Kai Nacke [Thu, 10 Oct 2019 13:24:00 +0000 (13:24 +0000)]
[Tests] Output of od can be lower or upper case (llvm-objcopy/yaml2obj).
The command `od -t x` is used to dump data in hex format.
The LIT tests assumes that the hex characters are in lowercase.
However, there are also platforms which use uppercase letter.
To solve this issue the tests are updated to use the new
`--ignore-case` option of FileCheck.
Kai Nacke [Thu, 10 Oct 2019 13:15:41 +0000 (13:15 +0000)]
[FileCheck] Implement --ignore-case option.
The FileCheck utility is enhanced to support a `--ignore-case`
option. This is useful in cases where the output of Unix tools
differs in case (e.g. case not specified by Posix).
Florian Hahn [Thu, 10 Oct 2019 13:07:01 +0000 (13:07 +0000)]
[LV][NFC] Factor out calculation of "best" estimated trip count.
This is just small refactoring to minimize changes in upcoming patch.
In the next path I'm going to introduce changes into heuristic for vectorization of "tiny trip count" loops.
Patch by Evgeniy Brevnov <evgueni.brevnov@gmail.com>
Pavel Labath [Thu, 10 Oct 2019 13:05:46 +0000 (13:05 +0000)]
MinidumpYAML: Add support for the memory info list stream
Summary:
The implementation is fairly straight-forward and uses the same patterns
as the existing streams. The yaml form does not attempt to preserve the
data in the "gaps" that can be created by setting a larger-than-required
header or entry size in the stream header, because the existing consumer
(lldb) does not make use of the information in the gap in any way, and
attempting to preserve that would make the implementation more
complicated.
Summary:
This is patch is part of a series to introduce an Alignment type.
See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2019-July/133851.html
See this patch for the introduction of the type: https://reviews.llvm.org/D64790
Roman Lebedev [Thu, 10 Oct 2019 12:22:33 +0000 (12:22 +0000)]
[ADR] ArrayRefTest: disable SizeTSizedOperations test - it's UB.
This test is not defined.
FAIL: LLVM-Unit :: ADT/./ADTTests/ArrayRefTest.SizeTSizedOperations (178 of 33926)
******************** TEST 'LLVM-Unit :: ADT/./ADTTests/ArrayRefTest.SizeTSizedOperations' FAILED ********************
Note: Google Test filter = ArrayRefTest.SizeTSizedOperations
[==========] Running 1 test from 1 test case.
[----------] Global test environment set-up.
[----------] 1 test from ArrayRefTest
[ RUN ] ArrayRefTest.SizeTSizedOperations
/b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/llvm/include/llvm/ADT/ArrayRef.h:180:32: runtime error: applying non-zero offset 9223372036854775806 to null pointer
#0 0x5ae8dc in llvm::ArrayRef<char>::slice(unsigned long, unsigned long) const /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/llvm/include/llvm/ADT/ArrayRef.h:180:32
#1 0x5ae44c in (anonymous namespace)::ArrayRefTest_SizeTSizedOperations_Test::TestBody() /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/llvm/unittests/ADT/ArrayRefTest.cpp:85:3
#2 0x928a96 in testing::Test::Run() /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/llvm/utils/unittest/googletest/src/gtest.cc:2474:5
#3 0x929793 in testing::TestInfo::Run() /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/llvm/utils/unittest/googletest/src/gtest.cc:2656:11
#4 0x92a152 in testing::TestCase::Run() /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/llvm/utils/unittest/googletest/src/gtest.cc:2774:28
#5 0x9319d2 in testing::internal::UnitTestImpl::RunAllTests() /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/llvm/utils/unittest/googletest/src/gtest.cc:4649:43
#6 0x931416 in testing::UnitTest::Run() /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/llvm/utils/unittest/googletest/src/gtest.cc:4257:10
#7 0x920ac3 in RUN_ALL_TESTS /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/llvm/utils/unittest/googletest/include/gtest/gtest.h:2233:46
#8 0x920ac3 in main /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/llvm/utils/unittest/UnitTestMain/TestMain.cpp:50:10
#9 0x7f66135b72e0 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x202e0)
#10 0x472c19 in _start (/b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm_build_ubsan/unittests/ADT/ADTTests+0x472c19)
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /b/sanitizer-x86_64-linux-bootstrap-ubsan/build/llvm-project/llvm/include/llvm/ADT/ArrayRef.h:180:32 in
Mirko Brkusanin [Thu, 10 Oct 2019 12:02:14 +0000 (12:02 +0000)]
[Mips] Fix 374055
EXPENSIVE_CHECKS build was failing on new test.
