Add support for the GNU C style __attribute__((error(""))) and
__attribute__((warning(""))). These attributes are meant to be put on
declarations of functions whom should not be called.
They are frequently used to provide compile time diagnostics similar to
_Static_assert, but which may rely on non-ICE conditions (ie. relying on
compiler optimizations). This is also similar to diagnose_if function
attribute, but can diagnose after optimizations have been run.
While users may instead simply call undefined functions in such cases to
get a linkage failure from the linker, these provide a much more
ergonomic and actionable diagnostic to users and do so at compile time
rather than at link time. Users instead may be able use inline asm .err
directives.
These are used throughout the Linux kernel in its implementation of
BUILD_BUG and BUILD_BUG_ON macros. These macros generally cannot be
converted to use _Static_assert because many of the parameters are not
ICEs. The Linux kernel still needs to be modified to make use of these
when building with Clang; I have a patch that does so I will send once
this feature is landed.
To do so, we create a new IR level Function attribute, "dontcall" (both
error and warning boil down to one IR Fn Attr). Then, similar to calls
to inline asm, we attach a !srcloc Metadata node to call sites of such
attributed callees.
The backend diagnoses these during instruction selection, while we still
know that a call is a call (vs say a JMP that's a tail call) in an arch
agnostic manner.
The frontend then reconstructs the SourceLocation from that Metadata,
and determines whether to emit an error or warning based on the callee's
attribute.
Link: https://bugs.llvm.org/show_bug.cgi?id=16428
Link: https://github.com/ClangBuiltLinux/linux/issues/1173
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D106030
Clang diagnostics refer to identifier names in quotes.
This patch makes inline remarks conform to the convention.
New behavior:
```
% clang -O2 -Rpass=inline -Rpass-missed=inline -S a.c
a.c:4:25: remark: 'foo' inlined into 'bar' with (cost=-30, threshold=337) at callsite bar:0:25; [-Rpass=inline]
int bar(int a) { return foo(a); }
^
```
Reviewed By: hoy
Differential Revision: https://reviews.llvm.org/D107791
We don't allowing inlining for functions with blockaddress with uses other than strictly callbr. This is because if the blockaddress escapes the function via a global variable, inlining may lead to an invalid cross-function reference.
We check against such cases during inlining, however the check can fail for ThinLTO post-link because CFG simplification can incorrectly removes blocks based on wrong block reachability.
When we import a function with blockaddress taken in a global variable but without importing that variable, we won't go through value mapping to reflect the real address-taken-ness of the cloned blocks. For the imported clone, this leads to blocks reachable from indirect branch through global variable being incorrectly treated as unreachable and removed by SimplifyCFG.
Since inlining for such cases shouldn't be allowed in the first place, I'm marking them as ineligible for importing during pre-link to save the problem of missing address-taken-ness of imported clone as well as bad DCE and inlining.
Differential Revision: https://reviews.llvm.org/D106930
Create an internal alias with the original name for static functions
that are renamed in promoteInternals to avoid breaking inline
assembly references to them. This version uses module inline assembly
to avoid issues with LowerTypeTestsModule.
Relands commmit 8e3b5cb39e with arch
specific tests fixed.
Link: https://github.com/ClangBuiltLinux/linux/issues/1354
Reviewed By: nickdesaulniers, pcc
Differential Revision: https://reviews.llvm.org/D104058
Create an internal alias with the original name for static functions
that are renamed in promoteInternals to avoid breaking inline
assembly references to them. This version uses module inline assembly
to avoid issues with LowerTypeTestsModule.
Link: https://github.com/ClangBuiltLinux/linux/issues/1354
Reviewed By: nickdesaulniers, pcc
Differential Revision: https://reviews.llvm.org/D104058
Previously we reliedy on pseudo probe descriptors to look up precomputed GUID during probe emission for inlined probes. Since we are moving to always using unique linkage names, GUID for functions can be computed in place from dwarf names. This eliminates the need of importing pseudo probe descs in thinlto, since those descs should be emitted by the original modules.
This significantly reduces thinlto memory footprint in some extreme case where the number of imported modules for a single module is massive.
Test Plan:
Reviewed By: wenlei
Differential Revision: https://reviews.llvm.org/D105248
D74751 added `ClearDSOLocalOnDeclarations` and dropped dso_local for
isDeclarationForLinker `GlobalValue`s. It missed a case for imported
declarations (`doImportAsDefinition` is false while `isPerformingImport` is
true). This can lead to a linker error for a default visibility symbol in
`ld.lld -shared`.
