[PATCH] Fix PR78588 - rtlanal.c:5210:38: runtime error: shift exponent 4294967295 is too large for 64-bit type

[Markus Trippelsdorf]

On 2016.11.29 at 15:21 +0100, Markus Trippelsdorf wrote:
> On 2016.11.29 at 15:14 +0100, Jakub Jelinek wrote:
> > On Tue, Nov 29, 2016 at 03:08:15PM +0100, Markus Trippelsdorf wrote:
> > > Building gcc with -fsanitize=undefined shows:
> > >  rtlanal.c:5210:38: runtime error: shift exponent 4294967295 is too
> > >  large for 64-bit type 'long unsigned int'
> > >
> > > 5210   return nonzero & (HOST_WIDE_INT_1U << (bitwidth - 1))
> > > 5211          ? 1 : bitwidth - floor_log2 (nonzero) - 1;
> > >
> > > Here (bitwidth - 1) wraps around because bitwidth is zero and unsigned.
> >
> > Which modes have precision of 0?  I'd expect just VOIDmode and BLKmode, any
> > others?  And for those I'd say it is a bug to call num_sign_bit_copies*.
> 
> Yes, only VOIDmode and BLKmode:
> 
>  233 const unsigned short mode_precision[NUM_MACHINE_MODES] =
>  234 {
>  235   0,                       /* VOID */
>  236   0,                       /* BLK */

markus@x4 libsupc++ % cat cp-demangle.i
d_demangle_callback_mangled() {
  if (strncmp(d_demangle_callback_mangled, "", 1))
    d_type();
}

markus@x4 libsupc++ % UBSAN_OPTIONS=print_stacktrace=1:halt_on_error=1 /var/tmp/gcc_build_dir_/./gcc/cc1 -w -fpreprocessed cp-demangle.i -quiet -dumpbase cp-demangle.i -mtune=generic -march=x86-64 -auxbase cp-demangle -O2 -version -o /dev/null
GNU C11 (GCC) version 7.0.0 20161129 (experimental) (x86_64-pc-linux-gnu)
        compiled by GNU C version 7.0.0 20161129 (experimental), GMP version 6.1.1, MPFR version 3.1.5, MPC version 1.0.3, isl version none
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
GNU C11 (GCC) version 7.0.0 20161129 (experimental) (x86_64-pc-linux-gnu)
        compiled by GNU C version 7.0.0 20161129 (experimental), GMP version 6.1.1, MPFR version 3.1.5, MPC version 1.0.3, isl version none
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
Compiler executable checksum: 7cca725773f8a0693a2905f8af7b733c
../../gcc/gcc/rtlanal.c:5210:38: runtime error: shift exponent 4294967295 is too large for 64-bit type 'long unsigned int'
    #0 0x1b40fe1 in num_sign_bit_copies1 ../../gcc/gcc/rtlanal.c:5210
    #1 0x35ef5f1 in if_then_else_cond ../../gcc/gcc/combine.c:9180
    #2 0x35ef199 in if_then_else_cond ../../gcc/gcc/combine.c:9034
    #3 0x35ef199 in if_then_else_cond ../../gcc/gcc/combine.c:9034
    #4 0x3625f98 in combine_simplify_rtx ../../gcc/gcc/combine.c:5604
    #5 0x3632525 in subst ../../gcc/gcc/combine.c:5487
    #6 0x36327d6 in subst ../../gcc/gcc/combine.c:5425
    #7 0x3632bd7 in subst ../../gcc/gcc/combine.c:5354
    #8 0x3641a74 in try_combine ../../gcc/gcc/combine.c:3347
    #9 0x365727b in combine_instructions ../../gcc/gcc/combine.c:1421
    #10 0x365727b in rest_of_handle_combine ../../gcc/gcc/combine.c:14581
    #11 0x365727b in execute ../../gcc/gcc/combine.c:14626
    #12 0x195ad18 in execute_one_pass(opt_pass*) ../../gcc/gcc/passes.c:2370
    #13 0x195cbab in execute_pass_list_1 ../../gcc/gcc/passes.c:2459
    #14 0x195cbd4 in execute_pass_list_1 ../../gcc/gcc/passes.c:2460
    #15 0x195cc64 in execute_pass_list(function*, opt_pass*) ../../gcc/gcc/passes.c:2470
    #16 0xc75deb in cgraph_node::expand() ../../gcc/gcc/cgraphunit.c:2001
    #17 0xc7b2fa in expand_all_functions ../../gcc/gcc/cgraphunit.c:2137
    #18 0xc7b2fa in symbol_table::compile() ../../gcc/gcc/cgraphunit.c:2494
    #19 0xc854b7 in symbol_table::compile() ../../gcc/gcc/cgraphunit.c:2587
    #20 0xc854b7 in symbol_table::finalize_compilation_unit() ../../gcc/gcc/cgraphunit.c:2584
    #21 0x1d3ea10 in compile_file ../../gcc/gcc/toplev.c:488
    #22 0x629a14 in do_compile ../../gcc/gcc/toplev.c:1983
    #23 0x629a14 in toplev::main(int, char**) ../../gcc/gcc/toplev.c:2117
    #24 0x62c046 in main ../../gcc/gcc/main.c:39
    #25 0x7f4b6600f310 in __libc_start_main ../csu/libc-start.c:286
    #26 0x62c469 in _start (/var/tmp/gcc_build_dir_/gcc/cc1+0x62c469)

-- 
Markus