Commit Graph

4019 Commits

Author SHA1 Message Date
Daniel Neilson 6e938effaa Change memcpy/memove/memset to have dest and source alignment attributes (Step 1).
Summary:
  Upstream LLVM is changing the the prototypes of the @llvm.memcpy/memmove/memset
intrinsics. This change updates the Clang tests for this change.

  The @llvm.memcpy/memmove/memset intrinsics currently have an explicit argument
which is required to be a constant integer. It represents the alignment of the
dest (and source), and so must be the minimum of the actual alignment of the
two.

 This change removes the alignment argument in favour of placing the alignment
attribute on the source and destination pointers of the memory intrinsic call.

 For example, code which used to read:
   call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dest, i8* %src, i32 100, i32 4, i1 false)
will now read
   call void @llvm.memcpy.p0i8.p0i8.i32(i8* align 4 %dest, i8* align 4 %src, i32 100, i1 false)

 At this time the source and destination alignments must be the same (Step 1).
Step 2 of the change, to be landed shortly, will relax that contraint and allow
the source and destination to have different alignments.

llvm-svn: 322964
2018-01-19 17:12:54 +00:00
Sanjay Patel 372c3f1f99 [CodeGenCXX] annotate a GEP to a derived class with 'inbounds' (PR35909)
The standard says:
[expr.static.cast] p11: "If the prvalue of type “pointer to cv1 B” points to a B 
that is actually a subobject of an object of type D, the resulting pointer points 
to the enclosing object of type D. Otherwise, the behavior is undefined."

Therefore, the GEP must be inbounds.

This should solve the failure to optimize away a null check shown in PR35909:
https://bugs.llvm.org/show_bug.cgi?id=35909 

Differential Revision: https://reviews.llvm.org/D42249

llvm-svn: 322950
2018-01-19 15:14:51 +00:00
Erich Keane 0a6fde4895 Move target MV resolver to COMDAT
As reported here: https://bugs.llvm.org/show_bug.cgi?id=35921
The resolver functions should be in their own
COMDAT regions. This patch sets that up.

Differential Revision: https://reviews.llvm.org/D42110

llvm-svn: 322592
2018-01-16 19:49:52 +00:00
Richard Smith d1036128ab When rebuilding an InitListExpr, don't give it a type.
InitListExprs without types (well, with type 'void') represent not-yet-analyzed
initializer lists; InitListExpr with types fool Sema into thinking they don't
need further analysis in some cases (particularly C++17 copy omission).

llvm-svn: 322414
2018-01-12 22:21:33 +00:00
Rafael Espindola cbca487f49 Make internal/private GVs implicitly dso_local.
While updating clang tests for having clang set dso_local I noticed
that:

- There are *a lot* of tests to update.
- Many of the updates are redundant.

They are redundant because a GV is "obviously dso_local". This patch
starts formalizing that a bit by requiring that internal and private
GVs be dso_local too. Since they all are, we don't have to print
dso_local to the textual representation, making it a bit more compact
and easier to read.

llvm-svn: 322318
2018-01-11 22:15:12 +00:00
Richard Smith 93ee9caaed In C++17, when instantiating an out-of-line definition of an inline static data
member, don't forget to instantiate the initializer too.

llvm-svn: 322236
2018-01-10 23:08:26 +00:00
Matt Morehouse f113deaa3c [MSan] Enable use-after-dtor instrumentation by default.
Summary:
Enable the compile-time flag -fsanitize-memory-use-after-dtor by
default. Note that the run-time option MSAN_OPTIONS=poison_in_dtor=1
still needs to be enabled for destructors to be poisoned.

Reviewers: eugenis, vitalybuka, kcc

Reviewed By: eugenis, vitalybuka

Subscribers: cfe-commits, llvm-commits

Differential Revision: https://reviews.llvm.org/D37860

llvm-svn: 322221
2018-01-10 20:27:48 +00:00
Erich Keane 281d20b601 Implement Attribute Target MultiVersioning
GCC's attribute 'target', in addition to being an optimization hint,
also allows function multiversioning. We currently have the former
implemented, this is the latter's implementation.

This works by enabling functions with the same name/signature to coexist,
so that they can all be emitted. Multiversion state is stored in the
FunctionDecl itself, and SemaDecl manages the definitions.
Note that it ends up having to permit redefinition of functions so
that they can all be emitted. Additionally, all versions of the function
must be emitted, so this also manages that.

