[Bug rtl-optimization/71634] New: Invalid write with in mark_loops_for_removal (ira-build.c:2256) with --param ira-max-loops-num=0

["marxin at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71634

            Bug ID: 71634
           Summary: Invalid write with in mark_loops_for_removal
                    (ira-build.c:2256) with --param ira-max-loops-num=0
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: marxin at gcc dot gnu.org
  Target Milestone: ---

Hello.

Following simple test-case produces invalid write of size 1B in:

==29696== Invalid write of size 1
==29696==    at 0xA05331: mark_loops_for_removal (ira-build.c:2256)
==29696==    by 0xA05331: remove_unnecessary_regions(bool) (ira-build.c:2595)
==29696==    by 0xA0838A: ira_build() (ira-build.c:3422)
==29696==    by 0x9FEFA3: ira (ira.c:5220)
==29696==    by 0x9FEFA3: (anonymous namespace)::pass_ira::execute(function*)
(ira.c:5525)
==29696==    by 0xAE0463: execute_one_pass(opt_pass*) (passes.c:2344)
==29696==    by 0xAE0A37: execute_pass_list_1(opt_pass*) [clone .constprop.81]
(passes.c:2428)
==29696==    by 0xAE0A49: execute_pass_list_1(opt_pass*) [clone .constprop.81]
(passes.c:2429)
==29696==    by 0xAE0A94: execute_pass_list(function*, opt_pass*)
(passes.c:2439)
==29696==    by 0x7D4713: cgraph_node::expand() (cgraphunit.c:1983)
==29696==    by 0x7D6000: expand_all_functions (cgraphunit.c:2119)
==29696==    by 0x7D6000: symbol_table::compile() [clone .part.48]
(cgraphunit.c:2475)
==29696==    by 0x7D8427: compile (cgraphunit.c:2539)
==29696==    by 0x7D8427: symbol_table::finalize_compilation_unit()
(cgraphunit.c:2565)
==29696==    by 0xBAAEB7: compile_file() (toplev.c:490)
==29696==    by 0x63F4B3: do_compile (toplev.c:1998)
==29696==    by 0x63F4B3: toplev::main(int, char**) (toplev.c:2132)
==29696==  Address 0x40 is not stack'd, malloc'd or (recently) free'd

$ valgrind --leak-check=yes --trac gcc -O3  --param ira-max-loops-num=0 tc.i

$ cat tc.i
fn1() {}

I consider having min value of the parameter to zero does not make much sense
and I'll send patch to mailing list.

Martin