Summary:
If MemorySSA is avaiable, we can skip checking all instructions if block has any Defs.
(volatile loads are also Defs).
We still need to check all instructions for "canThrow", even if no Defs are found.
Reviewers: chandlerc
Subscribers: sanjoy, jlebar, Prazek, george.burgess.iv, llvm-commits
Differential Revision: https://reviews.llvm.org/D57129
llvm-svn: 352393
Summary:
Set default value for retrieved attributes to 1, since the check is against 1.
Eliminates the warning noise generated when the attributes are not present.
Reviewers: sanjoy
Subscribers: jlebar, llvm-commits
Differential Revision: https://reviews.llvm.org/D57253
llvm-svn: 352238
2nd part of D57095 with the same reason, just in another place. We never
fold branches that are not immediately in the current loop, but this check
is missing in `IsEdgeLive` As result, it may think that the edge in subloop is
dead while it's live. It's a pessimization in the current stance.
Differential Revision: https://reviews.llvm.org/D57147
Reviewed By: rupprecht
llvm-svn: 352170
Summary:
MemorySSA needs updating each time an instruction is moved.
LICM and control flow hoisting re-hoists instructions, thus needing another update when re-moving those instructions.
Pending cleanup: the MSSA update is duplicated, should be moved inside moveInstructionBefore.
Reviewers: jnspaulsson
Subscribers: sanjoy, jlebar, Prazek, george.burgess.iv, llvm-commits
Differential Revision: https://reviews.llvm.org/D57176
llvm-svn: 352092
After submitting https://reviews.llvm.org/D57138, I realized it was slightly more conservative than needed. The scalar indices don't appear to be a problem on a vector gep, we even had a test for that.
Differential Revision: https://reviews.llvm.org/D57161
llvm-svn: 352061
This is an alternative to https://reviews.llvm.org/D57103. After discussion, we dedicided to check this in as a temporary workaround, and pursue a true fix under the original thread.
The issue at hand is that the base rewriting algorithm doesn't consider the fact that GEPs can turn a scalar input into a vector of outputs. We had handling for scalar GEPs and fully vector GEPs (i.e. all vector operands), but not the scalar-base + vector-index forms. A true fix here requires treating GEP analogously to extractelement or shufflevector.
This patch is merely a workaround. It simply hides the crash at the cost of some ugly code gen for this presumable very rare pattern.
Differential Revision: https://reviews.llvm.org/D57138
llvm-svn: 352059
When we choose whether or not we should mark block as dead, we have an
inconsistent logic in markup of live blocks.
- We take candidate IF its terminator branches on constant AND it is immediately
in current loop;
- We mark successor live IF its terminator doesn't branch by constant OR it branches
by constant and the successor is its always taken block.
What we are missing here is that when the terminator branches on a constant but is
not taken as a candidate because is it not immediately in the current loop, we will
mark only one (always taken) successor as live. Therefore, we do NOT do the actual
folding but may NOT mark one of the successors as live. So the result of markup is
wrong in this case, and we may then hit various asserts.
Thanks Jordan Rupprech for reporting this!
Differential Revision: https://reviews.llvm.org/D57095
Reviewed By: rupprecht
llvm-svn: 352024
This patch relaxes restrictions on types of latch condition and range check.
In current implementation, they should match. This patch allows to handle
wide range checks against narrow condition. The motivating example is the
following:
int N = ...
for (long i = 0; (int) i < N; i++) {
if (i >= length) deopt;
}
In this patch, the option that enables this support is turned off by
default. We'll wait until it is switched to true.
Differential Revision: https://reviews.llvm.org/D56837
Reviewed By: reames
llvm-svn: 351926
This patch adds support of guards expressed as branches by widenable
conditions in Loop Predication.
Differential Revision: https://reviews.llvm.org/D56081
Reviewed By: reames
llvm-svn: 351805
Deopt operands are generally intended to record information about a site in code with minimal perturbation of the surrounding code. Idiomatically, they also tend to appear down rare paths. Putting these together, we have an obvious case for extending CVP w/deopt operand constant folding. Arguably, we should be doing this for all operands on all instructions, but that's definitely a much larger and risky change.
Differential Revision: https://reviews.llvm.org/D55678
llvm-svn: 351774
As noted in https://bugs.llvm.org/show_bug.cgi?id=36651, the specialization for
isPodLike<std::pair<...>> did not match the expectation of
std::is_trivially_copyable which makes the memcpy optimization invalid.
This patch renames the llvm::isPodLike trait into llvm::is_trivially_copyable.
Unfortunately std::is_trivially_copyable is not portable across compiler / STL
versions. So a portable version is provided too.