When `ClearDSOLocalOnDeclarations` is true, we check
`isPerformingImport() && !doImportAsDefinition(&GV)` along with
`GV.isDeclarationForLinker()`. The new condition checks an imported declaration.
This patch fixes a `LLVMPolly.so` link error using a trunk clang -DLLVM_ENABLE_LTO=Thin.
Reviewed By: tejohnson
Differential Revision: https://reviews.llvm.org/D104986
This patch adds initial support for using the new pass manager when
doing ThinLTO via libLTO.
Reviewed By: steven_wu
Differential Revision: https://reviews.llvm.org/D102627
The order of global variables is generated in the order of recursively materializing variables if the global variable has the attribute of hasLocalLinkage or hasLinkOnceLinkage during the module merging. In practice, it is often the exact reverse of source order. This new order may cause performance regression.
The change is to preserve the original lexical order for global variables.
Reviewed By: jdoerfert, dexonsmith
Differential Revision: https://reviews.llvm.org/D94202
Being lazy with printing the banner seems hard to reason with, we should print it
unconditionally first (it could also lead to duplicate banners if we
have multiple functions in -filter-print-funcs).
The printIR() functions were doing too many things. I separated out the
call from PrintPassInstrumentation since we were essentially doing two
completely separate things in printIR() from different callers.
There were multiple ways to generate the name of some IR. That's all
been moved to getIRName(). The printing of the IR name was also
inconsistent, now it's always "IR Dump on $foo" where "$foo" is the
name. For a function, it's the function name. For a loop, it's what's
printed by Loop::print(), which is more detailed. For an SCC, it's the
list of functions in parentheses. For a module it's "[module]", to
differentiate between a possible SCC with a function called "module".
To preserve D74814, we have to check if we're going to print anything at
all first. This is unfortunate, but I would consider this a special
case that shouldn't be handled in the core logic.
Reviewed By: jamieschmeiser
Differential Revision: https://reviews.llvm.org/D100231
Using $ breaks demangling of the symbols. For example,
$ c++filt _Z3foov\$123
_Z3foov$123
This causes problems for developers who would like to see nice stack traces
etc., but also for automatic crash tracking systems which try to organize
crashes based on the stack traces.
Instead, use the period as suffix separator, since Itanium demanglers normally
ignore such suffixes:
$ c++filt _Z3foov.123
foo() [clone .123]
This is already done in some places; try to do it everywhere.
Differential revision: https://reviews.llvm.org/D97484
We encountered an issue where LTO running on IR that used the DSOLocalEquivalent
constant would result in bad codegen. The underlying issue was ValueMapper wasn't
properly handling DSOLocalEquivalent, so this just adds the machinery for handling
it. This code path is triggered by a fix to DSOLocalEquivalent::handleOperandChangeImpl
where DSOLocalEquivalent could potentially not have the same type as its underlying GV.
This updates DSOLocalEquivalent::handleOperandChangeImpl to change the type if
the GV type changes and handles this constant in ValueMapper.
Differential Revision: https://reviews.llvm.org/D97978
IR symbol table does not parse inline asm. A symbol only referenced by inline
asm is not in the IR symbol table, so LTO does not know that the definition (in
another translation unit) is referenced and may internalize it, even if that
definition has `__attribute__((used))` (which lowers to `llvm.compiler.used` on
ELF targets since D97446).
```
// cabac.c
__attribute__((used)) const uint8_t ff_h264_cabac_tables[...] = {...};
// h264_cabac.c
asm("lea ff_h264_cabac_tables(%rip), %0" : ...);
```
`__attribute__((used))` is the recommended way to tell the compiler there may
be inline asm references, so the usage is perfectly fine. This patch
conservatively sets the `FB_used` bit on `llvm.compiler.used` symbols to work
around the IR symbol table limitation. Note: before D97446, Clang never emitted
symbols in the `llvm.compiler.used` list, so this change does not punish any
Clang emitted global object.
Without the patch, `ff_h264_cabac_tables` may be assigned to a non-external
partition and get internalized. Then we will get a linker error because the
`cabac.c` definition is not exposed.
Differential Revision: https://reviews.llvm.org/D97755
The fix in 3c4c205060 caused an assert in
the case of a pure virtual base class. In that case, the vTableFuncs
list on the summary will be empty, so we were hitting the new assert
that the linkage type was not available_externally.
