[Bug target/116240] New: RISC-V: ICE during RTL pass: combine with -fwrapv -march=rv64imv_xtheadcondmov_xventanacondops at -O2

[patrick at rivosinc dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116240

            Bug ID: 116240
           Summary: RISC-V: ICE during RTL pass: combine with -fwrapv
                    -march=rv64imv_xtheadcondmov_xventanacondops at -O2
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: patrick at rivosinc dot com
  Target Milestone: ---

Testcase:
int a, b;
void c() {
  int e = a >= 2 ? b : a;
  short d = e * 2;
  if (d)
    for (;;)
      ;
}

Command/backtrace:
> /scratch/tc-testing/tc-compiler-fuzz-trunk/build-gcv/bin/riscv64-unknown-linux-gnu-gcc
>  -fwrapv -O2 -march=rv64imvxtheadcondmov_xventanacondops red.c -c -S -o 
> /dev/null
during RTL pass: combine
red.c: In function 'c':
red.c:8:1: internal compiler error: Segmentation fault
    8 | }
      | ^
0x2de6255 internal_error(char const*, ...)
        ../../../gcc/gcc/diagnostic-global-context.cc:491
0x1388d33 crash_signal
        ../../../gcc/gcc/toplev.cc:321
0x759e6644251f ???
        ./signal/../sysdeps/unix/sysv/linux/x86_64/libc_sigaction.c:0
0x1310816 rtx_equal_p(rtx_def const*, rtx_def const*, bool (*)(rtx_def const**,
rtx_def const**, rtx_def**, rtx_def**))
        ../../../gcc/gcc/rtl.cc:442
0x179f0a5 riscv_rtx_costs
        ../../../gcc/gcc/config/riscv/riscv.cc:3650
0x1318e37 rtx_cost(rtx_def*, machine_mode, rtx_code, int, bool)
        ../../../gcc/gcc/rtlanal.cc:4605
0x268427c set_src_cost(rtx_def*, machine_mode, bool)
        ../../../gcc/gcc/rtl.h:2953
0x268427c force_int_to_mode
        ../../../gcc/gcc/combine.cc:8833
0x268427c force_to_mode
        ../../../gcc/gcc/combine.cc:8747
0x26840d2 force_int_to_mode
        ../../../gcc/gcc/combine.cc:8991
0x26840d2 force_to_mode
        ../../../gcc/gcc/combine.cc:8747
0x2689dcb make_compound_operation_int
        ../../../gcc/gcc/combine.cc:8393
0x268a32f make_compound_operation(rtx_def*, rtx_code)
        ../../../gcc/gcc/combine.cc:8471
0x268a2fb make_compound_operation(rtx_def*, rtx_code)
        ../../../gcc/gcc/combine.cc:8496
0x268e07e simplify_set
        ../../../gcc/gcc/combine.cc:6975
0x268e07e combine_simplify_rtx
        ../../../gcc/gcc/combine.cc:6374
0x269031f subst
        ../../../gcc/gcc/combine.cc:5630
0x2694499 try_combine
        ../../../gcc/gcc/combine.cc:3349
0x2699d19 combine_instructions
        ../../../gcc/gcc/combine.cc:1285
0x2699d19 rest_of_handle_combine
        ../../../gcc/gcc/combine.cc:15127
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.

This is a bit of an obscure bug since it's mixing two vendor extensions. If ISA
strings like this aren't interesting let me know and I'll make the vendor
extensions mutually exclusive during fuzzing.

Found via fuzzer.