Commit Graph

765 Commits

Author SHA1 Message Date
Craig Topper a58b62b4a2 [IR] Replace all uses of CallBase::getCalledValue() with getCalledOperand().
This method has been commented as deprecated for a while. Remove
it and replace all uses with the equivalent getCalledOperand().

I also made a few cleanups in here. For example, to removes use
of getElementType on a pointer when we could just use getFunctionType
from the call.

Differential Revision: https://reviews.llvm.org/D78882
2020-04-27 22:17:03 -07:00
Christopher Tetreault 2dea3f1298 [SVE] Add new VectorType subclasses
Summary:
Introduce new types for fixed width and scalable vectors.

Does not remove getNumElements yet so as to not break code during transition
period.

Reviewers: deadalnix, efriedma, sdesmalen, craig.topper, huntergr

Reviewed By: sdesmalen

Subscribers: jholewinski, arsenm, jvesely, nhaehnle, mehdi_amini, rriddle, jpienaar, burmako, shauheen, antiagainst, nicolasvasilache, csigg, arpith-jacob, mgester, lucyrfox, liufengdb, kerbowa, Joonsoo, grosul1, frgossen, lldb-commits, tschuett, hiraditya, rkruppe, psnobl, llvm-commits

Tags: #llvm, #lldb

Differential Revision: https://reviews.llvm.org/D77587
2020-04-22 08:59:01 -07:00
Lang Hames 59ed45b483 [ORC] Add an OrcV2 C API function for configuring TargetMachines. 2020-04-10 15:51:29 -07:00
Lang Hames 37bcf2df01 [ORC] Require JITDylib to be specified when adding IR and objects in the C API. 2020-04-09 17:59:26 -07:00
Lang Hames 0d5f15f700 [ORC] Add C API support for adding object files to an LLJIT instance. 2020-04-09 16:18:46 -07:00
Lang Hames 1cd8493e69 [ORC] Expand the OrcV2 C API bindings.
Adds basic support for LLJITBuilder and DynamicLibrarySearchGenerator. This
allows C API clients to configure LLJIT to expose process symbols to JIT'd
code. An example of this is added in
llvm/examples/OrcV2CBindingsReflectProcessSymbols.
2020-04-09 16:18:46 -07:00
Reid Kleckner 3a29393b47 Remove math.h/cmath include from DataTypes.h
DataTypes.h is meant to wrap the integer type and limits headers, which
have some unfortunate variance. The FP math functions declared by math.h
are not unnecessary. math.h took a noticeable amount of time to parse
(~40ms), but that could be startup costs.

Anyway, we don't need to include it, so skipping it can't hurt.

This has been present since the initial CMake build was added in 2008.
2020-04-06 11:27:52 -07:00
Lang Hames 29a2b14be2 [ORC] Improve documention of memory ownership in the new Orc C bindings. 2020-04-03 12:33:02 -07:00
Adrian Prantl 5c261c9c45 Fix typo in parameter name. 2020-03-16 08:06:17 -07:00
Lang Hames 633ea07200 [Orc] Add basic OrcV2 C bindings and example.
Renames the llvm/examples/LLJITExamples directory to llvm/examples/OrcV2Examples
since it is becoming a home for all OrcV2 examples, not just LLJIT.

See http://llvm.org/PR31103.
2020-03-14 14:41:22 -07:00
Lang Hames 906a91aa4d [MCJIT] Check for RuntimeDyld errors in MCJIT::finalizeLoadedModules.
Patch based on https://reviews.llvm.org/D75912 by Alexander Shishkin. Thanks
Alexander!

To minimize disruption to existing clients, who may be relying on the fact that
unused references to unresolved symbols do not generate an error, this patch
makes error checking opt-in: Clients can call ExecutionEngine::hasError or
LLVMExecutionEngineGetError to check whether and error has occurred.

Differential revision: https://reviews.llvm.org/D75912
2020-03-13 13:58:41 -07:00
Adrian Prantl d5180ea134 Add debug info support for Swift/Clang APINotes.
In order for dsymutil to collect .apinotes files (which capture
attributes such as nullability, Swift import names, and availability),
I want to propose adding an apinotes: field to DIModule that gets
translated into a DW_AT_LLVM_apinotes (path) nested inside
DW_TAG_module. This will be primarily used by LLDB to indirectly
extract the Swift names of Clang declarations that were deserialized
from DWARF.

