Currently, WebAssembly/WASI target does not provide direct support for
code coverage.
This patch set fixes several issues to unlock the feature. The main
changes are:
1. Port `compiler-rt/lib/profile` to WebAssembly/WASI.
2. Adjust profile metadata sections for Wasm object file format.
- [CodeGen] Emit `__llvm_covmap` and `__llvm_covfun` as custom sections
instead of data segments.
- [lld] Align the interval space of custom sections at link time.
- [llvm-cov] Copy misaligned custom section data if the start address is
not aligned.
- [llvm-cov] Read `__llvm_prf_names` from data segments
3. [clang] Link with profile runtime libraries if requested
See each commit message for more details and rationale.
This is part of the effort to add code coverage support in Wasm target
of Swift toolchain.
MachineFunction's probably should not include a backreference to
the owning MachineModuleInfo. Most of these references were used
just to query the MCContext, which MachineFunction already directly
stores. Other contexts are using it to query the LLVMContext, which
can already be accessed through the IR function reference.
Follow-up to 05ba5c0648ae5e80d5afce270495bf3b1eef9af4. uint32_t is
preferred over const MCExpr * in the section stack uses because it
should only be evaluated once. Change the paramter type to match.
There are only three actual uses of the section kind in MCSection:
isText(), XCOFF, and WebAssembly. Store isText() in the MCSection, and
store other info in the actual section variants where required.
ELF and COFF flags also encode all relevant information, so for these
two section variants, remove the SectionKind parameter entirely.
This allows to remove the string switch (which is unnecessary and
inaccurate) from createELFSectionImpl. This was introduced in
[D133456](https://reviews.llvm.org/D133456), but apparently, it was
never hit for non-writable sections anyway and the resulting kind was
never used.
Gas uses encoding DW_EH_PE_absptr for PIC, and gnu ld converts it to
DW_EH_PE_sdata4|DW_EH_PE_pcrel.
LLD doesn't have this workarounding, thus complains
```
relocation R_MIPS_32 cannot be used against local symbol; recompile with -fPIC
relocation R_MIPS_64 cannot be used against local symbol; recompile with -fPIC
```
So, let's generates asm/obj files with `DW_EH_PE_sdata4|DW_EH_PE_pcrel`
encoding. In fact, GNU ld supports such OBJs well.
For N64, maybe we should use sdata8, while GNU ld doesn't support it
well, and in fact sdata4 is enough now. So we just ignore the `Large`
for `MCObjectFileInfo::initELFMCObjectFileInfo`. Maybe we should switch
back to sdata8 once GNU LD supports it well.
Fixes: #58377.
I'm planning to remove StringRef::equals in favor of
StringRef::operator==.
- StringRef::operator==/!= outnumber StringRef::equals by a factor of
53 under llvm/ in terms of their usage.
- The elimination of StringRef::equals brings StringRef closer to
std::string_view, which has operator== but not equals.
- S == "foo" is more readable than S.equals("foo"), especially for
!Long.Expression.equals("str") vs Long.Expression != "str".
When set, the compiler will use separate unique sections for global
symbols in named special sections (e.g. symbols that are annotated with
__attribute__((section(...)))). Doing so enables linker GC to collect
unused symbols without having to use a different section per-symbol.
D33412/D33413 introduced this to support a clang pragma to set section
names for a symbol depending on if it would be placed in
bss/data/rodata/text, which may not be known until the backend. However,
for text we know that only functions will go there, so just directly set
the section in clang instead of going through a completely separate
attribute.
Autoupgrade the "implicit-section-name" attribute to directly setting
the section on a Fuction.
Exploit the per global code model attribute on AIX. On AIX we need to
update both the code sequence used to access the global (either 1 or 2
instructions for small and large code model respectively) and the
storage mapping class that we emit the toc entry.
---------
Co-authored-by: Amy Kwan <akwan0907@gmail.com>
In WebAssembly, we have `WASM_SYMBOL_NO_STRIP` symbol flag to mark the
referenced content as retained. However, the flag is not enough to
express retained data that is not referenced by any symbol. This patch
adds a new segment flag`WASM_SEG_FLAG_RETAIN` to support "private"
linkage data that is retained by llvm.used.
