Generate nuw GEPs for struct member accesses, as inbounds + non-negative
implies nuw.
Regression tests are updated using update scripts where possible, and by
find + replace where not.
This is a follow-up from the conversation starting at
https://github.com/llvm/llvm-project/pull/93809#issuecomment-2173729801
The root problem that motivated the change are external AST sources that
compute `ASTRecordLayout`s themselves instead of letting Clang compute
them from the AST. One such example is LLDB using DWARF to get the
definitive offsets and sizes of C++ structures. Such layouts should be
considered correct (modulo buggy DWARF), but various assertions and
lowering logic around the `CGRecordLayoutBuilder` relies on the AST
having `[[no_unique_address]]` attached to them. This is a
layout-altering attribute which is not encoded in DWARF. This causes us
LLDB to trip over the various LLVM<->Clang layout consistency checks.
There has been precedent for avoiding such layout-altering attributes
from affecting lowering with externally-provided layouts (e.g., packed
structs).
This patch proposes to replace the `isZeroSize` checks in
`CGRecordLayoutBuilder` (which roughly means "empty field with
[[no_unique_address]]") with checks for
`CodeGen::isEmptyField`/`CodeGen::isEmptyRecord`.
**Details**
The main strategy here was to change the `isZeroSize` check in
`CGRecordLowering::accumulateFields` and
`CGRecordLowering::accumulateBases` to use the `isEmptyXXX` APIs
instead, preventing empty fields from being added to the `Members` and
`Bases` structures. The rest of the changes fall out from here, to
prevent lookups into these structures (for field numbers or base
indices) from failing.
Added `isEmptyRecordForLayout` and `isEmptyFieldForLayout` (open to
better naming suggestions). The main difference to the existing
`isEmptyRecord`/`isEmptyField` APIs, is that the `isEmptyXXXForLayout`
counterparts don't have special treatment for `unnamed bitfields`/arrays
and also treat fields of empty types as if they had
`[[no_unique_address]]` (i.e., just like the `AsIfNoUniqueAddr` in
`isEmptyField` does).
This makes codegen for array initialization simpler in two ways:
1. Drop the zero-index GEP at the start, which is no longer needed with
opaque pointers.
2. Emit GEPs directly to the correct element, instead of having a long
chain of +1 GEPs. This is more canonical, and also avoids regressions in
unoptimized builds from #93823.
This bug is caused by parenthesized list initialization not being
implemented in `CodeGenFunction::EmitNewArrayInitializer(...)`.
Parenthesized list initialization of `struct`s with `operator new`
already works in Clang and is not affected by this bug.
Additionally, fix the test new-delete.cpp as it incorrectly assumes that
using parentheses with operator new to initialize arrays is illegal for
C++ versions >= C++17.
Fixes#68198
Set the writable and dead_on_unwind attributes for sret arguments. These
indicate that the argument points to writable memory (and it's legal to
introduce spurious writes to it on entry to the function) and that the
argument memory will not be used if the call unwinds.
This enables additional MemCpyOpt/DSE/LICM optimizations.
Before this patch, initialized class members would have the LifetimeKind
LK_MemInitializer, which does not allow for binding a temporary to a
reference. Binding to a temporary however is allowed in parenthesized
aggregate initialization, even if it leads to a dangling reference. To
fix this, we create a new EntityKind, EK_ParenAggInitMember, which has
LifetimeKind LK_FullExpression.
This patch does *not* attempt to diagnose dangling references as a
result of using this feature.
This patch also refactors TryOrBuildParenListInitialization(...) to
accomodate creating different InitializedEntity objects.
Fixes#61567
[0]: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p0960r3.html
Reviewed By: shafik
Differential Revision: https://reviews.llvm.org/D148274
Previously, when checking whether an in-class initializer exists when
performing parenthesized aggregate initialization, Clang checks that the
output of FieldDecl::getInClassInitializer() is non-null. This is
incorrect; if the field is part of a templated type, then
getInClassInitializer() will return nullptr if we haven't called
Sem::BuildCXXDefaultInitExpr(...) before, even if
FieldDecl::hasInClassInitializer() returns true. The end result is that
Clang incorrectly ignores the in class initializer and
value-initializes the field. The fix therefore is to instead call
FieldDecl::hasInClassInitializer(), which is what we do for braced init
lists [0].
Before this patch, Clang does correctly recognize the in-class field
initializer in certain cases. This is Sema::BuildCXXDefaultInitExpr(...)
populates the in class initializer of the corresponding FieldDecl
object. Therefore, if that method was previously called with the same
FieldDecl object, as can happen with a decltype(...) or a braced list
initialization, FieldDecl::getInClassInitializer() will return a
non-null expression, and the field becomes properly initialized.