In the case of pure virtual, we do not want to assert, and additionally
need to set VS so that we don't treat it conservatively and quit the
analysis of the type id early.
This exposed a pre-existing issue where we were not updating the vcall
visibility on pure virtual functions when whole program visibility was
specified. We were skipping updating the visibility on any global vars
that didn't have any vTableFuncs, which meant all pure virtual were not
updated, and the later analysis would block any devirtualization of
calls that had a type id used on those pure virtual vtables (see the
handling in the other code modified in this patch). Simply remove that
check. It will mean that we may update the vcall visibility on global
vars that aren't vtables, but that setting is ignored for any global
vars that didn't have type metadata anyway.
Added a new test case that asserted without removing the assert, and
that requires the other fixes in this patch (updateVCallVisibilityInIndex
and not skipping all vtables without virtual funcs) to get a successful
devirtualization with index-only WPD. I added cases to test hybrid and
regular LTO for completeness, although those already worked without the
fixes here.
With this final fix, a clang multistage bootstrap with WPD builds and
runs all tests successfully.
Differential Revision: https://reviews.llvm.org/D97126
Currently, if there is a module that contains a strong definition of
a global variable and a module that has both a weak definition for
the same global and a reference to it, it may result in an undefined symbol error
while linking with ThinLTO.
It happens because:
* the strong definition become internal because it is read-only and can be imported;
* the weak definition gets replaced by a declaration because it's non-prevailing;
* the strong definition failed to be imported because the destination module
already contains another definition of the global yet this def is non-prevailing.
The patch adds a check to computeImportForReferencedGlobals() that allows
considering a global variable for being imported even if the module contains
a definition of it in the case this def has an interposable linkage type.
Note that currently the check is based only on the linkage type
(and this seems to be enough at the moment), but it might be worth to account
the information whether the def is prevailing or not.
Reviewed By: tejohnson
Differential Revision: https://reviews.llvm.org/D95943
This adds an internal option -wholeprogramdevirt-check which if enabled
will guard each devirtualization with a runtime check against the
expected target, and an invocation of a debug trap if the check fails.
This is useful for debugging WPD failures involving undefined behavior
(e.g. casting to another class type not in the inheritance chain).
Differential Revision: https://reviews.llvm.org/D95969
Imported functions and variable get the visibility from the module supplying the
definition. However, non-imported definitions do not get the visibility from
(ELF) the most constraining visibility among all modules (Mach-O) the visibility
of the prevailing definition.
This patch
* adds visibility bits to GlobalValueSummary::GVFlags
* computes the result visibility and propagates it to all definitions
Protected/hidden can imply dso_local which can enable some optimizations (this
is stronger than GVFlags::DSOLocal because the implied dso_local can be
leveraged for ELF -shared while default visibility dso_local has to be cleared
for ELF -shared).
Note: we don't have summaries for declarations, so for ELF if a declaration has
the most constraining visibility, the result visibility may not be that one.
Differential Revision: https://reviews.llvm.org/D92900
It's common for code that manipulates the stack via inline assembly or
that has to set up its own stack canary (such as the Linux kernel) would
like to avoid stack protectors in certain functions. In this case, we've
been bitten by numerous bugs where a callee with a stack protector is
inlined into an attribute((no_stack_protector)) caller, which
generally breaks the caller's assumptions about not having a stack
protector. LTO exacerbates the issue.
While developers can avoid this by putting all no_stack_protector
functions in one translation unit together and compiling those with
-fno-stack-protector, it's generally not very ergonomic or as
ergonomic as a function attribute, and still doesn't work for LTO. See also:
https://lore.kernel.org/linux-pm/20200915172658.1432732-1-rkir@google.com/https://lore.kernel.org/lkml/20200918201436.2932360-30-samitolvanen@google.com/T/#u
SSP attributes can be ordered by strength. Weakest to strongest, they
are: ssp, sspstrong, sspreq. Callees with differing SSP attributes may be
inlined into each other, and the strongest attribute will be applied to the
caller. (No change)
After this change:
* A callee with no SSP attributes will no longer be inlined into a
caller with SSP attributes.
* The reverse is also true: a callee with an SSP attribute will not be
inlined into a caller with no SSP attributes.
* The alwaysinline attribute overrides these rules.
Functions that get synthesized by the compiler may not get inlined as a
result if they are not created with the same stack protector function
attribute as their callers.
