<feed xmlns='http://www.w3.org/2005/Atom'>
<title>llvm-project.git/clang/lib/CodeGen/CodeGenFunction.h, branch users/mingmingl-llvm/samplefdo-profile-format</title>
<subtitle>Unnamed repository; edit this file 'description' to name the repository.
</subtitle>
<link rel='alternate' type='text/html' href='https://git.belthelziquor.com/llvm-project.git/'/>
<entry>
<title>[clang][OpenMP][SPIR-V] Fix addrspace of pointer kernel arguments (#157172)</title>
<updated>2025-09-09T18:42:26+00:00</updated>
<author>
<name>Nick Sarnie</name>
<email>nick.sarnie@intel.com</email>
</author>
<published>2025-09-09T18:42:26+00:00</published>
<link rel='alternate' type='text/html' href='https://git.belthelziquor.com/llvm-project.git/commit/?id=b6be44ad0deeb86e920873de87875d2eaa6c2d8b'/>
<id>b6be44ad0deeb86e920873de87875d2eaa6c2d8b</id>
<content type='text'>
In SPIR-V, kernel arguments are not allowed to be in the Generic AS, in
both Intel's internal SPIR-V offloading implementation as well as
HIPSPV, `CrossWorkgroup` AS1 is used. Do the same for OMPSPV.

Currently with Generic AS the `llvm-spirv` translator blows up if we are
using it, and if not, the GPU runtime blows up.

To get the existing logic to set the correct AS to kick in, we need to
know if the function is a kernel or not at the time we first create the
function that may end up as the kernel.

I use the existing `arrangeSYCLKernelCallerDeclaration` function to do
the right kernel ABI computation, but since the function is not specific
to SYCL anymore because I merged all the device kernel clang attributes
into one.

Rename the function to be accurate to the current behavior,
`arrangeDeviceKernelCallerDeclaration`.

---------

Signed-off-by: Sarnie, Nick &lt;nick.sarnie@intel.com&gt;</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
In SPIR-V, kernel arguments are not allowed to be in the Generic AS, in
both Intel's internal SPIR-V offloading implementation as well as
HIPSPV, `CrossWorkgroup` AS1 is used. Do the same for OMPSPV.

Currently with Generic AS the `llvm-spirv` translator blows up if we are
using it, and if not, the GPU runtime blows up.

To get the existing logic to set the correct AS to kick in, we need to
know if the function is a kernel or not at the time we first create the
function that may end up as the kernel.

I use the existing `arrangeSYCLKernelCallerDeclaration` function to do
the right kernel ABI computation, but since the function is not specific
to SYCL anymore because I merged all the device kernel clang attributes
into one.

Rename the function to be accurate to the current behavior,
`arrangeDeviceKernelCallerDeclaration`.

---------

Signed-off-by: Sarnie, Nick &lt;nick.sarnie@intel.com&gt;</pre>
</div>
</content>
</entry>
<entry>
<title>[Clang] [C2y] Implement N3355 ‘Named Loops’ (#152870)</title>
<updated>2025-09-02T16:37:19+00:00</updated>
<author>
<name>Sirraide</name>
<email>aeternalmail@gmail.com</email>
</author>
<published>2025-09-02T16:37:19+00:00</published>
<link rel='alternate' type='text/html' href='https://git.belthelziquor.com/llvm-project.git/commit/?id=e4a1b5f36e71c8c382bdd531867c5f6eb3f7deac'/>
<id>e4a1b5f36e71c8c382bdd531867c5f6eb3f7deac</id>
<content type='text'>
This implements support for [named
loops](https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3355.htm) for
C2y. 

When parsing a `LabelStmt`, we create the `LabeDecl` early before we parse 
the substatement; this label is then passed down to `ParseWhileStatement()` 
and friends, which then store it in the loop’s (or switch statement’s) `Scope`; 
when we encounter a `break/continue` statement, we perform a lookup for 
the label (and error if it doesn’t exist), and then walk the scope stack and 
check if there is a scope whose preceding label is the target label, which 
identifies the jump target.