Fixes 62266
[0]: be5f35e24f/clang/lib/Sema/SemaInit.cpp (L685)
Reviewed By: shafik
Differential Revision: https://reviews.llvm.org/D149389
* Fix an issue where temporaries initialized via parenthesized aggregate
initialization don't get destroyed.
* Fix an issue where aggregate initialization omits calls to class
members' move constructors after a TreeTransform. This occurs because
the CXXConstructExpr wrapping the call to the move constructor gets
unboxed during a TreeTransform of the wrapping FunctionalCastExpr (as with a
InitListExpr), but unlike InitListExpr, we dont reperform the
InitializationSequence for the list's expressions to regenerate the
CXXConstructExpr. This patch fixes this bug by treating
CXXParenListInitExpr identically to InitListExpr in this regard.
Fixes#61145
Reviewed By: rsmith
Differential Revision: https://reviews.llvm.org/D146465
This commit relands the patches for implementing P0960R3 and P1975R0,
which describe initializing aggregates via a parenthesized list.
The relanded commits are:
* 40c52159d3ee - P0960R3 and P1975R0: Allow initializing aggregates from
a parenthesized list of values
* c77a91bb7ba7 - Remove overly restrictive aggregate paren init logic
* 32d7aae04fdb - Fix a clang crash on invalid code in C++20 mode
This patch also fixes a crash in the original implementation.
Previously, if the input tried to call an implicitly deleted copy or
move constructor of a union, we would then try to initialize the union
by initializing it's first element with a reference to a union. This
behavior is incorrect (we should fail to initialize) and if the type of
the first element has a constructor with a single template typename
parameter, then Clang will explode. This patch fixes that issue by
checking that constructor overload resolution did not result in a
deleted function before attempting parenthesized aggregate
initialization.
Additionally, this patch also includes D140159, which contains some
minor fixes made in response to code review comments in the original
implementation that were made after that patch was submitted.
Co-authored-by: Sheng <ox59616e@gmail.com>
Fixes#54040, Fixes#59675
Reviewed By: ilya-biryukov
Differential Revision: https://reviews.llvm.org/D141546
This feature causes clang to crash when compiling Chrome - see
https://crbug.com/1405031 and
https://github.com/llvm/llvm-project/issues/59675
Revert "[clang] Fix a clang crash on invalid code in C++20 mode."
This reverts commit 32d7aae04fdb58e65a952f281ff2f2c3f396d98f.
Revert "[clang] Remove overly restrictive aggregate paren init logic"
This reverts commit c77a91bb7ba793ec3a6a5da3743ed55056291658.
Revert "[clang][C++20] P0960R3 and P1975R0: Allow initializing aggregates from a parenthesized list of values"
This reverts commit 40c52159d3ee337dbed14e4c73b5616ea354c337.
Previously, we would only attempt to perform a parenthesized aggregate
initialization if constructor initialization failed for only the default
constructor, default copy constructor, and default move constructor. The
original intent of this logic was to reject initializing objects that
have failed resolving a user-defined constructor. However, this check is
redundant because we check for isAggregate() before attempting to
perform a parenthesized aggregate initialization, and classes that have
user-defined or user-declared constructors are not aggregates.
Furthermore, this check is too restrictive - the following valid
examples fail:
* Aggregate class with user-defined destructor - fails because default
move constructors are not generated for classes with user-defined
destructors
(https://github.com/llvm/llvm-project/issues/54040#issuecomment-1356926048)
* Concept-guarded conversion operator on an aggregate's member:
(https://github.com/llvm/llvm-project/issues/54040#issuecomment-1356931745)
The solution therefore is to remove this logic; existing tests still
pass, and the previously failing examples now compile.
Reviewed By: ilya-biryukov
Differential Revision: https://reviews.llvm.org/D140327
This patch implements P0960R3, which allows initialization of aggregates
via parentheses.
As an example:
```
struct S { int i, j; };
S s1(1, 1);
int arr1[2](1, 2);
```
This patch also implements P1975R0, which fixes the wording of P0960R3
for single-argument parenthesized lists so that statements like the
following are allowed:
```
S s2(1);
S s3 = static_cast<S>(1);
S s4 = (S)1;
int (&&arr2)[] = static_cast<int[]>(1);
int (&&arr3)[2] = static_cast<int[2]>(1);
```
This patch was originally authored by @0x59616e and completed by
@ayzhao.
Fixes#54040, Fixes#54041
Co-authored-by: Sheng <ox59616e@gmail.com>
Full write up : https://discourse.llvm.org/t/c-20-rfc-suggestion-desired-regarding-the-implementation-of-p0960r3/63744
Reviewed By: ilya-biryukov
Differential Revision: https://reviews.llvm.org/D129531
