Commit Graph

1435 Commits

Author SHA1 Message Date
Adrian Kuegel 1d7fdbbc18 Revert "[clang] retain type sugar in auto / template argument deduction"
This reverts commit 9b6036deed.
Breaks two libc++ tests.
2021-11-12 13:21:59 +01:00
Matheus Izvekov 9b6036deed
[clang] retain type sugar in auto / template argument deduction
This implements the following changes:
* AutoType retains sugared deduced-as-type.
* Template argument deduction machinery analyses the sugared type all the way
down. It would previously lose the sugar on first recursion.
* Undeduced AutoType will be properly canonicalized, including the constraint
template arguments.
* Remove the decltype node created from the decltype(auto) deduction.

As a result, we start seeing sugared types in a lot more test cases,
including some which showed very unfriendly `type-parameter-*-*` types.

Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D110216
2021-11-12 01:16:31 +01:00
Jon Chesterfield 7ff4f48adb Relax assert in ExprConstant to a return None.
Fixes a compiler assert on passing a compile time integer to atomic builtins.

Assert introduced in D61522
Function changed from ->bool to ->Optional in D76646
Simplifies call sites to getIntegerConstantExpr to elide the now-redundant
isValueDependent checks.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D112159
2021-10-21 13:09:56 +01:00
Aaron Ballman 5b949a649a Fix crash when diagnosing a CTAD failure in an array new expression
This appears to be a think-o where the developer was trying to check for a null
pointer but was actually checking (redundantly) whether the optional held a
valid value or not. We now properly check the pointer for null.

This fixes PR51547.
2021-10-18 14:01:55 -04:00
Nathan Sidwell dcd74716f9 [clang] p0388 conversion to incomplete array
This implements the new implicit conversion sequence to an incomplete
(unbounded) array type.  It is mostly Richard Smith's work, updated to
trunk, testcases added and a few bugs fixed found in such testing.

It is not a complete implementation of p0388.

Differential Revision: https://reviews.llvm.org/D102645
2021-10-12 07:35:20 -07:00
Richard Smith 7063b76b02 PR50644: Do not warn on a declaration of `operator"" _foo`.
Also do not warn on `#define _foo` or `#undef _foo`.

Only global scope names starting with _[a-z] are reserved, not the use
of such an identifier in any other context.
2021-10-06 15:13:05 -07:00
Amy Huang c7104e5066 [Sema] Allow comparisons between different ms ptr size address space types.
We're currently using address spaces to implement __ptr32/__ptr64 attributes;
this patch fixes a bug where clang doesn't allow types with different pointer
size attributes to be compared.

Fixes https://bugs.llvm.org/show_bug.cgi?id=51889

Differential Revision: https://reviews.llvm.org/D110670
2021-10-05 10:56:29 -07:00
Yuanfang Chen 27a972a699 Diagnose -Wunused-value based on CFG reachability
(This relands 59337263ab and makes sure comma operator
 diagnostics are suppressed in a SFINAE context.)

While at it, add the diagnosis message "left operand of comma operator has no effect" (used by GCC) for comma operator.

This also makes Clang diagnose in the constant evaluation context which aligns with GCC/MSVC behavior. (https://godbolt.org/z/7zxb8Tx96)

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D103938
2021-09-28 10:00:15 -07:00
Yuanfang Chen 59337263ab Revert "Diagnose -Wunused-value based on CFG reachability"
This reverts commit cbbf2e8c8a.
It seems causing diagnoses in SFINAE context.
2021-09-23 11:12:00 -07:00
Yuanfang Chen cbbf2e8c8a Diagnose -Wunused-value based on CFG reachability
While at it, add the diagnosis message "left operand of comma operator has no effect" (used by GCC) for comma operator.

This also makes Clang diagnose in the constant evaluation context which aligns with GCC/MSVC behavior. (https://godbolt.org/z/7zxb8Tx96)

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D103938
2021-09-22 14:38:06 -07:00
Matheus Izvekov d9308aa39b [clang] don't mark as Elidable CXXConstruct expressions used in NRVO
See PR51862.

The consumers of the Elidable flag in CXXConstructExpr assume that
an elidable construction just goes through a single copy/move construction,
so that the source object is immediately passed as an argument and is the same
type as the parameter itself.

With the implementation of P2266 and after some adjustments to the
implementation of P1825, we started (correctly, as per standard)
allowing more cases where the copy initialization goes through
user defined conversions.

With this patch we stop using this flag in NRVO contexts, to preserve code
that relies on that assumption.
This causes no known functional changes, we just stop firing some asserts
in a cople of included test cases.

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D109800
2021-09-21 21:41:20 +02:00
Aaron Ballman 73a8bcd789 Revert "Diagnose -Wunused-value based on CFG reachability"
This reverts commit 63e0d038fc.

It causes test failures:

http://lab.llvm.org:8011/#/builders/119/builds/5612
https://logs.chromium.org/logs/fuchsia/buildbucket/cr-buildbucket/8835548361443044001/+/u/clang/test/stdout
2021-09-21 12:25:13 -04:00
Yuanfang Chen 63e0d038fc Diagnose -Wunused-value based on CFG reachability
While at it, add the diagnosis message "left operand of comma operator has no effect" (used by GCC) for comma operator.

This also makes Clang diagnose in the constant evaluation context which aligns with GCC/MSVC behavior. (https://godbolt.org/z/7zxb8Tx96)

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D103938
2021-09-20 10:43:34 -07:00
Ole Strohm 8008009fd2 [OpenCL] Initialize temporaries in the private address space
This patch fixes initializing temporaries, which are currently initialized
without an address space, meaning that no constructor can ever be applicable.
Now they will be constructed in the private addrspace.

Fixes the second issue in PR43296.

Reviewed By: Anastasia

Differential Revision: https://reviews.llvm.org/D107553
2021-09-13 12:56:04 +01:00
Chris Lattner 735f46715d [APInt] Normalize naming on keep constructors / predicate methods.
This renames the primary methods for creating a zero value to `getZero`
instead of `getNullValue` and renames predicates like `isAllOnesValue`
to simply `isAllOnes`.  This achieves two things:

1) This starts standardizing predicates across the LLVM codebase,
   following (in this case) ConstantInt.  The word "Value" doesn't
   convey anything of merit, and is missing in some of the other things.

