This reverts commit 7f230feeeac8a67b335f52bd2e900a05c6098f20.
Breaks CodeGenCUDA/link-device-bitcode.cu in check-clang,
and many LLVM tests, see comments on https://reviews.llvm.org/D121169
The "avoid trailing call pass" makes sure that no function ends with a call instruction for the purpose of the unwinder.
It starts of by skipping over any non real instruction, which is approximated via the Pseudo and Meta property. This sadly leads to issues when the last machine instruction is a STATEPOINT, as it is skipped despite it lowering to a call.
This patch fixes the use of a statepoint in the trailing call position by making sure call instructions are not skipped.
Differential Revision: https://reviews.llvm.org/D119644
Otherwise, the Win64 unwinder considers direct branches to such empty
trailing BBs to be a branch out of the function. It treats such a branch
as a tail call, which can only be part of an epilogue. If the unwinder
misclassifies such a branch as part of the epilogue, it will fail to
unwind the stack further. This can lead to bad stack traces, or failure
to handle exceptions properly. This is described in
https://llvm.org/PR45064#c4, and by the comment at the top of the
X86AvoidTrailingCallPass.cpp file.
It should be safe to insert int3 for such blocks. An empty trailing BB
that reaches this pass is pretty much guaranteed to be unreachable. If
a program executed such a block, it would fall off the end of the
function.
Most of the complexity in this patch comes from threading through the
"EHFuncletEntry" boolean on the MIRParser and registering the pass so we
can stop and start codegen around it. I used an MIR test because we
should teach LLVM to optimize away these branches as a follow-up.
Reviewed By: hans
Differential Revision: https://reviews.llvm.org/D76531
This is an alternative to D66980, which was reverted. Instead of
inserting a pseudo instruction that optionally expands to nothing, add a
pass that inserts int3 when appropriate after basic block layout.
Reviewers: hans
Differential Revision: https://reviews.llvm.org/D67201
llvm-svn: 371466
