This recommits 100e797a (reverted in
009e0326 for failing an assert). While the
root cause was independently reverted in eaff3004,
this commit includes a LIT to make sure IVDescriptor's SinkAfter logic does not
try to sink branch instructions.

 - uninitialized variables
 - documention warnings
 - shadow variable names

Summary:
D23319 introduced python3 compatibility to clang-format.py, this is however not reflected by the documentation in the comments at the beginning of the file, which show how to use the script with python2 in .vimrc. While the actual mapping a user might want to use may well differ from my suggestion, I think it's nice to show the python2 and python3 version, such that a user can pick from the suggestions instead of googeling the python3 replacement for `:pyf` which they might not be familiar with.

EDIT: picking reviewers according to https://llvm.org/docs/Phabricator.html#finding-potential-reviewers

Reviewers: klimek, MyDeveloperDay

Reviewed By: MyDeveloperDay

Subscribers: ilya-biryukov, cfe-commits, llvm-commits, ychen

Patch By: pseyfert

Tags: #clang-tools-extra, #llvm, #clang

Differential Revision: https://reviews.llvm.org/D38446

This reverts commit b0a03f29.

This reverts commit 3ffce13f.

This reverts commit 31820272.

This reverts commit 6b45e1bc.

This reverts commit 03b84e4f.

This breaks dfsan tests with a linking failure, in for example this build:

  http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux/builds/24312

Reverting this patch locally makes those tests succeed.

This reverts commit bdeb2724.

(Reverting 03b84e4f, so this must come out as well)

Refactor usage of isCopyInstrImpl, isCopyInstr and isAddImmediate methods
to return optional machine operand pair of destination and source
registers.

Patch by Nikola Prica

Differential Revision: https://reviews.llvm.org/D69622

Subscribers: JDevlieghere, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D70002

Summary:
All type in these functions need be valid and Clang types, so
we might as well replace these checks with IsClangType.

Also lets IsClangType explicitly check for validity instead of
assuming that the TypeSystem is a nullptr.

Subscribers: abidh, JDevlieghere, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D70001

This was enabled for other platforms. Added option for Windows/lld-link.

Differential Revision: https://reviews.llvm.org/D69941

This triggered asserts in the Chromium build, see https://crbug.com/1022729 for
details and reproducer.

> Without this change, when a nested tag type of any kind (enum, class,
> struct, union) is used as a variable type, it is emitted without
> emitting the parent type. In CodeView, parent types point to their inner
> types, and inner types do not point back to their parents. We already
> walk over all of the parent scopes to build the fully qualified name.
> This change simply requests their type indices as we go along to enusre
> they are all emitted.
>
> Fixes PR43905
>
> Reviewers: akhuang, amccarth
>
> Differential Revision: https://reviews.llvm.org/D69924

Summary:
The greedy register allocator occasionally decides to insert a large number of
unnecessary copies, see below for an example.  The -consider-local-interval-cost
option (which X86 already enables by default) fixes this.  We enable this option
for AArch64 only after receiving feedback that this change is not beneficial for
PowerPC.

We evaluated the impact of this change on compile time, code size and
performance benchmarks.

This option has a small impact on compile time, measured on CTMark. A 0.1%
geomean regression on -O1 and -O2, and 0.2% geomean for -O3, with at most 0.5%
on individual benchmarks.

The effect on both code size and performance on AArch64 for the LLVM test suite
is nil on the geomean with individual outliers (ignoring short exec_times)
between:

                 best     worst
  size..text     -3.3%    +0.0%
  exec_time      -5.8%    +2.3%

On SPEC CPU® 2017 (compiled for AArch64) there is a minor reduction (-0.2% at
most) in code size on some benchmarks, with a tiny movement (-0.01%) on the
geomean.  Neither intrate nor fprate show any change in performance.

This patch makes the following changes.

- For the AArch64 target, enableAdvancedRASplitCost() now returns true.

- Ensures that -consider-local-interval-cost=false can disable the new
  behaviour if necessary.

This matrix multiply example:

   $ cat test.c
   long A[8][8];
   long B[8][8];
   long C[8][8];

   void run_test() {
     for (int k = 0; k < 8; k++) {
       for (int i = 0; i < 8; i++) {
	 for (int j = 0; j < 8; j++) {
	   C[i][j] += A[i][k] * B[k][j];
	 }
       }
     }
   }

results in the following generated code on AArch64:

  $ clang --target=aarch64-arm-none-eabi -O3 -S test.c -o -
  [...]
                                        // %for.cond1.preheader
                                        // =>This Inner Loop Header: Depth=1
        add     x14, x11, x9
        str     q0, [sp, #16]           // 16-byte Folded Spill
        ldr     q0, [x14]
        mov     v2.16b, v15.16b
        mov     v15.16b, v14.16b
        mov     v14.16b, v13.16b
        mov     v13.16b, v12.16b
        mov     v12.16b, v11.16b
        mov     v11.16b, v10.16b
        mov     v10.16b, v9.16b
        mov     v9.16b, v8.16b
        mov     v8.16b, v31.16b
        mov     v31.16b, v30.16b
        mov     v30.16b, v29.16b
        mov     v29.16b, v28.16b
        mov     v28.16b, v27.16b
        mov     v27.16b, v26.16b
        mov     v26.16b, v25.16b
        mov     v25.16b, v24.16b
        mov     v24.16b, v23.16b
        mov     v23.16b, v22.16b
        mov     v22.16b, v21.16b
        mov     v21.16b, v20.16b
        mov     v20.16b, v19.16b
        mov     v19.16b, v18.16b
        mov     v18.16b, v17.16b
        mov     v17.16b, v16.16b
        mov     v16.16b, v7.16b
        mov     v7.16b, v6.16b
        mov     v6.16b, v5.16b
        mov     v5.16b, v4.16b
        mov     v4.16b, v3.16b
        mov     v3.16b, v1.16b
        mov     x12, v0.d[1]
        fmov    x15, d0
        ldp     q1, q0, [x14, #16]
        ldur    x1, [x10, #-256]
        ldur    x2, [x10, #-192]
        add     x9, x9, #64             // =64
        mov     x13, v1.d[1]
        fmov    x16, d1
        ldr     q1, [x14, #48]
        mul     x3, x15, x1
        mov     x14, v0.d[1]
        fmov    x17, d0
        mov     x18, v1.d[1]
        fmov    x0, d1
        mov     v1.16b, v3.16b
        mov     v3.16b, v4.16b
        mov     v4.16b, v5.16b
        mov     v5.16b, v6.16b
        mov     v6.16b, v7.16b
        mov     v7.16b, v16.16b
        mov     v16.16b, v17.16b
        mov     v17.16b, v18.16b
        mov     v18.16b, v19.16b
        mov     v19.16b, v20.16b
        mov     v20.16b, v21.16b
        mov     v21.16b, v22.16b
        mov     v22.16b, v23.16b
        mov     v23.16b, v24.16b
        mov     v24.16b, v25.16b
        mov     v25.16b, v26.16b
        mov     v26.16b, v27.16b
        mov     v27.16b, v28.16b
        mov     v28.16b, v29.16b
        mov     v29.16b, v30.16b
        mov     v30.16b, v31.16b
        mov     v31.16b, v8.16b
        mov     v8.16b, v9.16b
        mov     v9.16b, v10.16b
        mov     v10.16b, v11.16b
        mov     v11.16b, v12.16b
        mov     v12.16b, v13.16b
        mov     v13.16b, v14.16b
        mov     v14.16b, v15.16b
        mov     v15.16b, v2.16b
        ldr     q2, [sp]                // 16-byte Folded Reload
        fmov    d0, x3
        mul     x3, x12, x1
  [...]

With -consider-local-interval-cost the same section of code results in the
following:

  $ clang --target=aarch64-arm-none-eabi -mllvm -consider-local-interval-cost -O3 -S test.c -o -
  [...]
  .LBB0_1:                              // %for.cond1.preheader
                                        // =>This Inner Loop Header: Depth=1
        add     x14, x11, x9
        ldp     q0, q1, [x14]
        ldur    x1, [x10, #-256]
        ldur    x2, [x10, #-192]
        add     x9, x9, #64             // =64
        mov     x12, v0.d[1]
        fmov    x15, d0
        mov     x13, v1.d[1]
        fmov    x16, d1
        ldp     q0, q1, [x14, #32]
        mul     x3, x15, x1
        cmp     x9, #512                // =512
        mov     x14, v0.d[1]
        fmov    x17, d0
        fmov    d0, x3
        mul     x3, x12, x1
  [...]

Reviewers: SjoerdMeijer, samparker, dmgreen, qcolombet

Reviewed By: dmgreen

Subscribers: ZhangKang, jsji, wuzish, ppc-slack, lkail, steven.zhang, MatzeB, qcolombet, kristof.beyls, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69437

Previously, symbols passed by -init and -fini look as if they are
not referenced by anyone, and the LTO might eliminate them.
This patch fixes the issue.

Fixes a bug reported in https://bugs.llvm.org/show_bug.cgi?id=43927

Differential Revision: https://reviews.llvm.org/D69985

The following testcase

  function:
  .Lpcrel_label1:
  	auipc	a0, %pcrel_hi(other_function)
  	addi	a1, a0, %pcrel_lo(.Lpcrel_label1)
  	.p2align	2          # Causes a new fragment to be emitted

  	.type	other_function,@function
  other_function:
  	ret

exposes an odd behaviour in which only the %pcrel_hi relocation is
evaluated but not the %pcrel_lo.