This kind of data that is not referenced but must be retained is usually
used with encapsulation symbols (__start/__stop). Swift runtime uses
this technique and depends on the fact "all metadata sections in live
objects are retained", which was not guaranteed with `--gc-sections`
before this patch.
This is a revised version of https://reviews.llvm.org/D126950 (has been
reverted) based on @MaskRay's comments
This patch adds support for common and local symbols in the TOC for AIX.
Note that we need to update isVirtualSection so as a common symbol in
TOC will have the symbol type XTY_CM and will be initialized when placed
in the TOC so sections with this type are no longer virtual.
---------
Co-authored-by: Zaara Syeda <syzaara@ca.ibm.com>
For non-GlobalValue references, the small and medium code models can use
32 bit constants.
For GlobalValue references, use TargetMachine::isLargeGlobalObject().
Look through aliases for determining if a GlobalValue is small or large.
Even the large code model can reference small objects with 32 bit
constants as long as we're in no-pic mode, or if the reference is offset
from the GOT.
Original commit broke the build...
First reland broke large PIC builds referencing small data since it was using GOTOFF as a 32-bit constant.
## Motivation
Since we don't need the metadata sections at runtime, we can somehow
offload them from memory at runtime. Initially, I explored [debug info
correlation](https://discourse.llvm.org/t/instrprofiling-lightweight-instrumentation/59113),
which is used for PGO with value profiling disabled. However, it
currently only works with DWARF and it's be hard to add such artificial
debug info for every function in to CodeView which is used on Windows.
So, offloading profile metadata sections at runtime seems to be a
platform independent option.
## Design
The idea is to use new section names for profile name and data sections
and mark them as metadata sections. Under this mode, the new sections
are non-SHF_ALLOC in ELF. So, they are not loaded into memory at runtime
and can be stripped away as a post-linking step. After the process
exits, the generated raw profiles will contains only headers + counters.
llvm-profdata can be used correlate raw profiles with the unstripped
binary to generate indexed profile.
## Data
For chromium base_unittests with code coverage on linux, the binary size
overhead due to instrumentation reduced from 64M to 38.8M (39.4%) and
the raw profile files size reduce from 128M to 68M (46.9%)
```
$ bloaty out/cov/base_unittests.stripped -- out/no-cov/base_unittests.stripped
FILE SIZE VM SIZE
-------------- --------------
+121% +30.4Mi +121% +30.4Mi .text
[NEW] +14.6Mi [NEW] +14.6Mi __llvm_prf_data
[NEW] +10.6Mi [NEW] +10.6Mi __llvm_prf_names
[NEW] +5.86Mi [NEW] +5.86Mi __llvm_prf_cnts
+95% +1.75Mi +95% +1.75Mi .eh_frame
+108% +400Ki +108% +400Ki .eh_frame_hdr
+9.5% +211Ki +9.5% +211Ki .rela.dyn
+9.2% +95.0Ki +9.2% +95.0Ki .data.rel.ro
+5.0% +87.3Ki +5.0% +87.3Ki .rodata
[ = ] 0 +13% +47.0Ki .bss
+40% +1.78Ki +40% +1.78Ki .got
+12% +1.49Ki +12% +1.49Ki .gcc_except_table
[ = ] 0 +65% +1.23Ki .relro_padding
+62% +1.20Ki [ = ] 0 [Unmapped]
+13% +448 +19% +448 .init_array
+8.8% +192 [ = ] 0 [ELF Section Headers]
+0.0% +136 +0.0% +80 [7 Others]
+0.1% +96 +0.1% +96 .dynsym
+1.2% +96 +1.2% +96 .rela.plt
+1.5% +80 +1.2% +64 .plt
[ = ] 0 -99.2% -3.68Ki [LOAD #5 [RW]]
+195% +64.0Mi +194% +64.0Mi TOTAL
$ bloaty out/cov-cor/base_unittests.stripped -- out/no-cov/base_unittests.stripped
FILE SIZE VM SIZE
-------------- --------------