Note that this includes some additional rules that GCC does not, since
defining something as a MultiVersion function after a usage has been made illegal.

The only 'history rewriting' that happens is if a function is emitted before
it has been converted to a multiversion'ed function, at which point its name
needs to be changed.

Function templates and virtual functions are NOT yet supported (not supported
in GCC either).

Additionally, constructors/destructors are disallowed, but the former is 
planned.

llvm-svn: 322028
2018-01-08 21:34:17 +00:00
Stephan Bergmann 0b6b082223 Commit new test file forgotten in previous commit
llvm-svn: 321861
2018-01-05 07:59:57 +00:00
Adrian Prantl 6c63a6c9a1 Remove redundant test
llvm-svn: 321846
2018-01-05 01:28:59 +00:00
Adrian Prantl 6c5f03a1b2 Debug Info: Support DW_AT_calling_convention on composite types.
This implements the DWARF 5 feature described at
http://www.dwarfstd.org/ShowIssue.php?issue=141215.1

This allows a consumer to understand whether a composite data type is
trivially copyable and thus should be passed by value instead of by
reference. The canonical example is being able to distinguish the
following two types:

  // S is not trivially copyable because of the explicit destructor.
  struct S {
     ~S() {}
  };

  // T is a POD type.
  struct T {
    ~T() = default;
  };

<rdar://problem/36034993>
Differential Revision: https://reviews.llvm.org/D41039

llvm-svn: 321845
2018-01-05 01:13:52 +00:00
Stephan Bergmann d71ad177eb -fsanitize=vptr warnings on bad static types in dynamic_cast and typeid
...when such an operation is done on an object during con-/destruction.

This is the cfe part of a patch covering both cfe and compiler-rt.

Differential Revision: https://reviews.llvm.org/D40295

llvm-svn: 321519
2017-12-28 12:45:41 +00:00
Volodymyr Sapsai 22b00ec42e Revert "[CodeGen] Fix crash when a function taking transparent union is redeclared."
This reverts commit r321296. It caused performance regressions
FAIL: imp.execution_time
FAIL: 2007-01-04-KNR-Args.execution_time
FAIL: sse_expandfft.execution_time
FAIL: sse_stepfft.execution_time

llvm-svn: 321306
2017-12-21 20:52:59 +00:00
Reid Kleckner a283e48f69 Revert "Fix for PR32990"
This reverts commit r321239. It broke the Chromium DLL build:

[8834/50217] LINK(DLL) icui18n.dll icui18n.dll.lib icui18n.dll.pdb
FAILED: icui18n.dll icui18n.dll.lib icui18n.dll.pdb
zrule.obj : error LNK2001: unresolved external symbol
"__declspec(dllimport) public: void __cdecl icu_60::UnicodeString::`vbase destructor'(void)"
(__imp_??_DUnicodeString@icu_60@@QEAAXXZ)

llvm-svn: 321298
2017-12-21 19:44:23 +00:00
Volodymyr Sapsai 614f3702d9 [CodeGen] Fix crash when a function taking transparent union is redeclared.
When a function taking transparent union is declared as taking one of
union members earlier in the translation unit, clang would hit an
"Invalid cast" assertion during EmitFunctionProlog. This case
corresponds to function f1 in test/CodeGen/transparent-union-redecl.c.
We decided to cast i32 to union because after merging function
declarations function parameter type becomes int,
CGFunctionInfo::ArgInfo type matches with ABIArgInfo type, so we decide
it is a trivial case. But these types should also be castable to
parameter declaration type which is not the case here.

The fix is in checking for the trivial case if ABIArgInfo type matches with
parameter declaration type. It exposed inconsistency that we check
hasScalarEvaluationKind for different types in EmitParmDecl and
EmitFunctionProlog, and comment says they should match.

Additional tests in Sema/transparent-union.c capture current behavior and make
sure there are no regressions.

rdar://problem/34949329

Reviewers: rjmccall, rafael

Reviewed By: rjmccall

Subscribers: aemerson, cfe-commits, kristof.beyls

Differential Revision: https://reviews.llvm.org/D41311

llvm-svn: 321296
2017-12-21 19:42:37 +00:00
Erich Keane abf9d6648c Fix for PR32990
This fixes the bug in https://bugs.llvm.org/show_bug.cgi?id=32990.

