This reduces memory consumption for IRPositions by eliminating the
vtable pointer and the `KindOrArgNo` integer. Since each abstract
attribute has an associated IRPosition, the 12-16 bytes we save add up
quickly.

No functional change is intended.

---

Single run of the Attributor module and then CGSCC pass (oldPM)
for SPASS/clause.c (~10k LLVM-IR loc):

Before:
```
calls to allocation functions: 469545 (260135/s)
temporary memory allocations: 77137 (42735/s)
peak heap memory consumption: 30.50MB
peak RSS (including heaptrack overhead): 119.50MB
total memory leaked: 269.07KB
```

After:
```
calls to allocation functions: 468999 (274108/s)
temporary memory allocations: 77002 (45004/s)
peak heap memory consumption: 28.83MB
peak RSS (including heaptrack overhead): 118.05MB
total memory leaked: 269.07KB
```

Difference:
```
calls to allocation functions: -546 (5808/s)
temporary memory allocations: -135 (1436/s)
peak heap memory consumption: -1.67MB
peak RSS (including heaptrack overhead): 0B
total memory leaked: 0B
```

---

CTMark 15 runs

Metric: compile_time

Program                                        lhs    rhs    diff
 test-suite...:: CTMark/sqlite3/sqlite3.test    25.07  24.09 -3.9%
 test-suite...Mark/mafft/pairlocalalign.test    14.58  14.14 -3.0%
 test-suite...-typeset/consumer-typeset.test    21.78  21.58 -0.9%
 test-suite :: CTMark/SPASS/SPASS.test          21.95  22.03  0.4%
 test-suite :: CTMark/lencod/lencod.test        25.43  25.50  0.3%
 test-suite...ark/tramp3d-v4/tramp3d-v4.test    23.88  23.83 -0.2%
 test-suite...TMark/7zip/7zip-benchmark.test    60.24  60.11 -0.2%
 test-suite :: CTMark/kimwitu++/kc.test         15.69  15.69 -0.0%
 test-suite...:: CTMark/ClamAV/clamscan.test    25.43  25.42 -0.0%
 test-suite :: CTMark/Bullet/bullet.test        37.63  37.62 -0.0%
 Geomean difference                                          -0.8%

---

Reviewed By: lebedev.ri

Differential Revision: https://reviews.llvm.org/D78722

Since every AbstractAttribute so far, and for the foreseeable future,
corresponds to a single IRPosition we can simplify the class structure.
We already did this for IRAttribute but there is no reason to stop
there.

This reverts commit 53913a65.
Breaks VFSFromYAMLTest.DirectoryIterationSameDirMultipleEntries
in SupportTests on non-Windows.

Discussion is in https://reviews.llvm.org/D79215

LLD calls this on every source file string in every object file when
writing PDBs, so it is somewhat hot.

Avoid rewriting paths that do not contain path traversal components
(./..). Use find_first_not_of(separators) directly instead of using the
path iterators. The path component iterators appear to be slow, and
directly searching for slashes makes it easier to find double separators
that need to be canonicalized.

I discovered that the VFS relies on remote_dots to not canonicalize
early slashes (/foo or C:/foo) on Windows, so I had to leave that
behavior behind with unit tests for it. This is undesirable, but I claim
that my change is NFC.

Cond ? (X & ~C) : (X | C) --> (X & ~C) | (Cond ? 0 : C)
Cond ? (X | C) : (X & ~C) --> (X & ~C) | (Cond ? C : 0)

The select-of-constants form results in better codegen.
There's an existing test diff that shows a transform that
results in an extra IR instruction, but that's an existing
problem.

This is motivated by code seen in LLVM itself - see PR37581:
https://bugs.llvm.org/show_bug.cgi?id=37581

define i8 @src(i8 %x, i8 %C, i1 %b)  {
  %notC = xor i8 %C, -1
  %and = and i8 %x, %notC
  %or = or i8 %x, %C
  %cond = select i1 %b, i8 %or, i8 %and
  ret i8 %cond
}

define i8 @tgt(i8 %x, i8 %C, i1 %b)  {
  %notC = xor i8 %C, -1
  %and = and i8 %x, %notC
  %mul = select i1 %b, i8 %C, i8 0
  %or = or i8 %mul, %and
  ret i8 %or
}

http://volta.cs.utah.edu:8080/z/Vt2WVm

Differential Revision: https://reviews.llvm.org/D78880

This is a somewhat annoying API, but not without precedend in this low
level API.

[X86] Use splitVector helper in truncateVectorWithPACK/splitVectorStore/combineHorizontalMinMaxResult/combineReductionToHorizontal. NFC.

All these locations were performing the same type splitting/extractSubVector calls as the spltVector helper.

It can handle EVT just as well (and so can the extractSubVector calls).

Summary:
Current implementation of DWARFDie::getName(DINameKind Kind) could
lead to double call to DWARFDie::find(DW_AT_name) in following
scenario:

getName(LinkageName);
getName(ShortName);

getName(LinkageName) calls find(DW_AT_name) if linkage name is not
found. Then, it is called again in getName(ShortName). This patch
alows to request LinkageName and ShortName separately
to avoid extra call to find(DW_AT_name).

It helps D74169 to parse clang debuginfo faster(~1%).

Reviewers: clayborg, dblaikie

Differential Revision: https://reviews.llvm.org/D79173

Duplicate some tests in preparation for D79294.