The feature is only supported in C2y mode, though a cc1-only option
exists for testing (`-fnamed-loops`), which is mostly intended to try
and make sure that we don’t have to refactor this entire implementation
when/if we start supporting it in C++.

---------

Co-authored-by: Balazs Benics &lt;benicsbalazs@gmail.com&gt;</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This implements support for [named
loops](https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3355.htm) for
C2y. 

When parsing a `LabelStmt`, we create the `LabeDecl` early before we parse 
the substatement; this label is then passed down to `ParseWhileStatement()` 
and friends, which then store it in the loop’s (or switch statement’s) `Scope`; 
when we encounter a `break/continue` statement, we perform a lookup for 
the label (and error if it doesn’t exist), and then walk the scope stack and 
check if there is a scope whose preceding label is the target label, which 
identifies the jump target.

The feature is only supported in C2y mode, though a cc1-only option
exists for testing (`-fnamed-loops`), which is mostly intended to try
and make sure that we don’t have to refactor this entire implementation
when/if we start supporting it in C++.

---------

Co-authored-by: Balazs Benics &lt;benicsbalazs@gmail.com&gt;</pre>
</div>
</content>
</entry>
<entry>
<title>[UBSan][BoundsSafety] Implement support for more expressive "trap reasons" (#154618)</title>
<updated>2025-08-27T20:07:15+00:00</updated>
<author>
<name>Dan Liew</name>
<email>dan@su-root.co.uk</email>
</author>
<published>2025-08-27T20:07:15+00:00</published>
<link rel='alternate' type='text/html' href='https://git.belthelziquor.com/llvm-project.git/commit/?id=f1ee0473209e31b0d05f589e9091ffbbcc60be31'/>
<id>f1ee0473209e31b0d05f589e9091ffbbcc60be31</id>
<content type='text'>
In 29992cfd628ed5b968ccb73b17ed0521382ba317 (#145967) support was added
for "trap reasons" on traps emitted in UBSan in trapping mode (e.g.
`-fsanitize-trap=undefined`). This improved the debugging experience by
attaching the reason for trapping as a string on the debug info on trap
instructions. Consumers such as LLDB can display this trap reason string
when the trap is reached.

A limitation of that patch is that the trap reason string is hard-coded
for each `SanitizerKind` even though the compiler actually has much more
information about the trap available at compile time that could be shown
to the user.

This patch is an incremental step in fixing that. It consists of two
main steps.

**1. Introduce infrastructure for building trap reason strings**

To make it convenient to construct trap reason strings this patch
re-uses Clang's powerful diagnostic infrastructure to provide a
convenient API for constructing trap reason strings. This is achieved
by:

* Introducing a new `Trap` diagnostic kind to represent trap diagnostics
in TableGen files.
* Adding a new `Trap` diagnostic component. While this part probably
isn't technically necessary it seemed like I should follow the existing
convention used by the diagnostic system.
* Adding `DiagnosticTrapKinds.td` to describe the different trap
reasons.
* Add the `TrapReasonBuilder` and `TrapReason` classes to provide an
interface for constructing trap reason strings and the trap category.
Note this API while similar to `DiagnosticBuilder` has different
semantics which are described in the code comments. In particular the
behavior when the destructor is called is very different.
* Adding `CodeGenModule::BuildTrapReason()` as a convenient constructor
for the `TrapReasonBuilder`.

This use of the diagnostic system is a little unusual in that the
emitted trap diagnostics aren't actually consumed by normal diagnostic
consumers (e.g. the console). Instead the `TrapReasonBuilder` is just
used to format a string, so in effect the builder is somewhat analagous
to "printf". However, re-using the diagnostics system in this way brings
a several benefits:

* The powerful diagnostic templating languge (e.g. `%select`) can be
used.
* Formatting Clang data types (e.g. `Type`, `Expr`, etc.) just work
out-of-the-box.
* Describing trap reasons in tablegen files opens the door for
translation to different languages in the future.
* The `TrapReasonBuilder` API is very similar to `DiagnosticBuilder`
which makes it easy to use by anyone already familiar with Clang's
diagnostic system.