Patch By: zahiraam
Differential Revision: https://reviews.llvm.org/D39063

llvm-svn: 321239
2017-12-21 02:07:46 +00:00
Vedant Kumar 09b5bfdd85 [ubsan] Diagnose noreturn functions which return
Diagnose 'unreachable' UB when a noreturn function returns.

  1. Insert a check at the end of functions marked noreturn.

  2. A decl may be marked noreturn in the caller TU, but not marked in
     the TU where it's defined. To diagnose this scenario, strip away the
     noreturn attribute on the callee and insert check after calls to it.

Testing: check-clang, check-ubsan, check-ubsan-minimal, D40700

rdar://33660464

Differential Revision: https://reviews.llvm.org/D40698

llvm-svn: 321231
2017-12-21 00:10:25 +00:00
Richard Smith c70f1d63f8 [c++20] P0515R3: Parsing support and basic AST construction for operator <=>.
Adding the new enumerator forced a bunch more changes into this patch than I
would have liked. The -Wtautological-compare warning was extended to properly
check the new comparison operator, clang-format needed updating because it uses
precedence levels as weights for determining where to break lines (and several
operators increased their precedence levels with this change), thread-safety
analysis needed changes to build its own IL properly for the new operator.

All "real" semantic checking for this operator has been deferred to a future
patch. For now, we use the relational comparison rules and arbitrarily give
the builtin form of the operator a return type of 'void'.

llvm-svn: 320707
2017-12-14 15:16:18 +00:00
Peter Collingbourne 6010880bd1 IRGen: When performing CFI checks, load vtable pointer from vbase when necessary.
Under the Microsoft ABI, it is possible for an object not to have
a virtual table pointer of its own if all of its virtual functions
were introduced by virtual bases. In that case, we need to load the
vtable pointer from one of the virtual bases and perform the type
check using its type.

Differential Revision: https://reviews.llvm.org/D41036

llvm-svn: 320638
2017-12-13 21:53:04 +00:00
Tim Northover 36bb6d5d46 Switch to gnu++14 as the default dialect.
This is C++14 with conforming GNU extensions.

llvm-svn: 320250
2017-12-09 12:09:54 +00:00
Akira Hatanaka 502775a2ee [CodeGen][X86] Fix handling of __fp16 vectors.
This commit fixes a bug in IRGen where it generates completely broken
code for __fp16 vectors on X86. For example when the following code is
compiled:

half4 hv0, hv1, hv2; // these are vectors of __fp16.

void foo221() {
  hv0 = hv1 + hv2;
}

clang generates the following IR, in which two i16 vectors are added:

@hv1 = common global <4 x i16> zeroinitializer, align 8
@hv2 = common global <4 x i16> zeroinitializer, align 8
@hv0 = common global <4 x i16> zeroinitializer, align 8

define void @foo221() {
  %0 = load <4 x i16>, <4 x i16>* @hv1, align 8
  %1 = load <4 x i16>, <4 x i16>* @hv2, align 8
  %add = add <4 x i16> %0, %1
  store <4 x i16> %add, <4 x i16>* @hv0, align 8
  ret void
}

To fix the bug, this commit uses the code committed in r314056, which
modified clang to promote and truncate __fp16 vectors to and from float
vectors in the AST. It also fixes another IRGen bug where a short value
is assigned to an __fp16 variable without any integer-to-floating-point
conversion, as shown in the following example:

__fp16 a;
short b;

void foo1() {
  a = b;
}

@b = common global i16 0, align 2
@a = common global i16 0, align 2

define void @foo1() #0 {
  %0 = load i16, i16* @b, align 2
  store i16 %0, i16* @a, align 2
  ret void
}

rdar://problem/20625184

Differential Revision: https://reviews.llvm.org/D40112

llvm-svn: 320215
2017-12-09 00:02:37 +00:00
Dan Gohman b24e9dbafe [WebAssembly] Don't use Wasm function sections for more than one function
Patch by Nicholas Wilson!

Fixes PR35467.

Differential Revision: https://reviews.llvm.org/D40738

llvm-svn: 319801
2017-12-05 17:46:17 +00:00
Richard Smith 435e647a41 PR35456: Track definedness of variable template specializations separately from
whether they have an initializer.

