Turned out we were making overly simple assumptions about which sections (& section flags) would be used when emitting a global into a custom section. This lead to sections with read-only flags being used for globals of struct types with mutable members.
Fixed by porting the codegen function with the more nuanced handling/checking for mutable members out of codegen for use in the sema code that does this initial checking/mapping to section flags.
Differential Revision: https://reviews.llvm.org/D156726
Consider the following statements:
long x = 1;
short y = 1;
With the following AST:
|-VarDecl 0x55d289973730 <x.c:1:1, col:10> col:6 x 'long' cinit
| `-ImplicitCastExpr 0x55d289973800 <col:10> 'long' <IntegralCast>
| `-IntegerLiteral 0x55d2899737e0 <col:10> 'int' 1
`-VarDecl 0x55d289973830 <line:2:1, col:11> col:7 y 'short' cinit
`-ImplicitCastExpr 0x55d2899738b8 <col:11> 'short' <IntegralCast>
`-IntegerLiteral 0x55d289973898 <col:11> 'int' 1
Sign or Zero extend or truncate based on the source signedness and
destination width.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D156466
Consider the statement:
int x = -1;
And the following AST:
`-VarDecl 0x55c4823a7670 <x.c:2:1, col:10> col:5 x 'int' cinit
`-UnaryOperator 0x55c4823a7740 <col:9, col:10> 'int' prefix '-'
`-IntegerLiteral 0x55c4823a7720 <col:10> 'int' 1
Return the evaluation of the subexpression negated.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D156378
Consider the following statement:
void* foo = ((void *)0);
For the sub-AST:
| `-ImplicitCastExpr 'const void *' <NullToPointer>
| `-CStyleCastExpr 'void *' <NullToPointer>
| `-IntegerLiteral 'int' 0
If the subexpression of the cast is itself the NULL constant, then
ImplicitCastExpr should emit the NULL pointer constant.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D156175
Consider the following statement:
const char* foo = "foo";
For the sub-AST:
`-ImplicitCastExpr <col:19> 'const char *' <NoOp>
`-ImplicitCastExpr <col:19> 'char *' <ArrayToPointerDecay>
`-StringLiteral <col:19> 'char[4]' lvalue "foo"
The address of the StringLiteral can be emitted as the Constant.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D156185
Improves the ability of ConstExprEmitter to evaluate constants.
Found by adding asserts to ConstantEmitter::tryEmitPrivate to find cases
where ConstExprEmitter::Visit() fails to resolve (obvious) constants.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D156154
As suggested by @efriedma in:
https://reviews.llvm.org/D76096#4370369
This should speed up evaluating whether an expression is constant or
not, but due to the complexity of these two different implementations,
we may start getting different answers for edge cases for which we do
not yet have test cases in-tree (or perhaps even performance regressions
for some cases). As such, contributors have carte blanche to revert if
necessary.
For additional historical context about ExprConstant vs CGExprConstant,
here's snippets from a private conversation on discord:
ndesaulniers:
why do we have clang/lib/AST/ExprConstant.cpp and
clang/lib/CodeGen/CGExprConstant.cpp? Does clang constant fold during
ast walking/creation AND during LLVM codegen?
efriedma:
originally, clang needed to handle two things: integer constant
expressions (the "5" in "int x[5];"), and constant global initializers
(the "5" in "int x = 5;"). pre-C++11, the two could be handled mostly
separately; so we had the code for integer constants in AST/, and the
code for globals in CodeGen/. C++11 constexpr sort of destroyed that
separation, though. so now we do both kinds of constant evaluation on
the AST, then CGExprConstant translates the result of that evaluation
to LLVM IR. but we kept around some bits of the old cgexprconstant to
avoid performance/memory usage regressions on large arrays.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D151587
Partial progress towards replacing in-tree uses of `Type::getPointerTo()`.
This needs to be done before deprecating the API.