+121% +30.4Mi +121% +30.4Mi .text
[NEW] +5.86Mi [NEW] +5.86Mi __llvm_prf_cnts
+95% +1.75Mi +95% +1.75Mi .eh_frame
+108% +400Ki +108% +400Ki .eh_frame_hdr
+9.5% +211Ki +9.5% +211Ki .rela.dyn
+9.2% +95.0Ki +9.2% +95.0Ki .data.rel.ro
+5.0% +87.3Ki +5.0% +87.3Ki .rodata
[ = ] 0 +13% +47.0Ki .bss
+40% +1.78Ki +40% +1.78Ki .got
+12% +1.49Ki +12% +1.49Ki .gcc_except_table
+13% +448 +19% +448 .init_array
+0.1% +96 +0.1% +96 .dynsym
+1.2% +96 +1.2% +96 .rela.plt
+1.2% +64 +1.2% +64 .plt
+2.9% +64 [ = ] 0 [ELF Section Headers]
+0.0% +40 +0.0% +40 .data
+1.2% +32 +1.2% +32 .got.plt
+0.0% +24 +0.0% +8 [5 Others]
[ = ] 0 -22.9% -872 [LOAD #5 [RW]]
-74.5% -1.44Ki [ = ] 0 [Unmapped]
[ = ] 0 -76.5% -1.45Ki .relro_padding
+118% +38.8Mi +117% +38.8Mi TOTAL
```
A few things to note:
1. llvm-profdata doesn't support filter raw profiles by binary id yet,
so when a raw profile doesn't belongs to the binary being digested by
llvm-profdata, merging will fail. Once this is implemented,
llvm-profdata should be able to only merge raw profiles with the same
binary id as the binary and discard the rest (with mismatched/missing
binary id). The workflow I have in mind is to have scripts invoke
llvm-profdata to get all binary ids for all raw profiles, and
selectively choose the raw pnrofiles with matching binary id and the
binary to llvm-profdata for merging.
2. Note: In COFF, currently they are still loaded into memory but not
used. I didn't do it in this patch because I noticed that `.lcovmap` and
`.lcovfunc` are loaded into memory. A separate patch will address it.
3. This should works with PGO when value profiling is disabled as debug
info correlation currently doing, though I haven't tested this yet.
For non-GlobalValue references, the small and medium code models can use
32 bit constants.
For GlobalValue references, use TargetMachine::isLargeGlobalObject().
Look through aliases for determining if a GlobalValue is small or large.
Even the large code model can reference small objects with 32 bit
constants as long as we're in no-pic mode, or if the reference is offset
from the GOT.
Original commit broke the build...
For non-GlobalValue references, the small and medium code models can use
32 bit constants.
For GlobalValue references, use TargetMachine::isLargeGlobalObject().
Look through aliases for determining if a GlobalValue is small or large.
Even the large code model can reference small objects with 32 bit
constants as long as we're in no-pic mode, or if the reference is offset
from the GOT.
This patch replaces uses of StringRef::{starts,ends}with with
StringRef::{starts,ends}_with for consistency with
std::{string,string_view}::{starts,ends}_with in C++20.
I'm planning to deprecate and eventually remove
StringRef::{starts,ends}with.
This patch renames {starts,ends}with to {starts,ends}_with for
consistency with std::{string,string_view}::{starts,ends}_with in
C++20. Since there are only a handful of occurrences, this patch
skips the deprecation phase and simply renames them.
On AIX, the __ehinfo toc-entry is never referenced directly using
instructions, therefore we can allocate them with the TE storage mapping
class to move them to the end of TOC.
So that when mixing small and large text, large text stays out of the
way of the rest of the binary.
This is useful for mixing precompiled small code model object files and
built-from-source large code model binaries so that the the text
sections don't get merged.
The reland fixes an issue where a function in the large code model would reference small data without GOTOFF.