We cannot distinguish between a declaration of a variable template
specialization and a definition of one that lacks an initializer without this,
and would previously mistake the latter for the former.

llvm-svn: 319605
2017-12-02 02:48:42 +00:00
Richard Smith d30b23d6a5 [c++2a] P0515R3: Support for overloaded operator<=>.
No CodeGen support for MSABI yet, we don't know how to mangle this there.

llvm-svn: 319513
2017-12-01 02:13:10 +00:00
Hans Wennborg b8304a6aed MS ABI: Treat explicit instantiation definitions of dllimport function templates as explicit instantiation decls (PR35435)
This matches MSVC's behaviour, and we already do it for class templates
since r270897.

Differential revision: https://reviews.llvm.org/D40621

llvm-svn: 319386
2017-11-29 23:44:11 +00:00
Reid Kleckner 9dae73b9db [EH] Use __CxxFrameHandler3 for C++ EH in MS environments
Fixes regression introduced by r319297. MSVC environments still use SEH
unwind opcodes but they should use the Microsoft C++ EH personality, not
the mingw one.

llvm-svn: 319363
2017-11-29 21:35:34 +00:00
Martell Malone c950c651a4 Toolchain: Normalize dwarf, sjlj and seh eh
This is a re-apply of r319294.

adds -fseh-exceptions and -fdwarf-exceptions flags

clang will check if the user has specified an exception model flag,
in the absense of specifying the exception model clang will then check
the driver default and append the model flag for that target to cc1

-fno-exceptions has a higher priority then specifying the model

move __SEH__ macro definitions out of Targets into InitPreprocessor
behind the -fseh-exceptions flag

move __ARM_DWARF_EH__ macrodefinitions out of verious targets and into
InitPreprocessor behind the -fdwarf-exceptions flag and arm|thumb check

remove unused USESEHExceptions from the MinGW Driver

fold USESjLjExceptions into a new GetExceptionModel function that
gives the toolchain classes more flexibility with eh models

Reviewers: rnk, mstorsjo

Differential Revision: https://reviews.llvm.org/D39673

llvm-svn: 319297
2017-11-29 07:25:12 +00:00
Martell Malone 2fa25706ed Revert "Toolchain: Normalize dwarf, sjlj and seh eh"
This reverts rL319294.
The windows sanitizer does not like seh on x86.
Will re apply with None type for x86

llvm-svn: 319295
2017-11-29 06:51:27 +00:00
Martell Malone 390cfcb0b1 Toolchain: Normalize dwarf, sjlj and seh eh
adds -fseh-exceptions and -fdwarf-exceptions flags

clang will check if the user has specified an exception model flag,
in the absense of specifying the exception model clang will then check
the driver default and append the model flag for that target to cc1

clang cc1 assumes dwarf is the default if none is passed
and -fno-exceptions has a higher priority then specifying the model

move __SEH__ macro definitions out of Targets into InitPreprocessor
behind the -fseh-exceptions flag

move __ARM_DWARF_EH__ macrodefinitions out of verious targets and into
InitPreprocessor behind the -fdwarf-exceptions flag and arm|thumb check

remove unused USESEHExceptions from the MinGW Driver

fold USESjLjExceptions into a new GetExceptionModel function that
gives the toolchain classes more flexibility with eh models

Reviewers: rnk, mstorsjo

Differential Revision: https://reviews.llvm.org/D39673

llvm-svn: 319294
2017-11-29 06:25:13 +00:00
Martin Storsjo 0db60f3637 [test] Fix a typo in a test comment. NFC.
llvm-svn: 319145
2017-11-28 05:47:24 +00:00
Reid Kleckner 13a3d9eb7b [MS] Increase default new alignment for win64 and test it
Summary:
This raises __STDCPP_DEFAULT_NEW_ALIGNMENT__ from 8 to 16 on Win64.
This matches platforms that follow the usual `2 * sizeof(void*)`
alignment requirement for malloc. We might want to consider making that
the default rather than relying on long double alignment.

Fixes PR35356

Reviewers: STL_MSFT, rsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D40277

llvm-svn: 318723
2017-11-21 01:25:56 +00:00
Richard Smith e2467b7aed PR22763: if a defaulted (non-user-provided) special member function is
explicitly instantiated, still emit it with each use.

We don't emit a definition of the member with an explicit instantiation
definition (and indeed it appears that we're not allowed to, since an explicit
instantiation definition does not constitute an odr-use and only odr-use
permits definition for defaulted special members). So we still need to emit a
weak definition with each use.