Reviewed By: nikic, barannikov88
Differential Revision: https://reviews.llvm.org/D152321
Reported by Static Code Analyzer Tool:
Inside "CGExprConstant.cpp" file, VisitObjCEncodeExpr() returns null value which is dereferenced without checking.
This patch adds an assert.
Reviewed By: erichkeane
Differential Revision: https://reviews.llvm.org/D151280
flexible array member
A zero-element array type was incorrectly being used when an incomplete
array was being initialized with a non-empty initializer.
This fixes an assertion failure in AddInitializerToStaticVarDecl. See
the discussion here: https://reviews.llvm.org/D123649#4362210
Differential Revision: https://reviews.llvm.org/D151172
This follows 2b4fa53 which made Clang not emit destructor calls for such
objects. However, they would still not get emitted as constants since
CodeGenModule::isTypeConstant() returns false if the destructor is
constexpr. This change adds a param to make isTypeConstant() ignore the
dtor, allowing the caller to check it instead.
Fixes Issue #61212
Differential revision: https://reviews.llvm.org/D145369
This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated. The intent is to reduce
the amount of manual work required in migrating from Optional to
std::optional.
This is part of an effort to migrate from llvm::Optional to
std::optional:
https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716
This patch fixes a crash when trying to emit a constant compound literal.
For C++ Clang evaluates either casts or binary operations at translation time,
but doesn't pass on the InConstantContext information that was inferred when
parsing the statement. Because of this, strict FP evaluation (-ftrapping-math)
which shouldn't be in effect yet, then causes checkFloatingpointResult to return
false, which in tryEmitGlobalCompoundLiteral will trigger an assert that the
compound literal wasn't constant.
The discussion here around 'manifestly constant evaluated contexts' was very
helpful to me when trying to understand what LLVM's position is on what
evaluation context should be in effect, together with the explanatory text in
that patch itself:
https://reviews.llvm.org/D87528
Reviewed By: rjmccall, DavidSpickett
Differential Revision: https://reviews.llvm.org/D131555
Clang currently crashes when lowering a consteval list initialization
of a temporary. This is partially working around an issue in the
template instantiation code (TreeTransform::TransformCXXTemporaryObjectExpr())
that does not yet know how to handle list initialization of temporaries
in all cases. However, it's also helping reduce fragility by ensuring
we always have a valid QualType when trying to emit a constant
expression during IR generation.
Fixes#55871
Differential Revision: https://reviews.llvm.org/D131194
If a zero-sized field has a non-trivial initializer, it should prevent
the overall struct initialization from being folded to a constant during
IR generation. Don't just ignore zero-sized fields entirely in IR
constant emission.
In D123649, I got the formula for getFlexibleArrayInitChars slightly
wrong: the flexible array elements can be contained in the tail padding
of the struct. Fix the formula to account for that.
With the fixed formula, we run into another issue: in some cases, we
were emitting extra padding for flexible arrray initializers. Fix
CGExprConstant so it uses a packed struct when necessary, to avoid this
extra padding.
Differential Revision: https://reviews.llvm.org/D123826
We were generating wrong code for cxx20-consteval-crash.cpp: instead of
loading a value of a variable, we were using its address as the
initializer.
Found while adding code to verify the size of constant initializers.
Differential Revision: https://reviews.llvm.org/D123648
This builtin returns the address of a global instance of the
`std::source_location::__impl` type, which must be defined (with an
appropriate shape) before calling the builtin.
It will be used to implement std::source_location in libc++ in a
future change. The builtin is compatible with GCC's implementation,
and libstdc++'s usage. An intentional divergence is that GCC declares
the builtin's return type to be `const void*` (for
ease-of-implementation reasons), while Clang uses the actual type,
`const std::source_location::__impl*`.
