With the addition of the `willreturn` attribute, functions that may
not return (e.g. due to an infinite loop) are well defined, if they are
not marked as `willreturn`.

This patch updates `wouldInstructionBeTriviallyDead` to not consider
calls that may not return as dead.

This patch still provides an escape hatch for intrinsics, which are
still assumed as willreturn unconditionally. It will be removed once
all intrinsics definitions have been reviewed and updated.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D94106

Reviewed By: dylanmckay

Differential Revision: https://reviews.llvm.org/D89047

NFC

This patch adds the integer handling typemaps and the typemap for
string returning functions.

The integer handling typemaps overrides SWIG's own typemaps to distinct
the handling of integers from floating point.

The typemap for string returning functions is a port of Python's
typemap.

Differential Revision: https://reviews.llvm.org/D94937

This reverts commit 2325157c.

Unfortunately this commit produces linker errors on some builds:
http://lab.llvm.org:8011/#/builders/57/builds/3704
http://lab.llvm.org:8011/#/builders/112/builds/3216
http://lab.llvm.org:8011/#/builders/121/builds/3900

[SimplifyCFG] Change 'LoopHeaders' to be ArrayRef<WeakVH>, not a naked set, thus avoiding dangling pointers

If i change it to AssertingVH instead, a number of existing tests fail,
which means we don't consistently remove from the set when deleting blocks,
which means newly-created blocks may happen to appear in that set
if they happen to occupy the same memory chunk as did some block
that was in the set originally.

There are many places where we delete blocks,
and while we could probably consistently delete from LoopHeaders
when deleting a block in transforms located in SimplifyCFG.cpp itself,
transforms located elsewhere (Local.cpp/BasicBlockUtils.cpp) also may
delete blocks, and it doesn't seem good to teach them to deal with it.

Since we at most only ever delete from LoopHeaders,
let's just delegate to WeakVH to do that automatically.

But to be honest, personally, i'm not sure that the idea
behind LoopHeaders is sound.

This change adds an AssemblerInvocation class, similar to the
CompilerInvocation class. It can be used to invoke cc1as directly.

The project I'm working on wants to compile Clang and use it as a static
library. For that to work, there must be a way to invoke the assembler
programmatically, using the same arguments as you would otherwise pass
to cc1as.

Differential Revision: https://reviews.llvm.org/D63852

LSR should be dropping nowrap flags when adding new postinc users.

The target features are obtained as a list of features/attributes.
Instead of storing them in a single string, store the vector. This
matches lto::Config's behavior and simplifies the transition to
lto::backend().

Reviewed By: tejohnson

Differential Revision: https://reviews.llvm.org/D95224

Insert a llvm.experimental.noalias.scope.decl intrinsic that identifies where a noalias argument was inlined.

This patch includes some refactorings from D90104.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D93040

Avoid string copies and fix clang-tidy warning.

[RISCV][PrologEpilogInserter] "Float" emergency spill slots to avoid making them immediately unreachable from the stack pointer

In RISC-V there is a single addressing mode of the form imm(reg) where
imm is a signed integer of 12-bit with a range of [-2048..2047] bytes
from reg.

The test MultiSource/UnitTests/C++11/frame_layout of the LLVM test-suite
exercises several scenarios with the stack, including function calls
where the stack will need to be realigned to to a local variable having
a large alignment of 4096 bytes.

In situations of large stacks, the RISC-V backend (in
RISCVFrameLowering) reserves an extra emergency spill slot which can be
used (if no free register is found) by the register scavenger after the
frame indexes have been eliminated. PrologEpilogInserter already takes
care of keeping the emergency spill slots as close as possible to the
stack pointer or frame pointer (depending on what the function will
use). However there is a final alignment step to honour the maximum
alignment of the stack that, when using the stack pointer to access the
emergency spill slots, has the side effect of setting them farther from
the stack pointer.

In the case of the frame_layout testcase, the net result is that we do
have an emergency spill slot but it is so far from the stack pointer
(more than 2048 bytes due to the extra alignment of a variable to 4096
bytes) that it becomes unreachable via any immediate offset.

During elimination of the frame index, many (regular) offsets of the
stack may be immediately unreachable already. Their address needs to be
computed using a register. A virtual register is created and later
RegisterScavenger should be able to find an unused (physical) register.
However if no register is available, RegisterScavenger will pick a
physical register and spill it onto an emergency stack slot, while we
compute the offset (restoring the chosen register after all this). This
assumes that the emergency stack slot is easily reachable (this is,
without requiring another register!).

This is the assumption we seem to break when we perform the extra
alignment in PrologEpilogInserter.

We can "float" the emergency spill slots by increasing (in absolute
value) their offsets from the incoming stack pointer. This way the
emergency spill slots will remain close to the stack pointer (once the
function has allocated storage for the stack, including the needed
realignment). The new size computed in PrologEpilogInserter is padding
so it should be OK to move the emergency spill slots there. Also because
we're increasing the alignment, the new location should stay aligned for
the purpose of the emergency spill slots.

Note that this change also impacts other backends as shown by the tests.
Changes are minor adjustments to the emergency stack slot offset.

Differential Revision: https://reviews.llvm.org/D89239

This patch fixes llvm-link assertion when linking external variable
declaration with a definition with appending linkage.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D95126

Previously in ASan's `pthread_create` interceptor we would block in the
`pthread_create` interceptor waiting for the child thread to start.

Unfortunately this has bad performance characteristics because the OS
scheduler doesn't know the relationship between the parent and child
thread (i.e. the parent thread cannot make progress until the child
thread makes progress) and may make the wrong scheduling decision which
stalls progress.

