[BOLT] Optimized binary has premature terminator entry warning

[Zentrik]

Optimizing this binary with -split-functions -update-debug-sections -split-strategy=cdsplit and this profile causes the following warnings to show up:

$ llvm-dwarfdump --debug-aranges libjulia-internal.so >/dev/null
warning: address range table at offset 0x0 has a premature terminator entry at offset 0x10
warning: address range table at offset 0x0 has a premature terminator entry at offset 0x20
warning: address range table at offset 0x0 has a premature terminator entry at offset 0x30
warning: address range table at offset 0xb20 has a premature terminator entry at offset 0xb30
warning: address range table at offset 0xb20 has a premature terminator entry at offset 0xb40
warning: address range table at offset 0xb20 has a premature terminator entry at offset 0xb50
...
warning: address range table at offset 0x12af0 has a premature terminator entry at offset 0x12f00
warning: address range table at offset 0x13aa0 has a premature terminator entry at offset 0x13d50

I tested on 0dcabba and 18.1.4 (e6c3289).
Also adding -skip-funcs=.\*apply_cl.\* as discussed in #89117 didn't help.

[maksfb]

@ayermolo, any idea why the warnings are there?

[ayermolo]

@ayermolo, any idea why the warnings are there?

probably because we don't filter 0x0 addresses and that is what is used for aranges to indicate end of aranges entries.

[maksfb]

@ayermolo, any idea why the warnings are there?

probably because we don't filter 0x0 addresses and that is what is used for aranges to indicate end of aranges entries.

Do we need a fix on BOLT or llvm-dwarf side for them to go away?

[Zentrik]

Seems intentional on llvm-dwarf's side, https://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20200810/816972.html. They also claim 'the DWARF specification states that .debug_aranges entries can't have length zero'

[ayermolo]

BOLT, but it's a low priority. Also there was sentiment expressed by some in llvm community that this section should be dropped, as it's a duplicate of what's in unit die.