This is fixed by marking $ra register as undef.
Test now has -verify-machineinstrs to check for operand flags.
Summary:
llvm-ar's mri-utf8.test test relies on the en_US.UTF-8 locale to be
installed for its last RUN line to work. If not installed, the unicode
string gets encoded (interpreted) as ascii which fails since the most
significant byte is non zero. This commit changes the test to only rely
on the system being able to encode the pound sign in its default
encoding (e.g. UTF-16 for Microsoft Windows) by always opening the file
via input/output redirection. This avoids forcing a given locale to be
present and supported. A Byte Order Mark is also added to help
recognizing the encoding of the file and its endianness.
Oliver Stannard [Thu, 10 Oct 2019 09:58:28 +0000 (09:58 +0000)]
[IfCvt][ARM] Optimise diamond if-conversion for code size
Currently, the heuristics the if-conversion pass uses for diamond if-conversion
are based on execution time, with no consideration for code size. This adds a
new set of heuristics to be used when optimising for code size.
This is mostly target-independent, because the if-conversion pass can
see the code size of the instructions which it is removing. For thumb,
there are a few passes (insertion of IT instructions, selection of
narrow branches, and selection of CBZ instructions) which are run after
if conversion and affect these heuristics, so I've added target hooks to
better predict the code-size effect of a proposed if-conversion.
Roman Lebedev [Thu, 10 Oct 2019 09:25:02 +0000 (09:25 +0000)]
[UBSan][clang][compiler-rt] Applying non-zero offset to nullptr is undefined behaviour
Summary:
Quote from http://eel.is/c++draft/expr.add#4:
```
4 When an expression J that has integral type is added to or subtracted
from an expression P of pointer type, the result has the type of P.
(4.1) If P evaluates to a null pointer value and J evaluates to 0,
the result is a null pointer value.
(4.2) Otherwise, if P points to an array element i of an array object x with n
elements ([dcl.array]), the expressions P + J and J + P
(where J has the value j) point to the (possibly-hypothetical) array
element i+j of x if 0≤i+j≤n and the expression P - J points to the
(possibly-hypothetical) array element i−j of x if 0≤i−j≤n.
(4.3) Otherwise, the behavior is undefined.
```
Therefore, as per the standard, applying non-zero offset to `nullptr`
(or making non-`nullptr` a `nullptr`, by subtracting pointer's integral value
from the pointer itself) is undefined behavior. (*if* `nullptr` is not defined,
i.e. e.g. `-fno-delete-null-pointer-checks` was *not* specified.)
To make things more fun, in C (6.5.6p8), applying *any* offset to null pointer
is undefined, although Clang front-end pessimizes the code by not lowering
that info, so this UB is "harmless".
Since rL369789 (D66608 `[InstCombine] icmp eq/ne (gep inbounds P, Idx..), null -> icmp eq/ne P, null`)
LLVM middle-end uses those guarantees for transformations.
If the source contains such UB's, said code may now be miscompiled.
Such miscompilations were already observed:
* https://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20190826/687838.html
* https://github.com/google/filament/pull/1566
Surprisingly, UBSan does not catch those issues
... until now. This diff teaches UBSan about these UB's.
`getelementpointer inbounds` is a pretty frequent instruction,
so this does have a measurable impact on performance;
I've addressed most of the obvious missing folds (and thus decreased the performance impact by ~5%),
and then re-performed some performance measurements using my [[ https://github.com/darktable-org/rawspeed | RawSpeed ]] benchmark:
(all measurements done with LLVM ToT, the sanitizer never fired.)