While UBSan is the first consumer of this new infrastructure the intent
is to use this to overhaul how trap reasons are implemented in the
`-fbounds-safety` implementation (currently exists downstream).

**2. Apply the new infrastructure to UBSan checks for arithmetic
overflow**

To demonstrate using `TrapReasonBuilder` this patch applies it to UBSan
traps for arithmetic overflow. The intention is that we would
iteratively switch to using the `TrapReasonBuilder` for all UBSan traps
where it makes sense in future patches.

Previously for code like

```
int test(int a, int b) { return a + b; }
```

The trap reason string looked like

```
Undefined Behavior Sanitizer: Integer addition overflowed
```

now the trap message looks like:

```
Undefined Behavior Sanitizer: signed integer addition overflow in 'a + b'
```

This string is much more specific because

* It explains if signed or unsigned overflow occurred
* It actually shows the expression that overflowed

One possible downside of this approach is it may blow up Debug info size
because now there can be many more distinct trap reason strings. To
allow users to avoid this a new driver/cc1 flag
`-fsanitize-debug-trap-reasons=` has been added which can either be
`none` (disable trap reasons entirely), `basic` (use the per
`SanitizerKind` hard coded strings), and `detailed` (use the new
expressive trap reasons implemented in this patch). The default is
`detailed` to give the best out-of-the-box debugging experience. The
existing `-fsanitize-debug-trap-reasons` and
`-fno-sanitize-debug-trap-reasons` have been kept for compatibility and
are aliases of the new flag with `detailed` and `none` arguments passed
respectively.


rdar://158612755</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
In 29992cfd628ed5b968ccb73b17ed0521382ba317 (#145967) support was added
for "trap reasons" on traps emitted in UBSan in trapping mode (e.g.
`-fsanitize-trap=undefined`). This improved the debugging experience by
attaching the reason for trapping as a string on the debug info on trap
instructions. Consumers such as LLDB can display this trap reason string
when the trap is reached.

A limitation of that patch is that the trap reason string is hard-coded
for each `SanitizerKind` even though the compiler actually has much more
information about the trap available at compile time that could be shown
to the user.

This patch is an incremental step in fixing that. It consists of two
main steps.

**1. Introduce infrastructure for building trap reason strings**

To make it convenient to construct trap reason strings this patch
re-uses Clang's powerful diagnostic infrastructure to provide a
convenient API for constructing trap reason strings. This is achieved
by:

* Introducing a new `Trap` diagnostic kind to represent trap diagnostics
in TableGen files.
* Adding a new `Trap` diagnostic component. While this part probably
isn't technically necessary it seemed like I should follow the existing
convention used by the diagnostic system.
* Adding `DiagnosticTrapKinds.td` to describe the different trap
reasons.
* Add the `TrapReasonBuilder` and `TrapReason` classes to provide an
interface for constructing trap reason strings and the trap category.
Note this API while similar to `DiagnosticBuilder` has different
semantics which are described in the code comments. In particular the
behavior when the destructor is called is very different.
* Adding `CodeGenModule::BuildTrapReason()` as a convenient constructor
for the `TrapReasonBuilder`.

This use of the diagnostic system is a little unusual in that the
emitted trap diagnostics aren't actually consumed by normal diagnostic
consumers (e.g. the console). Instead the `TrapReasonBuilder` is just
used to format a string, so in effect the builder is somewhat analagous
to "printf". However, re-using the diagnostics system in this way brings
a several benefits:

* The powerful diagnostic templating languge (e.g. `%select`) can be
used.
* Formatting Clang data types (e.g. `Type`, `Expr`, etc.) just work
out-of-the-box.
* Describing trap reasons in tablegen files opens the door for
translation to different languages in the future.
* The `TrapReasonBuilder` API is very similar to `DiagnosticBuilder`
which makes it easy to use by anyone already familiar with Clang's
diagnostic system.

While UBSan is the first consumer of this new infrastructure the intent
is to use this to overhaul how trap reasons are implemented in the
`-fbounds-safety` implementation (currently exists downstream).

