With ThinLTO enabled (now the default again):

>>> Print(size_info.symbols.Filter(lambda s: not s.source_path and s.IsBss()).Sorted())

Showing 10,638 symbols (10,638 unique) with total pss: 0 bytes
Histogram of symbols based on PSS:
     [1,2): 629      [16,32): 238     [256,512): 30     [4096,8192): 12    [65536,131072): 1
     [2,4): 7        [32,64): 279    [512,1024): 16    [8192,16384): 5    [131072,262144): 2
     [4,8): 8925    [64,128): 143   [1024,2048): 24   [16384,32768): 3    [262144,524288): 1
    [8,16): 255    [128,256): 53    [2048,4096): 10   [32768,65536): 5
Sizes: .bss=1.07mb     total=0 bytes
Counts: .bss=12941
Number of unique paths: 28

Section Legend: b=.bss
Index | Running Total | Section@Address | PSS | Path
------------------------------------------------------------
0)          0 (0.0%)  b@0x2f4f3c0  262164         {no path}
             ff_cos_131072
1)          0 (0.0%)  b@0x2f93700  131312         {no path}
             table_4_3_value
2)          0 (0.0%)  b@0x2f068c0  131072         {no path}
             ff_cos_65536
3)          0 (0.0%)  b@0x2ef4440  65536          {no path}
             ff_cos_32768
4)          0 (0.0%)  b@0x2fec164  60000          {no path}
             vr::g_vertices
5)          0 (0.0%)  b@Group      50614          {no path}
             .L_MergedGlobals (count=2044)
6)          0 (0.0%)  b@0x2fb37f0  32828          {no path}
             table_4_3_exp
7)          0 (0.0%)  b@0x2fbb82c  32768          {no path}
             expval_table_fixed
8)          0 (0.0%)  b@0x2eeb200  32768          {no path}
             ff_cos_16384
9)          0 (0.0%)  b@0x2fdba40  22288          {no path}
             about_flags::kFeatureEntries
10)         0 (0.0%)  b@0x2f342d0  18724          {no path}
             v8::internal::compiler::kMachineOperatorGlobalCache
...



>>> Print(size_info.symbols.Filter(lambda s: not s.source_path and not s.object_path and not s.IsBss()).Sorted())

Showing 1,004 symbols (1,004 unique) with total pss: 1907626 bytes
Histogram of symbols based on PSS:
      {0}: 1     [8,16): 154    [64,128): 473    [512,1024): 11      [8192,16384): 2   [1048576,2097152): 1
    [2,4): 3    [16,32): 168   [128,256): 47    [1024,2048): 5    [131072,262144): 1
    [4,8): 61   [32,64): 47    [256,512): 25    [2048,4096): 4    [262144,524288): 1
Sizes: .text=1.30mb     .rodata=36.9kb     .data.rel.ro=25.4kb     .data=49.2kb     .pak.translations=1879 bytes .pak.nontranslated=59 bytes   .other=421kb      total=1.82mb
Counts: .text=5 .rodata=1569 .data.rel.ro=1605 .data=494 .pak.translations=96 .pak.nontranslated=4 .other=2
Number of unique paths: 1