* no sanitization vs. existing check: average `+21.62%` slowdown
* existing check vs. check after this patch: average `22.04%` slowdown
* no sanitization vs. this patch: average `48.42%` slowdown
to make the expected test output depend on as few optimization phases
as possible, for stability. But when you write a RUN line of this
form, you lose the ability to use update_cc_test_checks.py to
automatically generate the expected output, because it only supports
two-stage pipelines consisting of '%clang | FileCheck' (or %clang_cc1).
This change extends the set of supported RUN lines so that pipelines
with an invocation of `opt` in the middle can still be automatically
handled.
To implement it, I've adjusted `get_function_body()` so that it can
cope with an arbitrary sequence of intermediate pipeline commands. But
the code that decides which RUN lines to consider is more
conservative: it only adds clang | opt | FileCheck to the set of
supported lines, because I didn't want to accidentally include some
other kind of line that doesn't output IR at all.
(Also in this commit is the minimal change to make this script work at
all, after r373912 added an extra parameter to `add_ir_checks`.)
Matt Arsenault [Thu, 10 Oct 2019 07:11:33 +0000 (07:11 +0000)]
AMDGPU: Use SGPR_128 instead of SReg_128 for vregs
SGPR_128 only includes the real allocatable SGPRs, and SReg_128 adds
the additional non-allocatable TTMP registers. There's no point in
allocating SReg_128 vregs. This shrinks the size of the classes
regalloc needs to consider, which is usually good.
[Attributor] Handle `null` differently in capture and alias logic
Summary:
`null` in the default address space (=AS 0) cannot be captured nor can
it alias anything. We make this clear now as it can be important for
callbacks and other cases later on. In addition, this patch improves the
debug output for noalias deduction.
Reid Kleckner [Thu, 10 Oct 2019 01:06:01 +0000 (01:06 +0000)]
[codeview] Try to avoid emitting .cv_loc with line zero
Summary:
Visual Studio doesn't like it while stepping. It kicks you out of the
source view of the file being stepped through and tries to fall back to
the disassembly view.
Fixes PR43530
The fix is incomplete, because it's possible to have a basic block with
no source locations at all. In this case, we don't emit a .cv_loc, but
that will result in wrong stepping behavior in the debugger if the
layout predecessor of the location-less BB has an unrelated source
location. We could try harder to find a valid location that dominates or
post-dominates the current BB, but in general it's a dataflow problem,
and one still might not exist. I left a FIXME about this.
As an alternative, we might want to consider having the middle-end check
if its emitting codeview and get it to stop using line zero.
Philip Reames [Wed, 9 Oct 2019 23:43:33 +0000 (23:43 +0000)]
Conservatively add volatility and atomic checks in a few places
As background, starting in D66309, I'm working on support unordered atomics analogous to volatile flags on normal LoadSDNode/StoreSDNodes for X86.
As part of that, I spent some time going through usages of LoadSDNode and StoreSDNode looking for cases where we might have missed a volatility check or need an atomic check. I couldn't find any cases that clearly miscompile - i.e. no test cases - but a couple of pieces in code loop suspicious though I can't figure out how to exercise them.
This patch adds defensive checks and asserts in the places my manual audit found. If anyone has any ideas on how to either a) disprove any of the checks, or b) hit the bug they might be fixing, I welcome suggestions.
Matt Arsenault [Wed, 9 Oct 2019 22:51:42 +0000 (22:51 +0000)]
AMDGPU: Don't fold copies to physregs
In a future patch, this will help cleanup m0 handling.
The register coalescer handles copies from a register that
materializes an immediate, but doesn't handle move immediates
itself. The virtual register uses will often be allocated to the same
register, so there end up being no real copy.
Thomas Lively [Wed, 9 Oct 2019 21:42:08 +0000 (21:42 +0000)]
[WebAssembly] Make returns variadic
Summary:
This is necessary and sufficient to get simple cases of multiple
return working with multivalue enabled. More complex cases will
require block and loop signatures to be generalized to potentially be
type indices as well.
Wei Mi [Wed, 9 Oct 2019 21:36:03 +0000 (21:36 +0000)]
[SampleFDO] Add indexing for function profiles so they can be loaded on demand
in ExtBinary format
Currently for Text, Binary and ExtBinary format profiles, when we compile a
module with samplefdo, even if there is no function showing up in the profile,
we have to load all the function profiles from the profile input. That is a
waste of compile time.