**2. Apply the new infrastructure to UBSan checks for arithmetic
overflow**

To demonstrate using `TrapReasonBuilder` this patch applies it to UBSan
traps for arithmetic overflow. The intention is that we would
iteratively switch to using the `TrapReasonBuilder` for all UBSan traps
where it makes sense in future patches.

Previously for code like

```
int test(int a, int b) { return a + b; }
```

The trap reason string looked like

```
Undefined Behavior Sanitizer: Integer addition overflowed
```

now the trap message looks like:

```
Undefined Behavior Sanitizer: signed integer addition overflow in 'a + b'
```

This string is much more specific because

* It explains if signed or unsigned overflow occurred
* It actually shows the expression that overflowed

One possible downside of this approach is it may blow up Debug info size
because now there can be many more distinct trap reason strings. To
allow users to avoid this a new driver/cc1 flag
`-fsanitize-debug-trap-reasons=` has been added which can either be
`none` (disable trap reasons entirely), `basic` (use the per
`SanitizerKind` hard coded strings), and `detailed` (use the new
expressive trap reasons implemented in this patch). The default is
`detailed` to give the best out-of-the-box debugging experience. The
existing `-fsanitize-debug-trap-reasons` and
`-fno-sanitize-debug-trap-reasons` have been kept for compatibility and
are aliases of the new flag with `detailed` and `none` arguments passed
respectively.


rdar://158612755</pre>
</div>
</content>
</entry>
<entry>
<title>[clang] NFC: reintroduce clang/include/clang/AST/Type.h (#155050)</title>
<updated>2025-08-27T16:11:34+00:00</updated>
<author>
<name>Matheus Izvekov</name>
<email>mizvekov@gmail.com</email>
</author>
<published>2025-08-27T16:11:34+00:00</published>
<link rel='alternate' type='text/html' href='https://git.belthelziquor.com/llvm-project.git/commit/?id=249167a8982afc3f55237baf1532c5c8ebd850b3'/>
<id>249167a8982afc3f55237baf1532c5c8ebd850b3</id>
<content type='text'>
This reintroduces `Type.h`, having earlier been renamed to `TypeBase.h`,
as a redirection to `TypeBase.h`, and redirects most users to include
the former instead.

This is a preparatory patch for being able to provide inline definitions
for `Type` methods which would otherwise cause a circular dependency
with `Decl{,CXX}.h`.

Doing these operations into their own NFC patch helps the git rename
detection logic work, preserving the history.

This patch makes clang just a little slower to build (~0.17%), just
because it makes more code indirectly include `DeclCXX.h`.</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This reintroduces `Type.h`, having earlier been renamed to `TypeBase.h`,
as a redirection to `TypeBase.h`, and redirects most users to include
the former instead.

This is a preparatory patch for being able to provide inline definitions
for `Type` methods which would otherwise cause a circular dependency
with `Decl{,CXX}.h`.

Doing these operations into their own NFC patch helps the git rename
detection logic work, preserving the history.

This patch makes clang just a little slower to build (~0.17%), just
because it makes more code indirectly include `DeclCXX.h`.</pre>
</div>
</content>
</entry>
<entry>
<title>[clang] NFC: rename clang/include/clang/AST/Type.h to TypeBase.h (#155049)</title>
<updated>2025-08-27T16:09:48+00:00</updated>
<author>
<name>Matheus Izvekov</name>
<email>mizvekov@gmail.com</email>
</author>
<published>2025-08-27T16:09:48+00:00</published>
<link rel='alternate' type='text/html' href='https://git.belthelziquor.com/llvm-project.git/commit/?id=bcd153083634c9f4d6de45c636a58884623dbc52'/>
<id>bcd153083634c9f4d6de45c636a58884623dbc52</id>
<content type='text'>
This is a preparatory patch, to be able to provide inline definitions
for `Type` functions which depend on `Decl{,CXX}.h`. As the latter also
depends on `Type.h`, this would not be possible without some
reorganizing.

Splitting this rename into its own patch allows git to track this as a
rename, and preserve all git history, and not force any code
reformatting.