2) Calling an integer "null" doesn't make any sense.  The original sin
   here is mine and I've regretted it for years.  This moves us to calling
   it "zero" instead, which is correct!

APInt is widely used and I don't think anyone is keen to take massive source
breakage on anything so core, at least not all in one go.  As such, this
doesn't actually delete any entrypoints, it "soft deprecates" them with a
comment.

Included in this patch are changes to a bunch of the codebase, but there are
more.  We should normalize SelectionDAG and other APIs as well, which would
make the API change more mechanical.

Differential Revision: https://reviews.llvm.org/D109483
2021-09-09 09:50:24 -07:00
Yuanfang Chen 61d1cce2f8 PR45881: Properly use CXXThisOverride for templated lambda
- `this` used in lambda expression parameter declarations needs no capture.
- Set up CXXThisOverride for default template arguments of a lambda.

A similar fix to this is c3d2ebb60f.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D102531
2021-09-07 17:02:24 -07:00
modimo b40a2a533a [clang] Add support for optional flag -fnew-infallible to restrict exception propagation
The declaration for the global new function in C++ is generated in the compiler front-end. When examining exception propagation, we found that this is the largest root throw site propagator requiring unwind code to be generated for callers up the stack. Allowing this to be handled immediately with termination stops upward propagation and leads to significantly less landing pads generated. This in turns leads to a performance and .text size win.

With `-fnew-infallible` this annotates the declaration with `throw()` and `__attribute__((returns_nonnull))`.  `throw()` allows the compiler to assume exceptions do not propagate out of new and eliminate it as a root throw site. Note that the definition of global new is user-replaceable so users should ensure that the one used follows these semantics.

Measuring internally, we're seeing at 0.5% CPU win in one of our large internal FB workload. Measuring on clang self-build (cd0a1226b5) we get:

thinlto/

        "dwarfehprepare.NumCleanupLandingPadsRemaining": 153494,
        "dwarfehprepare.NumNoUnwind": 26309,
thinlto_newinfallible/

        "dwarfehprepare.NumCleanupLandingPadsRemaining": 143660,
        "dwarfehprepare.NumNoUnwind": 28744,

a 1-143660/153494 = 6.4% reduction in landing pads and a 28744/26309 = 9.3% increase in the number of nounwind functions.

Testing:
ninja check-all
new test case to make sure these attributes are added correctly to global new.

Reviewed By: urnathan

Differential Revision: https://reviews.llvm.org/D105225
2021-08-02 15:45:06 -07:00
Melanie Blower bc5b5ea037 [clang][patch][FPEnv] Make initialization of C++ globals strictfp aware
@kpn pointed out that the global variable initialization functions didn't
have the "strictfp" metadata set correctly, and @rjmccall said that there
was buggy code in SetFPModel and StartFunction, this patch is to solve
those problems. When Sema creates a FunctionDecl, it sets the
FunctionDeclBits.UsesFPIntrin to "true" if the lexical FP settings
(i.e. a combination of command line options and #pragma float_control
settings) correspond to ConstrainedFP mode. That bit is used when CodeGen
starts codegen for a llvm function, and it translates into the
"strictfp" function attribute. See bugs.llvm.org/show_bug.cgi?id=44571

Reviewed By: Aaron Ballman

Differential Revision: https://reviews.llvm.org/D102343
2021-07-29 12:02:37 -04:00
Matheus Izvekov 0c7cd4a873 [clang] NFC: refactor multiple implementations of getDecltypeForParenthesizedExpr
This cleanup patch refactors a bunch of functional duplicates of
getDecltypeForParenthesizedExpr into a common implementation.

Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>

Reviewed By: aaronpuchert

Differential Revision: https://reviews.llvm.org/D100713
2021-07-28 23:27:43 +02:00
Matheus Izvekov 4819b751bd [clang] NFC: change uses of `Expr->getValueKind` into `is?Value`
Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D100733
2021-07-28 03:09:31 +02:00
Corentin Jabot 8747234032 Partially implement P1401R5 (Narrowing contextual conversions to bool)
Support Narrowing conversions to bool in if constexpr condition
under C++23 language mode.

Only if constexpr is implemented as the behavior of static_assert
is already conforming. Still need to work on explicit(bool) to
complete support.
2021-07-12 08:06:27 -04:00
Haojian Wu 47653db6d2 [clang] Fix an infinite loop during typo-correction
See https://bugs.llvm.org/show_bug.cgi?id=50797#c6

Differential Revision: https://reviews.llvm.org/D105533
2021-07-09 12:03:57 +02:00
Matheus Izvekov 5a1c50410c [clang] fix constexpr code generation for user conversions.
When building the member call to a user conversion function during an
implicit cast, the expression was not being checked for immediate
invocation, so we were never adding the ConstantExpr node to AST.

This would cause the call to the user conversion operator to be emitted
even if it was constantexpr evaluated, and this would even trip an
assert when said user conversion was declared consteval:
`Assertion failed: !cast<FunctionDecl>(GD.getDecl())->isConsteval() && "consteval function should never be emitted", file clang\lib\CodeGen\CodeGenModule.cpp, line 3530`

Fixes PR48855.

Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D105446
2021-07-08 20:23:19 +02:00
serge-sans-paille a0d05ed848 Handle interactions between reserved identifier and user-defined suffixes
According to https://eel.is/c++draft/over.literal

> double operator""_Bq(long double);  // OK: does not use the reserved identifier _­Bq ([lex.name])
> double operator"" _Bq(long double); // ill-formed, no diagnostic required: uses the reserved identifier _­Bq ([lex.name])

Obey that rule by keeping track of the operator literal name status wrt. leading whitespace.

Fix: https://bugs.llvm.org/show_bug.cgi?id=50644

Differential Revision: https://reviews.llvm.org/D104299
2021-06-23 15:38:42 +02:00
Matheus Izvekov ced6b204d1 [clang] Implement P2266 Simpler implicit move
This Implements [[http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2266r1.html|P2266 Simpler implicit move]].

Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>

Reviewed By: Quuxplusone

Differential Revision: https://reviews.llvm.org/D99005
2021-06-18 17:08:59 +02:00
Matheus Izvekov 12c90e2e25 [clang] NRVO: Improvements and handling of more cases.
This expands NRVO propagation for more cases:

Parse analysis improvement:
* Lambdas and Blocks with dependent return type can have their variables
  marked as NRVO Candidates.