CompactBinary format profile has already had the support of loading function
profiles on demand. In this patch, we add the support to load profile on
demand for ExtBinary format. It will work no matter the sections in ExtBinary
format profile are compressed or not. Experiment shows it reduces the time to
compile a server benchmark by 30%.
When profile remapping and loading function profiles on demand are both used,
extra work needs to be done so that the loading on demand process will take
the name remapping into consideration. It will be addressed in a follow-up
patch.
Adds links to Getting Started/Tutorials, User Guides, and Reference documentation pages to sidebar. Also adds a new section for LLVM IR on the Reference documentation page.
David Greene [Wed, 9 Oct 2019 19:51:48 +0000 (19:51 +0000)]
[System Model] [TTI] Update cache and prefetch TTI interfaces
Re-apply 9fdfb045ae8b/r365676 with fixes for PPC and Hexagon. This involved
moving defaults from TargetTransformInfoImplBase to MCSubtargetInfo.
Rework the TTI cache and software prefetching APIs to prepare for the
introduction of a general system model. Changes include:
- Marking existing interfaces const and/or override as appropriate
- Adding comments
- Adding BasicTTIImpl interfaces that delegate to a subtarget
implementation
- Moving the default TargetTransformInfoImplBase implementation to a default
MCSubtarget implementation
Only a handful of targets use these interfaces currently: AArch64, Hexagon, PPC
and SystemZ. AArch64 already has a custom subtarget implementation, so its
custom TTI implementation is migrated to use the new facilities in BasicTTIImpl
to invoke its custom subtarget implementation. The custom TTI implementations
continue to exist for the other targets with this change. They are not moved
over to subtarget-based implementations.
The end goal is to have the default subtarget implementation defer to the system
model defined by the target. With this change, the default MCSubtargetInfo
implementation essentially returns the defaults TargetTransformInfoImplBase used
to return. Existing users of TTI defaults will hit the defaults now in
MCSubtargetInfo. Targets that define their own custom TTI implementations won't
use the BasicTTIImpl implementations that route to the subtarget.
Once system models are in place for the targets that use these interfaces, their
custom TTI implementations can be removed.
David Blaikie [Wed, 9 Oct 2019 18:37:13 +0000 (18:37 +0000)]
DebugInfo: Shot in the dark attempt to fix ubsan error from r374122
(specifying an underlying type for the enum might also be suitable - but
this seems better/as good, since there's a clear expectation this can
contain values other than the actual enumerators of this enum)
Julian Lettner [Wed, 9 Oct 2019 18:23:30 +0000 (18:23 +0000)]
[lit] Refactor ProgressDisplay
Move progress display to separate file. Simplify some code paths.
Decouple from other components via progress callback. Remove unused
`_Display` class.
Thomas Lively [Wed, 9 Oct 2019 17:45:47 +0000 (17:45 +0000)]
[WebAssembly] Add builtin and intrinsic for v8x16.swizzle
Summary:
This clang builtin and corresponding LLVM intrinsic are necessary to
expose the exact semantics of the underlying WebAssembly instruction
to users. LLVM produces a poison value if the dynamic swizzle indices
are greater than the vector size, but the WebAssembly instruction sets
the corresponding output lane to zero. Users who depend on this
behavior can safely use this builtin.
Thomas Lively [Wed, 9 Oct 2019 17:39:19 +0000 (17:39 +0000)]
[WebAssembly] v8x16.swizzle and rewrite BUILD_VECTOR lowering
Summary:
Adds the new v8x16.swizzle SIMD instruction as specified at
https://github.com/WebAssembly/simd/blob/master/proposals/simd/SIMD.md#swizzling-using-variable-indices.
In addition to adding swizzles as a candidate lowering in
LowerBUILD_VECTOR, also rewrites and simplifies the lowering to
minimize the number of replace_lanes necessary rather than trying to
minimize code size. This leads to more uses of v128.const instead of
splats, which is expected to increase performance.
The new code will be easier to tune once V8 implements all the vector
construction operations, and it will also be easier to add new
candidate instructions in the future if necessary.
