[Bug target/116275] New: [15 regression] ICE when building llvm-18.1.8 (convert_insn, at config/i386/i386-features.cc:1502)

[Bug target/116275] New: [15 regression] ICE when building llvm-18.1.8 (convert_insn, at config/i386/i386-features.cc:1502)

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116275

            Bug ID: 116275
           Summary: [15 regression] ICE when building llvm-18.1.8
                    (convert_insn, at config/i386/i386-features.cc:1502)
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sjames at gcc dot gnu.org
                CC: roger at nextmovesoftware dot com
  Target Milestone: ---

Created attachment 58862
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58862&action=edit
SymbolizableObjectFile.cpp.ii.xz

```
$ g++
../llvm_build-abi_x86_32.x86/lib/DebugInfo/Symbolize/CMakeFiles/LLVMSymbolize.dir/SymbolizableObjectFile.cpp.ii
-std=c++17 -m32 -O2 -c
/var/tmp/portage/sys-devel/llvm-18.1.8-r4/work/llvm/lib/DebugInfo/Symbolize/SymbolizableObjectFile.cpp:
In member function ‘llvm::Error
llvm::symbolize::SymbolizableObjectFile::addSymbo (const
llvm::object::SymbolRef&, uint64_t, llvm::DataExtractor*, uint64_t)’:
/var/tmp/portage/sys-devel/llvm-18.1.8-r4/work/llvm/lib/DebugInfo/Symbolize/SymbolizableObjectFile.cpp:220:1:
error: unrecognizable insn:
  220 | }
      | ^
(insn 395 394 396 55 (set (subreg:V2DI (reg/v:DI 113 [ SymbolAddress ]) 0)
        (ashiftrt:V2DI (ashift:V2DI (subreg:V2DI (reg/v:DI 113 [ SymbolAddress
]) 0)
                (const_int 8 [0x8]))
            (const_int 8 [0x8])))
"/var/tmp/portage/sys-devel/llvm-18.1.8-r4/work/llvm/lib/DebugInfo/Symbolize/SymbolizableObjectFile.cpp":200:19
-1
     (expr_list:REG_UNUSED (reg:CC 17 flags)
        (nil)))
during RTL pass: stv
/var/tmp/portage/sys-devel/llvm-18.1.8-r4/work/llvm/lib/DebugInfo/Symbolize/SymbolizableObjectFile.cpp:220:1:
internal compiler error: in convert_insn, at config/i386/i386-features.cc:1502
0x559e7ebf3927 internal_error(char const*, ...)
       
/usr/src/debug/sys-devel/gcc-15.0.9999/gcc-15.0.9999/gcc/diagnostic-global-context.cc:491
0x559e7ebf3ac2 fancy_abort(char const*, int, char const*)
       
/usr/src/debug/sys-devel/gcc-15.0.9999/gcc-15.0.9999/gcc/diagnostic.cc:1772
0x559e7e455e5b _fatal_insn(char const*, rtx_def const*, char const*, int, char
const*)
       
/usr/src/debug/sys-devel/gcc-15.0.9999/gcc-15.0.9999/gcc/rtl-error.cc:108
0x559e7e45602e _fatal_insn_not_found(rtx_def const*, char const*, int, char
const*)
       
/usr/src/debug/sys-devel/gcc-15.0.9999/gcc-15.0.9999/gcc/rtl-error.cc:116
0x559e7e172935 convert_insn
       
/usr/src/debug/sys-devel/gcc-15.0.9999/gcc-15.0.9999/gcc/config/i386/i386-features.cc:1502
0x559e7f3e0a68 convert
       
/usr/src/debug/sys-devel/gcc-15.0.9999/gcc-15.0.9999/gcc/config/i386/i386-features.cc:1987
0x559e7f3e0a68 convert_scalars_to_vector
       
/usr/src/debug/sys-devel/gcc-15.0.9999/gcc-15.0.9999/gcc/config/i386/i386-features.cc:2532
0x559e7f3e0a68 execute
       
/usr/src/debug/sys-devel/gcc-15.0.9999/gcc-15.0.9999/gcc/config/i386/i386-features.cc:2746
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://bugs.gentoo.org/> for instructions.
```

```
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/15/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with:
/var/tmp/portage/sys-devel/gcc-15.0.9999/work/gcc-15.0.9999/configure
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --prefix=/usr
--bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/15
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/15/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/15
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/15/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/15/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/15/include/g++-v15
--disable-silent-rules --disable-dependency-tracking
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/15/python
--enable-languages=c,c++,fortran --enable-obsolete --enable-secureplt
--disable-werror --with-system-zlib --enable-nls --without-included-gettext
--disable-libunwind-exceptions --enable-checking=yes,extra,rtl,df
--with-bugurl=https://bugs.gentoo.org/ --with-pkgversion='Gentoo 15.0.9999 p,
commit 767d91209f8983d23caae12e2337eca6c2b5dbdb' --with-gcc-major-version-only
--enable-libstdcxx-time --enable-lto --disable-libstdcxx-pch --enable-shared
--enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu
--enable-multilib --with-multilib-list=m32,m64 --disable-fixed-point
--enable-targets=all --enable-libgomp --disable-libssp --disable-libada
--disable-cet --disable-systemtap --disable-valgrind-annotations
--disable-vtable-verify --disable-libvtv --with-zstd --without-isl
--enable-default-pie --enable-host-pie --disable-host-bind-now
--enable-default-ssp --disable-fixincludes --with-build-config='bootstrap-O3
bootstrap-lto'
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 15.0.0 20240807 (experimental)
2083389a18d36684a88d9e2653bacc87ad894b50 (Gentoo 15.0.9999 p, commit
767d91209f8983d23caae12e2337eca6c2b5dbdb)
```