A later NFC patch will reintroduce `Type.h` as redirection to
`TypeBase.h`, rewriting most places back to directly including `Type.h`
instead of `TypeBase.h`, leaving only a handful of places where this is
necessary.

Then yet a later patch will exploit this by making more stuff inline.</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This is a preparatory patch, to be able to provide inline definitions
for `Type` functions which depend on `Decl{,CXX}.h`. As the latter also
depends on `Type.h`, this would not be possible without some
reorganizing.

Splitting this rename into its own patch allows git to track this as a
rename, and preserve all git history, and not force any code
reformatting.

A later NFC patch will reintroduce `Type.h` as redirection to
`TypeBase.h`, rewriting most places back to directly including `Type.h`
instead of `TypeBase.h`, leaving only a handful of places where this is
necessary.

Then yet a later patch will exploit this by making more stuff inline.</pre>
</div>
</content>
</entry>
<entry>
<title>[clang] NFC: change more places to use Type::getAsTagDecl and friends (#155313)</title>
<updated>2025-08-25T23:18:56+00:00</updated>
<author>
<name>Matheus Izvekov</name>
<email>mizvekov@gmail.com</email>
</author>
<published>2025-08-25T23:18:56+00:00</published>
<link rel='alternate' type='text/html' href='https://git.belthelziquor.com/llvm-project.git/commit/?id=dc8596d5485a52abee2967cec72f81ef4872270c'/>
<id>dc8596d5485a52abee2967cec72f81ef4872270c</id>
<content type='text'>
This changes a bunch of places which use getAs&lt;TagType&gt;, including
derived types, just to obtain the tag definition.

This is preparation for #155028, offloading all the changes that PR used
to introduce which don't depend on any new helpers.</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This changes a bunch of places which use getAs&lt;TagType&gt;, including
derived types, just to obtain the tag definition.

This is preparation for #155028, offloading all the changes that PR used
to introduce which don't depend on any new helpers.</pre>
</div>
</content>
</entry>
<entry>
<title>[clang][CodeGen] cast addr space of ReturnValue if needed (#154380)</title>
<updated>2025-08-21T09:38:55+00:00</updated>
<author>
<name>macurtis-amd</name>
<email>macurtis@amd.com</email>
</author>
<published>2025-08-21T09:38:55+00:00</published>
<link rel='alternate' type='text/html' href='https://git.belthelziquor.com/llvm-project.git/commit/?id=0c480dd4b61e285bfda4de99c77da28922e64b94'/>
<id>0c480dd4b61e285bfda4de99c77da28922e64b94</id>
<content type='text'>
Fixes a bug on AMDGPU targets where a pointer was stored as address
space 5, but then loaded as address space 0.

Issue found as part of [Kokkos](https://github.com/kokkos/kokkos)
testing, specifically `hip.atomics` (see
[core/unit_test/TestAtomics.hpp](https://github.com/kokkos/kokkos/blob/develop/core/unit_test/TestAtomics.hpp)).

Issue was introduced by commit
[39ec9de7c230](https://github.com/llvm/llvm-project/commit/39ec9de7c230)
- [clang][CodeGen] sret args should always point to the alloca AS, so
use that (https://github.com/llvm/llvm-project/pull/114062).</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Fixes a bug on AMDGPU targets where a pointer was stored as address
space 5, but then loaded as address space 0.

Issue found as part of [Kokkos](https://github.com/kokkos/kokkos)
testing, specifically `hip.atomics` (see
[core/unit_test/TestAtomics.hpp](https://github.com/kokkos/kokkos/blob/develop/core/unit_test/TestAtomics.hpp)).

Issue was introduced by commit
[39ec9de7c230](https://github.com/llvm/llvm-project/commit/39ec9de7c230)
- [clang][CodeGen] sret args should always point to the alloca AS, so
use that (https://github.com/llvm/llvm-project/pull/114062).</pre>
</div>
</content>
</entry>
<entry>
<title>[WIP] [clang] Align cleanup structs to prevent SIGBUS on sparc32 (#152866)</title>
<updated>2025-08-13T16:26:36+00:00</updated>
<author>
<name>Koakuma</name>
<email>koachan@protonmail.com</email>
</author>
<published>2025-08-13T16:26:36+00:00</published>
<link rel='alternate' type='text/html' href='https://git.belthelziquor.com/llvm-project.git/commit/?id=8071d279fd97134f798699795dfb0b16747ce247'/>
<id>8071d279fd97134f798699795dfb0b16747ce247</id>
<content type='text'>
The cleanup structs expect that pointers and (u)int64_t have the same
alignment requirements, which isn't true on sparc32, which causes
SIGBUSes.