In order to support this new functionality, I've also added a new
'UnnamedGlobalConstantDecl'. This artificial Decl is modeled after
MSGuidDecl, and is used to represent a generic concept of an lvalue
constant with global scope, deduplicated by its value. It's possible
that MSGuidDecl itself, or some of the other similar sorts of things
in Clang might be able to be refactored onto this more-generic
concept, but there's enough special-case weirdness in MSGuidDecl that
I gave up attempting to share code there, at least for now.
Finally, for compatibility with libstdc++'s <source_location> header,
I've added a second exception to the "cannot cast from void* to T* in
constant evaluation" rule. This seems a bit distasteful, but feels
like the best available option.
Reviewers: aaron.ballman, erichkeane
Differential Revision: https://reviews.llvm.org/D120159
ConstStructBuilder::Finalize in CGExprConstant.ccp assumes that the
passed in QualType is a RecordType. In some instances, the type is a
reference to a RecordType and the reference needs to be removed first.
Differential Revision: https://reviews.llvm.org/D117376
Control-Flow Integrity (CFI) replaces references to address-taken
functions with pointers to the CFI jump table. This is a problem
for low-level code, such as operating system kernels, which may
need the address of an actual function body without the jump table
indirection.
This change adds the __builtin_function_start() builtin, which
accepts an argument that can be constant-evaluated to a function,
and returns the address of the function body.
Link: https://github.com/ClangBuiltLinux/linux/issues/1353
Depends on D108478
Reviewed By: pcc, rjmccall
Differential Revision: https://reviews.llvm.org/D108479
Change all uses of the deprecated constructor to pass the
element type explicitly and drop it.
For cases where the correct element type was not immediately
obvious to me or would require a slightly larger change I'm
falling back to explicitly calling getPointerElementType() for now.
Not all constants are emitted within the context of a function, so use
the module's ASTContext instead because 1) that's the same as the
current function ASTContext, and 2) the module can never be null.
Fixes PR50787.
This implements C-style type conversions for matrix types, as specified
in clang/docs/MatrixTypes.rst.
Fixes PR47141.
Reviewed By: fhahn
Differential Revision: https://reviews.llvm.org/D99037
Most of CGExprConstant.cpp is using the CharUnits abstraction
and is using getCharWidth() (directly of indirectly) when converting
between size of a char and size in bits. This patch is making that
abstraction more consistent by adding CharTy to the CodeGenTypeCache
(honoring getCharWidth() when mapping from char to LLVM IR types,
instead of using Int8Ty directly).
Reviewed By: rjmccall
Differential Revision: https://reviews.llvm.org/D94979
Combined with 'da98651 - Revert "DR2064:
decltype(E) is only a dependent', this change (5a391d3) caused verifier
errors when building Chromium. See https://crbug.com/1168494#c1 for a
reproducer.
Additionally it reverts changes that were dependent on this one, see
below.
> Following up on PR48517, fix handling of template arguments that refer
> to dependent declarations.
>
> Treat an id-expression that names a local variable in a templated
> function as being instantiation-dependent.
>
> This addresses a language defect whereby a reference to a dependent
> declaration can be formed without any construct being value-dependent.
> Fixing that through value-dependence turns out to be problematic, so
> instead this patch takes the approach (proposed on the core reflector)
> of allowing the use of pointers or references to (but not values of)
> dependent declarations inside value-dependent expressions, and instead
> treating template arguments as dependent if they evaluate to a constant
> involving such dependent declarations.
>
> This ends up affecting a bunch of OpenMP tests, due to OpenMP
> imprecisely handling instantiation-dependent constructs, bailing out
> early instead of processing dependent constructs to the extent possible
> when handling the template.
>
> Previously committed as 8c1f2d15b826591cdf6bd6b468b8a7d23377b29e, and
> reverted because a dependency commit was reverted.
This reverts commit 5a391d38ac6c561ba908334d427f26124ed9132e.
It also restores clang/test/SemaCXX/coroutines.cpp to its state before
da986511fb9da1a46a0ca4dba2e49e2426036303.
Revert "[c++20] P1907R1: Support for generalized non-type template arguments of scalar type."
