[Bug target/99596] New: arm: internal error in single_pred_edge

["arnd at linaro dot org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99596

            Bug ID: 99596
           Summary: arm: internal error in single_pred_edge
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: arnd at linaro dot org
  Target Milestone: ---

I ran into this internal compiler error while building the Linux kernel in
random configurations, made a reduced test case:

$ arm-linux-gnueabihf-gcc-11 -Os -mtune=xscale -c cfi_cmdset_0002.c 
during RTL pass: fwprop2
cfi_cmdset_0002.c: In function ‘i’:
cfi_cmdset_0002.c:16:1: internal compiler error: in single_pred_edge, at
basic-block.h:350
   16 | }
      | ^
0x7bf679 single_pred_edge
        ../../src/gcc/basic-block.h:350
0x7bf679 single_pred
        ../../src/gcc/basic-block.h:369
0x7bf679 rtl_ssa::function_info::create_degenerate_phi(rtl_ssa::ebb_info*,
rtl_ssa::set_info*)
        ../../src/gcc/rtl-ssa/blocks.cc:535
0x1860f6d rtl_ssa::function_info::finalize_new_accesses(rtl_ssa::insn_change&)
        ../../src/gcc/rtl-ssa/changes.cc:508
0x18617c3
rtl_ssa::function_info::change_insns(array_slice<rtl_ssa::insn_change*>)
        ../../src/gcc/rtl-ssa/changes.cc:659
0x1862078 rtl_ssa::function_info::change_insn(rtl_ssa::insn_change&)
        ../../src/gcc/rtl-ssa/changes.cc:717
0x172f1cd try_fwprop_subst_pattern
        ../../src/gcc/fwprop.c:552
0x172f1cd try_fwprop_subst
        ../../src/gcc/fwprop.c:625
0x172f73e forward_propagate_and_simplify
        ../../src/gcc/fwprop.c:823
0x172f73e forward_propagate_into
        ../../src/gcc/fwprop.c:883
0x172fb8a forward_propagate_into
        ../../src/gcc/fwprop.c:835
0x172fb8a fwprop_insn
        ../../src/gcc/fwprop.c:954
0x172fc49 fwprop
        ../../src/gcc/fwprop.c:992
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <file:///usr/share/doc/gcc-11/README.Bugs> for instructions.


$ cat cfi_cmdset_0002.c
register int a asm("sp");
extern int b;
typedef struct {
  long c[16 * 8 / 32];
} d;
int e;
int f;
int g;
d h;
int j(int, int, int, d);
int i(void) {
  for (;;) {
    b &&j(e, f, g, h);
    j(e, f, g, h);
  }
}

$ arm-linux-gnueabihf-gcc-11 --version
arm-linux-gnueabihf-gcc-11 (Ubuntu 11-20210310-1ubuntu1) 11.0.1 20210310
(experimental) [master revision
8dc225d311e:2453ef06221:5987d8a79cda1069c774e5c302d5597310270026]