See also: https://github.com/llvm/llvm-project/issues/66620</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The cleanup structs expect that pointers and (u)int64_t have the same
alignment requirements, which isn't true on sparc32, which causes
SIGBUSes.

See also: https://github.com/llvm/llvm-project/issues/66620</pre>
</div>
</content>
</entry>
<entry>
<title>[clang] Improve nested name specifier AST representation (#147835)</title>
<updated>2025-08-09T08:06:53+00:00</updated>
<author>
<name>Matheus Izvekov</name>
<email>mizvekov@gmail.com</email>
</author>
<published>2025-08-09T08:06:53+00:00</published>
<link rel='alternate' type='text/html' href='https://git.belthelziquor.com/llvm-project.git/commit/?id=91cdd35008e9ab32dffb7e401cdd7313b3461892'/>
<id>91cdd35008e9ab32dffb7e401cdd7313b3461892</id>
<content type='text'>
This is a major change on how we represent nested name qualifications in
the AST.

* The nested name specifier itself and how it's stored is changed. The
prefixes for types are handled within the type hierarchy, which makes
canonicalization for them super cheap, no memory allocation required.
Also translating a type into nested name specifier form becomes a no-op.
An identifier is stored as a DependentNameType. The nested name
specifier gains a lightweight handle class, to be used instead of
passing around pointers, which is similar to what is implemented for
TemplateName. There is still one free bit available, and this handle can
be used within a PointerUnion and PointerIntPair, which should keep
bit-packing aficionados happy.
* The ElaboratedType node is removed, all type nodes in which it could
previously apply to can now store the elaborated keyword and name
qualifier, tail allocating when present.
* TagTypes can now point to the exact declaration found when producing
these, as opposed to the previous situation of there only existing one
TagType per entity. This increases the amount of type sugar retained,
and can have several applications, for example in tracking module
ownership, and other tools which care about source file origins, such as
IWYU. These TagTypes are lazily allocated, in order to limit the
increase in AST size.

This patch offers a great performance benefit.

It greatly improves compilation time for
[stdexec](https://github.com/NVIDIA/stdexec). For one datapoint, for
`test_on2.cpp` in that project, which is the slowest compiling test,
this patch improves `-c` compilation time by about 7.2%, with the
`-fsyntax-only` improvement being at ~12%.

This has great results on compile-time-tracker as well:

![image](https://github.com/user-attachments/assets/700dce98-2cab-4aa8-97d1-b038c0bee831)

This patch also further enables other optimziations in the future, and
will reduce the performance impact of template specialization resugaring
when that lands.

It has some other miscelaneous drive-by fixes.

About the review: Yes the patch is huge, sorry about that. Part of the
reason is that I started by the nested name specifier part, before the
ElaboratedType part, but that had a huge performance downside, as
ElaboratedType is a big performance hog. I didn't have the steam to go
back and change the patch after the fact.

There is also a lot of internal API changes, and it made sense to remove
ElaboratedType in one go, versus removing it from one type at a time, as
that would present much more churn to the users. Also, the nested name
specifier having a different API avoids missing changes related to how
prefixes work now, which could make existing code compile but not work.

How to review: The important changes are all in
`clang/include/clang/AST` and `clang/lib/AST`, with also important
changes in `clang/lib/Sema/TreeTransform.h`.

The rest and bulk of the changes are mostly consequences of the changes
in API.

PS: TagType::getDecl is renamed to `getOriginalDecl` in this patch, just
for easier to rebasing. I plan to rename it back after this lands.

