r245459 - According to i686 ABI, long double size on x86 is 12 bytes not 16 bytes.

Sat Sep 19 04:43:45 PDT 2015

Thanks, I have replied there.

2015-09-19 13:33 GMT+03:00 Hal Finkel <hfinkel at anl.gov>:

> FYI: https://llvm.org/bugs/show_bug.cgi?id=24398 was just reopened
> pointing to a lack of resolution here.
>
>  -Hal
>
> ----- Original Message -----
> > From: "Yaron Keren via cfe-commits" <cfe-commits at lists.llvm.org>
> > To: "Martell Malone" <martellmalone at gmail.com>
> > Cc: "Richard Smith" <richard at metafoo.co.uk>, "cfe-commits" <
> cfe-commits at lists.llvm.org>
> > Sent: Friday, August 21, 2015 2:47:50 AM
> > Subject: Re: r245459 - According to i686 ABI, long double size on x86 is
> 12 bytes not 16 bytes.
> >
> >
> >
> >
> > The testcase from r245459 was not reverted and still in SVN.
> >
> >
> >
> >
> >
> > 2015-08-21 2:05 GMT+03:00 Martell Malone < martellmalone at gmail.com >
> > :
> >
> >
> >
> >
> >
> > I feel very silly now.
> > After testing the testcase again on svn it still works.
> > It appears the OP was looking for this patch to go onto the 3.6
> > branch and was applying my patch to that.
> >
> >
> > I'll know in future to recheck the testcase afterwards myself in
> > future.
> >
> >
> > Apologies for the noise guys.
> >
> >
> > Yaron I think the test case from r245459 would be useful to ensure it
> > is never broken in the future?
> >
> > Would you be able to recommit the test case?
> >
> >
> >
> > Kind Regards
> >
> > Martell
> >
> >
> >
> >
> >
> >
> >
> > On Thu, Aug 20, 2015 at 3:57 PM, Martell Malone <
> > martellmalone at gmail.com > wrote:
> >
> >
> >
> >
> >
> > There is no testcase for PR24398 nor the OP reporting the problem was
> > actually solved. Martell?
> > I'm just re-looking through it now.
> >
> >
> > X86TargetInfo sets LongDoubleFormat =
> > &llvm::APFloat::x87DoubleExtended;
> > X86_64TargetInfo then sets LongDoubleWidth = LongDoubleAlign = 128 ;
> > X86_32 TargetInfo then sets LongDoubleWidth = 96 ; LongDoubleAlign =
> > 32 ;
> >
> >
> > From this I can see that the patch I committed actually doesn't
> > change anything but only breaks mingw x86.
> >
> >
> > I can only see these values changed in Microsoft*TargetInfo classes
> > which is not a parent of MINGW
> >
> >
> > When I submitted the patch I just wanted to explicitly set the values
> > in MinGWX86_64TargetInfo to ensure it was in fact that.
> >
> > It seemed as though it was not inheriting the value from the root
> > parent class somehow.
> >
> >
> >
> > I was told on irc that it did fix the bug which is even stranger.
> > I'm actually at a bit of a loss as to what the proper fix to this is
> > then.
> >
> > Apologies for breaking mingw i686 long double.
> >
> >
> > I will do up a test case and try to find the actual cause of the long
> > double bug and reopen the issue.
> >
> >
> >
> >
> >
> > On Thu, Aug 20, 2015 at 3:09 PM, Yaron Keren < yaron.keren at gmail.com
> > > wrote:
> >
> >
> >
> >
> > Hi, I've just done this exactly this in r245618 (32 bit) and r245620
> > (64 bits).
> >
> >
> > mingw i686 long double values were correct before r245084 and wrong
> > after it.
> > mingw x86_64 long double values were not modified at all by r245084
> > for the reason you stated, so I agree and do not see how this
> > non-change can solve anything . There is no testcase for PR24398 nor
> > the OP reporting the problem was actually solved. Martell?
> >
> >
> > About PR24398, long double support was in clang long ago and b oth
> > code examples compile and run correctly with current svn (without
> > r245084) and gcc version 5.1.0 (i686-posix-dwarf-rev0, Built by
> > MinGW-W64 project).
> > It's not x86_64 but as said r245084 didn't actually modify x86_64
> > configuration.
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > 2015-08-21 0:52 GMT+03:00 Richard Smith < richard at metafoo.co.uk > :
> >
> >
> > OK, so here's the problem:
> >
> >
> > The right way to fix this seems to be to delete the assignments to
> > LongDouble* from the MinGWX86_32TargetInfo constructor; the
> > X86_32TargetInfo and X86TargetInfo base classes already set them to
> > the right values. Likewise we can delete the assignments to
> > LongDouble* from the MinGWX86_64TargetInfo constructor for the same
> > reason.