<rdar://problem/59514626>

Differential Revision: https://reviews.llvm.org/D75585
2020-03-11 18:47:30 -07:00
Adrian Prantl e4e7e44765 Add an SDK attribute to DICompileUnit
This is part of PR44213 https://bugs.llvm.org/show_bug.cgi?id=44213

When importing (system) Clang modules, LLDB needs to know which SDK
(e.g., MacOSX, iPhoneSimulator, ...) they came from. While the sysroot
attribute contains the absolute path to the SDK, this doesn't work
well when the debugger is run on a different machine than the
compiler, and the SDKs are installed in different directories. It thus
makes sense to just store the name of the SDK instead of the absolute
path, so it can be found relative to LLDB.

rdar://problem/51645582

Differential Revision: https://reviews.llvm.org/D75646
2020-03-11 14:14:06 -07:00
Francis Visoiu Mistrih e551b737c3 [LTO][Legacy] Add new API to query Mach-O CPU (sub)type
Tools working with object files on Darwin (e.g. lipo) may need to know
properties like the CPU type and subtype of a bitcode file. The logic of
converting a triple to a Mach-O CPU_(SUB_)TYPE should be provided by
LLVM instead of relying on tools to re-implement it.

Differential Revision: https://reviews.llvm.org/D75067
2020-02-28 12:56:05 -08:00
Ayke van Laethem 2a7a989c3e
[LLVM-C] Add bindings for addCoroutinePassesToExtensionPoints
This patch adds bindings to C and Go for
addCoroutinePassesToExtensionPoints, which is used to add coroutine
passes to the correct locations in PassManagerBuilder.

Differential Revision: https://reviews.llvm.org/D51642
2020-02-24 20:15:51 +01:00
Jim Lin 466f8843f5 [NFC] Remove trailing space
sed -Ei 's/[[:space:]]+$//' include/**/*.{def,h,td} lib/**/*.{cpp,h,td}
2020-02-18 10:49:13 +08:00
Adrian Prantl 7b30370e5b Move the sysroot attribute from DIModule to DICompileUnit
[this re-applies c0176916a4
 with the correct commit message and phabricator link]

This addresses point 1 of PR44213.
https://bugs.llvm.org/show_bug.cgi?id=44213

The DW_AT_LLVM_sysroot attribute is used for Clang module debug info,
to allow LLDB to import a Clang module from source. Currently it is
part of each DW_TAG_module, however, it is the same for all modules in
a compile unit. It is more efficient and less ambiguous to store it
once in the DW_TAG_compile_unit.

This should have no effect on DWARF consumers other than LLDB.

Differential Revision: https://reviews.llvm.org/D71732
2020-01-17 12:55:40 -08:00
Adrian Prantl c17aee67f1 Revert "Rename DW_AT_LLVM_isysroot to DW_AT_LLVM_sysroot"
This reverts commit 12e479475a.

I accidentally landed this patch with the wrong commit message ...
2020-01-17 12:52:36 -08:00
Adrian Prantl 12e479475a Rename DW_AT_LLVM_isysroot to DW_AT_LLVM_sysroot
This is a purely cosmetic change that is NFC in terms of the binary
output. I bugs me that I called the attribute DW_AT_LLVM_isysroot
since the "i" is an artifact of GCC command line option syntax
(-isysroot is in the category of -i options) and doesn't carry any
useful information otherwise.

This attribute only appears in Clang module debug info.

Differential Revision: https://reviews.llvm.org/D71722
2020-01-17 09:36:48 -08:00
Brian Gesiak 2fcf7691df [Coroutines] Rename "legacy" passes (NFC)
A series of patches beginning with https://reviews.llvm.org/D71898
propose to add an implementation of the coroutine passes to the new pass
manager. As part of these changes, the coroutine passes that implement
the legacy pass manager interface are renamed, to `<PassName>Legacy`.
This mirrors similar changes that have been made to many other passes in
LLVM as they've been transitioned to support both old and new pass
managers.

