On 2016.11.29 at 16:01 +0100, Markus Trippelsdorf wrote:
> 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)
(gdb) p mode
$1 = BLKmode
#6 0x00000000035ef5f2 in if_then_else_cond (x=0x7ffff60d3888,
ptrue=ptrue@entry=0x7fffffffd940, pfalse=pfalse@entry=0x7fffffffd950) at
../../gcc/gcc/combine.c:9180
9180 && num_sign_bit_copies (x, mode) == GET_MODE_PRECISION
(mode)))
(gdb) l
9175
9176 /* If X is known to be either 0 or -1, those are the true and
9177 false values when testing X. */
9178 else if (x == constm1_rtx || x == const0_rtx
9179 || (mode != VOIDmode
9180 && num_sign_bit_copies (x, mode) == GET_MODE_PRECISION
(mode)))
9181 {
9182 *ptrue = constm1_rtx, *pfalse = const0_rtx;
9183 return x;
9184 }
--
Markus
