LLVM ERROR: sleb128 and uleb128 expressions must be absolute

[jroelofs]

$ cat <<EOF > rdar113994760.ll
source_filename = "rdar113994760.ll"
target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-macosx"

define swiftcc void @"$s4main11call_foobaryyF"() personality ptr @__gcc_personality_v0 {
entry:
  %swifterror = alloca swifterror ptr, align 8
  invoke swiftcc void null(i64 0, ptr null, ptr swifterror %swifterror)
          to label %.noexc unwind label %tsan_cleanup

.noexc:                                           ; preds = %entry
  ret void

tsan_cleanup:                                     ; preds = %entry
  %cleanup.lpad = landingpad { ptr, i32 }
          cleanup
  resume { ptr, i32 } zeroinitializer
}

declare i32 @__gcc_personality_v0(...)

EOF

$ ./build/bin/llc rdar113994760.ll -filetype=obj -o out
LLVM ERROR: sleb128 and uleb128 expressions must be absolute
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.      Program arguments: ./build/bin/llc rdar113994760.ll -filetype=obj -o out
Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it):
0  llc                      0x0000000105f11d60 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1  llc                      0x0000000105f12134 SignalHandler(int) + 188
2  libsystem_platform.dylib 0x00000001a87e1a84 _sigtramp + 56
3  libsystem_pthread.dylib  0x00000001a87b2c28 pthread_kill + 288
4  libsystem_c.dylib        0x00000001a86c1b28 abort + 180
5  llc                      0x0000000105e98e48 llvm::report_fatal_error(llvm::Twine const&, bool) + 328
6  llc                      0x0000000105e98d00 llvm::report_fatal_error(llvm::Twine const&, bool) + 0
7  llc                      0x0000000105a79690 llvm::MCAssembler::relaxBoundaryAlign(llvm::MCAsmLayout&, llvm::MCBoundaryAlignFragment&) + 0
8  llc                      0x0000000105a79d64 llvm::MCAssembler::layoutSectionOnce(llvm::MCAsmLayout&, llvm::MCSection&) + 72
9  llc                      0x0000000105a78ecc llvm::MCAssembler::layoutOnce(llvm::MCAsmLayout&) + 112
10 llc                      0x0000000105a78a88 llvm::MCAssembler::layout(llvm::MCAsmLayout&) + 404
11 llc                      0x0000000105a78ffc llvm::MCAssembler::Finish() + 64
12 llc                      0x0000000105a976a8 (anonymous namespace)::MCMachOStreamer::finishImpl() + 644
13 llc                      0x000000010554014c llvm::AsmPrinter::doFinalization(llvm::Module&) + 3232
14 llc                      0x00000001059fe330 llvm::FPPassManager::doFinalization(llvm::Module&) + 76
15 llc                      0x00000001059fa568 llvm::legacy::PassManagerImpl::run(llvm::Module&) + 960
16 llc                      0x0000000104d2d6e8 main + 6100
17 dyld                     0x00000001a8457f28 start + 2236
Abort trap: 6

rdar://113994760

This regression happened sometime between clang-15 and clang-16. Bisection points at 648ce3d:

commit 648ce3d358560c0f60340fcf28ad2563d213eca2
Author: James Y Knight <jyknight@google.com>
Date:   Fri Jan 6 13:26:03 2023 -0500

    Cleanup unwind table emission code a bit.
    
    This change removes the `tidyLandingPads` function, which previously
    had a few responsibilities:
    
    1. Dealing with the deletion of an invoke, after MachineFunction lowering.
    2. Dealing with the deletion of a landing pad BB, after MachineFunction lowering.
    3. Cleaning up the type-id list generated by `MachineFunction::addLandingPad`.
    
    Case 3 has been fixed in the generator, and the others are now handled
    during table emission.
    
    This change also removes `MachineFunction`'s `addCatchTypeInfo`,
    `addFilterTypeInfo`, and `addCleanup` helper fns, as they had a single
    caller, and being outlined didn't make it simpler.
    
    Finally, as calling `tidyLandingPads` was effectively the only thing
    `DwarfCFIExceptionBase` did, that class has been eliminated.

[MaskRay]

llc -mtriple=x86_64-apple-macosx rdar113994760.ll (default -filetype=asm) suggests that Ltmp1 is not defined, therefore the subtraction in .uleb128 Ltmp1-Ltmp0 cannot be folded to a constant, leading to this assembler error.

[jyknight]

(Note, I'm mostly unavailable this week.)

From a glance, looks like SelectionDAGBuilder::lowerInvokable isn't updating Result.second after the call to lowerEndEH, which results in the SwiftErrorVal-handling code in SelectionDAGBuilder::LowerCallTo to reset the DAG root, thus forgetting to include the EH_LABEL DAG node it was supposed to have added.

It doesn't look like I changed that, so I dunno why it broke only from my change.