[Bug middle-end/105263] New: [9/10/11/12 Regression] ICE: gimple check: expected gimple_assign(error_mark), have gimple_nop() in gimple_assign_rhs1, at gimple.h:2655 with _Decimal64 -ffast-math

["zsojka at seznam dot cz" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105263

            Bug ID: 105263
           Summary: [9/10/11/12 Regression] ICE: gimple check: expected
                    gimple_assign(error_mark), have gimple_nop() in
                    gimple_assign_rhs1, at gimple.h:2655 with _Decimal64
                    -ffast-math
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu

Created attachment 52800
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52800&action=edit
reduced testcase

Compiler output:
$ x86_64-pc-linux-gnu-gcc -O -ffast-math testcase.c 
during GIMPLE pass: reassoc
testcase.c: In function 'foo':
testcase.c:7:1: internal compiler error: gimple check: expected
gimple_assign(error_mark), have gimple_nop() in gimple_assign_rhs1, at
gimple.h:2655
    7 | foo (U u)
      | ^~~
0x6e6c4d gimple_check_failed(gimple const*, char const*, int, char const*,
gimple_code, tree_code)
        /repo/gcc-trunk/gcc/gimple.cc:1292
0x7d830d GIMPLE_CHECK2<const gassign*>
        /repo/gcc-trunk/gcc/gimple.h:74
0x7d833d GIMPLE_CHECK2<const gassign*>
        /repo/gcc-trunk/gcc/gimple.h:2653
0x7d833d gimple_assign_rhs1
        /repo/gcc-trunk/gcc/gimple.h:2655
0x7d886f gimple_assign_rhs1
        /repo/gcc-trunk/gcc/tree.h:3571
0x7d886f rewrite_expr_tree
        /repo/gcc-trunk/gcc/tree-ssa-reassoc.cc:5248
0x155514e rewrite_expr_tree
        /repo/gcc-trunk/gcc/tree-ssa-reassoc.cc:5339
0x155514e rewrite_expr_tree
        /repo/gcc-trunk/gcc/tree-ssa-reassoc.cc:5339
0x15665fa reassociate_bb
        /repo/gcc-trunk/gcc/tree-ssa-reassoc.cc:6848
0x156593a reassociate_bb
        /repo/gcc-trunk/gcc/tree-ssa-reassoc.cc:6897
0x1567ede do_reassoc
        /repo/gcc-trunk/gcc/tree-ssa-reassoc.cc:7009
0x1567ede execute_reassoc
        /repo/gcc-trunk/gcc/tree-ssa-reassoc.cc:7098
0x1567ede execute
        /repo/gcc-trunk/gcc/tree-ssa-reassoc.cc:7139
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

$ x86_64-pc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-amd64/bin/x86_64-pc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-r12-8113-20220412190241-gaa7874596b9-checking-yes-rtl-df-extra-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/12.0.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++
--enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra
--with-cloog --with-ppl --with-isl --build=x86_64-pc-linux-gnu
--host=x86_64-pc-linux-gnu --target=x86_64-pc-linux-gnu
--with-ld=/usr/bin/x86_64-pc-linux-gnu-ld
--with-as=/usr/bin/x86_64-pc-linux-gnu-as --disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-r12-8113-20220412190241-gaa7874596b9-checking-yes-rtl-df-extra-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 12.0.1 20220412 (experimental) (GCC)