It turns out that ASan didn't use to block in this interceptor but was
changed to do so to try to address
http://llvm.org/bugs/show_bug.cgi?id=21621/.

In that bug the problem being addressed was a LeakSanitizer false
positive. That bug concerns a heap object being passed
as `arg` to `pthread_create`. If:

* The calling thread loses a live reference to the object (e.g.
  `pthread_create` finishes and the thread no longer has a live
  reference to the object).
* Leak checking is triggered.
* The child thread has not yet started (once it starts it will have a
  live reference).

then the heap object will incorrectly appear to be leaked.

This bug is covered by the `lsan/TestCases/leak_check_before_thread_started.cpp` test case.

In b029c510 ASan was changed to block
in `pthread_create()` until the child thread starts so that `arg` is
kept alive for the purposes of leaking check.

While this change "works" its problematic due to the performance
problems it causes. The change is also completely unnecessary if leak
checking is disabled (via detect_leaks runtime option or
CAN_SANITIZE_LEAKS compile time config).

This patch does two things:

1. Takes a different approach to solving the leak false positive by
   making LSan's leak checking mechanism treat the `arg` pointer of
   created but not started threads as reachable.  This is done by
   implementing the `ForEachRegisteredThreadContextCb` callback for
   ASan.

2. Removes the blocking behaviour in the ASan `pthread_create`
   interceptor.

rdar://problem/63537240

Differential Revision: https://reviews.llvm.org/D95184

Identified with misc-static-assert.

In the PPC32 SVR4 ABI, a va_list has copies of registers from the function call.
va_arg looked in the wrong registers for (the pointer representation of) an
object in Objective-C, and for some types in C++. Fix va_arg to look in the
general-purpose registers, not the floating-point registers. Also fix va_arg
for some C++ types, like a member function pointer, that are aggregates for
the ABI.

Anthony Richardby found the problem in Objective-C. Eli Friedman suggested
part of this fix.

Fixes https://bugs.llvm.org/show_bug.cgi?id=47921

Reviewed By: efriedma, nemanjai

Differential Revision: https://reviews.llvm.org/D90329

The test wasn't sensitive to alias analysis. As you can seen from D95117 when AA is added by default this is affected.
Updating the test so that it coveres both cases for AA analysis.
Note that this patch depends on D95117 to land first.

Differential Revision: https://reviews.llvm.org/D95247

[LSan] Introduce a callback mechanism to allow adding data reachable from ThreadContexts to the frontier.

This mechanism is intended to provide a way to treat the `arg` pointer
of a created (but not yet started) thread as reachable. In future
patches this will be implemented in `GetAdditionalThreadContextPtrs`.

A separate implementation of `GetAdditionalThreadContextPtrs` exists
for ASan and LSan runtimes because they need to be implemented
differently in future patches.

rdar://problem/63537240

Differential Revision: https://reviews.llvm.org/D95183

D94280 also fixed PR48702.

The expansion for wide subtractions includes G_USUBO.

Differential Revision: https://reviews.llvm.org/D95032

This was miscompiling on ubsan bots.

Like D95088, remove incompatible attribute in more lib calls.

Differential Revision: https://reviews.llvm.org/D95278

Also, return NULL from unsuccessful OMPT function lookup.

Differential Revision: https://reviews.llvm.org/D95277

Differential Revision: https://reviews.llvm.org/D95195

Differential Revision: https://reviews.llvm.org/D95194

Differential Revision: https://reviews.llvm.org/D95197

Differential Revision: https://reviews.llvm.org/D95196

Define vsoxseg/vsuxseg intrinsics and pseudo instructions.
Lower vsoxseg/vsuxseg intrinsics to pseudo instructions in RISCVDAGToDAGISel.

Differential Revision: https://reviews.llvm.org/D94940

Differential Revision: https://reviews.llvm.org/D95192

Differential Revision: https://reviews.llvm.org/D95191

Differential Revision: https://reviews.llvm.org/D95190

Differential Revision: https://reviews.llvm.org/D95193

Define vloxseg/vluxseg intrinsics and pseudo instructions.
Lower vloxseg/vluxseg intrinsics to pseudo instructions in RISCVDAGToDAGISel.

Differential Revision: https://reviews.llvm.org/D94903

This builds on the restricted after initial revert form of D93906, and adds back support for breaking backedges of inner loops. It turns out the original invalidation logic wasn't quite right, specifically around the handling of LCSSA.

When breaking the backedge of an inner loop, we can cause blocks which were in the outer loop only because they were also included in a sub-loop to be removed from both loops. This results in the exit block set for our original parent loop changing, and thus a need for new LCSSA phi nodes.

This case happens when the inner loop has an exit block which is also an exit block of the parent, and there's a block in the child which reaches an exit to said block without also reaching an exit to the parent loop.

(I'm describing this in terms of the immediate parent, but the problem is general for any transitive parent in the nest.)

The approach implemented here involves a potentially expensive LCSSA rebuild.  Perf testing during review didn't show anything concerning, but we may end up needing to revert this if anyone encounters a practical compile time issue.

Differential Revision: https://reviews.llvm.org/D94378

Rather than reimplement, use a `using` declaration to bring in
`SmallVectorImpl<char>`'s assign and append implementations in
`SmallString`.

The `SmallString` versions were missing reference invalidation
assertions from `SmallVector`. This patch also fixes a bug in
`llvm::FileCollector::addFileImpl`, which was a copy/paste from
`clang::ModuleDependencyCollector::copyToRoot`, both caught by the
no-longer-skipped assertions.

As a drive-by, this also sinks the `const SmallVectorImpl&` versions of
these methods down into `SmallVectorImpl`, since I imagine they'd be
useful elsewhere.

Differential Revision: https://reviews.llvm.org/D95202