This was incorrectly reverted in 76f78ecc789d58baa3a88b2fe2a57428f07e5362.
This reverts commit 4bf8a688956a759b7b6b8d94f42d25c13c7af130.
This commit seems to be breaking the semantics of the
ObjectFile::isSectionText method, which breaks numba/llvmlite bindings.
So that when mixing small and large text, large text stays out of the
way of the rest of the binary.
This is useful for mixing precompiled small code model object files and
built-from-source large code model binaries so that the the text
sections don't get merged.
The reland fixes an issue where a function in the large code model would reference small data without GOTOFF.
So that when mixing small and large text, large text stays out of the
way of the rest of the binary.
This is useful for mixing precompiled small code model object files and
built-from-source large code model binaries so that the the text
sections don't get merged.
This PR makes `-basic-block-sections` handle functions with custom
non-dot-text sections correctly. Cold parts of such functions must be
placed in the same section (not in `.text.split`) but with a unique id.
Currently clang's medium code model treats all data as large, putting them in a large data section and using more expensive instruction sequences to access them.
Following gcc's -mlarge-data-threshold, which allows putting data under a certain size in a normal data section as opposed to a large data section. This allows using cheaper code sequences to access some portion of data in the binary (which will be implemented in LLVM in a future patch).
And under the medium codel mode, only put data above the large data threshold into large data sections, not all data.
Reviewed By: MaskRay, rnk
Differential Revision: https://reviews.llvm.org/D149288
The current implementation generates a csect with a
".rodata.str.x.y" prefix for a MergeableCString variable definition.
However, a reference to such variable does not get the prefix in its
name because there's not enough information in the containing IR.
In particular, without seeing the initializer and absent of some other
indicators, we cannot tell that the referenced variable is a null-
terminated string.
When the AIX codegen in llvm was being developed, the prefixing was copied
from ELF without having the linker take advantage of the info.
Currently, the AIX linker does not have the capability to merge
MergeableCString variables. If such feature would ever get implemented,
the contract between the linker and compiler would have to be reconsidered.
Here's the before and after of this change:
```
@a = global i64 320255973571806, align 8
@strA = unnamed_addr constant [7 x i8] c"hello\0A\00", align 1 ;; Mergeable1ByteCString
@strB = unnamed_addr constant [8 x i8] c"Blahah\0A\00", align 1 ;; Mergeable1ByteCString
@strC = unnamed_addr constant [2 x i16] [i16 1, i16 0], align 2 ;; Mergeable2ByteCString
@strD = unnamed_addr constant [2 x i16] [i16 1, i16 1], align 2 ;; !isMergeableCString
@strE = external unnamed_addr constant [2 x i16], align 2
-fdata-sections:
.text extern .rodata.str1.1strA .text extern strA
0 SD RO 0 SD RO
.text extern .rodata.str1.1strB .text extern strB
0 SD RO 0 SD RO
.text extern .rodata.str2.2strC ===> .text extern strC
0 SD RO 0 SD RO
.text extern strD .text extern strD
0 SD RO 0 SD RO
.data extern a .data extern a
0 SD RW 0 SD RW
undef extern strE undef extern strE
0 ER UA 0 ER UA
-fno-data-sections:
.text unamex .rodata.str1.1 .text unamex .rodata
0 SD RO 0 SD RO
.text extern strA .text extern strA
0 LD RO 0 LD RO
.text extern strB .text extern strB
0 LD RO 0 LD RO
.text unamex .rodata.str2.2 ===> .text extern strC
0 SD RO 0 LD RO
.text extern strC .text extern strD
0 LD RO 0 LD RO
.text unamex .rodata .data unamex .data
0 SD RO 0 SD RW
.text extern strD .data extern a
0 LD RO 0 LD RW
.data unamex .data undef extern strE
0 SD RW 0 ER UA
.data extern a
0 LD RW
undef extern strE
0 ER UA
```
Reviewed by: David Tenty, Fangrui Song
Differential Revision: https://reviews.llvm.org/D156202
Summary: D80642 added support for emitting AvailableExternally Linkage on AIX. However, an assertion of "Trying to get csect representation of this symbol but none was set." occurred when a function is declared as available_externally. This is due to we missing to generate a csect for the function. This patch fixes it.
