[Bug rtl-optimization/115992] New: [15 regression] ICE when building linux-6.9.10 (RTL check: expected code 'reg', have 'subreg' in rhs_regno, at rtl.h:1934)

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115992

            Bug ID: 115992
           Summary: [15 regression] ICE when building linux-6.9.10 (RTL
                    check: expected code 'reg', have 'subreg' in
                    rhs_regno, at rtl.h:1934)
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sjames at gcc dot gnu.org
  Target Milestone: ---

I can't include the original as it required the kernel's GCC plugins to
reproduce and I didn't try to kill that dependency, sorry.

Only notable patch to mention on this build is that -fno-ext-dce is default,
not -fext-dce, for -O2.

```
typedef unsigned u32;
u32 gm200_acr_wpr_build_acrgm200_acr_wpr_build__size;
int gm200_acr_wpr_build_acrgm200_acr_wpr_build_lsfw_1;
void ptrs_0(int, long, u32);
void gm200_acr_wpr_build_acrgm200_acr_wpr_build() {
  u32 offset = 0;
  for (; gm200_acr_wpr_build_acrgm200_acr_wpr_build_lsfw_1;) {
    int hdr;
    u32 _addr = offset, *_data = &hdr;
    while (gm200_acr_wpr_build_acrgm200_acr_wpr_build__size) {
      ptrs_0(0, _addr, *_data++);
      _addr += 4;
    }
    offset += sizeof(hdr);
  }
  ptrs_0(0, offset, 0);
}
```

```
$ gcc -c gm200.i -O2 -fno-PIE
during RTL pass: final
gm200.i: In function ‘gm200_acr_wpr_build_acrgm200_acr_wpr_build’:
gm200.i:17:1: internal compiler error: RTL check: expected code 'reg', have
'subreg' in rhs_regno, at rtl.h:1934
   17 | }
      | ^
0x55558ecf32c7 internal_error(char const*, ...)
       
/usr/src/debug/sys-devel/gcc-15.0.0_pre20240714-r1/gcc-15-20240714/gcc/diagnostic-global-context.cc:491
0x55558e598015 rtl_check_failed_code1(rtx_def const*, rtx_code, char const*,
int, char const*)
       
/usr/src/debug/sys-devel/gcc-15.0.0_pre20240714-r1/gcc-15-20240714/gcc/rtl.cc:770
0x55558ddfd393 rhs_regno(rtx_def const*)
       
/usr/src/debug/sys-devel/gcc-15.0.0_pre20240714-r1/gcc-15-20240714/gcc/rtl.h:1934
0x55558ddfd393 print_reg(rtx_def*, int, _IO_FILE*)
       
/usr/src/debug/sys-devel/gcc-15.0.0_pre20240714-r1/gcc-15-20240714/gcc/config/i386/i386.cc:13388
0x55558f5a5e15 ix86_print_operand_address_as
       
/usr/src/debug/sys-devel/gcc-15.0.0_pre20240714-r1/gcc-15-20240714/gcc/config/i386/i386.cc:14505
0x55558f46de0d ix86_print_operand_address
       
/usr/src/debug/sys-devel/gcc-15.0.0_pre20240714-r1/gcc-15-20240714/gcc/config/i386/i386.cc:14575
0x55558f46de0d output_address(machine_mode, rtx_def*)
       
/usr/src/debug/sys-devel/gcc-15.0.0_pre20240714-r1/gcc-15-20240714/gcc/final.cc:3647
0x55558f46de0d ix86_print_operand(_IO_FILE*, rtx_def*, int)
       
/usr/src/debug/sys-devel/gcc-15.0.0_pre20240714-r1/gcc-15-20240714/gcc/config/i386/i386.cc:13581
0x55558f46d704 output_operand(rtx_def*, int)
       
/usr/src/debug/sys-devel/gcc-15.0.0_pre20240714-r1/gcc-15-20240714/gcc/final.cc:3631
0x55558f46b8c9 output_asm_insn(char const*, rtx_def**)
       
/usr/src/debug/sys-devel/gcc-15.0.0_pre20240714-r1/gcc-15-20240714/gcc/final.cc:3524
0x55558f46833d final_scan_insn_1
       
/usr/src/debug/sys-devel/gcc-15.0.0_pre20240714-r1/gcc-15-20240714/gcc/final.cc:2840
0x55558f45dbcc final_scan_insn(rtx_insn*, _IO_FILE*, int, int, int*)
       
/usr/src/debug/sys-devel/gcc-15.0.0_pre20240714-r1/gcc-15-20240714/gcc/final.cc:2886
0x55558f45dbcc final_1
       
/usr/src/debug/sys-devel/gcc-15.0.0_pre20240714-r1/gcc-15-20240714/gcc/final.cc:1977
0x55558f7a2d3f rest_of_handle_final
       
/usr/src/debug/sys-devel/gcc-15.0.0_pre20240714-r1/gcc-15-20240714/gcc/final.cc:4239
0x55558f7a2d3f execute
       
/usr/src/debug/sys-devel/gcc-15.0.0_pre20240714-r1/gcc-15-20240714/gcc/final.cc:4317
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-15.0.0_pre20240714-r1/work/gcc-15-20240714/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
--with-bugurl=https://bugs.gentoo.org/ --with-pkgversion='Gentoo Hardened
15.0.0_pre20240714-r1 p5' --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 --enable-cet
--disable-systemtap --disable-valgrind-annotations --disable-vtable-verify
--disable-libvtv --with-zstd --without-isl --enable-default-pie
--enable-host-pie --enable-host-bind-now --enable-default-ssp
--disable-fixincludes --with-build-config='bootstrap-O3 bootstrap-lto
bootstrap-cet'
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 15.0.0 20240714 (experimental) (Gentoo Hardened
15.0.0_pre20240714-r1 p5)
```