> Previously committed as 9e08e51a20d0d2b1c5724bb17e969d036fced4cd, and
> reverted because a dependency commit was reverted. This incorporates the
> following follow-on commits that were also reverted:
>
> 7e84aa1b81e72d44bcc58ffe1731bfc7abb73ce0 by Simon Pilgrim
> ed13d8c66781b50ff007cb089c5905f9bb9e8af2 by me
> 95c7b6cadbc9a3d4376ef44edbeb3c8bb5b8d7fc by Sam McCall
> 430d5d8429473c2b10b109991d7577a3cea41140 by Dave Zarzycki
This reverts commit 4b574008aef5a7235c1f894ab065fe300d26e786.
Revert "[msabi] Mangle a template argument referring to array-to-pointer decay"
> [msabi] Mangle a template argument referring to array-to-pointer decay
> applied to an array the same as the array itself.
>
> This follows MS ABI, and corrects a regression from the implementation
> of generalized non-type template parameters, where we "forgot" how to
> mangle this case.
This reverts commit 18e093faf726d15f210ab4917142beec51848258.
Previously committed as 9e08e51a20d0d2b1c5724bb17e969d036fced4cd, and
reverted because a dependency commit was reverted. This incorporates the
following follow-on commits that were also reverted:
7e84aa1b81e72d44bcc58ffe1731bfc7abb73ce0 by Simon Pilgrim
ed13d8c66781b50ff007cb089c5905f9bb9e8af2 by me
95c7b6cadbc9a3d4376ef44edbeb3c8bb5b8d7fc by Sam McCall
430d5d8429473c2b10b109991d7577a3cea41140 by Dave Zarzycki
This reverts commit 9e08e51a20d0d2b1c5724bb17e969d036fced4cd.
This is part of 5 commits being reverted due to https://crbug.com/1161059. See bug for repro.
non-type template parameters.
Create a unique TemplateParamObjectDecl instance for each such value,
representing the globally unique template parameter object to which the
template parameter refers.
No IR generation support yet; that will follow in a separate patch.
This fixes miscomputation of __builtin_constant_evaluated in the
initializer of a variable that's not usable in constant expressions, but
is readable when constant-folding.
If evaluation of a constant initializer fails, we throw away the
evaluated result instead of keeping it as a non-constant-initializer
value for the variable, because it might not be a correct value.
To avoid regressions for initializers that are foldable but not formally
constant initializers, we now try constant-evaluating some globals in
C++ twice: once to check for a constant initializer (in an mode where
is_constannt_evaluated returns true) and again to determine the runtime
value if the initializer is not a constant initializer.
References to different declarations of the same entity aren't different
values, so shouldn't have different representations.
Recommit of e6393ee813178e9d3306b8e3c6949a4f32f8a2cb, most recently
reverted in 9a33f027ac7d73e14ae287e78ab554142d1cbc8f due to a bug caused
by ObjCInterfaceDecls not propagating availability attributes along
their redeclaration chains; that bug was fixed in
e2d4174e9c66251d1b408234b53f53d0903c0285.
References to different declarations of the same entity aren't different
values, so shouldn't have different representations.
Recommit of e6393ee813178e9d3306b8e3c6949a4f32f8a2cb with fixed handling
for weak declarations. We now look for attributes on the most recent
declaration when determining whether a declaration is weak. (Second
recommit with further fixes for mishandling of weak declarations. Our
behavior here is fundamentally unsound -- see PR47663 -- but this
approach attempts to not make things worse.)
As mentioned in the bug report, tryEmitPrivate chokes on the
MaterializeTemporaryExpr in the reproducers, since it assumes that if
there are elements, than it must be a ConstantArrayType. However, the
MaterializeTemporaryExpr (which matches exactly the AST when it is NOT a
global/static) has an incomplete array type.
This changes the section where the number-of-elements is non-zero to
properly handle non-CAT types by just extracting it as an array type
(since all we needed was the element type out of it).