Variable instantiation improvements:
* Fixes crash when instantiating NRVO variables in Blocks.
* Functions, Lambdas, and Blocks which have auto return type have their
  variables' NRVO status propagated. For Blocks with non-auto return type,
  as a limitation, this propagation does not consider the actual return
  type.

This also implements exclusion of VarDecls which are references to
dependent types.

Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>

Reviewed By: Quuxplusone

Differential Revision: https://reviews.llvm.org/D99696
2021-06-17 01:56:38 +02:00
Hans Wennborg c60dd3b262 Revert "[clang] NRVO: Improvements and handling of more cases."
This change caused build errors related to move-only __block variables,
see discussion on https://reviews.llvm.org/D99696

> This expands NRVO propagation for more cases:
>
> Parse analysis improvement:
> * Lambdas and Blocks with dependent return type can have their variables
>   marked as NRVO Candidates.
>
> Variable instantiation improvements:
> * Fixes crash when instantiating NRVO variables in Blocks.
> * Functions, Lambdas, and Blocks which have auto return type have their
>   variables' NRVO status propagated. For Blocks with non-auto return type,
>   as a limitation, this propagation does not consider the actual return
>   type.
>
> This also implements exclusion of VarDecls which are references to
> dependent types.
>
> Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>
>
> Reviewed By: Quuxplusone
>
> Differential Revision: https://reviews.llvm.org/D99696

This also reverts the follow-on change which was hard to tease apart
form the one above:

> "[clang] Implement P2266 Simpler implicit move"
>
> This Implements [[http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2266r1.html|P2266 Simpler implicit move]].
>
> Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>
>
> Reviewed By: Quuxplusone
>
> Differential Revision: https://reviews.llvm.org/D99005

This reverts commits 1e50c3d785 and
bf20631782.
2021-06-14 16:46:58 +02:00
Stephan Bergmann b5b9489b24 Only consider built-in compound assignment operators for -Wunused-but-set-*
At least LibreOffice has, for mainly historic reasons that would be hard to
change now, a class Any with an overloaded operator >>= that semantically does
not assign to the LHS but rather extracts into the (by-reference) RHS.  Which
thus caused false positive -Wunused-but-set-parameter and
-Wunused-but-set-variable after those have been introduced recently.

This change is more conservative about the assumed semantics of overloaded
operators, excluding compound assignment operators but keeping plain operator =
ones.  At least for LibreOffice, that strikes a good balance of not producing
false positives but still finding lots of true ones.

(The change to the BinaryOperator case in MaybeDecrementCount is necessary
because e.g. the template f4 test code in warn-unused-but-set-variables-cpp.cpp
turns the += into a BinaryOperator.)

Differential Revision: https://reviews.llvm.org/D103949
2021-06-14 08:04:03 +02:00
Matheus Izvekov bf20631782 [clang] Implement P2266 Simpler implicit move
This Implements [[http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2266r1.html|P2266 Simpler implicit move]].

Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>

Reviewed By: Quuxplusone

Differential Revision: https://reviews.llvm.org/D99005
2021-06-13 12:10:56 +02:00
Matheus Izvekov 1e50c3d785 [clang] NRVO: Improvements and handling of more cases.
This expands NRVO propagation for more cases:

Parse analysis improvement:
* Lambdas and Blocks with dependent return type can have their variables
  marked as NRVO Candidates.

Variable instantiation improvements:
* Fixes crash when instantiating NRVO variables in Blocks.
* Functions, Lambdas, and Blocks which have auto return type have their
  variables' NRVO status propagated. For Blocks with non-auto return type,
  as a limitation, this propagation does not consider the actual return
  type.

This also implements exclusion of VarDecls which are references to
dependent types.

Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>

Reviewed By: Quuxplusone

Differential Revision: https://reviews.llvm.org/D99696
2021-06-12 16:43:32 +02:00
Simon Pilgrim 61cdaf66fe [ADT] Remove APInt/APSInt toString() std::string variants
<string> is currently the highest impact header in a clang+llvm build:

https://commondatastorage.googleapis.com/chromium-browser-clang/llvm-include-analysis.html

One of the most common places this is being included is the APInt.h header, which needs it for an old toString() implementation that returns std::string - an inefficient method compared to the SmallString versions that it actually wraps.

This patch replaces these APInt/APSInt methods with a pair of llvm::toString() helpers inside StringExtras.h, adjusts users accordingly and removes the <string> from APInt.h - I was hoping that more of these users could be converted to use the SmallString methods, but it appears that most end up creating a std::string anyhow. I avoided trying to use the raw_ostream << operators as well as I didn't want to lose having the integer radix explicit in the code.

Differential Revision: https://reviews.llvm.org/D103888
2021-06-11 13:19:15 +01:00
Arthur Eubanks 85ca7e424f Revert "[clang] NRVO: Improvements and handling of more cases."
This reverts commit 667fbcdd0b.

Causes crashes on a stage 2 build on Windows.
2021-06-10 20:37:01 -07:00
Arthur Eubanks db26615aa6 Revert "[clang] Implement P2266 Simpler implicit move"
This reverts commit cbd0054b9e.
2021-06-10 19:54:50 -07:00
Matheus Izvekov cbd0054b9e [clang] Implement P2266 Simpler implicit move
This Implements [[http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2266r1.html|P2266 Simpler implicit move]].

Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>

Reviewed By: Quuxplusone

Differential Revision: https://reviews.llvm.org/D99005
2021-06-11 00:56:06 +02:00
Matheus Izvekov 667fbcdd0b [clang] NRVO: Improvements and handling of more cases.
This expands NRVO propagation for more cases:

Parse analysis improvement:
* Lambdas and Blocks with dependent return type can have their variables
  marked as NRVO Candidates.

Variable instantiation improvements:
* Fixes crash when instantiating NRVO variables in Blocks.
* Functions, Lambdas, and Blocks which have auto return type have their
  variables' NRVO status propagated. For Blocks with non-auto return type,
  as a limitation, this propagation does not consider the actual return
  type.

This also implements exclusion of VarDecls which are references to
dependent types.

Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>

Reviewed By: Quuxplusone

Differential Revision: https://reviews.llvm.org/D99696
2021-06-10 23:02:51 +02:00
Matheus Izvekov aef5d8fdc7 [clang] NFC: Rename rvalue to prvalue
This renames the expression value categories from rvalue to prvalue,
keeping nomenclature consistent with C++11 onwards.

C++ has the most complicated taxonomy here, and every other language
only uses a subset of it, so it's less confusing to use the C++ names
consistently, and mentally remap to the C names when working on that
context (prvalue -> rvalue, no xvalues, etc).

Renames:
* VK_RValue -> VK_PRValue
* Expr::isRValue -> Expr::isPRValue
* SK_QualificationConversionRValue -> SK_QualificationConversionPRValue
* JSON AST Dumper Expression nodes value category: "rvalue" -> "prvalue"

Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D103720
2021-06-09 12:27:10 +02:00
Michael Benfield cf49cae278 [Clang] -Wunused-but-set-parameter and -Wunused-but-set-variable
These are intended to mimic warnings available in gcc.

Differential Revision: https://reviews.llvm.org/D100581
2021-06-01 15:38:48 -07:00
Nathan Sidwell c138f3ce5c [clang] Fix ICE with typeid & polymorphic class (pr50497)
This addresses pr50497. The argument of a typeid expression is
unevaluated, *except* when it's a polymorphic type. We handle this by
parsing as unevaluated and then transforming to evaluated if we
discover it should have been an evaluated context.

We do the same in TreeTransform<Derived>::TransformCXXTypeidExpr,
entering unevaluated context before transforming and rebuilding the
typeid. But that's incorrect and can lead us to converting to
evaluated context twice -- and hitting an assert.

During normal template instantiation we're always cloning the
expression, but during generic lambda processing we do not necessarily
AlwaysRebuild, and end up with TransformDeclRefExpr unconditionally
calling MarkDeclRefReferenced around line 10226. That triggers the
assert.

// Mark it referenced in the new context regardless.
// FIXME: this is a bit instantiation-specific.
SemaRef.MarkDeclRefReferenced(E);

This patch makes 2 changes.

a) TreeTransform<Derived>::TransformCXXTypeidExpr only enters
unevaluated context if the typeid's operand is not a polymorphic
glvalue. If it is, it keeps the same evaluation context.

b) Sema::BuildCXXTypeId is altered to only transform to evaluated, if
the current context is unevaluated.

Differential Revision: https://reviews.llvm.org/D103258
2021-06-01 12:55:29 -07:00
Ole Strohm 94b0aec0f5 [OpenCL] Fix ICE with invalid use of half
Because half is limited to the `cl_khr_fp16` extension being enabled,
`DefaultLvalueConversion` can fail when it's not enabled.
The original assumption that it will never fail is therefore wrong now.

Fixes: PR47976

Reviewed By: Anastasia

Differential Revision: https://reviews.llvm.org/D103175
2021-06-01 13:43:07 +01:00
Arthur Eubanks 3a0b6dc3e8 Revert "[Clang] -Wunused-but-set-parameter and -Wunused-but-set-variable"
This reverts commit 14dfb3831c.

More false positives, see D100581.
2021-05-17 12:16:10 -07:00
Michael Benfield 14dfb3831c [Clang] -Wunused-but-set-parameter and -Wunused-but-set-variable
These are intended to mimic warnings available in gcc.

Reviewed By: aeubanks

Differential Revision: https://reviews.llvm.org/D100581
2021-05-17 11:02:26 -07:00
Richard Smith e1aa528d3a Handle unexpanded packs appearing in type-constraints.
For a type-constraint in a lambda signature, this makes the lambda
contain an unexpanded pack; for requirements in a requires-expressions
it makes the requires-expression contain an unexpanded pack; otherwise
it's invalid.
2021-05-12 18:45:34 -07:00
Matheus Izvekov 3ad6dd5d8f [clang] Use decltype((E)) for compound requirement type constraint
See PR45088.

Compound requirement type constraints were using decltype(E) instead of
decltype((E)), as per `[expr.prim.req]p1.3.3`.

Since neither instantiation nor type dependence should matter for
the constraints, this uses an approach where a `decltype` type is not built,
and just the canonical type of the expression after template instantiation
is used on the requirement.

Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D98160
2021-03-30 22:00:33 +02:00
Nathan James cb559c8d5e
[Sema] Add some basic lambda capture fix-its
Adds fix-its when users forget to explicitly capture variables or this in lambdas

Addresses https://github.com/clangd/clangd/issues/697

Reviewed By: kbobyrev

Differential Revision: https://reviews.llvm.org/D96975
2021-03-11 13:46:25 +00:00
zoecarver a89ac0dd18 Update __is_unsigned builtin to match the Standard.
Updates __is_unsigned to have the same behavior as the standard
specifies. This is in line with 511dbd8, which applied the same change
to __is_signed.

Refs D67897.

Differential Revision: https://reviews.llvm.org/D98104
2021-03-10 15:00:26 -08:00
Florian Hahn fc8d3766d7
[ExtVectorType] Support conditional select operator for C++.
This patch implements the conditional select operator for
ext_vector_types in C++. It does so by using the same semantics as for
C.

D71463 added support for the conditional select operator for VectorType
in C++. Unfortunately the semantics between ext_vector_type in C are
different to VectorType in C++. Select for ext_vector_type is based on
the MSB of the condition vector, whereas for VectorType it is `!= 0`.

This unfortunately means that the behavior is inconsistent between
ExtVectorType and VectorType, but I think using the C semantics for
ExtVectorType in C++ as well should be less surprising for users.

Reviewed By: erichkeane, aaron.ballman

Differential Revision: https://reviews.llvm.org/D98055
2021-03-09 13:08:52 +00:00
Tomas Matheson 7e5cea5b50 [Clang][Sema] Warn when function argument is less aligned than parameter
See https://bugs.llvm.org/show_bug.cgi?id=42154.

GCC's __attribute__((align)) can reduce the alignment of a type when applied to
a typedef.  However, functions which take a pointer or reference to the
original type are compiled assuming the original alignment.  Therefore when any
such function is passed an object of the new, less-aligned type, an alignment
fault can occur.  In particular, this applies to the constructor, which is
defined for the original type and called for the less-aligned object.

