[Bug rtl-optimization/67029] [5/6 regression] gcc-5.2.0 unable to find a register to spill with O3 fsched-pressure fschedule-insns

["hjl.tools at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67029

--- Comment #10 from H.J. Lu <hjl.tools at gmail dot com> ---
The problem is

/* The value of get_preferred_alternatives for the current instruction,
   supplemental to recog_data.  */
static alternative_mask preferred_alternatives;

ira_implicitly_set_insn_hard_regs may use the staled preferred_alternatives:

#0  ira_implicitly_set_insn_hard_regs (set=0x7fffffffd950)
    at /export/gnu/import/git/sources/gcc/gcc/ira-lives.c:847
#1  0x000000000156d604 in sched_analyze_insn (deps=0x7fffffffdba0, 
    x=0x7ffff18277d0, insn=0x7ffff1823240)
    at /export/gnu/import/git/sources/gcc/gcc/sched-deps.c:2901
#2  0x00000000015703f5 in deps_analyze_insn (deps=0x7fffffffdba0, 
    insn=0x7ffff1823240)
    at /export/gnu/import/git/sources/gcc/gcc/sched-deps.c:3675
#3  0x0000000001570aa6 in sched_analyze (deps=0x7fffffffdba0, 
    head=0x7ffff1823240, tail=0x7ffff1708990)
    at /export/gnu/import/git/sources/gcc/gcc/sched-deps.c:3822
#4  0x0000000000c4b3d0 in compute_block_dependences (bb=0)
    at /export/gnu/import/git/sources/gcc/gcc/sched-rgn.c:2743
#5  0x0000000000c4ccae in sched_rgn_compute_dependencies (rgn=0)
    at /export/gnu/import/git/sources/gcc/gcc/sched-rgn.c:3267
#6  0x0000000000c4c2bf in schedule_region (rgn=0)
    at /export/gnu/import/git/sources/gcc/gcc/sched-rgn.c:3023
#7  0x0000000000c4d3e6 in schedule_insns ()
    at /export/gnu/import/git/sources/gcc/gcc/sched-rgn.c:3426
#8  0x0000000000c4dca4 in rest_of_handle_sched ()