https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88535
john henning <mailboxnotfound at yahoo dot com> changed:
What |Removed |Added
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CC| |mailboxnotfound at yahoo dot
com
--- Comment #2 from john henning <mailboxnotfound at yahoo dot com> ---
Thank you Rainer for reproducing this and filing the bug. As the originator of
the complaint, I (john henning) add a few more points.
All of my attempts were with gcc 8.2.0; failures were observed on 2 different
SPARC Solaris 11 systems, one with 11.4 and one with 11.5.
(1) dwarf2out.o is the only object that differs.
(2) output_file_names is the only routine within dwarf2out.o to have a
differing size (according to nm)
(3) An early difference (possibly the first) seems to be the code that is
generated for dwarf2out.c line 12301
$ cat -n ../gcc-8.2.0/gcc/dwarf2out.c | head -12312 | tail -17
12296 /* If there are more than 65536 directories, we have to use
12297 DW_FORM_udata, DW_FORM_data2 can't refer to them.
12298 Otherwise, compute what space would occupy if all the indexes
12299 used DW_FORM_udata - sum - and compare that to how large would
12300 be DW_FORM_data2 encoding, and pick the more efficient one. */
12301 else if (ndirs + idx_offset <= 65536)
12302 {
12303 unsigned HOST_WIDE_INT sum = 1;
12304 for (i = 0; i < numfiles; i++)
12305 {
12306 int file_idx = backmap[i];
12307 int dir_idx = dirs[files[file_idx].dir_idx].dir_idx;
12308 sum += size_of_uleb128 (dir_idx);
12309 }
12310 if (sum >= HOST_WIDE_INT_UC (2) * (numfiles + 1))
12311 idx_form = DW_FORM_data2;
12312
Here are the first 40 instructions for that line, according to gdb
(shrunk/excerpted to fit a small number of columns for ease of side-by-side
viewing):
$ gdb -q stage2-gcc/lto1 $ gdb -q stage3-gcc/lto1
. break dwarf2out.c:12301 . break dwarf2out.c:12301
Breakpoint 1 at 0x435fb8: file Breakpoint 1 at 0x435fb0: file
gcc-8.2.0/gcc/dwarf2out.c, line 12301 gcc-8.2.0/gcc/dwarf2out.c, line 12301
. x/40i 0x435fb8 . x/40i 0x435fb0
sethi %hi(0x10000), %g1 sethi %hi(0x10000), %g1
cmp %l0, %g1 cmp %l0, %g1
bg %icc, 0x436164 <output_file_name bg %icc, 0x436188 <output_file_name
clr %o1 clr %o1
clr %l0 clr %l0
cmp %i4, 0 cmp %i4, 0
ble,pn %icc, 0x436030 <output_file ble,pn %icc, 0x436054 <output_file
mov 1, %l1 mov 1, %l1
mov %l6, %l7 mov %l2, %g1
add %l5, %l6, %l5 st %l3, [ %fp + -24 ]
st %i2, [ %fp + -20 ] mov %i0, %l2
st %i3, [ %fp + -24 ] mov %i2, %l3
ld [ %l7 ], %g1 mov %i1, %i0
smul %g1, 0x14, %g1 add %l5, %l6, %l5
add %i5, %g1, %g1 st %i4, [ %fp + -20 ]
ld [ %g1 + 0x10 ], %g1 mov %l6, %i1
smul %g1, 0x14, %g1 mov %i5, %i2
add %l4, %g1, %g1 mov %g1, %l7
ld [ %g1 + 0x10 ], %o1 ld [ %i1 ], %g1
call 0x40af9c <size_of_uleb128(unsi> smul %g1, 0x14, %g1
sra %o1, 0x1f, %o0 add %i2, %g1, %g1
addcc %l1, %o0, %l1 ld [ %g1 + 0x10 ], %g1
sra %o0, 0x1f, %i2 smul %g1, 0x14, %g1
add %l7, 4, %l7 add %l4, %g1, %g1
addc %l0, %i2, %l0 ld [ %g1 + 0x10 ], %o1
cmp %l7, %l5 call 0x40af94 <size_of_uleb128(unsi
bne,a %icc, 0x435fec <output_file_ sra %o1, 0x1f, %o0
ld [ %l7 ], %g1 addcc %l1, %o0, %l1
ld [ %fp + -20 ], %i2 sra %o0, 0x1f, %i4
ld [ %fp + -24 ], %i3 add %i1, 4, %i1
addcc %l2, %l2, %o5 addc %l0, %i4, %l0
addc %l3, %l3, %o4 cmp %i1, %l5
cmp %o4, %l0 bne,a %icc, 0x435ffc <output_file_
bgu %icc, 0x436164 <output_file_nam ld [ %i1 ], %g1
clr %o1 mov %i0, %i1
bne %icc, 0x436060 <output_file_nam mov %i2, %i5
mov 2, %o2 mov %l2, %i0
cmp %o5, %l1 mov %l3, %i2
bgu,a %icc, 0x43616c <output_file_ ld [ %fp + -20 ], %i4
mov 1, %o0 mov %l7, %l2