Alternative approach to https://reviews.llvm.org/D87956.
Fixes pr/47479.
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed By: rnk, MaskRay
Differential Revision: https://reviews.llvm.org/D91816
This restores commit ab1b4810b5 which was
reverted in 01b9deba76, with a fix for the
issue it caused. We should use a temporary BitstreamCursor when
loading the global decl attachment records so that the abbrev ids held
in the lazy loading IndexCursor are not clobbered. Enhanced the test so
that the issue is exposed there.
Original description:
When performing ThinLTO importing, the metadata loader attempts to lazy
load, by building an index. However, module level global decl attachment
metadata was being parsed early while building the index, since the
associated (module level) global values aren't materialized on demand.
This results in the creation of forward reference temporary metadatas,
which are expensive.
Normally, these module level global values don't have much attached
metadata. However, in the case of -fwhole-program-vtables (e.g. for
whole program devirtualization), the vtables may have many attached type
metadatas. This was resulting in very slow performance when performing
ThinLTO importing with the default lazy loading.
This patch restructures the handling of these global decl attachment
records, delaying their parsing until after the lazy loading index has
been built. Then the parser can use the interface that loads from the
index, which resolves forward references immediately instead of creating
expensive temporaries.
For one ThinLTO backend that imports from modules containing huge
numbers of vtables and associated types, I measured the following
compile times for the metadata materialization during function
importing, rounded to nearest second:
No -fwhole-program-vtables:
Lazy loading on (head): 1s
Lazy loading off (head): 3s
Lazy loading on (patch): 1s
With -fwhole-program-vtables:
Lazy loading on (head): 440s
Lazy loading off (head): 4s
Lazy loading on (patch): 2s
Differential Revision: https://reviews.llvm.org/D87970
This reverts commit ab1b4810b5.
It caused an issue in llvm::lto::thinBackend for a -fsanitize=cfi build.
```
AbbrevNo is 0 => "Invalid abbrev number"
0 llvm::BitstreamCursor::getAbbrev (this=0x9db4c8, AbbrevID=4) at llvm/include/llvm/Bitstream/BitstreamReader.h:528
1 0x00007f5f777a6eb4 in llvm::BitstreamCursor::readRecord (this=0x9db4c8, AbbrevID=4, Vals=llvm::SmallVector of Size 0, Capacity 64, Blob=0x7ffcd0e26558) at
usr/local/google/home/maskray/llvm/llvm/lib/Bitstream/Reader/BitstreamReader.cpp:228
2 0x00007f5f796bf633 in llvm::MetadataLoader::MetadataLoaderImpl::lazyLoadOneMetadata (this=0x9db3a0, ID=188, Placeholders=...) at /usr/local/google/home/mas
ray/llvm/llvm/lib/Bitcode/Reader/MetadataLoader.cpp:1091
3 0x00007f5f796c2527 in llvm::MetadataLoader::MetadataLoaderImpl::getMetadataFwdRefOrLoad (this=0x9db3a0, ID=188) at llvm
lib/Bitcode/Reader/MetadataLoader.cpp:668
4 0x00007f5f796bfff3 in llvm::MetadataLoader::getMetadataFwdRefOrLoad (this=0xd31580, Idx=188) at llvm/lib/Bitcode/Reader
MetadataLoader.cpp:2290
5 0x00007f5f79638265 in (anonymous namespace)::BitcodeReader::parseFunctionBody (this=0xd312e0, F=0x9de758) at llvm/lib/B
tcode/Reader/BitcodeReader.cpp:3938
6 0x00007f5f79635d32 in (anonymous namespace)::BitcodeReader::materialize (this=0xd312e0, GV=0x9de758) at llvm/lib/Bitcod
/Reader/BitcodeReader.cpp:5408
7 0x00007f5f7f8dbe3e in llvm::Module::materialize (this=0x9b92c0, GV=0x9de758) at llvm/lib/IR/Module.cpp:442
8 0x00007f5f7f7f8fbe in llvm::GlobalValue::materialize (this=0x9de758) at llvm/lib/IR/Globals.cpp:50
9 0x00007f5f83b9b5f5 in llvm::FunctionImporter::importFunctions (this=0x7ffcd0e2a730, DestModule=..., ImportList=...) at
llvm/lib/Transforms/IPO/FunctionImport.cpp:1182
```
When performing ThinLTO importing, the metadata loader attempts to lazy
load, by building an index. However, module level global decl attachment
metadata was being parsed early while building the index, since the
associated (module level) global values aren't materialized on demand.
