[Bug target/79912] New: [7 regression] LRA unable to generate reloads after r245655

["npickito at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79912

            Bug ID: 79912
           Summary: [7 regression] LRA unable to generate reloads after
                    r245655
           Product: gcc
           Version: 6.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: npickito at gmail dot com
                CC: matthew.fortune at imgtec dot com, vmakarov at redhat dot com
  Target Milestone: ---
            Target: riscv32-unknown-linux-gnu

Created attachment 40893
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40893&action=edit
vfscanf.i

It's ICE after r245655, and work if revert it.

Configure:  --target=riscv32-unknown-linux-gnu --with-abi=ilp32d
--with-arch=rv32imafd

riscv32-elf-gcc vfscanf.i -O2

vfscanf.c: In function ‘_IO_vfscanf_internal’:
vfscanf.c:3050:1: error: unable to generate reloads for:
(insn 11026 11523 5651 1080 (set (reg:QI 3515)
        (mem/c:QI (plus:SI (reg/f:SI 65 frame)
                (const_int -1568 [0xfffffffffffff9e0])) [65 %sfp+-1504 S1
A32])) "vfscanf.c":266 138 {*movqi_internal}
     (expr_list:REG_DEAD (reg:QI 3956)
        (nil)))
vfscanf.c:3050:1: internal compiler error: in curr_insn_transform, at
lra-constraints.c:3785
0xa9f028 _fatal_insn(char const*, rtx_def const*, char const*, int, char
const*)
        ../../../src/gcc/trunk/gcc/rtl-error.c:108
0x9a1d91 curr_insn_transform
        ../../../src/gcc/trunk/gcc/lra-constraints.c:3785
0x9a3016 lra_constraints(bool)
        ../../../src/gcc/trunk/gcc/lra-constraints.c:4754
0x98cd0c lra(_IO_FILE*)
        ../../../src/gcc/trunk/gcc/lra.c:2392
0x942b6b do_reload
        ../../../src/gcc/trunk/gcc/ira.c:5451
0x942b6b execute
        ../../../src/gcc/trunk/gcc/ira.c:5635
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