This change adds a warning whenever an pointer or reference to an object is
passed to a function that was defined for a more-aligned type.

The calls to ASTContext::getTypeAlignInChars seem change the order in which
record layouts are evaluated, which caused changes to the output of
-fdump-record-layouts. As such some tests needed to be updated:

  * Use CHECK-LABEL rather than counting the number of "Dumping AST Record
    Layout" headers.

  * Check for end of line in labels, so that struct B1 doesn't match struct B
    etc.

  * Add --strict-whitespace, since the whitespace shows meaningful structure.

  * The order in which record layouts are printed has changed in some cases.

  * clang-format for regions changed

Differential Revision: https://reviews.llvm.org/D97187
2021-03-09 10:37:32 +00:00
Richard Smith abbe42d8b5 PR49260: Improve diagnostics for no matching 'operator new'.
Fix duplicate diagnostic for an over-aligned allocation with no matching
function, and add custom diagnostic for the case where the
non-allocating placement new was intended but <new> was not included.
2021-03-05 15:53:10 -08:00
Melanie Blower 08d46d5059 [clang][PATCH] Fix bug 48848 assertion related to recoverFromMSUnqualifiedLookup
Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D95482
2021-02-01 10:56:47 -08:00
Artem Belevich 127091bfd5 [CUDA] Normalize handling of defauled dtor.
Defaulted destructor was treated inconsistently, compared to other
compiler-generated functions.

When Sema::IdentifyCUDATarget() got called on just-created dtor which didn't
have implicit __host__ __device__ attributes applied yet, it would treat it as a
host function.  That happened to (sometimes) hide the error when dtor referred
to a host-only functions.

Even when we had identified defaulted dtor as a HD function, we still treated it
inconsistently during selection of usual deallocators, where we did not allow
referring to wrong-side functions, while it is allowed for other HD functions.

This change brings handling of defaulted dtors in line with other HD functions.

Differential Revision: https://reviews.llvm.org/D94732
2021-01-21 10:48:07 -08:00
Richard Smith aab25fa7d8 Never call a destroying operator delete when cleaning up from an
exception thrown during construction in a new-expression.

Instead, when performing deallocation function lookup for a
new-expression, ignore all destroying operator delete candidates, and
fall back to global operator delete if there is no member operator
delete other than a destroying operator delete.

Use of destroying operator delete only makes sense when there is an
object to destroy, which there isn't in this case. The language wording
doesn't cover this case; this oversight has been reported to WG21, with
the approach in this patch as the proposed fix.
2021-01-08 16:51:47 -08:00
Thorsten Schütt 2fd11e0b1e Revert "[NFC, Refactor] Modernize StorageClass from Specifiers.h to a scoped enum (II)"
This reverts commit efc82c4ad2.
2021-01-04 23:17:45 +01:00
Thorsten Schütt efc82c4ad2 [NFC, Refactor] Modernize StorageClass from Specifiers.h to a scoped enum (II)
Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D93765
2021-01-04 22:58:26 +01:00
Richard Smith 569676c057 Make Expr::HasSideEffect more precise for instantiation-dependent
expressions.

Fixes a regression in the clang-tidy test suite from making DeclRefExprs
referring to dependent declarations be instantiation-dependent.
2020-12-18 01:08:42 -08:00
David Blaikie c4af1c8d93 PR48383: Disallow decltype(auto) in pseudodestructor calls 2020-12-03 20:41:06 -08:00
Baptiste Saleil f976ba6139 [PowerPC] Add Sema checks for MMA types
The use of the new types introduced for PowerPC MMA instructions needs to be restricted.
We add a PowerPC function checking that the given type is valid in a context in which we don't allow MMA types.
This function is called from various places in Sema where we want to prevent the use of these types.

Differential Revision: https://reviews.llvm.org/D82035
2020-11-04 17:01:47 -06:00
Richard Smith fc031d29be Switch the default of VerifyIntegerConstantExpression from constant
folding to not constant folding.

Constant folding of ICEs is done as a GCC compatibility measure, but new
code was picking it up, presumably by accident, due to the bad default.

While here, also switch the flag from a bool to an enum to make it more
obvious what it means at call sites. This highlighted a couple of places
where our behavior is different between C++11 and C++14 due to switching
from checking for an ICE to checking for a converted constant
expression (where there is no 'fold' codepath).
2020-10-15 16:58:47 -07:00
Erik Pilkington 351317167e [SemaObjC] Fix composite pointer type calculation for `void*` and pointer to lifetime qualified ObjC pointer type
Fixes a regression introduced in 9a6f4d451c. rdar://70101809

Differential revision: https://reviews.llvm.org/D89475
2020-10-15 15:21:01 -04:00
Richard Smith 9dbb0886ea Perform lvalue conversions on the left of a pseudo-destructor call 'p->~T()'.
Previously we failed to convert 'p' from array/function to pointer type,
and to represent the load of 'p' in the AST. The latter causes problems
for constant evaluation.
2020-10-14 22:09:01 -07:00
Erik Pilkington 498c7fa48a [SemaObjC] Fix a crash on an invalid ternary with ARC pointers
FindCompositeObjCPointerType nulls out the subexpressions on error, so bail out
instead of trying to deref them.
2020-10-13 21:20:20 -04:00
Richard Smith d1751d14a6 PR47175: Ensure type-dependent function-style casts have dependent
types.

Previously, a type-dependent cast to a deduced class template
specialization type would end up with a non-dependent class template
specialization type, leading to confusion downstream.
2020-10-08 17:00:22 -07:00
Fanbo Meng 2240ca0bd1 [SystemZ][z/OS] Set aligned allocation unavailable by default for z/OS
Aligned allocation is not supported on z/OS. This patch sets -faligned-alloc-unavailable as default in z/OS toolchain.

Reviewed By: abhina.sreeskantharajan, hubert.reinterpretcast

Differential Revision: https://reviews.llvm.org/D87611
2020-09-16 14:49:03 -04:00
Zequan Wu ebf267b87d [Sema][MSVC] warn at dynamic_cast/typeid when /GR- is given
Differential Revision: https://reviews.llvm.org/D86369
2020-09-16 10:38:52 -07:00
Serge Pavlov f1cd6593da [AST][FPEnv] Keep FP options in trailing storage of CastExpr
This is recommit of 6c8041aa0f, reverted in de044f7562 because of some
fails. Original commit message is below.

