[Bug middle-end/66785] New: internal compiler error in record_operand_use

["chris_s_jones at yahoo dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66785

            Bug ID: 66785
           Summary: internal compiler error in record_operand_use
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: chris_s_jones at yahoo dot com
  Target Milestone: ---

Created attachment 35920
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35920&action=edit
Source file to repro error

Using GCC from a recent trunk checkout (rev 225476), I am seeing the following
error on a simple input file.  I'm using an ARM AArch64 cross-compiler running
on a x86_64 host, though I'm unsure if that makes a difference for this case. 
Both -O3 and -funroll-loops are required to hit the error.

% aarch64-linux-gnu-gcc -c -o place_test.o -O3 -mcpu=cortex-a57 -march=armv8-a
-funroll-loops place_test.c
place_test.c: In function 'place_and_route':
place_test.c:23:1: internal compiler error: in record_operand_use, at
regrename.c:215
 }
 ^
0xabc68d record_operand_use
       
/local/chrisj/cd110/dev/cpu/tools/compiler/gcc/gcc-trunk/gcc/regrename.c:215
0xabcf74 scan_rtx_reg
       
/local/chrisj/cd110/dev/cpu/tools/compiler/gcc/gcc-trunk/gcc/regrename.c:1130
0xabe9ec build_def_use
       
/local/chrisj/cd110/dev/cpu/tools/compiler/gcc/gcc-trunk/gcc/regrename.c:1710
0xabe9ec regrename_analyze(bitmap_head*)
       
/local/chrisj/cd110/dev/cpu/tools/compiler/gcc/gcc-trunk/gcc/regrename.c:726
0xe5dd12 func_fma_steering::execute_fma_steering()
       
/local/chrisj/cd110/dev/cpu/tools/compiler/gcc/gcc-trunk/gcc/config/aarch64/cortex-a57-fma-steering.c:1034
0xe5e85d pass_fma_steering::execute(function*)
       
/local/chrisj/cd110/dev/cpu/tools/compiler/gcc/gcc-trunk/gcc/config/aarch64/cortex-a57-fma-steering.c:1071
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.

The function is simple (full file attached) after being pruned as much as
possible.

void place_and_route (int num_regions)
{
    int i, j;
    float capacity;

    for (i=0;i<num_regions;i++) {
        for (j=0;j<num_regions;j++) {
            place_region_y[i][j].capacity = capacity;
            place_region_y[i][j].inv_capacity = 1. / capacity;
            place_region_y[i][j].occupancy = 0.;
            place_region_y[i][j].cost = 0.;
        }
    }
}

Setting 'capacity' to a known non-zero value also makes the ICE go away. 
Explicitly setting it to zero results in the same error and eliminates the
obvious -Wunused-value warning.

Output of gcc -v (paths trimmed)
Using built-in specs.
COLLECT_GCC=/gcc-aarch64-225476/bin/aarch64-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/gcc-aarch64-225476/libexec/gcc/aarch64-linux-gnu/6.0.0/lto-wrapper
Target: aarch64-linux-gnu
Configured with: /gcc-trunk/configure CC=/gcc-x86/4.8.1/bin/gcc
CXX=/gcc-x86/4.8.1/r0/bin/g++
LDFLAGS=-Wl,-rpath,/gcc-aarch64-225476/lib,-rpath,/gcc-x86/4.8.1/x86_64/lib64
'CFLAGS_FOR_TARGET=-march=armv8-a -mcpu=cortex-a57 -O3'
'CXXFLAGS_FOR_TARGET=-march=armv8-a -mcpu=cortex-a57 -O3'
--prefix=/gcc-aarch64-225476 --target=aarch64-linux-gnu
--with-sysroot=/gcc-aarch64-225476/sysroot --with-gmp=/gcc-aarch64-225476
--with-mpc=/gcc-aarch64-225476 --with-mpfr=/gcc-aarch64-225476
--with-isl=/gcc-aarch64-225476 --enable-__cxa_atexit --with-gnu-as
--with-gnu-ld --enable-shared --disable-libssp --disable-libmudflap
--enable-languages=c,c++,fortran --disable-libsanitizer --disable-nls
Thread model: posix
gcc version 6.0.0 20150706 (experimental) (GCC)