This also makes defaulted-in-class declarations behave more like
implicitly-declared special members, which matches their design intent.
And it matches the way this problem was solved in GCC.

llvm-svn: 318474
2017-11-16 23:54:56 +00:00
Reid Kleckner 06239e42c6 [MS] Apply adjustments after storing 'this'
Summary:
The MS ABI convention is that the 'this' pointer on entry is the address
of the vfptr that was used to make the virtual method call. In other
words, the pointer on entry always points to the base subobject that
introduced the virtual method. Consider this hierarchy:

  struct A { virtual void f() = 0; };
  struct B { virtual void g() = 0; };
  struct C : A, B {
    void f() override;
    void g() override;
  };

On entry to C::g, [ER]CX will contain the address of C's B subobject,
and C::g will have to subtract sizeof(A) to recover a pointer to C.

Before this change, we applied this adjustment in the prologue and
stored the new value into the "this" local variable alloca used for
debug info. However, MSVC does not do this, presumably because it is
often profitable to fold the adjustment into later field accesses. This
creates a problem, because the debugger expects the variable to be
unadjusted. Unfortunately, CodeView doesn't have anything like DWARF
expressions for computing variables that aren't in the program anymore,
so we have to declare 'this' to be the unadjusted value if we want the
debugger to see the right value.

This has the side benefit that, in optimized builds, the 'this' pointer
will usually be available on function entry because it doesn't require
any adjustment.

Reviewers: hans

Subscribers: aprantl, cfe-commits

Differential Revision: https://reviews.llvm.org/D40109

llvm-svn: 318440
2017-11-16 19:09:36 +00:00
Yaxun Liu abf5b27f7a Update tests for llvm.invariant.group.barrier becoming mangled
Differential Revision: https://reviews.llvm.org/D40062

llvm-svn: 318414
2017-11-16 16:33:04 +00:00
Hans Wennborg 57dd59d472 Try to fix the instrument-functions tests
On e.g. PPC the return value and argument were marked 'signext'. This
makes the test expectations a bit more flexible.

Follow-up to r318199.

llvm-svn: 318214
2017-11-14 23:10:04 +00:00
Hans Wennborg 76c26c1dca Switch -mcount and -finstrument-functions to emit EnterExitInstrumenter attributes
This updates -mcount to use the new attribute names (LLVM r318195), and
switches over -finstrument-functions to also use these attributes rather
than inserting instrumentation in the frontend.

It also adds a new flag, -finstrument-functions-after-inlining, which
makes the cygprofile instrumentation get inserted after inlining rather
than before.

Differential Revision: https://reviews.llvm.org/D39331

llvm-svn: 318199
2017-11-14 21:13:27 +00:00
Martell Malone b22e600484 CodeGenCXX: no default dllimport storage for mingw
GNU frontends don't have options like /MT, /MD
This fixes a few link error regressions with libc++ and libc++abi

Reviewers: rnk, mstorsjo, compnerd

Differential Revision: https://reviews.llvm.org/D33620

llvm-svn: 317398
2017-11-04 02:15:49 +00:00
Richard Smith e124612eda [c++17] Visit class template explicit specializations just like all other class definitions in codegen.
If an explicit specialization has a static data member, it may be a definition and we may need to register it for emission.

llvm-svn: 317296
2017-11-03 01:26:01 +00:00
Erich Keane a957ffbce3 Add default calling convention support for regcall.
Added support for regcall as default calling convention. Also added code to
exclude main when applying default calling conventions.

Patch-By: eandrews

Differential Revision: https://reviews.llvm.org/D39210

llvm-svn: 317268
2017-11-02 21:08:00 +00:00
Wolfgang Pieb 173b47ca05 Making a couple of tests a bit more flexible wrt thunk mangling. Fixes checkin for r317047.
llvm-svn: 317053
2017-11-01 00:01:20 +00:00
Wolfgang Pieb a347c47f5d Fix for PR33930. Short-circuit metadata mapping when cloning a varargs thunk.
The cloning happens before all metadata nodes are resolved. Prevent the value
mapper from running into unresolved or temporary MD nodes.

Differential Revision: https://reviews.llvm.org/D39396

llvm-svn: 317047
2017-10-31 22:49:48 +00:00
Vlad Tsyrklevich 634c601fe3 [CFI] Add CFI-icall pointer type generalization
Summary:
This change allows generalizing pointers in type signatures used for
cfi-icall by enabling the -fsanitize-cfi-icall-generalize-pointers flag.
This works by 1) emitting an additional generalized type signature
metadata node for functions and 2) llvm.type.test()ing for the
generalized type for translation units with the flag specified.