Kevin P. Neal [Wed, 9 Oct 2019 17:24:56 +0000 (17:24 +0000)]
[FPEnv][NFC] Change test to conform to strictfp attribute rules.
In particular, the function definition is not marked strictfp despite
containing a function marked strictfp. Also, if any function call is marked
strictfp then all function calls in that function must be marked.
This change to move the one strictfp call to a new properly marked function
meets all the new rules.
Sanjay Patel [Wed, 9 Oct 2019 16:32:49 +0000 (16:32 +0000)]
[SLP] respect target register width for GEP vectorization (PR43578)
We failed to account for the target register width (max vector factor)
when vectorizing starting from GEPs. This causes vectorization to
proceed to obviously illegal widths as in:
https://bugs.llvm.org/show_bug.cgi?id=43578
For x86, this also means that SLP can produce rogue AVX or AVX512
code even when the user specifies a narrower vector width.
The AArch64 test in ext-trunc.ll appears to be better using the
narrower width. I'm not exactly sure what getelementptr.ll is trying
to do, but it's testing with "-slp-threshold=-18", so I'm not worried
about those diffs. The x86 test is an over-reduction from SPEC h264;
this patch appears to restore the perf loss caused by SLP when using
-march=haswell.
Momchil Velikov [Wed, 9 Oct 2019 16:31:50 +0000 (16:31 +0000)]
[AArch64] Ensure no tagged memory is left in the unallocated portion of the
stack
This patch makes sure that if we tag some memory, we untag that memory before
the function returns/throws via any exit, reachable from the tag operation. For
that we place the untag operation either at:
a) the lifetime end call for the alloca, if that call post-dominates the
lifetime start call (where the tag operation is placed), or it (the
lifetime end call) dominates all reachable exits, otherwise
b) at the reachable exits
Jason Liu [Wed, 9 Oct 2019 16:19:39 +0000 (16:19 +0000)]
[AIX][XCOFF][NFC] Change the SectionLen field name of CSect Auxiliary entry to SectionOrLength.
Summary:
According the the XCOFF document,
If
Then
XTY_SD
x_scnlen contains the csect length.
XTY_LD
x_scnlen contains the symbol table index of the containing csect.
XTY_CM
x_scnlen contains the csect length.
XTY_ER
x_scnlen contains 0.
Change the SectionLen member name to SectionOrLength is more reasonable.
Re-land "[dsymutil] Fix handling of common symbols in multiple object files."
The original patch got reverted because it hit a long-standing legacy
issue on Windows that prevents files from being named `com`. Thanks
Kristina & Jeremy for pointing this out.
Alina Sbirlea [Wed, 9 Oct 2019 15:54:24 +0000 (15:54 +0000)]
[MemorySSA] Make the use of moveAllAfterMergeBlocks consistent.
Summary:
The rule for the moveAllAfterMergeBlocks API si for all instructions
from `From` to have been moved to `To`, while keeping the CFG edges (and
block terminators) unchanged.
Update all the callsites for moveAllAfterMergeBlocks to follow this.
Pending follow-up: since the same behavior is needed everytime, merge
all callsites into one. The common denominator may be the call to
`MergeBlockIntoPredecessor`.
Simon Atanasyan [Wed, 9 Oct 2019 13:12:21 +0000 (13:12 +0000)]
[mips] Split expandLoadImmReal into multiple methods. NFC
The `expandLoadImmReal` handles four different and almost non-overlapping
cases: loading a "single" float immediate into a GPR, loading a "single"
float immediate into a FPR, and the same couple for a "double" float
immediate.
It's better to move each `else if` branch into separate methods.
James Molloy [Wed, 9 Oct 2019 09:15:34 +0000 (09:15 +0000)]
[TableGen] Fix crash when using HwModes in CodeEmitterGen
When an instruction has an encoding definition for only a subset of
the available HwModes, ensure we just avoid generating an encoding
rather than crash.
Hans Wennborg [Wed, 9 Oct 2019 09:06:30 +0000 (09:06 +0000)]
Unify the two CRC implementations
David added the JamCRC implementation in r246590. More recently, Eugene
added a CRC-32 implementation in r357901, which falls back to zlib's
crc32 function if present.