[Bug target/116275] [15 regression] ICE when building llvm-18.1.8 (convert_insn, at config/i386/i386-features.cc:1502)

[roger at nextmovesoftware dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116275

Roger Sayle <roger at nextmovesoftware dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
           Assignee|unassigned at gcc dot gnu.org      |roger at nextmovesoftware dot com
   Last reconfirmed|                            |2024-08-07
   Target Milestone|---                         |15.0

--- Comment #1 from Roger Sayle <roger at nextmovesoftware dot com> ---
Doh!  This is almost certainly caused by my recent ashrv2di patch. 
Investigating.

[Bug target/116275] [15 regression] ICE when building llvm-18.1.8 (convert_insn, at config/i386/i386-features.cc:1502)

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116275

--- Comment #2 from Sam James <sjames at gcc dot gnu.org> ---
Thank you Roger!

Reduced:
```
struct SymbolDesc push_back(SymbolDesc);
struct SymbolDesc {
  long long ELFLocalSymIdx;
};
struct Expected {
  long long &operator*();
};
void SymbolizableObjectFileaddSymbol() {
  Expected SymbolAddressOrErr;
  long long SymbolAddress = *SymbolAddressOrErr << 8 >> 8;
  push_back({SymbolAddress});
}
```

[Bug target/116275] [15 regression] ICE when building llvm-18.1.8 (convert_insn, at config/i386/i386-features.cc:1502)

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116275

--- Comment #3 from Sam James <sjames at gcc dot gnu.org> ---
(In reply to Sam James from comment #2)

(Make SymbolAddressOrErr a parameter for it to be well-defined.)

[Bug target/116275] [15 regression] ICE when building llvm-18.1.8 (convert_insn, at config/i386/i386-features.cc:1502)

[roger at nextmovesoftware dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116275

--- Comment #4 from Roger Sayle <roger at nextmovesoftware dot com> ---
Created attachment 58868
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=58868&action=edit
proposed patch

Here's my proposed fix (the first of two patches) that resolves the ICE with
the testcase.  The problem is that i386.md has a *extenddi2_doubleword_highpart
pattern on !TARGET_64BIT for noticing that sign-extending a doubleword can be
optimized to just manipulating the highpart.  The STV pass recognizes this as a
candidate, where previously ASHIFTRT of V2DI required AVX512VL, which runs into
problems as the post-reload splitter *extendv2di2_highpart_stv is conditional
on AVX512VL.

The first patch resolves this problem by adding a pre-reload splitter for this
case, called imaginatively called *extendv2di2_highpart_stv_noavx512vl.  This
relies on split1's recursive splitting, so that the generated code for
(x<<8)>>8 in the testcase becomes:

        vpsllq  $8, %xmm0, %xmm0
        vpsrad  $8, %xmm0, %xmm1
        vpsrlq  $8, %xmm0, %xmm0
        vpblendd        $5, %xmm0, %xmm1, %xmm0

I'll post a follow-up patch (part 2) that provides a better implementation for
this V2DI highpart sign extension, which can be done in 3 insns (taking
advantage of SSE's ability to arithmetic shift right the "highpart"):

        vpsllq  $8, %xmm0, %xmm1
        vpsrad  $8, %xmm1, %xmm1
        vpblendd        $5, %xmm0, %xmm1, %xmm0

Sorry for the inconvenience.  In the meantime, -mno-stv can be used as a
workaround.  The bootstrap and regression testing should finish in a little
while.

[Bug target/116275] [15 regression] ICE when building llvm-18.1.8 (convert_insn, at config/i386/i386-features.cc:1502)

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116275

--- Comment #5 from Sam James <sjames at gcc dot gnu.org> ---
Thank you, I'll use that for now, but please don't apologise. I do the testing
because I enjoy it and to help. No harm done.