This flag is incompatible with -fsanitize-cfi-cross-dso because it would
require emitting twice as many type hashes which would increase artifact
size.

Reviewers: pcc, eugenis

Reviewed By: pcc

Subscribers: kcc

Differential Revision: https://reviews.llvm.org/D39358

llvm-svn: 317044
2017-10-31 22:39:44 +00:00
Yaxun Liu 561ac06ff2 CodeGen: Fix insertion position of addrspace cast for alloca
For non-zero alloca addr space, alloca is usually casted to default addr
space immediately.

For non-vla, alloca is inserted at AllocaInsertPt, therefore the addr
space cast should also be insterted at AllocaInsertPt. However,
for vla, alloca is inserted at the current insertion point of IRBuilder,
therefore the addr space cast should also inserted at the current
insertion point of IRBuilder.

Currently clang always insert addr space cast at AllocaInsertPt, which
causes invalid IR.

This patch fixes that.

Differential Revision: https://reviews.llvm.org/D39374

llvm-svn: 316909
2017-10-30 14:38:30 +00:00
Richard Smith 72db888389 PR35039: Materialize temporary objects before wrapping them in an
OpaqueValueExpr in a GNU binary conditional expression.

It's not meaningful for a non-materialized temporary object to be used as a
common subexpression of multiple expressions.

llvm-svn: 316836
2017-10-28 18:59:51 +00:00
Reid Kleckner 2e87a21c7c [MS] Allow access to ambiguous, inaccessible direct bases
Summary:
Clang typically warns that in the following class hierarchy, 'A' is
inaccessible because there is no series of casts that the user can
write to access it unambiguously:
  struct A { };
  struct B : A { };
  struct C : A, B { };

MSVC allows the user to convert from C* to A*, though, and we've
encountered this issue in the latest Windows SDK headers.

This patch allows this conversion when -fms-compatibility is set and
adds a warning for it under -Wmicrosoft-inaccessible-base.

Reviewers: rsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D39389

llvm-svn: 316807
2017-10-27 22:48:41 +00:00
Adrian Prantl e8dd2bd834 Fix C++ testcase I forgot to add to r316689.
llvm-svn: 316695
2017-10-26 20:16:03 +00:00
Erich Keane 5759fa798b Correct behavior of fastcall when default CC is set.
Fastcall doesn't support variadic function calls, so
setting the default calling convention to Fastcall would
result in incorrect code being emitted for these conditions.

This patch adds a 'variadic' test to the default calling conv
test, as well as fixes the behavior of fastcall.

llvm-svn: 316528
2017-10-24 23:12:01 +00:00
Richard Smith 8910fe699e For better compatibility with C++11 and C++14, emit a nondiscardable definition
of a static constexpr data member if it's defined 'constexpr' out of line, not
only if it's defined 'constexpr' in the class.

llvm-svn: 316310
2017-10-23 03:58:34 +00:00
Richard Smith 4309b66710 Don't suppress instantiation of definitions for variables subject to explicit
instantiation declarations if they are usable from constant expressions.

We are permitted to instantiate in these cases, and required to do so in order
to have an initializer available for use within constant evaluation.

llvm-svn: 316136
2017-10-18 22:45:01 +00:00
Wei Mi 9b3d627280 [Bitfield] Add an option to access bitfield in a fine-grained manner.
Currently all the consecutive bitfields are wrapped as a large integer unless there is unamed zero sized bitfield in between. The patch provides an alternative manner which makes the bitfield to be accessed as separate memory location if it has legal integer width and is naturally aligned. Such separate bitfield may split the original consecutive bitfields into subgroups of consecutive bitfields, and each subgroup will be wrapped as an integer. Now This is all controlled by an option -ffine-grained-bitfield-accesses. The alternative of bitfield access manner can improve the access efficiency of those bitfields with legal width and being aligned, but may reduce the chance of load/store combining of other bitfields, so it depends on how the bitfields are defined and actually accessed to choose when to use the option. For now the option is off by default.

Differential revision: https://reviews.llvm.org/D36562

llvm-svn: 315915
2017-10-16 16:50:27 +00:00