Fixes #136624
Fixes https://github.com/llvm/llvm-project/issues/43179
Fixes https://github.com/llvm/llvm-project/issues/68670
Fixes https://github.com/llvm/llvm-project/issues/92757</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This is a major change on how we represent nested name qualifications in
the AST.

* The nested name specifier itself and how it's stored is changed. The
prefixes for types are handled within the type hierarchy, which makes
canonicalization for them super cheap, no memory allocation required.
Also translating a type into nested name specifier form becomes a no-op.
An identifier is stored as a DependentNameType. The nested name
specifier gains a lightweight handle class, to be used instead of
passing around pointers, which is similar to what is implemented for
TemplateName. There is still one free bit available, and this handle can
be used within a PointerUnion and PointerIntPair, which should keep
bit-packing aficionados happy.
* The ElaboratedType node is removed, all type nodes in which it could
previously apply to can now store the elaborated keyword and name
qualifier, tail allocating when present.
* TagTypes can now point to the exact declaration found when producing
these, as opposed to the previous situation of there only existing one
TagType per entity. This increases the amount of type sugar retained,
and can have several applications, for example in tracking module
ownership, and other tools which care about source file origins, such as
IWYU. These TagTypes are lazily allocated, in order to limit the
increase in AST size.

This patch offers a great performance benefit.

It greatly improves compilation time for
[stdexec](https://github.com/NVIDIA/stdexec). For one datapoint, for
`test_on2.cpp` in that project, which is the slowest compiling test,
this patch improves `-c` compilation time by about 7.2%, with the
`-fsyntax-only` improvement being at ~12%.

This has great results on compile-time-tracker as well:

![image](https://github.com/user-attachments/assets/700dce98-2cab-4aa8-97d1-b038c0bee831)

This patch also further enables other optimziations in the future, and
will reduce the performance impact of template specialization resugaring
when that lands.

It has some other miscelaneous drive-by fixes.

About the review: Yes the patch is huge, sorry about that. Part of the
reason is that I started by the nested name specifier part, before the
ElaboratedType part, but that had a huge performance downside, as
ElaboratedType is a big performance hog. I didn't have the steam to go
back and change the patch after the fact.

There is also a lot of internal API changes, and it made sense to remove
ElaboratedType in one go, versus removing it from one type at a time, as
that would present much more churn to the users. Also, the nested name
specifier having a different API avoids missing changes related to how
prefixes work now, which could make existing code compile but not work.

How to review: The important changes are all in
`clang/include/clang/AST` and `clang/lib/AST`, with also important
changes in `clang/lib/Sema/TreeTransform.h`.

The rest and bulk of the changes are mostly consequences of the changes
in API.

PS: TagType::getDecl is renamed to `getOriginalDecl` in this patch, just
for easier to rebasing. I plan to rename it back after this lands.

Fixes #136624
Fixes https://github.com/llvm/llvm-project/issues/43179
Fixes https://github.com/llvm/llvm-project/issues/68670
Fixes https://github.com/llvm/llvm-project/issues/92757</pre>
</div>
</content>
</entry>
<entry>
<title>[Clang][CodeGen] Move `EmitPointerArithmetic` into `CodeGenFunction`. NFC. (#152634)</title>
<updated>2025-08-08T13:41:03+00:00</updated>
<author>
<name>Yingwei Zheng</name>
<email>dtcxzyw2333@gmail.com</email>
</author>
<published>2025-08-08T13:41:03+00:00</published>
<link rel='alternate' type='text/html' href='https://git.belthelziquor.com/llvm-project.git/commit/?id=ac8295550b4e0abe044099485f95f7ac08cbb19f'/>
<id>ac8295550b4e0abe044099485f95f7ac08cbb19f</id>
<content type='text'>
`CodeGenFunction::EmitPointerArithmetic` is needed by
https://github.com/llvm/llvm-project/pull/152575. Separate the NFC
changes into a new PR for smooth review.</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
`CodeGenFunction::EmitPointerArithmetic` is needed by
https://github.com/llvm/llvm-project/pull/152575. Separate the NFC
changes into a new PR for smooth review.</pre>
</div>
</content>
</entry>
</feed>