[Bug target/116275] [15 regression] ICE when building llvm-18.1.8 (convert_insn, at config/i386/i386-features.cc:1502)

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116275

--- Comment #6 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Roger Sayle <sayle@gcc.gnu.org>:

https://gcc.gnu.org/g:7a970bd03f1d8eed7703db8a8db3c753ea68899f

commit r15-2880-g7a970bd03f1d8eed7703db8a8db3c753ea68899f
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Mon Aug 12 06:52:48 2024 +0100

    PR target/116275: Handle STV of *extenddi2_doubleword_highpart on i386.

    This patch resolves PR target/116275, a recent ICE-on-valid regression on
    -m32 caused by my recent change to enable STV of DImode arithmeric right
    shift on non-AVX512VL targets.  The oversight is that the i386 backend
    contains an *extenddi2_doubleword_highpart instruction (whose pattern
    is an arithmetic right shift of a left shift) that optimizes the case where
    sign-extension need only update the highpart word of a DImode value when
    generating 32-bit code (!TARGET_64BIT).  STV accepts this pattern as a
    candidate, as there are patterns to handle this form of extension on SSE
    using AVX512VL instructions (and previously ASHIFTRT was only allowed on
    AVX512VL).  Now that ASHIFTRT is a candidate on non-AVX512vL targets, we
    either need to check that the first operand is a register, or as done
    below provide the define_insn_and_split that provides a non-AVX512VL
    implementation of *extendv2di_highpart_stv.

    The new testcase only ICEed with -m32, so this test could be limited to
    target ia32, but there's no harm also running this test on -m64 to
    provide a little extra test coverage.

    2024-08-12  Roger Sayle  <roger@nextmovesoftware.com>

    gcc/ChangeLog
            PR target/116275
            * config/i386/i386.md (*extendv2di2_highpart_stv_noavx512vl): New
            define_insn_and_split to handle the STV conversion of the DImode
            pattern *extendsi2_doubleword_highpart.

    gcc/testsuite/ChangeLog
            PR target/116275
            * g++.target/i386/pr116275.C: New test case.

[Bug target/116275] [15 regression] ICE when building llvm-18.1.8 (convert_insn, at config/i386/i386-features.cc:1502)

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116275

--- Comment #7 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Roger Sayle <sayle@gcc.gnu.org>:

https://gcc.gnu.org/g:b6fb4f7f651d2aa89548c5833fe2679af2638df5

commit r15-2940-gb6fb4f7f651d2aa89548c5833fe2679af2638df5
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Thu Aug 15 22:02:05 2024 +0100

    i386: Improve split of *extendv2di2_highpart_stv_noavx512vl.

    This patch follows up on the previous patch to fix PR target/116275 by
    improving the code STV (ultimately) generates for highpart sign extensions
    like (x<<8)>>8.  The arithmetic right shift is able to take advantage of
    the available common subexpressions from the preceding left shift.

    Hence previously with -O2 -m32 -mavx -mno-avx512vl we'd generate:

            vpsllq  $8, %xmm0, %xmm0
            vpsrad  $8, %xmm0, %xmm1
            vpsrlq  $8, %xmm0, %xmm0
            vpblendw        $51, %xmm0, %xmm1, %xmm0

    But with improved splitting, we now generate three instructions:

            vpslld  $8, %xmm1, %xmm0
            vpsrad  $8, %xmm0, %xmm0
            vpblendw        $51, %xmm1, %xmm0, %xmm0

    This patch also implements Uros' suggestion that the pre-reload
    splitter could introduced a new pseudo to hold the intermediate
    to potentially help reload with register allocation, which applies
    when not performing the above optimization, i.e. on TARGET_XOP.

    2024-08-15  Roger Sayle  <roger@nextmovesoftware.com>
                Uros Bizjak  <ubizjak@gmail.com>

    gcc/ChangeLog
            * config/i386/i386.md (*extendv2di2_highpart_stv_noavx512vl): Split
            to an improved implementation on !TARGET_XOP.  On TARGET_XOP, use
            a new pseudo for the intermediate to simplify register allocation.

    gcc/testsuite/ChangeLog
            * g++.target/i386/pr116275-2.C: New test case.

[Bug target/116275] [15 regression] ICE when building llvm-18.1.8 (convert_insn, at config/i386/i386-features.cc:1502)

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116275

Sam James <sjames at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED
           Keywords|                            |ice-on-valid-code

--- Comment #8 from Sam James <sjames at gcc dot gnu.org> ---
Confirmed fixed. Thank you Roger!