  $ llvm-mc -triple riscv64 -filetype obj t.s | llvm-objdump  -d -r -

  <stdin>:	file format ELF64-riscv

  Disassembly of section .text:
  0000000000000000 function:
         0:	17 05 00 00	auipc	a0, 0
         4:	93 05 05 00	mv	a1, a0
  		0000000000000004:  R_RISCV_PCREL_LO12_I	other_function+4

  0000000000000008 other_function:
         8:	67 80 00 00	ret

The reason seems to be that in RISCVAsmBackend::shouldForceRelocation we
only consider the fragment but in RISCVMCExpr::evaluatePCRelLo we
consider the section. This usually works but there are cases where the
section may still be the same but the fragment may be another one. In
that case we end forcing a %pcrel_lo relocation without any %pcrel_hi.

This patch makes RISCVAsmBackend::shouldForceRelocation use the section,
if any, to determine if the relocation must be forced or not.

Differential Revision: https://reviews.llvm.org/D60657

For white-box testing correct container and iterator modelling it is essential
to access the internal data structures stored for container and iterators. This
patch introduces a simple debug checkers called debug.IteratorDebugging to
achieve this.

Differential Revision: https://reviews.llvm.org/D67156

(test commit)

This was pointed out in review,
but forgot to stage this change into the commit itself..

Summary:
To be used in `ConstantRange::shlWithNoOverflow()`,
may in future be useful for when saturating shift/mul ops are added.

Unlike `ConstantRange::shl()`, these are precise.

Reviewers: nikic, spatel, reames

Reviewed By: nikic

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69960

-mattr=+alu32 has shown good performance vs. without this attribute.
Based on discussion at
  https://lore.kernel.org/bpf/1ec37838-966f-ec0b-5223-ca9b6eb0860d@fb.com/T/#t
cpu version v3 should support -mattr=+alu32.
This patch enabled alu32 if cpu version is v3, either specified by user
or probed by the llvm.

Differential Revision: https://reviews.llvm.org/D69957

so we only call ModulesDidLoad at the end of the method
after the new module has been added to the target and
the sections have all been adjusted to their actual
load addresses.  Solves a problem where an operating
system plugin in the kernel could be loaded multiple
times; the first before the binary had even been
added to the target.

<rdar://problem/50523558>

As we currently have it implemented in altivec.h, the offsets for these two
intrinsics are element offsets. The documentation in the ABI (as well as the
implementation in both XL and GCC) states that these should be byte offsets.

Differential revision: https://reviews.llvm.org/D63636

We currently emit a double precision comparison instruction for this, whereas we
need to emit the single precision version.

Differential revision: https://reviews.llvm.org/D64024

This option allows the user to specify the use of absolute jumptables instead
of relative which is the default on most PPC subtargets.

Patch by Kamauu Bridgeman

Differential revision: https://reviews.llvm.org/D69108

Namely, for the following items:
- Handle constructors within new[];
- Handle constructors for default arguments.

Update the open projects page with a link to the newly added tests
and more hints for potential contributors.

Patch by Daniel Krupp!

Differential Revision: https://reviews.llvm.org/D69308

- Fix false positive reports of strlcat.
- The return value of strlcat and strlcpy is now correctly calculated.
- The resulting string length of strlcat and strlcpy is now correctly
  calculated.

Patch by Daniel Krupp!

Differential Revision: https://reviews.llvm.org/D66049

x86_mmx is conceptually a vector already. Don't introduce an extra conversion between it and scalar i64.

I'm using VectorType::isValidElementType which checks for floating point, integer, and pointers to hopefully make this more readable than just blacklisting x86_mmx.

Differential Revision: https://reviews.llvm.org/D69964

While here, wordsmith the error a bit. Now clang says:
  error: filter expression has non-integral type 'Foo'

Fixes PR43779

Reviewers: amccarth

Differential Revision: https://reviews.llvm.org/D69969

A "signal frame" is a function or block of code where execution arrives via a signal or interrupt, rather than via a normal call instruction. In fact, a particular instruction is interrupted by the signal and needs to be restarted. Therefore, when the signal handler is complete, execution needs to return to the interrupted instruction, rather than the instruction immediately following the call instruction, as in a normal call.

Stack unwinders need to know this to correctly unwind signal frames. Dwarf handily provides an "S" in the CIE augmentation string to describe this case, and the libunwind API provides various functions to for unwinders to determine it,.

The llvm libunwind implementation correctly sets it's internal variable "isSignalFrame" when initializing an unwind context. However, upon stepping up the stack, the current implementation correctly reads the augmentation string and sets it in the CIE info (which it then discards), libunwind doesn't update it's internal unwind context data structure.

This change fixes that, and provides compatibility with both the canonical libunwind and the libgcc implementation.

Reviewers: jfb

Subscribers: christof, libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D69677

Summary:
I need to make use of this pass from a driver program that isn't opt.
Therefore this patch moves this pass into the LLVM library so that it is
available for use elsewhere.

There was one function I kept in tools/opt which is exportDebugifyStats()
this is because it's serializing the statistics into a human readable
format and this seemed more in keeping with opt than a library function

Reviewers: vsk, aprantl

Subscribers: mgorny, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69926