This results in the creation of forward reference temporary metadatas,
which are expensive.
Normally, these module level global values don't have much attached
metadata. However, in the case of -fwhole-program-vtables (e.g. for
whole program devirtualization), the vtables may have many attached type
metadatas. This was resulting in very slow performance when performing
ThinLTO importing with the default lazy loading.
This patch restructures the handling of these global decl attachment
records, delaying their parsing until after the lazy loading index has
been built. Then the parser can use the interface that loads from the
index, which resolves forward references immediately instead of creating
expensive temporaries.
For one ThinLTO backend that imports from modules containing huge
numbers of vtables and associated types, I measured the following
compile times for the metadata materialization during function
importing, rounded to nearest second:
No -fwhole-program-vtables:
Lazy loading on (head): 1s
Lazy loading off (head): 3s
Lazy loading on (patch): 1s
With -fwhole-program-vtables:
Lazy loading on (head): 440s
Lazy loading off (head): 4s
Lazy loading on (patch): 2s
Differential Revision: https://reviews.llvm.org/D87970
For ThinLTO importing we don't need to import all the fields of the DICompileUnit, such as enums, macros, retained types lists. The importation of those fields were previously disabled by setting their value map entries to nullptr. Unfortunately a metadata node can be shared by multiple metadata operands. Setting the map entry to nullptr might result in not importing other metadata unexpectedly. The issue is fixed by explicitly setting the original DICompileUnit fields (still a copy of the source module metadata) to null.
Reviewed By: wenlei, dblaikie
Differential Revision: https://reviews.llvm.org/D86675
Instead of computing GUID based on some assumption about symbol mangling
rule from IRName to symbol name, lookup the IRName from all the symtabs
from all the input files to see if there are any matching symbols entry
provides the IRName for GUID computation.
rdar://65853754
Reviewed By: mehdi_amini
Differential Revision: https://reviews.llvm.org/D84803
The test output files whose atime is altered in the test were getting
accessed by Spotlight indexing on macOS, causing them to get an updated
atime and leading to the test not behaving as expected.
Reviewed By: jhenderson, steven_wu
Differential Revision: https://reviews.llvm.org/D84700
This restores commit 80d0a137a5, and the
follow on fix in 873c0d0786, with a new
fix for test failures after a 2-stage clang bootstrap, and a more robust
fix for the Chromium build failure that an earlier version partially
fixed. See also discussion on D75201.
Reviewers: evgeny777
Subscribers: mehdi_amini, Prazek, hiraditya, steven_wu, dexonsmith, arphaman, davidxl, cfe-commits, llvm-commits
Tags: #clang, #llvm
Differential Revision: https://reviews.llvm.org/D73242
Summary:
The actual transform i was going after was:
https://rise4fun.com/Alive/Tp9H
```
Name: zz
Pre: isPowerOf2(C0) && isPowerOf2(C1) && C1 == C0
%t0 = and i8 %x, C0
%r = icmp eq i8 %t0, C1
=>
%t = icmp eq i8 %t0, 0
%r = xor i1 %t, -1
Name: zz
Pre: isPowerOf2(C0)
%t0 = and i8 %x, C0
%r = icmp ne i8 %t0, 0
=>
%t = icmp eq i8 %t0, 0
%r = xor i1 %t, -1
```
but as it can be seen from the current tests, we already canonicalize most of it,
and we are only missing handling multi-use non-canonical icmp predicates.
If we have both `!=0` and `==0`, even though we can CSE them,
we end up being stuck with them. We should canonicalize to the `==0`.
I believe this is one of the cleanup steps i'll need after `-scalarizer`
if i end up proceeding with my WIP alloca promotion helper pass.
Reviewers: spatel, jdoerfert, nikic
Reviewed By: nikic
Subscribers: zzheng, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D83139
Summary:
In D52514 I had fixed a bug with WPD after indirect call promotion, by
checking that a type test being analyzed dominates potential virtual
calls. With that fix I included a small effiency enhancement to avoid
processing a devirt candidate multiple times (when there are multiple
type tests). This latter change wasn't in response to any measured
efficiency issues, it was merely theoretical. Unfortuantely, it turns
out to limit optimization opportunities after inlining.