> >
> >
> > But... that completely reverts Martell's r245084, which apparently
> > fixed PR24398. So you two need to figure out what the actual problem
> > is here, and what the right fix is. r245084 didn't provide any test
> > cases, and had no apparent effect other than to break long double
> > for mingw32; did it really fix PR24398 (and if so, how)?
> >
> >
> >
> >
> >
> > On Thu, Aug 20, 2015 at 2:27 PM, Yaron Keren < yaron.keren at gmail.com
> > > wrote:
> >
> >
> >
> >
> > OK, based on testing, mingw i686 aligns long doubles to 4 bytes:
> >
> >
> >
> >
> > sh-4.3$ cat < a.cpp
> > #include <iostream>
> > int main() {
> > struct {
> > char c[1];
> > long double d;
> > } s;
> > std::cout<<&s.c<<std::endl;
> > std::cout<<&s.d<<std::endl;
> > }
> > sh-4.3$ g++ a.cpp&&./a.exe
> > 0x28fea0
> > 0x28fea4
> >
> >
> > I'll fix that.
> >
> >
> >
> >
> >
> >
> >
> > 2015-08-21 0:13 GMT+03:00 Richard Smith < richard at metafoo.co.uk > :
> >
> >
> >
> >
> >
> >
> > On Wed, Aug 19, 2015 at 11:42 AM, Yaron Keren < yaron.keren at gmail.com
> > > wrote:
> >
> >
> >
> >
> > Yes, it looks like a legacy issue. Documentation says so:
> >
> >
> >
> >
> https://gcc.gnu.org/onlinedocs/gcc-4.8.2/gcc/i386-and-x86-64-Options.html
> >
> >
> >
> > -m96bit-long-double -m128bit-long-double These switches control the
> > size of long double type. The i386 application binary interface
> > specifies the size to be 96 bits, so -m96bit-long-double is the
> > default in 32-bit mode.
> >
> > Modern architectures (Pentium and newer) prefer long double to be
> > aligned to an 8- or 16-byte boundary. In arrays or structures
> > conforming to the ABI, this is not possible. So specifying
> > -m128bit-long-double aligns long double to a 16-byte boundary by
> > padding the long double with an additional 32-bit zero.
> >
> > In the x86-64 compiler, -m128bit-long-double is the default choice as
> > its ABI specifies that long double is aligned on 16-byte boundary.
> >
> > Notice that neither of these options enable any extra precision over
> > the x87 standard of 80 bits for a long double .
> >
> > Warning: if you override the default value for your target ABI, this
> > changes the size of structures and arrays containing long double
> > variables, as well as modifying the function calling convention for
> > functions taking long double . Hence they are not binary-compatible
> > with code compiled without that switch.
> >
> >
> > And practical testing agrees:
> >
> >
> >
> >
> > sh-4.3$ cat < a.cpp
> > #include <iostream>
> > int main() {
> > long double a;
> > std::cout<<sizeof(a)<<std::endl;
> > }
> > sh-4.3$ g++ -v
> > Using built-in specs.
> > COLLECT_GCC=C:\mingw32\bin\g++.exe
> >
> COLLECT_LTO_WRAPPER=C:/mingw32/bin/../libexec/gcc/i686-w64-mingw32/5.1.0/lto-wrapper.exe
> > Target: i686-w64-mingw32
> > Configured with: ../../../src/gcc-5.1.0/configure
> > --host=i686-w64-mingw32 --build=i686-w64-mingw32
> > --target=i686-w64-mingw32 --prefix=/mingw32
> > --with-sysroot=/c/mingw510/i686-510-posix-dwarf-rt_v4-rev0/mingw32
> > --with-gxx-include-dir=/mingw32/i686-w64-mingw32/include/c++
> > --enable-shared --enable-static --disable-multilib
> > --enable-languages=c,c++,fortran,objc,obj-c++,lto
> > --enable-libstdcxx-time=yes --enable-threads=posix --enable-libgomp
> > --enable-libatomic --enable-lto --enable-graphite
> > --enable-checking=release --enable-fully-dynamic-string
> > --enable-version-specific-runtime-libs --disable-sjlj-exceptions
> > --with-dwarf2 --disable-isl-version-check --disable-libstdcxx-pch
> > --disable-libstdcxx-debug --enable-bootstrap --disable-rpath
> > --disable-win32-registry --disable-nls --disable-werror
> > --disable-symvers --with-gnu-as --with-gnu-ld --with-arch=i686
> > --with-tune=generic --with-libiconv --with-system-zlib
> > --with-gmp=/c/mingw510/prerequisites/i686-w64-mingw32-static
> > --with-mpfr=/c/mingw510/prerequisites/i686-w64-mingw32-static
> > --with-mpc=/c/mingw510/prerequisites/i686-w64-mingw32-static
> > --with-isl=/c/mingw510/prerequisites/i686-w64-mingw32-static
> > --with-pkgversion='i686-posix-dwarf-rev0, Built by MinGW-W64
> > project' --with-bugurl= http://sourceforge.net/projects/mingw-w64
> > CFLAGS='-O2 -pipe
> > -I/c/mingw510/i686-510-posix-dwarf-rt_v4-rev0/mingw32/opt/include
> > -I/c/mingw510/prerequisites/i686-zlib-static/include
> > -I/c/mingw510/prerequisites/i686-w64-mingw32-static/include'
> > CXXFLAGS='-O2 -pipe
> > -I/c/mingw510/i686-510-posix-dwarf-rt_v4-rev0/mingw32/opt/include
> > -I/c/mingw510/prerequisites/i686-zlib-static/include
> > -I/c/mingw510/prerequisites/i686-w64-mingw32-static/include'
> > CPPFLAGS= LDFLAGS='-pipe
> > -L/c/mingw510/i686-510-posix-dwarf-rt_v4-rev0/mingw32/opt/lib
> > -L/c/mingw510/prerequisites/i686-zlib-static/lib
> > -L/c/mingw510/prerequisites/i686-w64-mingw32-static/lib
> > -Wl,--large-address-aware'
> > Thread model: posix
> > gcc version 5.1.0 (i686-posix-dwarf-rev0, Built by MinGW-W64 project)
> >
> >
> > sh-4.3$ g++ a.cpp
> > sh-4.3$ ./a.exe
> >
> > 12
> >
> >
> > Without the patch clang outputs 16 and seg faults on a boost::math
> > example.