This commit splits out the renaming portion of that patch and commits it
in advance as an NFC (no functional change intended) commit. It renames:

* `CoroEarly` => `CoroEarlyLegacy`
* `CoroSplit` => `CoroSplitLegacy`
* `CoroElide` => `CoroElideLegacy`
* `CoroCleanup` => `CoroCleanupLegacy`
2020-01-01 21:41:16 -05:00
Adrian Prantl 44b4b833ad Rename DW_AT_LLVM_isysroot to DW_AT_LLVM_sysroot
This is a purely cosmetic change that is NFC in terms of the binary
output. I bugs me that I called the attribute DW_AT_LLVM_isysroot
since the "i" is an artifact of GCC command line option syntax
(-isysroot is in the category of -i options) and doesn't carry any
useful information otherwise.

This attribute only appears in Clang module debug info.

Differential Revision: https://reviews.llvm.org/D71722
2019-12-20 13:11:17 -08:00
Sourabh Singh Tomar f1e3988aa6 Recommit "[DWARF5]Addition of alignment atrribute in typedef DIE."
This revision is revised to update Go-bindings and Release Notes.

The original commit message follows.

This patch, adds support for DW_AT_alignment[DWARF5] attribute, to be emitted with typdef DIE.
When explicit alignment is specified.

Patch by Awanish Pandey <Awanish.Pandey@amd.com>

Reviewers: aprantl, dblaikie, jini.susan.george, SouraVX, alok,
deadalinx

Differential Revision: https://reviews.llvm.org/D70111
2019-12-03 09:51:43 +05:30
Francis Visoiu Mistrih bffdee8ef3 [LTO][Legacy] Add API for passing LLVM options separately
In order to correctly pass options to LLVM, including options containing
spaces which are used as delimiters for multiple options in
lto_codegen_debug_options, add a new API:
lto_codegen_debug_options_array.

Unfortunately, tools/lto has no testing infrastructure yet, so there are
no tests associated with this patch.

Differential Revision: https://reviews.llvm.org/D70463
2019-11-19 16:30:37 -08:00
Duncan P. N. Exon Smith 8c48405069 Wrap C APIs with pragmas enforcing -Werror=strict-prototypes
Force `-Werror=strict-prototypes` so that C API tests fail to compile if
we add a non-prototype declaration.  This should help avoid regressions
like bddecba4b3 was fixing.

https://reviews.llvm.org/D70285
rdar://problem/57203137
2019-11-19 13:18:43 -08:00
Sam McCall d27a16eb39 Revert "[DWARF5]Addition of alignment atrribute in typedef DIE."
This reverts commit 423f541c1a, which
breaks llvm-c ABI.
2019-11-18 15:53:22 +01:00
Sourabh Singh Tomar 423f541c1a [DWARF5]Addition of alignment atrribute in typedef DIE.
This patch, adds support for DW_AT_alignment[DWARF5] attribute, to be emitted with typdef DIE.
When explicit alignment is specified.

Patch by Awanish Pandey <Awanish.Pandey@amd.com>

Reviewers: aprantl, dblaikie, jini.susan.george, SouraVX, alok,
deadalinx

Differential Revision: https://reviews.llvm.org/D70111
2019-11-16 21:56:53 +05:30
aqjune e87d71668e [IR] Redefine Freeze instruction
Summary:
This patch redefines freeze instruction from being UnaryOperator to a subclass of UnaryInstruction.

ConstantExpr freeze is removed, as discussed in the previous review.
FreezeOperator is not added because there's no ConstantExpr freeze.
`freeze i8* null` test is added to `test/Bindings/llvm-c/freeze.ll` as well, because the null pointer-related bug in `tools/llvm-c/echo.cpp` is now fixed.
InstVisitor has visitFreeze now because freeze is not unaryop anymore.

Reviewers: whitequark, deadalnix, craig.topper, jdoerfert, lebedev.ri

Reviewed By: craig.topper, lebedev.ri

Subscribers: regehr, nlopes, mehdi_amini, hiraditya, steven_wu, dexonsmith, jfb, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69932
2019-11-12 10:49:00 +09:00
aqjune 58acbce3de [IR] Add Freeze instruction
Summary:
- Define Instruction::Freeze, let it be UnaryOperator
- Add support for freeze to LLLexer/LLParser/BitcodeReader/BitcodeWriter
  The format is `%x = freeze <ty> %v`
- Add support for freeze instruction to llvm-c interface.
- Add m_Freeze in PatternMatch.
- Erase freeze when lowering IR to SelDag.