Reviewed By: hubert.reinterpretcast, shchenz
Differential Revision: https://reviews.llvm.org/D156213
Signed-off-by: Esme Yi <esme.yi@ibm.com>
And also set the SHF_X86_64_LARGE section flag.
gcc only uses the "l" prefix and SHF_X86_64_LARGE in the medium code model for data larger than -mlarge-data-threshold. But it seems more consistent to use it in the large code model as well in case separate parts of the binary aren't compiled with the large code model and also have a .data/.bss/.rodata section.
Reviewed By: MaskRay, tkoeppe
Differential Revision: https://reviews.llvm.org/D148836
The kernel and kext environments do not provide the `__cxa_atexit()`
function, so we can't use it for lowering global module destructors.
Unfortunately, just querying for "compiling for kernel/kext?" in the LTO
pipeline isn't possible (kernel/kext identifier isn't part of the triple
yet) so we need to pass down a CodeGen flag.
rdar://93536111
Differential Revision: https://reviews.llvm.org/D148967
This patch adds an `llc` option `-mroptr` to specify storage locations for constant pointers on AIX.
When the `-mroptr` option is specified, constant pointers, virtual function tables, and virtual type tables are placed in read-only storage. Otherwise, by default, pointers, virtual function tables, and virtual type tables are placed are placed in read/write storage.
https://reviews.llvm.org/D144190 enables the `-mroptr` option for `clang`.
Reviewed By: hubert.reinterpretcast, stephenpeckham, myhsu, MaskRay, serge-sans-paille
Differential Revision: https://reviews.llvm.org/D144189
Remove the `-lower-global-dtors-via-cxa-atexit` escape hatch introduced
in D121736 [1], which switched the default lowering of global
destructors on MachO to use `__cxa_atexit()` to avoid emitting
deprecated `__mod_term_func` sections.
I added this flag as an escape hatch in case the switch causes any
problems. We didn't discover any problems so now we can remove it.
[1] https://reviews.llvm.org/D121736
rdar://90277838
Differential Revision: https://reviews.llvm.org/D145715
These attributes have been accepted in ELF for a while, and are generated by
Clang in some places, so it makes sense to support them on MachO too.
https://reviews.llvm.org/D143173
Put jump table in .rdata for Windows to align with that for Linux.
It can avoid loading the same code page into I$ and D$ simultaneously
and thus favor performance.
Differential Revision: https://reviews.llvm.org/D144701
For -fno-pic, without DW_EH_PE_indirect, the personality routine pointer in a
CIE needs an R_AARCH64_ABS64 relocation. In common configurations that
`__gcc_personality_v0` is defined in a shared object, this will lead to a
discouraged canonical PLT entry, or, if `ld.lld -z notext` (betwen D122459 and
D143136), a dynamic R_AARCH64_ABS64 relocation with an incorrect offset:
https://github.com/llvm/llvm-project/issues/60392
Since GCC uses DW_EH_PE_indirect for -fno-pic code (the behavior hasn't changed
since the initial port in 2012), let's follow suit by simplifying the code.
(
For tiny and small code models, we use DW_EH_PE_sdata8 instead of GCC's
DW_EH_PE_sdata4. This is a deliberate choice to support personality-.eh_frame
offset > 2GiB. This is unneeded for small code model since "Max text segment
size < 2GiB" but making `-fno-pic -mcmodel={tiny,small}` different seems
unnecessary: the scenarios that uses both -fno-pic and C++ exceptions have been
increasingly rare now, so there is little advantage optimizing for the little
size saving with code complexity.
)
---
Two clang/test/Interpreter tests would fail without 6747fc07d1aa94e22622e278e5a02ba70675ac9b
([ORC] Use JITLink as the default linker for LLJIT on Linux/arm64.)
Reviewed By: MatzeB
Differential Revision: https://reviews.llvm.org/D143039
