[PATCH] IPA: prevent an UBSAN error

[Jan Hubicka]

> Prevents the following UBSAN error:
> 
> ./xgcc -B. /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/torture/pr49770.C -O2 -c
> /home/marxin/Programming/gcc2/gcc/ipa-modref-tree.h:482:22: runtime error: load of value 2, which is not a valid value for type 'bool'
>     #0 0x1fdb4d1 in modref_tree<int>::merge(modref_tree<int>*, vec<modref_parm_map, va_heap, vl_ptr>*) /home/marxin/Programming/gcc2/gcc/ipa-modref-tree.h:482
>     #1 0x1fcadaa in merge_call_side_effects(modref_summary*, gimple*, modref_summary*, bool) /home/marxin/Programming/gcc2/gcc/ipa-modref.c:511
>     #2 0x1fcbadd in analyze_call /home/marxin/Programming/gcc2/gcc/ipa-modref.c:642
>     #3 0x1fcc061 in analyze_stmt /home/marxin/Programming/gcc2/gcc/ipa-modref.c:732
>     #4 0x1fccf31 in analyze_function /home/marxin/Programming/gcc2/gcc/ipa-modref.c:823
>     #5 0x1fd17e5 in execute /home/marxin/Programming/gcc2/gcc/ipa-modref.c:1441
>     #6 0x25cca6e in execute_one_pass(opt_pass*) /home/marxin/Programming/gcc2/gcc/passes.c:2509
>     #7 0x25cd39b in execute_pass_list_1 /home/marxin/Programming/gcc2/gcc/passes.c:2597
>     #8 0x25cd450 in execute_pass_list_1 /home/marxin/Programming/gcc2/gcc/passes.c:2598
>     #9 0x25cd4ee in execute_pass_list(function*, opt_pass*) /home/marxin/Programming/gcc2/gcc/passes.c:2608
>     #10 0x25c7a5a in do_per_function_toporder(void (*)(function*, void*), void*) /home/marxin/Programming/gcc2/gcc/passes.c:1726
>     #11 0x25cfa3f in execute_ipa_pass_list(opt_pass*) /home/marxin/Programming/gcc2/gcc/passes.c:2941
>     #12 0x173572d in ipa_passes /home/marxin/Programming/gcc2/gcc/cgraphunit.c:2642
>     #13 0x17364ee in symbol_table::compile() /home/marxin/Programming/gcc2/gcc/cgraphunit.c:2777
>     #14 0x17372d9 in symbol_table::finalize_compilation_unit() /home/marxin/Programming/gcc2/gcc/cgraphunit.c:3022
>     #15 0x2a1f00a in compile_file /home/marxin/Programming/gcc2/gcc/toplev.c:485
>     #16 0x2a27dc8 in do_compile /home/marxin/Programming/gcc2/gcc/toplev.c:2321
>     #17 0x2a283cc in toplev::main(int, char**) /home/marxin/Programming/gcc2/gcc/toplev.c:2460
>     #18 0x54f21cd in main /home/marxin/Programming/gcc2/gcc/main.c:39
>     #19 0x7ffff6f0de09 in __libc_start_main ../csu/libc-start.c:314
>     #20 0x9eac09 in _start (/home/marxin/Programming/gcc2/objdir/gcc/cc1plus+0x9eac09)
> 
> Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
> 
> Ready to be installed?

OK (to silence valgrind).  The situation here is harmless - when
param_index is -1 the param_offset_known has no meaning, but we still
merge it into the summary.

Honza