> >
> >
> > None of that answers my question. Our default GCC-compatible behavior
> > for x86_32 long double is to give it 4-byte alignment, 12-byte size,
> > and this matches the behavior I observe with GCC. Does MinGW
> > /really/ deviate from this and give long double a 16-byte alignment?
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > 2015-08-19 21:29 GMT+03:00 Richard Smith < richard at metafoo.co.uk > :
> >
> >
> >
> >
> >
> >
> > On Wed, Aug 19, 2015 at 10:02 AM, Yaron Keren via cfe-commits <
> > cfe-commits at lists.llvm.org > wrote:
> >
> >
> > Author: yrnkrn
> > Date: Wed Aug 19 12:02:32 2015
> > New Revision: 245459
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=245459&view=rev
> > Log:
> > According to i686 ABI, long double size on x86 is 12 bytes not 16
> > bytes.
> > See
> > https://gcc.gnu.org/onlinedocs/gcc-3.2/gcc/i386-and-x86-64-Options.html
> >
> >
> > Added:
> > cfe/trunk/test/CodeGen/mingw-long-double-size.c
> > Modified:
> > cfe/trunk/lib/Basic/Targets.cpp
> >
> > Modified: cfe/trunk/lib/Basic/Targets.cpp
> > URL:
> >
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Basic/Targets.cpp?rev=245459&r1=245458&r2=245459&view=diff
> >
> ==============================================================================
> > --- cfe/trunk/lib/Basic/Targets.cpp (original)
> > +++ cfe/trunk/lib/Basic/Targets.cpp Wed Aug 19 12:02:32 2015
> > @@ -3785,7 +3785,8 @@ class MinGWX86_32TargetInfo : public Win
> > public:
> > MinGWX86_32TargetInfo(const llvm::Triple &Triple)
> > : WindowsX86_32TargetInfo(Triple) {
> > - LongDoubleWidth = LongDoubleAlign = 128;
> > + LongDoubleWidth = 96;
> > + LongDoubleAlign = 128;
> >
> >
> >
> > Is this really correct? It's deeply suspicious that the size is not a
> > multiple of the alignment.
> >
> >
> > LongDoubleFormat = &llvm::APFloat::x87DoubleExtended;
> > }
> > void getTargetDefines(const LangOptions &Opts,
> >
> > Added: cfe/trunk/test/CodeGen/mingw-long-double-size.c
> > URL:
> >
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/mingw-long-double-size.c?rev=245459&view=auto
> >
> ==============================================================================
> > --- cfe/trunk/test/CodeGen/mingw-long-double-size.c (added)
> > +++ cfe/trunk/test/CodeGen/mingw-long-double-size.c Wed Aug 19
> > 12:02:32 2015
> > @@ -0,0 +1,5 @@
> > +// RUN: %clang_cc1 -triple i686-pc-windows-gnu -S %s -o - |
> > FileCheck %s -check-prefix=CHECK_I686
> > +// CHECK_I686: lda,12
> > +// RUN: %clang_cc1 -triple x86_64-pc-windows-gnu -S %s -o - |
> > FileCheck %s -check-prefix=CHECK_X86_64
> > +// CHECK_X86_64: lda,16
> > +long double lda;
> >
> >
> > _______________________________________________
> > cfe-commits mailing list
> > cfe-commits at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
> >
> >
> >
> >
> >
> >
> > _______________________________________________
> > cfe-commits mailing list
> > cfe-commits at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
> >
>
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20150919/577a1c13/attachment-0001.html>