These checksums are essentially the same, so having multiple
implementations seems unnecessary. This replaces the CRC-32
implementation with the simpler one from JamCRC, and implements the
JamCRC interface in terms of CRC-32 since this means it can use zlib's
implementation when available, saving a few bytes and potentially making
it faster.
JamCRC took an ArrayRef<char> argument, and CRC-32 took a StringRef.
This patch changes it to ArrayRef<uint8_t> which I think is the best
choice, and simplifies a few of the callers nicely.
[dsymutil] Fix handling of common symbols in multiple object files.
For common symbols the linker emits only a single symbol entry in the
debug map. This caused dsymutil to not relocate common symbols when
linking DWARF coming form object files that did not have this entry.
This patch fixes that by keeping track of common symbols in the object
files and synthesizing a debug map entry for them using the address from
the main binary.
The verbose output for finding relocations assumed that we'd always dump
the DIE after (which starts with a newline) and therefore didn't include
one itself. However, this isn't always true, leading to garbled output.
This patch adds a newline to the verbose output and adds a line that
says that the DIE is being kept (which isn't obvious otherwise). It also
adds a 0x prefix to the relocations.
Roman Lebedev [Tue, 8 Oct 2019 20:29:48 +0000 (20:29 +0000)]
[CVP} Replace SExt with ZExt if the input is known-non-negative
Summary:
zero-extension is far more friendly for further analysis.
While this doesn't directly help with the shift-by-signext problem, this is not unrelated.
TLDR: we produce -0.11% less instructions, -6.84% less `sext`, +10.75% more `zext`.
To be noted, clearly, not all new `zext`'s are produced by this fold.
(And now i guess it might have been interesting to measure this for D68103 :S)
Daniel Sanders [Tue, 8 Oct 2019 18:41:32 +0000 (18:41 +0000)]
[tblgen] Add getOperatorAsDef() to Record
Summary:
While working with DagInit's, it's often the case that you expect the
operator to be a reference to a def. This patch adds a wrapper for this
common case to reduce the amount of boilerplate callers need to duplicate
repeatedly.
getOperatorAsDef() returns the record if the DagInit has an operator that is
a DefInit. Otherwise, it prints a fatal error.
There's only a few pre-existing examples in LLVM at the moment and I've
left a few instances of the code this simplifies as they had more specific
error messages than the generic one this produces. I'm going to be using
this a fair bit in my subsequent patches.
Yonghong Song [Tue, 8 Oct 2019 18:23:17 +0000 (18:23 +0000)]
[BPF] do compile-once run-everywhere relocation for bitfields
A bpf specific clang intrinsic is introduced:
u32 __builtin_preserve_field_info(member_access, info_kind)
Depending on info_kind, different information will
be returned to the program. A relocation is also
recorded for this builtin so that bpf loader can
patch the instruction on the target host.
This clang intrinsic is used to get certain information
to facilitate struct/union member relocations.
The offset relocation is extended by 4 bytes to
include relocation kind.
Currently supported relocation kinds are
enum {
FIELD_BYTE_OFFSET = 0,
FIELD_BYTE_SIZE,
FIELD_EXISTENCE,
FIELD_SIGNEDNESS,
FIELD_LSHIFT_U64,
FIELD_RSHIFT_U64,
};
for __builtin_preserve_field_info. The old
access offset relocation is covered by
FIELD_BYTE_OFFSET = 0.
