Date: Wed, 15 Sep 2021 19:32:43 +0000 From: bugzilla-noreply@freebsd.org To: erlang@FreeBSD.org Subject: [Bug 258494] lang/erlang lang/erlang-runtime21 lang/erlang-runtime23: clang 13 build breaks dtrace if PGO is enabled Message-ID: <bug-258494-38768-wbnLHhCVM3@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-258494-38768@https.bugs.freebsd.org/bugzilla/> References: <bug-258494-38768@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D258494 --- Comment #1 from Dimitry Andric <dim@FreeBSD.org> --- (In reply to Dimitry Andric from comment #0) > Something in beam_emu_pu.o (emitted by clang or llvm 13) is tripping up d= trace, but I have very little knowledge about dtrace so I need help here. :) So there are two objects that are instrumented with profile generation code, beam_emu_pg.o and erl_process_pg.o. These are linked into a beam.smp execut= able which generates profile data, and the data is used to build beam_emu_pu.o a= nd erl_process_pu.o. The difference between llvm 12 and llvm 13 output is in the produced sectio= ns for the _pu.o files. With llvm 12, there is a .llvm.call-graph-profile sect= ion (to be used by the linker to rearrange 'hot' and 'cold' parts): [Nr] Name Type Address Off Size ES = Flg Lk Inf Al ... [19] .llvm.call-graph-profile LOOS+0xfff4c02 0000000000000000 02e9f0 000= e80 10 E 21 0 1 whereas with llvm 13, there is an additional .rel.llvm.call-graph-profile section: [Nr] Name Type Address Off Size ES = Flg Lk Inf Al ... [17] .llvm.call-graph-profile LOOS+0xfff4c09 0000000000000000 0279a9 000= 750 08 E 22 0 1 [18] .rel.llvm.call-graph-profile REL 0000000000000000 030888 001d40 10 22 17 8 I have verified that removing the .rel.llvm.call-graph-profile section from= the _pu.o files (using objcopy --remove .rel.llvm.call-graph-profile) makes dtr= ace not crash anymore. However, I think the .rel.llvm.call-graph-profile section might contain information that is useful to the linker. So the question is still what is = in this particular section that makes dtrace crash. --=20 You are receiving this mail because: You are the assignee for the bug.=
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