The splitVector helper uses extractSubVector which splits build vectors like we do here, so avoid reimplementing it.

splitVector could easily be extended to peek through bitcasts as well but I'd prefer to keep this commit NFC.

Use the ISD::matchUnaryPredicate helper to check for inrange constants.

Test this directly, rather than going through InstSimplify.

This is a Test commit.

The number of public symbols is very large, and each deserialization
does a few heap allocations. The public symbols are serialized by the
linker, so we can assume they have the expected layout and use it
directly.

Saves O(#publics) temporary heap allocations and shrinks some data
structures.

Don't use $noreg for instructions that take register inputs.
Only allow $noreg for parts of memory operands.

Don't use index register with $rip base.

Use RETQ instead of the RET pseudo. This pass is after the
ExpandPseudo pass that converts RET to RETQ.

[PDB] Remove a couple asserts that are no longer valid now that C13Builders does not use unique_ptr.

These asserts used to check that unique_ptr was not null.

This fixes failures from 7af4bb16

This accounts for a large portion of the memory allocations in LLD.
This DebugSubsectionRecordBuilder object can be stored directly in
C13Builders, it mostly wraps other subsections.

Remove the container kind field from the object. It is always the same
for all elements in the vector, and we can pass it in during writing.

Summary:
FileCheck documentation contains an example of a numeric variable
defined and used on the same line. This is not currently supported by
FileCheck so this commit fixes the example to use CHECK-SAME for the
variable use.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D79253

The two code paths have the same goal, legalizing a load of a non-byte-sized vector by loading the "flattened" representation in memory, slicing off each single element and then building a vector out of those pieces.

The technique employed by `ExpandLoad`  is slightly more convoluted and produces slightly better codegen on ARM, AMDGPU and x86 but suffers from some bugs (D78480) and is wrong for BE machines.

Differential Revision: https://reviews.llvm.org/D79096

Causing buildbot failures

rL368553 added SimplifyMultipleUseDemandedBits handling for ISD::TRUNCATE to SimplifyDemandedBits so we don't need to duplicate this (and it gets rid of another GetDemandedBits call which is slowly being replaced with SimplifyMultipleUseDemandedBits anyhow).

std::pair has a trivial copy ctor, std::tuple doesn't.

The failures only happened in fully clean builds.

Also put all current dependencies of LibraryDependencies.inc in the
build graph, so that this type of thing will cause a failure in
incremental builds next time as well.

This generalizes the main Windows command line tokenizer to be able to
produce StringRef substrings as well as freshly copied C strings. The
implementation is still shared with the normal tokenizer, which is
important, because we have unit tests for that.

.drective sections can be very long. They can potentially list up to
every symbol in the object file by name. It is worth avoiding these
string copies.

This saves a lot of memory when linking chrome.dll with PGO
instrumentation:

             BEFORE      AFTER      % IMP
peak memory: 6657.76MB   4983.54MB  -25%
real:        4m30.875s   2m26.250s  -46%

The time improvement may not be real, my machine was noisy while running
this, but that the peak memory usage improvement should be real.

This change may also help apps that heavily use dllexport annotations,
because those also use linker directives in object files. Apps that do
not use many directives are unlikely to be affected.

Reviewed By: thakis

Differential Revision: https://reviews.llvm.org/D79262

We don't require the type to be trivially assignable. While the standard
says that only is_trivially_copyable types may be memcpy'd, this seems
overly strict. We never assign the type, so there's no way for the type
to observe that the copy/move construction got elided. This is important
for std::pair<POD, POD>, which is not trivially assignable and probably
never will be because changing that would break ABI.

As a side-effect this no longer allows types with deleted copy/move
constructors in SmallVector. That's an unintended side-effect of
is_trivially_copyable anyways.

Shrinks Release+Asserts clang by 20k.

This seems to be working by accident.

This lets it use sized deallocation and make more efficient alignment
decisions. Also adjust BumpPtrAllocator to always allocate at
alignof(std::max_align_t).

Summary:
The current lowering of `select` on RISC-V uses a branch instruction to load a
register with one or other value. This is inefficient, especially in the case of
small constants that can be computed easily.

By implementing the TargetLowering::convertSelectOfConstantsToMath hook, some of
the simpler cases are covered that let us avoid introducing a branch in these
cases.

Reviewed By: luismarques

Differential Revision: https://reviews.llvm.org/D79260

Summary:
This just adds some simple cases for testing select of constants. There will be
a follow-up patch that improves code generation in some of these cases.

Reviewed By: luismarques

Differential Revision: https://reviews.llvm.org/D79259

Summary:
This patch addresses some weird assembly sequences we were seeing during
comparing floats. In particular, comparing a float to itself tells you whether
it is NaN or not, which we were doing correctly, but with an extra unneeded
`and` instruction.

This patch specialises the existing patterns to remove the `and` instructions
when both their operands are the same.

Reviewed By: luismarques, asb

Differential Revision: https://reviews.llvm.org/D78908

Summary:
I worked on adding some SelectionDag patterns to address code generated by these
examples, which came out of some differential testing against GCC. The pattern
additions will be in a follow-up patch.

Reviewers: luismarques, asb

Reviewed By: luismarques, asb

Differential Revision: https://reviews.llvm.org/D78907

I've left out some cases where I wasn't totally sure this was right or
whether the include was ok (compiler-rt) or idiomatic (flang).

Use this in clangd, will follow up with replacements for isspace where
locale-dependent is clearly not intended.