FAIL:+} g++.old-deja/g++.other/crash11.C -std=c++14 (test for excess errors)
[-PASS:-]{+FAIL:+} g++.old-deja/g++.other/crash11.C -std=c++17 (test for excess errors)
[-PASS:-]{+FAIL:+} g++.old-deja/g++.other/crash11.C -std=c++20 (test for excess errors)
[-PASS:-]{+FAIL:+} g++.old-deja/g++.other/crash11.C -std=c++98 (test for excess errors)
[-PASS:-]{+FAIL:+} g++.old-deja/g++.pt/crash29.C -std=c++14 (test for excess errors)
[-PASS:-]{+FAIL:+} g++.old-deja/g++.pt/crash29.C -std=c++17 (test for excess errors)
[-PASS:-]{+FAIL:+} g++.old-deja/g++.pt/crash29.C -std=c++20 (test for excess errors)
[-PASS:-]{+FAIL:+} g++.old-deja/g++.pt/crash29.C -std=c++98 (test for excess errors)
[-PASS:-]{+FAIL:+} 23_containers/map/56613.cc -std=gnu++17 (test for excess errors)
... as well as one more of the already-known
'sorry, unimplemented: target cannot support nonlocal goto':
PASS: g++.dg/tree-ssa/pr22488.C -std=gnu++14 (test for excess errors)
PASS: g++.dg/tree-ssa/pr22488.C -std=gnu++17 (test for excess errors)
PASS: g++.dg/tree-ssa/pr22488.C -std=gnu++20 (test for excess errors)
[-PASS:-]{+FAIL:+} g++.dg/tree-ssa/pr22488.C -std=gnu++98 (test for excess errors)
We shall look into these, later.
gcc/
* config/nvptx/nvptx.h (MAKE_DECL_ONE_ONLY): Define.
---
gcc/config/nvptx/nvptx.h | 3 +++
1 file changed, 3 insertions(+)
diff --git a/gcc/config/nvptx/nvptx.h b/gcc/config/nvptx/nvptx.h
index 129427e5654..407fd70f06a 100644
--- a/gcc/config/nvptx/nvptx.h
+++ b/gcc/config/nvptx/nvptx.h
@@ -319,6 +319,9 @@ struct GTY(()) machine_function
#define SUPPORTS_WEAK 1
+#define MAKE_DECL_ONE_ONLY(DECL) \
+ (DECL_WEAK (DECL) = 1)
+
/* The documentation states that ASM_OUTPUT_DEF_FROM_DECLS is used in
preference to ASM_OUTPUT_DEF if the tree nodes are available. However, we
need the tree nodes to emit the prototype, so at this point it's not clear
--
2.34.1
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2023-11-06 14:57 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-07-14 16:42 libstdc++ "freestanding" ('--disable-hosted-libstdcxx') with '-fno-rtti', '-fno-exceptions': 'libstdc++-v3/libsupc++/tinfo.cc' Thomas Schwinge
2022-07-14 18:39 ` Jonathan Wakely
2023-11-06 14:57 ` nvptx: Use the usual '#define MAKE_DECL_ONE_ONLY(DECL) (DECL_WEAK (DECL) = 1)' (was: libstdc++ "freestanding" ('--disable-hosted-libstdcxx') with '-fno-rtti', '-fno-exceptions': 'libstdc++-v3/libsupc++/tinfo.cc') Thomas Schwinge
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).