This implements a function annotation that disables TSan checking for the
function at run time. The benefit over attribute((no_sanitize("thread")))
is that the accesses within the callees will also be suppressed.
The motivation for this attribute is a guarantee given by the objective C
language that the calls to the reference count decrement and object
deallocation will be synchronized. To model this properly, we would need
to intercept all ref count decrement calls (which are very common in ObjC
due to use of ARC) and also every single message send. Instead, we propose
to just ignore all accesses made from within dealloc at run time. The main
downside is that this still does not introduce any synchronization, which
means we might still report false positives if the code that relies on this
synchronization is not executed from within dealloc. However, we have not seen
this in practice so far and think these cases will be very rare.
Differential Revision: https://reviews.llvm.org/D25858
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This is PR28376.
Unfortunately given the current structure of optimization diagnostics we
lack the capability to tell whether the user has
passed -Rpass-analysis=loop-vectorize since this is local to the
front-end (BackendConsumer::OptimizationRemarkHandler).
So rather than printing this even if the user has already
passed -Rpass-analysis, this patch just punts and stops recommending
this option. I don't think that getting this right is worth the
complexity.
Differential Revision: https://reviews.llvm.org/D26563
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This is a follow-up on the recent refactoring of the FunctionMerge pass.
It should fix a fail of the new FunctionComparator unittest whe compiling with MSVC.
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When a function pointer is replaced with a jumptable pointer, special
case is needed to preserve the semantics of extern_weak functions.
Since a jumptable entry can not be extern_weak, we emulate that
behaviour by replacing all references to F (the extern_weak function)
with the following expression: F != nullptr ? JumpTablePtr : nullptr.
Extra special care is needed for global initializers, since most (or
probably all) backends can not lower an initializer that includes
this kind of constant expression. Initializers like that are replaced
with a global constructor (i.e. a runtime initializer).
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This is pure refactoring. NFC.
This change moves the FunctionComparator (together with the GlobalNumberState
utility) in to a separate file so that it can be used by other passes.
For example, the SwiftMergeFunctions pass in the Swift compiler:
https://github.com/apple/swift/blob/master/lib/LLVMPasses/LLVMMergeFunctions.cpp
Details of the change:
*) The big part is just moving code out of MergeFunctions.cpp into FunctionComparator.h/cpp
*) Make FunctionComparator member functions protected (instead of private)
so that a derived comparator class can use them.
Following refactoring helps to share code between the base FunctionComparator
class and a derived class:
*) Add a beginCompare() function
*) Move some basic function property comparisons into a separate function compareSignature()
*) Do the GEP comparison inside cmpOperations() which now has a new
needToCmpOperands reference parameter
https://reviews.llvm.org/D25385
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The current implementation is emitting a global constant that happens
to evaluate to the same bytes + relocation as a jump instruction on
X86. This does not work for PIE executables and shared libraries
though, because we end up with a wrong relocation type. And it has no
chance of working on ARM/AArch64 which use different relocation types
for jump instructions (R_ARM_JUMP24) that is never generated for
data.
This change replaces the constant with module-level inline assembly
followed by a hidden declaration of the jump table. Works fine for
ARM/AArch64, but has some drawbacks.
* Extra symbols are added to the static symbol table, which inflate
the size of the unstripped binary a little. Stripped binaries are not
affected. This happens because jump table declarations must be
external (because their body is in the inline asm).
* Original functions that were anonymous are now named
<original name>.cfi, and it affects symbolization sometimes. This is
necessary because the only user of these functions is the (inline
asm) jump table, so they had to be added to @llvm.used, which does
not allow unnamed functions.
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Removing the limitation in visitInsertElementInst() causes several regressions
because we're not prepared to fold sequences of shuffles or inserts and extracts
separated by shuffles. Fixing that appears to be a difficult mission because we
are purposely trying to avoid creating shuffles with arbitrary shuffle masks
because some targets may choke on those.
https://llvm.org/bugs/show_bug.cgi?id=30923
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No testcase included because I can't figure out how to reduce it.
(It's easy to write a testcase where rotation clones an assume,
but that doesn't actually seem to trigger the crash in opt on
its own; maybe an issue with the laziness?)
Differential Revision: https://reviews.llvm.org/D26434
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Summary:
Unrolled Loop Size calculations moved to a function.
Constant representing number of optimized instructions
when "back edge" becomes "fall through" replaced with
variable.
Some comments added.
Reviewers: mzolotukhin
Differential Revision: http://reviews.llvm.org/D21719
From: Evgeny Stupachenko <evstupac@gmail.com>
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Scalar Evolution asserts when not all the operands of an Add Recurrence
Expression are loop invariants. Loop Strength Reduction should only
create affine Add Recurrences, so that both the start and the step of
the expression are loop invariants.
Differential Revision: https://reviews.llvm.org/D26185
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Summary: For functions with profile data, we are confident that loop sink will be optimal in sinking code.