This change allow a CastExpr to have optional FPOptionsOverride object,
stored in trailing storage. Of all cast nodes only ImplicitCastExpr,
CStyleCastExpr, CXXFunctionalCastExpr and CXXStaticCastExpr are allowed
to have FPOptions.

Differential Revision: https://reviews.llvm.org/D85960
2020-09-14 12:15:21 +07:00
Serge Pavlov de044f7562 Revert "[AST][FPEnv] Keep FP options in trailing storage of CastExpr"
This reverts commit 6c8041aa0f.
It caused some fails on buildbots.
2020-09-12 17:06:42 +07:00
Serge Pavlov 6c8041aa0f [AST][FPEnv] Keep FP options in trailing storage of CastExpr
This change allow a CastExpr to have optional FPOptionsOverride object,
stored in trailing storage. Of all cast nodes only ImplicitCastExpr,
CStyleCastExpr, CXXFunctionalCastExpr and CXXStaticCastExpr are allowed
to have FPOptions.

Differential Revision: https://reviews.llvm.org/D85960
2020-09-12 14:30:44 +07:00
Hans Wennborg 2d9d270e77 Revert 3e782bf809 "[Sema][MSVC] warn at dynamic_cast when /GR- is given"
This caused more warnings than expected, see https://crbug.com/1126019

Also reverts the follow-up 7907e5516.

> Differential Revision: https://reviews.llvm.org/D86369
2020-09-08 16:10:18 +02:00
Zequan Wu 3e782bf809 [Sema][MSVC] warn at dynamic_cast when /GR- is given
Differential Revision: https://reviews.llvm.org/D86369
2020-09-07 16:46:58 -07:00
Cullen Rhodes feed5a7239 [Sema][AArch64] Support arm_sve_vector_bits attribute
This patch implements the semantics for the 'arm_sve_vector_bits' type
attribute, defined by the Arm C Language Extensions (ACLE) for SVE [1].
The purpose of this attribute is to define vector-length-specific (VLS)
versions of existing vector-length-agnostic (VLA) types.

The semantics were already implemented by D83551, although the
implementation approach has since changed to represent VLSTs as
VectorType in the AST and fixed-length vectors in the IR everywhere
except in function args/returns. This is described in the prototype
patch D85128 demonstrating the new approach.

The semantic changes added in D83551 are changed since the
AttributedType is replaced by VectorType in the AST. Minimal changes
were necessary in the previous patch as the canonical type for both VLA
and VLS was the same (i.e. sizeless), except in constructs such as
globals and structs where sizeless types are unsupported. This patch
reverts the changes that permitted VLS types that were represented as
sizeless types in such circumstances, and adds support for implicit
casting between VLA <-> VLS types as described in section 3.7.3.2 of the
ACLE.

Since the SVE builtin types for bool and uint8 are both represented as
BuiltinType::UChar in VLSTs, two new vector kinds are implemented to
distinguish predicate and data vectors.

[1] https://developer.arm.com/documentation/100987/latest

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D85736
2020-08-27 10:38:32 +00:00
Richard Smith c1c1bed5d0 [c++14] Implement missed piece of N3323: use "converted constant" rules
for array bounds, not "integer constant" rules.

For an array bound of class type, this causes us to perform an implicit
conversion to size_t, instead of looking for a unique conversion to
integral or unscoped enumeration type. This affects which cases are
valid when a class has multiple implicit conversion functions to
different types.
2020-08-19 15:45:51 -07:00
Richard Smith fb943696cb PR47025, PR47043: Diagnose unexpanded parameter packs in concept
declarations and requires-expressions.
2020-08-07 18:19:39 -07:00
Serge Pavlov 70e7aa4a4e [AST][FPEnv] Keep FP options in trailing storage of CallExpr
This change allow a CallExpr to have optional FPOptionsOverride object,
stored in trailing storage. The implementaion is made similar to the way
used in BinaryOperator.

Differential Revision: https://reviews.llvm.org/D84343
2020-07-24 12:04:19 +07:00
David Blaikie 36036aa70e Reapply "Rename/refactor isIntegerConstantExpression to getIntegerConstantExpression"
Reapply 49e5f603d4
which had been reverted in c94332919b.

Originally reverted because I hadn't updated it in quite a while when I
got around to committing it, so there were a bunch of missing changes to
new code since I'd written the patch.

Reviewers: aaron.ballman

Differential Revision: https://reviews.llvm.org/D76646
2020-07-21 20:57:12 -07:00
David Goldman dde98c82c0 Fix issue in typo handling which could lead clang to hang
Summary:
We need to detect when certain TypoExprs are not being transformed
due to invalid trees, otherwise we risk endlessly trying to fix it.

Reviewers: rsmith

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D84067
2020-07-20 11:42:11 -04:00
Benjamin Kramer 33c9d0320e Upgrade SmallSets of pointer-like types to SmallPtrSet
This is slightly more efficient. NFC.
2020-07-20 16:54:29 +02:00
Haojian Wu 17ef788df5 [AST][RecoveryExpr] Preserve the AST for invalid class constructions.
Differential Revision: https://reviews.llvm.org/D81090
2020-07-20 13:11:15 +02:00
David Blaikie c94332919b Revert "Rename/refactor isIntegerConstantExpression to getIntegerConstantExpression"
Broke buildbots since I hadn't updated this patch in a while. Sorry for
the noise.

This reverts commit 49e5f603d4.
2020-07-12 20:29:19 -07:00
David Blaikie 49e5f603d4 Rename/refactor isIntegerConstantExpression to getIntegerConstantExpression
There is a version that just tests (also called
isIntegerConstantExpression) & whereas this version is specifically used
when the value is of interest (a few call sites were actually refactored
to calling the test-only version) so let's make the API look more like
it.

Reviewers: aaron.ballman

Differential Revision: https://reviews.llvm.org/D76646
2020-07-12 19:43:24 -07:00
Richard Smith 065fc1eafe PR45521: Preserve the value kind when performing a standard conversion
sequence on a glvalue expression.

If the sequence is supposed to perform an lvalue-to-rvalue conversion,
then one will be specified as the first conversion in the sequence.
Otherwise, one should not be invented.
2020-07-07 18:28:28 -07:00
Haojian Wu 910689f0aa [AST] Move the "fallback to recovery expr" mechanism to CorrectDelayedTyposInExpr, NFC
Summary: Also delete two overloads, which don't seem necessary.