Specifically, consider code that looks like:
class A {
virtual void foo();
};
class B : public A {
void foo();
}
void callee(A *a) {
a->foo(); // Call 1
}
void caller(B *b) {
b->foo(); // Call 2
callee(b);
}
After inlining callee into caller, because of the existing call to
b->foo() in caller there will be 2 type tests in caller for the vtable
pointer of b: the original type test against B from Call 2, and the
inlined type test against A from Call 1. If the code was compiled with
-fstrict-vtable-pointers, then after optimization WPD will see that
both type tests are associated with the inlined virtual Call 1.
With my earlier change to only process a virtual call against one type
test, we may only consider virtual Call 1 against the base class A type
test, which can't be devirtualized. With my change here to remove this
restriction, it also gets considered for the type test against the
derived class B type test, where it can be devirtualized.
Note that if caller didn't include it's own earlier virtual call
b->foo() we will not be able to devirtualize after inlining callee even
after this fix, since there would not be a type test against B in the
IR. As a future enhancement we can consider inserting type tests at call
sites that pass pointers to classes with virtual calls, to enable
context-sensitive devirtualization after inlining.
Reviewers: pcc, vitalybuka, evgeny777
Subscribers: Prazek, hiraditya, steven_wu, dexonsmith, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D79235
Summary:
Count the per-module number of basic blocks when the module summary is computed
and sum them up during Thin LTO indexing.
This is used to estimate the working set size under the partial sample PGO.
This is split off of D79831.
Reviewers: davidxl, espindola
Subscribers: emaste, inglorion, hiraditya, MaskRay, steven_wu, dexonsmith, arphaman, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D80403
Summary:
That unless the user requested an output object (--lto-obj-path), the an
unused empty combined module is not emitted.
This changed is helpful for some target (ex. RISCV-V) which encoded the
ABI info in IR module flags (target-abi). Empty unused module has no ABI
info so the linker would get the linking error during merging
incompatible ABIs.
Reviewers: tejohnson, espindola, MaskRay
Subscribers: emaste, inglorion, arichardson, hiraditya, simoncook, MaskRay, steven_wu, dexonsmith, PkmX, dang, lenary, s.egerton, luismarques, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78988
dso_local leads to direct access even if the definition is not within this compilation unit (it is
still in the same linkage unit). On ELF, such a relocation (e.g. R_X86_64_PC32) referencing a
STB_GLOBAL STV_DEFAULT object can cause a linker error in a -shared link.
If the linkage is changed to available_externally, the dso_local flag should be dropped, so that no
direct access will be generated.
The current behavior is benign, because -fpic does not assume dso_local
(clang/lib/CodeGen/CodeGenModule.cpp:shouldAssumeDSOLocal).
If we do that for -fno-semantic-interposition (D73865), there will be an
R_X86_64_PC32 linker error without this patch.
Reviewed By: tejohnson
Differential Revision: https://reviews.llvm.org/D74751
Follow-up for D74433
What the function returns are almost standard BFD names, except that "ELF" is
in uppercase instead of lowercase.
This patch changes "ELF" to "elf" and changes ARM/AArch64 to use their BFD names.
MIPS and PPC64 have endianness differences as well, but this patch does not intend to address them.
Advantages:
* llvm-objdump: the "file format " line matches GNU objdump on ARM/AArch64 objects
* "file format " line can be extracted and fed into llvm-objcopy -O literally.
(https://github.com/ClangBuiltLinux/linux/issues/779 has such a use case)
Affected tools: llvm-readobj, llvm-objdump, llvm-dwarfdump, MCJIT (internal implementation detail, not exposed)
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D76046
This reverts commit 80d0a137a5, and the
follow on fix in 873c0d0786. It is
causing test failures after a multi-stage clang bootstrap. See
discussion on D73242 and D75201.
Summary:
Fixes an issue that cropped up after the changes in D73242 to delay
the lowering of type tests. LTT couldn't handle any type tests with
non-string type id (which happens for local vtables, which we try to
promote during the compile step but cannot always when there are no
exported symbols).
We can simply treat the same as having an Unknown resolution, which
delays their lowering, still allowing such type tests to be used in
subsequent optimization (e.g. planned usage during ICP). The final
lowering which simply removes these handles them fine.
Beefed up an existing ThinLTO test for such unpromoted type ids so that
the internal vtable isn't removed before lower type tests, which hides
the problem.
Reviewers: evgeny777, pcc
Subscribers: inglorion, hiraditya, steven_wu, dexonsmith, aganea, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D75201
Nick Desaulniers