An example:
struct s {
int a;
int b1:9;
int b2:4;
};
enum {
FIELD_BYTE_OFFSET = 0,
FIELD_BYTE_SIZE,
FIELD_EXISTENCE,
FIELD_SIGNEDNESS,
FIELD_LSHIFT_U64,
FIELD_RSHIFT_U64,
};
void bpf_probe_read(void *, unsigned, const void *);
int field_read(struct s *arg) {
unsigned long long ull = 0;
unsigned offset = __builtin_preserve_field_info(arg->b2, FIELD_BYTE_OFFSET);
unsigned size = __builtin_preserve_field_info(arg->b2, FIELD_BYTE_SIZE);
#ifdef USE_PROBE_READ
bpf_probe_read(&ull, size, (const void *)arg + offset);
unsigned lshift = __builtin_preserve_field_info(arg->b2, FIELD_LSHIFT_U64);
#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
lshift = lshift + (size << 3) - 64;
#endif
#else
switch(size) {
case 1:
ull = *(unsigned char *)((void *)arg + offset); break;
case 2:
ull = *(unsigned short *)((void *)arg + offset); break;
case 4:
ull = *(unsigned int *)((void *)arg + offset); break;
case 8:
ull = *(unsigned long long *)((void *)arg + offset); break;
}
unsigned lshift = __builtin_preserve_field_info(arg->b2, FIELD_LSHIFT_U64);
#endif
ull <<= lshift;
if (__builtin_preserve_field_info(arg->b2, FIELD_SIGNEDNESS))
return (long long)ull >> __builtin_preserve_field_info(arg->b2, FIELD_RSHIFT_U64);
return ull >> __builtin_preserve_field_info(arg->b2, FIELD_RSHIFT_U64);
}
There is a minor overhead for bpf_probe_read() on big endian.
The code and relocation generated for field_read where bpf_probe_read() is
used to access argument data on little endian mode:
r3 = r1
r1 = 0
r1 = 4 <=== relocation (FIELD_BYTE_OFFSET)
r3 += r1
r1 = r10
r1 += -8
r2 = 4 <=== relocation (FIELD_BYTE_SIZE)
call bpf_probe_read
r2 = 51 <=== relocation (FIELD_LSHIFT_U64)
r1 = *(u64 *)(r10 - 8)
r1 <<= r2
r2 = 60 <=== relocation (FIELD_RSHIFT_U64)
r0 = r1
r0 >>= r2
r3 = 1 <=== relocation (FIELD_SIGNEDNESS)
if r3 == 0 goto LBB0_2
r1 s>>= r2
r0 = r1
LBB0_2:
exit
Compare to the above code between relocations FIELD_LSHIFT_U64 and
FIELD_LSHIFT_U64, the code with big endian mode has four more
instructions.
r1 = 41 <=== relocation (FIELD_LSHIFT_U64)
r6 += r1
r6 += -64
r6 <<= 32
r6 >>= 32
r1 = *(u64 *)(r10 - 8)
r1 <<= r6
r2 = 60 <=== relocation (FIELD_RSHIFT_U64)
Considering verifier is able to do limited constant
propogation following branches. The following is the
code actually traversed.
r2 = 0
r3 = 4 <=== relocation
r4 = 4 <=== relocation
if r4 s> 3 goto LBB0_3
LBB0_3: # %entry
if r4 == 4 goto LBB0_7
LBB0_7: # %sw.bb5
r1 += r3
r2 = *(u32 *)(r1 + 0)
LBB0_9: # %sw.epilog
r1 = 51 <=== relocation
r2 <<= r1
r1 = 60 <=== relocation
r0 = r2
r0 >>= r1
r3 = 1
if r3 == 0 goto LBB0_11
r2 s>>= r1
r0 = r2
LBB0_11: # %sw.epilog
exit
For native load case, the load size is calculated to be the
same as the size of load width LLVM otherwise used to load
the value which is then used to extract the bitfield value.
Matt Arsenault [Tue, 8 Oct 2019 17:36:38 +0000 (17:36 +0000)]
AMDGPU: Fix i16 arithmetic pattern redundancy
There were 2 problems here. First, these patterns were duplicated to
handle the inverted shift operands instead of using the commuted
PatFrags.
Second, the point of the zext folding patterns don't apply to the
non-0ing high subtargets. They should be skipped instead of inserting
the extension. The zeroing high code would be emitted when necessary
anyway. This was also emitting unnecessary zexts in cases where the
high bits were undefined.
Testing: check-llvm, and comparing the AMDGPUDisassembler.cpp.o binary
pre- vs. post-patch.
An alternate approach is to hide CodeExtractorAnalysisCache from clients
of CodeExtractor, and to recompute the analysis from scratch inside of
CodeExtractor::extractCodeRegion(). This eliminates some redundant work
in the shrinkwrapping legality check. However, some clients continue to
exhibit O(n^2) compile time behavior as computing the analysis is O(n).
projects / llvm / log