Reviewers: deadalnix, hfinkel, efriedma, lebedev.ri, nlopes, jdoerfert, regehr, filcab, delcypher, whitequark

Reviewed By: lebedev.ri, jdoerfert

Subscribers: jfb, kristof.beyls, hiraditya, lebedev.ri, steven_wu, dexonsmith, xbolva00, delcypher, spatel, regehr, trentxintong, vsk, filcab, nlopes, mehdi_amini, deadalnix, llvm-commits

Differential Revision: https://reviews.llvm.org/D29011
2019-11-05 15:54:56 +09:00
Joerg Sonnenberger 9681ea9560 Reapply r374743 with a fix for the ocaml binding
Add a pass to lower is.constant and objectsize intrinsics

This pass lowers is.constant and objectsize intrinsics not simplified by
earlier constant folding, i.e. if the object given is not constant or if
not using the optimized pass chain. The result is recursively simplified
and constant conditionals are pruned, so that dead blocks are removed
even for -O0. This allows inline asm blocks with operand constraints to
work all the time.

The new pass replaces the existing lowering in the codegen-prepare pass
and fallbacks in SDAG/GlobalISEL and FastISel. The latter now assert
on the intrinsics.

Differential Revision: https://reviews.llvm.org/D65280

llvm-svn: 374784
2019-10-14 16:15:14 +00:00
Dmitri Gribenko 1a21f98ac3 Revert "Add a pass to lower is.constant and objectsize intrinsics"
This reverts commit r374743. It broke the build with Ocaml enabled:
http://lab.llvm.org:8011/builders/clang-x86_64-debian-fast/builds/19218

llvm-svn: 374768
2019-10-14 12:22:48 +00:00
Joerg Sonnenberger e4300c392d Add a pass to lower is.constant and objectsize intrinsics
This pass lowers is.constant and objectsize intrinsics not simplified by
earlier constant folding, i.e. if the object given is not constant or if
not using the optimized pass chain. The result is recursively simplified
and constant conditionals are pruned, so that dead blocks are removed
even for -O0. This allows inline asm blocks with operand constraints to
work all the time.

The new pass replaces the existing lowering in the codegen-prepare pass
and fallbacks in SDAG/GlobalISEL and FastISel. The latter now assert
on the intrinsics.

Differential Revision: https://reviews.llvm.org/D65280

llvm-svn: 374743
2019-10-13 23:00:15 +00:00
Simon Pilgrim 604b7c22be Fix Wdocumentation unknown parameter warning. NFCI.
llvm-svn: 374171
2019-10-09 14:26:09 +00:00
Cameron McInally 60786f9143 [llvm-c] Add UnaryOperator to LLVM_FOR_EACH_VALUE_SUBCLASS macro
Note that we are not sure where the tests for these functions lives. This was discussed in the Phab Diff.

Differential Revision: https://reviews.llvm.org/D68588

llvm-svn: 373969
2019-10-07 21:33:39 +00:00
whitequark b63db94fa5 [LLVM-C] Add bindings to create macro debug info
Summary: The C API doesn't have the bindings to create macro debug information.

Reviewers: whitequark, CodaFi, deadalnix

Reviewed By: whitequark

Subscribers: aprantl, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58334

llvm-svn: 373903
2019-10-07 13:57:13 +00:00
Aditya Kumar a6d9d31279 [LLVM-C][Ocaml] Add MergeFunctions and DCE pass
MergeFunctions and DCE pass are missing from OCaml/C-api. This patch
adds them.

Differential Revision: https://reviews.llvm.org/D65071

Reviewers: whitequark, hiraditya, deadalnix

Reviewed By: whitequark

Subscribers: llvm-commits

Tags: #llvm

Authored by: kren1

llvm-svn: 373170
2019-09-29 16:06:22 +00:00
Nick Lewycky f57e968dd0 Improve C API support for atomicrmw and cmpxchg.
atomicrmw and cmpxchg have a volatile flag, so allow them to be get and set with LLVM{Get,Set}Volatile. atomicrmw and fence have orderings, so allow them to be get and set with LLVM{Get,Set}Ordering. Add missing LLVMAtomicRMWBinOpFAdd and LLVMAtomicRMWBinOpFSub enum constants. AtomicCmpXchg also has a weak flag, add a getter/setter for that too. Add a getter/setter for the binary-op of an atomicrmw.

atomicrmw and cmpxchg have a volatile flag, so allow it to be set/get with LLVMGetVolatile and LLVMSetVolatile. Add missing LLVMAtomicRMWBinOpFAdd and LLVMAtomicRMWBinOpFSub enum constants. AtomicCmpXchg also has a weak flag, add a getter/setter for that too. Add a getter/setter for the binary-op of an atomicrmw.