Reviewers: sammccall

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D82047
2020-06-18 08:20:05 +02:00
Richard Smith 56a872947a Remove improper uses of DiagnosticErrorTrap and hasErrorOccurred.
DiagnosticErrorTrap is usually inappropriate because it indicates
whether an error message was rendered in a given region (and is
therefore affected by -ferror-limit and by suppression of errors if we
see an invalid declaration).

hasErrorOccurred() is usually inappropriate because it indicates
whethere an "error:" message was displayed, regardless of whether the
message was a warning promoted to an error, and therefore depends on
things like -Werror that are usually irrelevant.

Where applicable, CodeSynthesisContexts are used to attach notes to
the first diagnostic produced in a region of code, isnstead of using an
error trap and then attaching a note to whichever diagnostic happened to
be produced last (or suppressing the note if the final diagnostic is a
disabled warning!).

This is mostly NFC.
2020-06-08 14:19:57 -07:00
Haojian Wu 28c2bdf18f [AST] Record SourceLocation for TypoExpr.
Reviewers: sammccall

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D81008
2020-06-05 17:03:32 +02:00
Haojian Wu 21ccc684ff [AST][RecoveryExpr] Build RecoveryExpr for "undef_var" cases.
Summary:
For a none-function-like unresolved expression, clang builds a TypoExpr
for it, and tries to correct it afterwards. If the typo-correction
fails, clang just drops the whole expr.

This patch improves the recovery strategy -- if the typo-correction
fails, we preserve the AST by degrading the typo exprs to recovery
exprs.

This would improve toolings for "undef_var" broken cases:
```
void foo();
void test() {
  fo^o(undef_var); // go-to-def, hover still works.
}
```

TESTED=ran tests with this patch + turn-on-recovery-ast patch, it breaks
one declare_variant_messages testcase (the diagnostics are slightly
changed), I think it is acceptable.

```
Error: 'error' diagnostics seen but not expected:
  File llvm-project/clang/test/OpenMP/declare_variant_messages.cpp Line 16: expected 'match' clause on 'omp declare variant' directive
  File llvm-project/clang/test/OpenMP/declare_variant_messages.cpp Line 57: expected 'match' clause on 'omp declare variant' directive
error: 'warning' diagnostics expected but not seen:
  File llvm-project/clang/test/OpenMP/declare_variant_messages.cpp Line 47: the context selector 'kind' in the context set 'device' cannot have a score ('<invalid>'); score ignored
  File llvm-project/clang/test/OpenMP/declare_variant_messages.cpp Line 87: the context selector 'kind' in the context set 'device' cannot have a score ('<invalid>'); score ignored
error: 'warning' diagnostics seen but not expected:
  File llvm-project/clang/test/OpenMP/declare_variant_messages.cpp Line 47: the context selector 'kind' in the context set 'device' cannot have a score ('<recovery-expr>()'); score ignored
  File llvm-project/clang/test/OpenMP/declare_variant_messages.cpp Line 87: the context selector 'kind' in the context set 'device' cannot have a score ('<recovery-expr>()'); score ignored
6 errors generated.
```

Reviewers: sammccall, jdoerfert

Subscribers: sstefan1, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D80733
2020-06-02 15:58:56 +02:00
Richard Smith 00e5d38d40 Do not warn that an expression of the form (void)arr; is unused when
arr is a volatile non-local array.

This fixes a recent regression exposed by removing lvalue-to-rvalue
conversion of discarded volatile arrays. In passing, regularize the
rules we use to determine whether '(void)expr;' warns when expr is a
volatile glvalue.
2020-05-27 17:26:29 -07:00
Benjamin Kramer c0f210d636 Don't stash types that aren't copyable or moveable into a SmallVector
This seems to be working by accident.
2020-05-02 19:13:06 +02:00
Aaron Ballman 6a30894391 C++2a -> C++20 in some identifiers; NFC. 2020-04-21 15:37:19 -04:00
Benjamin Kramer 3ee1ec0b9d LangOptions cannot depend on ASTContext, make it not use ASTContext directly
Fixes a layering violation introduced in 2ba4e3a459.
2020-04-16 11:46:35 +02:00
Melanie Blower 2ba4e3a459 Move BinaryOperators.FPOptions to trailing storage
Reviewers: rjmccall

Differential Revision: https://reviews.llvm.org/D76384
2020-04-15 12:57:31 -07:00
Richard Smith bab6df86ae Rework how UuidAttr, CXXUuidofExpr, and GUID template arguments and constants are represented.
Summary:
Previously, we treated CXXUuidofExpr as quite a special case: it was the
only kind of expression that could be a canonical template argument, it
could be a constant lvalue base object, and so on. In addition, we
represented the UUID value as a string, whose source form we did not
preserve faithfully, and that we partially parsed in multiple different
places.

With this patch, we create an MSGuidDecl object to represent the
implicit object of type 'struct _GUID' created by a UuidAttr. Each
UuidAttr holds a pointer to its 'struct _GUID' and its original
(as-written) UUID string. A non-value-dependent CXXUuidofExpr behaves
like a DeclRefExpr denoting that MSGuidDecl object. We cache an APValue
representation of the GUID on the MSGuidDecl and use it from constant
evaluation where needed.

This allows removing a lot of the special-case logic to handle these
expressions. Unfortunately, many parts of Clang assume there are only
a couple of interesting kinds of ValueDecl, so the total amount of
special-case logic is not really reduced very much.

This fixes a few bugs and issues:
 * PR38490: we now support reading from GUID objects returned from
   __uuidof during constant evaluation.
 * Our Itanium mangling for a non-instantiation-dependent template
   argument involving __uuidof no longer depends on which CXXUuidofExpr
   template argument we happened to see first.
 * We now predeclare ::_GUID, and permit use of __uuidof without
   any header inclusion, better matching MSVC's behavior. We do not
   predefine ::__s_GUID, though; that seems like a step too far.
 * Our IR representation for GUID constants now uses the correct IR type
   wherever possible. We will still fall back to using the
      {i32, i16, i16, [8 x i8]}
   layout if a definition of struct _GUID is not available. This is not
   ideal: in principle the two layouts could have different padding.

