[Bug tree-optimization/66510] New: gcc.target/arm/pr53636.c FAILs after r224221

[jgreenhalgh at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66510

            Bug ID: 66510
           Summary: gcc.target/arm/pr53636.c FAILs after r224221
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jgreenhalgh at gcc dot gnu.org
                CC: rguenth at gcc dot gnu.org
  Target Milestone: ---
            Target: arm-none-eabi, arm-none-linux-gnueabihf

Created attachment 35762
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=35762&action=edit
Minimal reproduced (derived from gcc.target/arm/pr53636.c )

r224221 caused an ICE in the ARM port (arm-none-eabi,
arm-none-linux-gnueabihf):

    FAIL: gcc.target/arm/pr53636.c (internal compiler error)

Full ICE text below, and reduced testcase attached (bug.c), compile with:

    arm-none-eabi-gcc -O -ftree-vectorize -mfpu=neon -mcpu=cortex-a9
-mfloat-abi=hard bug.c 

I tried to take a look to see what was happening, but I couldn't see
the root of the problem. The access to dr_chain in
vect_create_mask_and_perm:

    second_vec = dr_chain[second_vec_indx];

Fails as dr_chain has length 1, and second_vec_indx is 2.

I think that the mask that the code is trying to produce is { 1, 2, 3, 4 }.

    bug.c:4:3: note: add new stmt: vect__8.6_108 = VEC_PERM_EXPR
<vect__8.4_104, vect__8.5_106, { 1, 2, 3, 4 }>;

But that's about as far as I got.

Thanks,
James

---
bug.c: In function 'test':
bug.c:1:6: internal compiler error: in operator[], at vec.h:738
 void test(unsigned char *dst) {
      ^
0xd759fe vec<tree_node*, va_heap, vl_embed>::operator[](unsigned int)
        .../src/gcc/gcc/vec.h:738
0xd759fe vec<tree_node*, va_heap, vl_ptr>::operator[](unsigned int)
        .../src/gcc/gcc/vec.h:1204
0xd759fe vect_create_mask_and_perm
        .../src/gcc/gcc/tree-vect-slp.c:3072
0xd759fe vect_transform_slp_perm_load(_slp_tree*, vec<tree_node*, va_heap,
vl_ptr>, gimple_stmt_iterator*, int, _slp_instance*, bool)
        .../src/gcc/gcc/tree-vect-slp.c:3350
0xd51613 vectorizable_load
        .../src/gcc/gcc/tree-vect-stmts.c:6847
0xd57ad2 vect_transform_stmt(gimple_statement_base*, gimple_stmt_iterator*,
bool*, _slp_tree*, _slp_instance*)
        .../src/gcc/gcc/tree-vect-stmts.c:7490
0xd7aac1 vect_schedule_slp_instance
        .../src/gcc/gcc/tree-vect-slp.c:3500
0xd7a117 vect_schedule_slp_instance
        .../src/gcc/gcc/tree-vect-slp.c:3381
0xd7a117 vect_schedule_slp_instance
        .../src/gcc/gcc/tree-vect-slp.c:3381
0xd7a117 vect_schedule_slp_instance
        .../src/gcc/gcc/tree-vect-slp.c:3381
0xd7a117 vect_schedule_slp_instance
        .../src/gcc/gcc/tree-vect-slp.c:3381
0xd7a117 vect_schedule_slp_instance
        .../src/gcc/gcc/tree-vect-slp.c:3381
0xd7a117 vect_schedule_slp_instance
        .../src/gcc/gcc/tree-vect-slp.c:3381
0xd7a117 vect_schedule_slp_instance
        .../src/gcc/gcc/tree-vect-slp.c:3381
0xd7abce vect_schedule_slp(_loop_vec_info*, _bb_vec_info*)
        .../src/gcc/gcc/tree-vect-slp.c:3570
0xd5e564 vect_transform_loop(_loop_vec_info*)
        .../src/gcc/gcc/tree-vect-loop.c:6223
0xd7eca8 vectorize_loops()
        .../src/gcc/gcc/tree-vectorizer.c:499
0xc88c54 execute
        .../src/gcc/gcc/tree-ssa-loop.c:292
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