Add LLVMIsA## for CatchSwitchInst, CallBrInst and FenceInst, as well as AtomicCmpXchgInst and AtomicRMWInst.

Update llvm-c-test to include atomicrmw and fence, and to copy volatile for the four applicable instructions.

Differential Revision: https://reviews.llvm.org/D67132

llvm-svn: 372938
2019-09-26 00:58:55 +00:00
Adrian Prantl 0779dffbd4 Remove the obsolete BlockByRefStruct flag from LLVM IR
DIFlagBlockByRefStruct is an unused DIFlag that originally was used by
clang to express (Objective-)C block captures in debug info. For the
last year Clang has been emitting complex DIExpressions to describe
block captures instead, which makes all the code supporting this flag
redundant.

This patch removes the flag and all supporting "dead" code, so we can
reuse the bit for something else in the future.

Since this only affects debug info generated by Clang with the block
extension this mostly affects Apple platforms and I don't have any
bitcode compatibility concerns for removing this. The Verifier will
reject debug info that uses the bit and thus degrade gracefully when
LTO'ing older bitcode with a newer compiler.

rdar://problem/44304813

Differential Revision: https://reviews.llvm.org/D67453

llvm-svn: 372272
2019-09-18 22:38:56 +00:00
Steven Wu 34d80461ff [LTO][Legacy] Add new C inferface to query libcall functions
Summary:
This is needed to implemented the same approach as lld (implemented in r338434)
for how to handling symbols that can be generated by LTO code generator
but not present in the symbol table for linker that uses legacy C APIs.

libLTO is in charge of providing the list of symbols. Linker is in
charge of implementing the eager loading from static libraries using
the list of symbols.

rdar://problem/52853974

Reviewers: tejohnson, bd1976llvm, deadalnix, espindola

Reviewed By: tejohnson

Subscribers: emaste, arichardson, hiraditya, MaskRay, dang, kledzik, mehdi_amini, inglorion, jkorous, dexonsmith, ributzka, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67568

llvm-svn: 372021
2019-09-16 18:49:54 +00:00
Steven Wu aa89c5ffc3 [NFC][libLTO] Rearrange declaration in lto.h
Summary:
Rearrange the function declaration in lto.h so they falls in the correct
doxygen group.

Reviewers: tejohnson, bd1976llvm, deadalnix

Reviewed By: tejohnson

Subscribers: mehdi_amini, inglorion, jkorous, dexonsmith, ributzka, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67565

llvm-svn: 371900
2019-09-13 21:19:12 +00:00
Francis Visoiu Mistrih a85d9ef11a [Remarks] Add parser for bitstream remarks
The bitstream remark serializer landed in r367372.

This adds a bitstream remark parser that parser bitstream remark files
to llvm::remarks::Remark objects through the RemarkParser interface.

A few interesting things to point out:

* There are parsing helpers to parse the different types of blocks
* The main parsing helper allows us to parse remark metadata and open an
external file containing the encoded remarks
* This adds a dependency from the Remarks library to the BitstreamReader
library
* The testing strategy is to create a remark entry through YAML, parse
it, serialize it to bitstream, parse that back and compare the objects.
* There are close to no tests for malformed bitstream remarks, due to
the lack of textual format for the bitstream format.
* This adds a new C API for parsing bitstream remarks:
LLVMRemarkParserCreateBitstream.
* This bumps the REMARKS_API_VERSION to 1.

Differential Revision: https://reviews.llvm.org/D67134

llvm-svn: 371429
2019-09-09 17:43:50 +00:00
Jonas Devlieghere ed3b6d1bb2 Revert "Expose TailCallKind via the LLVM C API"
This is failing on several build bots. Reverting as discussed in
https://reviews.llvm.org/D66061.

llvm-svn: 368953
2019-08-15 03:49:51 +00:00
Robert Widmann 708c4605a1 Expose TailCallKind via the LLVM C API
Summary: This exposes `CallInst`'s tail call kind via new `LLVMGetTailCallKind` and `LLVMSetTailCallKind` functions. The motivation for this is to be able to see `musttail` for languages that require mandatory tail calls for correctness. Today only the weaker `LLVMSetTail` is exposed and there is no way to set `GuaranteedTailCallOpt` via the C API.