Section Legend: t=.text, r=.rodata, R=.data.rel.ro, d=.data, p=.pak.translations, P=.pak.nontranslated, o=.other
Index | Running Total | Section@Address | PSS | Path
------------------------------------------------------------
0)    1173768 (61.5%) t@0xde56c0   1173768        {no path}
1)    1595813 (83.7%) o@0x0        422045         {no path}
             Overhead: APK file
2)    1781885 (93.4%) t@Group      186072         {no path}
             ** thunk (count=2)
3)    1794984 (94.1%) r@Group      13099          {no path}
             .L.ref.tmp (count=561)
4)    1804510 (94.6%) o@0x0        9526           {no path}
             Overhead: ELF file
5)    1808362 (94.8%) R@Group      3852           {no path}
             .L.ref.tmp (count=449)
6)    1811569 (95.0%) r@Group      3207           {no path}
             .L.ref.tmp.1 (count=149)
7)    1814129 (95.1%) r@Group      2560           {no path}
             .L.ref.tmp.2 (count=118)
8)    1816178 (95.2%) r@0x53ebfc   2049           {no path}
             string literal
9)    1818088 (95.3%) r@Group      1910           {no path}
             .L.ref.tmp.3 (count=85)
10)   1819691 (95.4%) r@Group      1603           {no path}
             .L.ref.tmp.4 (count=69)
11)   1821249 (95.5%) r@Group      1558           {no path}
             .L.ref.tmp.5 (count=68)
12)   1822775 (95.6%) d@Group      1526           {no path}
             .L_MergedGlobals (count=58)
13)   1824135 (95.6%) R@Group      1360           {no path}
             .L.ref.tmp.48 (count=7)
14)   1825158 (95.7%) r@Group      1023           {no path}
             .L.ref.tmp.6 (count=46)
15)   1825886 (95.7%) p@0x0        728            {no path}
             artifacts
16)   1826611 (95.8%) r@Group      725            {no path}
             .L.ref.tmp.7 (count=32)
17)   1827263 (95.8%) R@Group      652            {no path}
             .L.ref.tmp.16 (count=22)
18)   1827895 (95.8%) R@Group      632            {no path}
             .L.ref.tmp.21 (count=13)
19)   1828504 (95.9%) r@Group      609            {no path}
             .L.ref.tmp.8 (count=27)
20)   1829072 (95.9%) R@Group      568            {no path}
             .L.ref.tmp.4 (count=69)
21)   1829640 (95.9%) R@Group      568            {no path}
             .L.ref.tmp.83 (count=2)
22)   1830184 (95.9%) R@Group      544            {no path}
             .L.ref.tmp.55 (count=5)
23)   1830704 (96.0%) R@Group      520            {no path}
             .L.ref.tmp.76 (count=3)
24)   1831218 (96.0%) r@Group      514            {no path}
             .L.ref.tmp.10 (count=24)
25)   1831722 (96.0%) R@Group      504            {no path}
             .L.ref.tmp.46 (count=6)
26)   1832226 (96.0%) R@Group      504            {no path}
             .L.ref.tmp.63 (count=2)
27)   1832709 (96.1%) r@Group      483            {no path}
             .L.ref.tmp.9 (count=22)
28)   1833189 (96.1%) R@Group      480            {no path}
             .L.ref.tmp.6 (count=46)
29)   1833637 (96.1%) R@Group      448            {no path}
             .L.ref.tmp.10 (count=47)
30)   1834077 (96.1%) R@Group      440            {no path}
             .L.ref.tmp.44 (count=6)
31)   1834509 (96.2%) R@Group      432            {no path}
             .L.ref.tmp.8 (count=37)
32)   1834933 (96.2%) R@Group      424            {no path}
             .L.ref.tmp.53 (count=4)
33)   1835347 (96.2%) r@Group      414            {no path}
             .L.ref.tmp.13 (count=18)
34)   1835712 (96.2%) r@Group      365            {no path}
             .L.ref.tmp.12 (count=17)
35)   1836076 (96.2%) r@Group      364            {no path}
             .L.ref.tmp.11 (count=17)
36)   1836436 (96.3%) R@Group      360            {no path}
             .L.ref.tmp.5 (count=38)
37)   1836792 (96.3%) r@Group      356            {no path}
             .L.ref.tmp.14 (count=16)
38)   1837136 (96.3%) R@Group      344            {no path}
             .L.ref.tmp.2 (count=39)
...



For just .text, it's a mere 3 symbols:

>>> Print(size_info.symbols.Filter(lambda s: not s.source_path and not s.object_path and not s.IsBss() and s.section == 't').Sorted())
Showing 4 symbols (4 unique) with total pss: 1359906 bytes
Histogram of symbols based on PSS:
    {0}: 1   [64,128): 1   [131072,262144): 1   [1048576,2097152): 1
Sizes: .text=1.30mb     total=1.30mb
Counts: .text=5
Number of unique paths: 1

Section Legend: t=.text
Index | Running Total | Section@Address | PSS | Path
------------------------------------------------------------
0)    1173768 (86.3%) t@0xde56c0   1173768        {no path}
1)    1359840 (100.0%) t@Group      186072         {no path}
             ** thunk (count=2)
2)    1359906 (100.0%) t@0x86cbb0   66 (size=200)  {no path}
             .udivsi3_skip_div0_test (num_aliases=3)
3)    1359906 (100.0%) t@0xacdd48   0              {no path}


The linker map for the giant symbol shows:
  de56c0   de56c0   11e900    32         thinlto-cache/llvmcache-5573B54B4EDC1E7F3AF7D65CC252AD2E88FA98CA:(.text)
  de56c0   de56c0        0     1                 v8_Default_embedded_blob_
  de8360   de8360        0     1                 Builtins_RecordWrite
  de8680   de8680        0     1                 Builtins_AdaptorWithExitFrame
...

I've filed  bug 892648  to track the fact that we're not giving a proper name to this symbol, but the bigger bug here is that the path is lost. Pre-lto, it knew the symbol was from "gen/v8/embedded.cc"


I'd guess the problem for both is that llvm-nm is not finding the symbols in the .o files (or the names aren't matching up, or for v8's case, the name is empty so we're ignoring it).