Anton (Mar 02 2024 at 19:17): Anton (Mar 02 2024 at 19:17):I compared the llvm IR for a simple program between Roc, Rust and Zig. We were using tail call frequently, whereas the Zig and Rust versions never used it (all were compiled unoptimized). I'm investigating a possible llvm bug and I would like to try emitting regular llvm IR calls. Anybody know how I can do that?
I've tried changing call.set_tail_call(true); to false in refcounting.rs but that did not reduce the number of tail calls for my program.
Brendan Hansknecht (Mar 02 2024 at 19:34):I think it would be in the actual ir emission.
Brendan Hansknecht (Mar 02 2024 at 19:34):I think we set it too much.
Folkert de Vries (Mar 02 2024 at 22:57):no LLVM just infers those tail annotations. they almost never turn into actual tail calls
Brendan Hansknecht (Mar 02 2024 at 23:32):Oh. Inferred, not explicit. Ok.
Anton (Mar 05 2024 at 16:13):Replacing tail calls with calls fixed the issue :)
From my understanding the call to @"#UserApp_diffSelf... should not be marked as a tail call right?
define internal fastcc { %str.RocStr, {} } @"#UserApp_main_f03bf86f79d121cbfd774dec4a65912e99f5f17c33852bbc45e81916e62b53b"() !dbg !52 {
entry:
%const_str_store3 = alloca %str.RocStr, align 8, !dbg !53
%const_str_store = alloca %str.RocStr, align 8, !dbg !53
%call = tail call fastcc i128 @"#UserApp_diffSelf_beb22fad19423347b2aa99b33212e862ded3f83df5d6238acb1a6a9ade3e"(i128 1), !dbg !53
%call1 = tail call fastcc i1 @Bool_structuralEq_c610e85212d0697cb161d4ba431ba63f273feee7dcb7927c9ff5d74ae6cbfa3(i128 %call, i128 0), !dbg !53
br i1 %call1, label %then_block, label %else_block, !dbg !53
it should be harmless? but yeah it's not even in tail position so there is nothing the tail attribute can do
Anton (Mar 06 2024 at 09:23):it should be harmless?
Uhu, yeah it should be, but it was not due to this llvm bug https://github.com/llvm/llvm-project/issues/70207
Folkert de Vries (Mar 06 2024 at 09:24):ah, cool!
Last updated: Jul 06 2025 at 12:14 UTC