Reviewers: CodaFi, jyknight, deadalnix, rnk

Reviewed By: CodaFi

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66061

llvm-svn: 368945
2019-08-14 23:54:35 +00:00
Robert Widmann fcf3c55a8c [LLVM-C] Improve Bindings to The Internalize Pass
Summary: Adds a binding to the internalize pass that allows the caller to pass a function pointer that acts as the visibility-preservation predicate.  Previously, one could only pass an unsigned value (not LLVMBool?) that directed the pass to consider "main" or not.

Reviewers: whitequark, deadalnix, harlanhaskins

Reviewed By: whitequark, harlanhaskins

Subscribers: kren1, hiraditya, llvm-commits, harlanhaskins

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D62456

llvm-svn: 366777
2019-07-23 04:56:44 +00:00
Francis Visoiu Mistrih 94bad22c2c [Remarks] Simplify and refactor the RemarkParser interface
Before, everything was based on some kind of type erased parser
implementation which container a lot of boilerplate code when multiple
formats were to be supported.

This simplifies it by:

* the remark now owns its arguments
* *always* returning an error from the implementation side
* working around the way the YAML parser reports errors: catch them through
callbacks and re-insert them in a proper llvm::Error
* add a CParser wrapper that is used when implementing the C API to
avoid cluttering the C++ API with useless state
* LLVMRemarkParserGetNext now returns an object that needs to be
released to avoid leaking resources
* add a new API to dispose of a remark entry: LLVMRemarkEntryDispose

llvm-svn: 366217
2019-07-16 15:25:05 +00:00
Ben Dunbobbin 564d248ec2 [ThinLTO]LTO]Legacy] Fix dependent libraries support by adding querying of the IRSymtab
Dependent libraries support for the legacy api was committed in a
broken state (see: https://reviews.llvm.org/D60274). This was missed
due to the painful nature of having to integrate the changes into a
linker in order to test. This change implements support for dependent
libraries in the legacy LTO api:

- I have removed the current api function, which returns a single
string, and   added functions to access each dependent library
specifier individually.

- To reduce the testing pain, I have made the api functions as thin as
possible to   maximize coverage from llvm-lto.

- When doing ThinLTO the system linker will load the modules lazily
when scanning   the input files. Unfortunately, when modules are
lazily loaded there is no access   to module level named metadata. To
fix this I have added api functions that allow   querying the IRSymtab
for the dependent libraries. I hope to expand the api in the   future
so that, eventually, all the information needed by a client linker
during   scan can be retrieved from the IRSymtab.

Differential Revision: https://reviews.llvm.org/D62935

llvm-svn: 363140
2019-06-12 11:07:56 +00:00
Robert Widmann b0fd12b689 [LLVM-C] Add Accessor for Mach-O Universal Binary Slices
Summary: Allow for retrieving an object file corresponding to an architecture-specific slice in a Mach-O universal binary file.

Reviewers: whitequark, deadalnix

Reviewed By: whitequark

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60378

llvm-svn: 361705
2019-05-25 16:47:27 +00:00
Ben Dunbobbin 1d16515fb4 [ELF] Implement Dependent Libraries Feature
This patch implements a limited form of autolinking primarily designed to allow
either the --dependent-library compiler option, or "comment lib" pragmas (
https://docs.microsoft.com/en-us/cpp/preprocessor/comment-c-cpp?view=vs-2017) in
C/C++ e.g. #pragma comment(lib, "foo"), to cause an ELF linker to automatically
add the specified library to the link when processing the input file generated
by the compiler.

Currently this extension is unique to LLVM and LLD. However, care has been taken
to design this feature so that it could be supported by other ELF linkers.

The design goals were to provide:

- A simple linking model for developers to reason about.
- The ability to to override autolinking from the linker command line.
- Source code compatibility, where possible, with "comment lib" pragmas in other
  environments (MSVC in particular).

Dependent library support is implemented differently for ELF platforms than on
the other platforms. Primarily this difference is that on ELF we pass the
dependent library specifiers directly to the linker without manipulating them.
This is in contrast to other platforms where they are mapped to a specific
linker option by the compiler. This difference is a result of the greater
variety of ELF linkers and the fact that ELF linkers tend to handle libraries in
a more complicated fashion than on other platforms. This forces us to defer
handling the specifiers to the linker.