Reviewers: davidxl, hfinkel
Subscribers: mehdi_amini, mzolotukhin, llvm-commits
Differential Revision: https://reviews.llvm.org/D26155
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As the test change shows, we can increase the critical path by adding
a 'not' instruction, so make sure that we're actually removing an
instruction if we do this transform.
This transform could also cause us to miss folds of min/max pairs.
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From experiments, discriminator is rarely greater than 127. Here we enforce it to be no greater than 127 so that it will always fit in 1 byte.
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Summary:
These are good candidates for jump threading. This enables later opts
(such as InstCombine) to combine instructions from the selects with
instructions out of the selects. SimplifyCFG will fold the select
again if unfolding wasn't worth it.
Patch by James Molloy and Pablo Barrio.
Reviewers: rengolin, haicheng, sebpop
Subscribers: jojo, jmolloy, llvm-commits
Differential Revision: https://reviews.llvm.org/D26391
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Summary:
In some specific scenarios with well understood operand bundle types
(like `"deopt"`) it may be possible to go ahead and convert recursion to
iteration, but TailRecursionElimination does not have that logic today
so avoid doing the right thing for now.
I need some input on whether `"funclet"` operand bundles should also
block tail recursion elimination. If not, I'll allow TRE across calls
with `"funclet"` operand bundles and add a test case.
Reviewers: rnk, majnemer, nlewycky, ahatanak
Subscribers: mcrosier, llvm-commits
Differential Revision: https://reviews.llvm.org/D26270
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Although rare, atomic accesses to floating-point types seem to be valid, i.e. `%a = load atomic float ...`. The TSan instrumentation pass however tries to emit inttoptr, which is incorrect, we should use a bitcast here. Anyway, IRBuilder already has a convenient helper function for this.
Differential Revision: https://reviews.llvm.org/D26266
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Argument evaluation order is one of the edge cases where Clang differs
from GCC, yielding different IR depending on which compiler LLVM was
built with. Make the order deterministic and tune the test to actually
verify the order instead of trying to hide it.
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This was reverted at r285866 because there was a crash handling a scalar
select of vectors. I added a check for that pattern and a test case based
on the example provided in the post-commit thread for r285732.
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Summary:
SmallSetVector uses DenseSet, but that means we need to reserve some
values for the empty and tombstone keys.
It seems to me we should have a general way to let us store full-range
ints inside of DenseSets, and furthermore that we probably shouldn't
silently let you add ints into DenseSets without explicitly promising
that they're in range. But that's a battle for another day; for now,
just fix this code, since we currently do something Very Bad when
compiling ffmpeg.
Fixes PR30914.
Reviewers: jeremyhu
Subscribers: llvm-commits, mzolotukhin
Differential Revision: https://reviews.llvm.org/D26323
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instruction.
This avoids dereferencing null in the debug logging if the instruction
was not in fact a return instruction. This potential bug was found by
PVS-Studio.
This actually fixes the last of the "dereferenced a pointer before
checking it for null" reports in the recent PVS-Studio run. However,
there are quite a few reports of this nature that I did not do anything
to fix because they are pretty glaring false positives. They usually
took the form of quite clear correlated checks or a check made in
a separate function. I've even added asserts anywhere this correlation
wasn't pretty obvious and fundamental to the code.
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This condition is trivially always true prior to the change. The comment
at the call site makes it clear that we expect *all* of these to be '=',
'S', or 'I' so fix the code.
We have a bug I will update to track the fact that Clang doesn't warn on
this: http://llvm.org/PR13101
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Summary:
The recent change I made to consult the summary when deciding whether to
rename (to handle inline asm) in r285513 broke the distributed build
case. In a distributed backend we will only have a portion of the
combined index, specifically for imported modules we only have the
summaries for any imported definitions. When renaming on import we were
asserting because no summary entry was found for a local reference being
linked in (def wasn't imported).
We only need to consult the summary for a renaming decision for the
exporting module. For imports, we would have prevented importing any
references to NoRename values already.
Reviewers: mehdi_amini
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D26250
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This reverts commit r285732.
This change introduced a new assertion failure in the following
testcase at -O2:
typedef short __v8hi __attribute__((__vector_size__(16)));
__v8hi foo(__v8hi &V1, __v8hi &V2, unsigned mask) {
__v8hi Result = V1;
if (mask & 0x80)
Result[0] = V2[0];
return Result;
}
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Summary:
It was detected that the reassociate pass could enter an inifite
loop when analysing dead code. Simply skipping to analyse basic
blocks that are dead avoids such problems (and as a side effect
we avoid spending time on optimising dead code).
The solution is using the same Reverse Post Order ordering of the
basic blocks when doing the optimisations, as when building the
precalculated rank map. A nice side-effect of this solution is
that we now know that we only try to do optimisations for blocks
with ranked instructions.
Fixes https://llvm.org/bugs/show_bug.cgi?id=30818
Reviewers: llvm-commits, davide, eli.friedman, mehdi_amini
Subscribers: dberlin
Differential Revision: https://reviews.llvm.org/D26154
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