Reviewers: rnk, jdoerfert

Subscribers: arphaman, cfe-commits, aeubanks

Tags: #clang

Differential Revision: https://reviews.llvm.org/D78171
2020-04-15 12:20:42 -07:00
zoecarver b25ec45809 Fix __is_pointer builtin type trait to work with Objective-C pointer types.
Summary: 5ade17e broke __is_pointer for Objective-C pointer types. This patch fixes the builtin and re-applies the change to type_traits.

Tags: #clang, #libc

Differential Revision: https://reviews.llvm.org/D77519
2020-04-08 10:02:53 -07:00
Akira Hatanaka d35a454170 [CodeGen] Emit destructor calls to destruct non-trivial C struct objects
returned by function calls or loaded from volatile objects

rdar://problem/51867864

Differential Revision: https://reviews.llvm.org/D66094
2020-03-20 18:34:22 -07:00
Richard Sandiford 4ece6f051b [Sema][SVE] Reject "delete" with sizeless types
Sizeless types can't be used with "new", so it doesn't make sense
to use them with "delete" either.  The SVE ACLE therefore doesn't
allow that.

This is slightly stronger than for normal incomplete types, since:

  struct S;
  void f(S *s) { delete s; }

is (by necessity) just a default-on warning rather than an error.

Differential Revision: https://reviews.llvm.org/D76219
2020-03-17 12:45:00 +00:00
Richard Sandiford 506406c4d5 [Sema][SVE] Reject "new" with sizeless types
new-expressions for a type T require sizeof(T) to be computable,
so the SVE ACLE does not allow them for sizeless types.  At the moment:

  auto f() { return new __SVInt8_t; }

creates a call to operator new with a zero size:

  %call = call noalias nonnull i8* @_Znwm(i64 0)

This patch reports an appropriate error instead.

Differential Revision: https://reviews.llvm.org/D76218
2020-03-17 12:23:46 +00:00
Richard Sandiford c47f971694 [Sema][SVE] Don't allow sizeless objects to be thrown
Summary:
The same rules for throwing and catching incomplete types also apply
to sizeless types.  This patch enforces that for throw statements.
It also make sure that we use "sizeless type" rather "incomplete type"
in the associated message.  (Both are correct, but "sizeless type" is
more specific and hopefully more user-friendly.)

The SVE ACLE simply extends the rule for incomplete types to
sizeless types.  However, throwing pointers to sizeless types
should not pose any real difficulty, so as an extension,
the clang implementation allows that.

Reviewers: sdesmalen, efriedma, rovka, rjmccall

Subscribers: tschuett, rkruppe, psnobl, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D76088
2020-03-17 11:52:37 +00:00
Richard Smith 5c845c1c50 PR45083: Mark statement expressions as being dependent if they appear in
a dependent context.

This matches the GCC behavior.

We track the enclosing template depth when determining whether a
statement expression is within a dependent context; there doesn't appear
to be any other reliable way to determine this.

We previously assumed they were neither value- nor
instantiation-dependent under any circumstances, which would lead to
crashes and other misbehavior.
2020-03-10 14:45:04 -07:00
Benjamin Kramer 66addf8e80 Revert "Fix regression in bdad0a1: force rebuilding of StmtExpr nodes in", "PR45083: Mark statement expressions as being dependent if they appear in"
This reverts commit f545ede91c.
This reverts commit bdad0a1b79.

This crashes clang. I'll follow up with reproduction instructions.
2020-03-05 14:14:31 +01:00
Simon Pilgrim 94885431e1 Fix some getAs/castAs null dereference static analyzer warnings.
Use castAs if we know the cast should succeed (or we're dereferencing without check), the castAs will assert as well so we can remove local non-null asserts.
2020-03-04 11:25:50 +00:00
Richard Smith bdad0a1b79 PR45083: Mark statement expressions as being dependent if they appear in
dependent contexts.

We previously assumed they were neither value- nor
instantiation-dependent under any circumstances, which would lead to
crashes and other misbehavior.
2020-03-03 15:20:40 -08:00
Richard Smith 98ed0c5475 PR44978: Accept as an extension some cases where destructor name lookup
is ambiguous, but only one of the possible lookup results could possibly
be right.

Clang recently started diagnosing ambiguity in more cases, and this
broke the build of Firefox. GCC, ICC, MSVC, and previous versions of
Clang all accept some forms of ambiguity here (albeit different ones in
each case); this patch mostly accepts anything any of those compilers
accept.
2020-02-26 14:55:31 -08:00
Roman Lebedev 3dd5a298bf
[clang] Annotating C++'s `operator new` with more attributes
Summary:
Right now we annotate C++'s `operator new` with `noalias` attribute,
which very much is healthy for optimizations.

However as per [[ http://eel.is/c++draft/basic.stc.dynamic.allocation | `[basic.stc.dynamic.allocation]` ]],
there are more promises on global `operator new`, namely:
* non-`std::nothrow_t` `operator new` *never* returns `nullptr`
* If `std::align_val_t align` parameter is taken, the pointer will also be `align`-aligned
* ~~global `operator new`-returned pointer is `__STDCPP_DEFAULT_NEW_ALIGNMENT__`-aligned ~~ It's more caveated than that.

Supplying this information may not cause immediate landslide effects
on any specific benchmarks, but it for sure will be healthy for optimizer
in the sense that the IR will better reflect the guarantees provided in the source code.

The caveat is `-fno-assume-sane-operator-new`, which currently prevents emitting `noalias`
attribute, and is automatically passed by Sanitizers ([[ https://bugs.llvm.org/show_bug.cgi?id=16386 | PR16386 ]]) - should it also cover these attributes?
The problem is that the flag is back-end-specific, as seen in `test/Modules/explicit-build-flags.cpp`.
But while it is okay to add `noalias` metadata in backend, we really should be adding at least
the alignment metadata to the AST, since that allows us to perform sema checks on it.

Reviewers: erichkeane, rjmccall, jdoerfert, eugenis, rsmith

Reviewed By: rsmith

Subscribers: xbolva00, jrtc27, atanasyan, nlopes, cfe-commits

Tags: #llvm, #clang

Differential Revision: https://reviews.llvm.org/D73380
2020-02-26 01:37:17 +03:00