In order to achieve a level of source code compatibility with other platforms
we have restricted this feature to work with libraries that meet the following
"reasonable" requirements:

1. There are no competing defined symbols in a given set of libraries, or
   if they exist, the program owner doesn't care which is linked to their
   program.
2. There may be circular dependencies between libraries.

The binary representation is a mergeable string section (SHF_MERGE,
SHF_STRINGS), called .deplibs, with custom type SHT_LLVM_DEPENDENT_LIBRARIES
(0x6fff4c04). The compiler forms this section by concatenating the arguments of
the "comment lib" pragmas and --dependent-library options in the order they are
encountered. Partial (-r, -Ur) links are handled by concatenating .deplibs
sections with the normal mergeable string section rules. As an example, #pragma
comment(lib, "foo") would result in:

.section ".deplibs","MS",@llvm_dependent_libraries,1
         .asciz "foo"

For LTO, equivalent information to the contents of a the .deplibs section can be
retrieved by the LLD for bitcode input files.

LLD processes the dependent library specifiers in the following way:

1. Dependent libraries which are found from the specifiers in .deplibs sections
   of relocatable object files are added when the linker decides to include that
   file (which could itself be in a library) in the link. Dependent libraries
   behave as if they were appended to the command line after all other options. As
   a consequence the set of dependent libraries are searched last to resolve
   symbols.
2. It is an error if a file cannot be found for a given specifier.
3. Any command line options in effect at the end of the command line parsing apply
   to the dependent libraries, e.g. --whole-archive.
4. The linker tries to add a library or relocatable object file from each of the
   strings in a .deplibs section by; first, handling the string as if it was
   specified on the command line; second, by looking for the string in each of the
   library search paths in turn; third, by looking for a lib<string>.a or
   lib<string>.so (depending on the current mode of the linker) in each of the
   library search paths.
5. A new command line option --no-dependent-libraries tells LLD to ignore the
   dependent libraries.

Rationale for the above points:

1. Adding the dependent libraries last makes the process simple to understand
   from a developers perspective. All linkers are able to implement this scheme.
2. Error-ing for libraries that are not found seems like better behavior than
   failing the link during symbol resolution.
3. It seems useful for the user to be able to apply command line options which
   will affect all of the dependent libraries. There is a potential problem of
   surprise for developers, who might not realize that these options would apply
   to these "invisible" input files; however, despite the potential for surprise,
   this is easy for developers to reason about and gives developers the control
   that they may require.
4. This algorithm takes into account all of the different ways that ELF linkers
   find input files. The different search methods are tried by the linker in most
   obvious to least obvious order.
5. I considered adding finer grained control over which dependent libraries were
   ignored (e.g. MSVC has /nodefaultlib:<library>); however, I concluded that this
   is not necessary: if finer control is required developers can fall back to using
   the command line directly.

RFC thread: http://lists.llvm.org/pipermail/llvm-dev/2019-March/131004.html.

Differential Revision: https://reviews.llvm.org/D60274

llvm-svn: 360984
2019-05-17 03:44:15 +00:00
Anders Waldenborg 4732d3abdf [llvm-c] Make LLVMGetStringErrorTypeId a proper prototype
In C a function declaration with an empty argument list isn't a real
prototype, it will allow calling the function with any number of
arguments. It will also cause warnings when used in C code compiled with
'-Wstrict-prototypes'

Reviewed By: whitequark
Differential Revision: https://reviews.llvm.org/D61568

llvm-svn: 360012
2019-05-06 06:42:06 +00:00
Robert Widmann 09c5b883cb [LLVM-C] Deprecate the LLVMValueRef-returning metadata creation functions
Summary: There is still some value in using these functions while the remaining LLVMValueRef-based accessors are still around, but LLVMMDNodeInContext in particular has some wonky semantics that make it worth replacing outright.

Reviewers: whitequark, deadalnix

Reviewed By: whitequark

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60524

llvm-svn: 359114
2019-04-24 17:05:08 +00:00
Robert Widmann ff8febcb6d [LLVM-C] Add accessors to the default floating-point metadata node
Summary: Add a getter and setter pair for floating-point accuracy metadata.

Reviewers: whitequark, deadalnix

Reviewed By: whitequark

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60527

llvm-svn: 358883
2019-04-22 13:13:22 +00:00