Note that the following specialization were invalid:
std::pair<T0, T1>
llvm::Optional<T>
Tests have been added to assert that former specialization are respected by the
standard usage of llvm::is_trivially_copyable, and that when a decent version
of std::is_trivially_copyable is available, llvm::is_trivially_copyable is
compared to std::is_trivially_copyable.
As of this patch, llvm::Optional is no longer considered trivially copyable,
even if T is. This is to be fixed in a later patch, as it has impact on a
long-running bug (see r347004)
Note that GCC warns about this UB, but this got silented by https://reviews.llvm.org/D50296.
Differential Revision: https://reviews.llvm.org/D54472
llvm-svn: 351701
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
During the transforms in LoopSimplifyCFG, when we remove a dead exiting edge, the
parent loop may stop being reachable from the child loop, and therefore they become
siblings. If the former child loop had uses of some values from its former parent loop,
now such uses will require LCSSA Phis, even if they weren't needed before. So we must
form LCSSA for all loops that stopped being ancestors of the current loop in this case.
Differential Revision: https://reviews.llvm.org/D56144
Reviewed By: fedor.sergeev
llvm-svn: 351434
Function `DeleteDeadBlock` requires that all predecessors of a block
being deleted have already been deleted, with the exception of a
single-block loop. When we use it for removal of dead subloops that
contain more than one block, we may not fulfull this requirement and
fail an assertion.
This patch replaces invocation of `DeleteDeadBlock` with a generalized
version `DeleteDeadBlocks` that is able to deal with multiple dead blocks,
even if they contain some cycles.
Differential Revision: https://reviews.llvm.org/D56121
Reviewed By: fedor.sergeev
llvm-svn: 351433
For the given test SROA detects possible replacement and creates a correct alloca. After that SROA is adding lifetime markers for this new alloca. The function getNewAllocaSlicePtr is trying to deduce the pointer type based on the original alloca, which is split, to use it later in lifetime intrinsic.
For the test we ended up with such code (rA is initial alloca [10 x float], which is split, and rA.sroa.0.0 is a new split allocation)
```
%rA.sroa.0.0.rA.sroa_cast = bitcast i32* %rA.sroa.0 to [10 x float]* <----- this one causing the assertion and is an extra bitcast
%5 = bitcast [10 x float]* %rA.sroa.0.0.rA.sroa_cast to i8*
call void @llvm.lifetime.start.p0i8(i64 4, i8* %5)
```
isAllocaPromotable code assumes that a user of alloca may go into lifetime marker through bitcast but it must be the only one bitcast to i8* type. In the test it's not a i8* type, return false and throw the assertion.
As we are creating a pointer, which will be used in lifetime markers only, the proposed fix is to create a bitcast to i8* immediately to avoid extra bitcast creation.
The test is a greatly simplified to just reproduce the assertion.
Author: Igor Tsimbalist <igor.v.tsimbalist@intel.com>
Reviewers: chandlerc, craig.topper
Reviewed By: chandlerc
Differential Revision: https://reviews.llvm.org/D55934
llvm-svn: 351325
Increment statistics counter NumSwitches at unswitchNontrivialInvariants() for
unswitching a non-trivial switch instruction. This is to fix a bug that it
increments NumBranches even for the case of switch instruction.
There is no functional change in this patch.
Differential Revision: https://reviews.llvm.org/D56408
llvm-svn: 351193
Currently when a select has a constant value in one branch and the select feeds
a conditional branch (via a compare/ phi and compare) we unfold the select
statement. This results in threading the conditional branch later on. Similar
opportunity exists when a select (with a constant in one branch) feeds a
switch (via a phi node). The patch unfolds select under this condition.
A testcase is provided.
llvm-svn: 350931
Summary:
The original patch addressed the use of BlockRPONumber by forcing a sequence point when accessing that map in a conditional. In short we found cases where that map was being accessed with blocks that had not yet been added to that structure. For context, I've kept the wall of text below, to what we are trying to fix, by always ensuring a updated BlockRPONumber.
== Backstory ==
I was investigating an ICE (segfault accessing a DenseMap item). This failure happened non-deterministically, with no apparent reason and only on a Windows build of LLVM (from October 2018).
After looking into the crashes (multiple core files) and running DynamoRio, the cores and DynamoRio (DR) log pointed to the same code in `GVN::performScalarPRE()`. The values in the map are unsigned integers, the keys are `llvm::BasicBlock*`. Our test case that triggered this warning and periodic crash is rather involved. But the problematic line looks to be:
GVN.cpp: Line 2197
```
if (BlockRPONumber[P] >= BlockRPONumber[CurrentBlock] &&
```
To test things out, I cooked up a patch that accessed the items in the map outside of the condition, by forcing a sequence point between accesses. DynamoRio stopped warning of the issue, and the test didn't seem to crash after 1000+ runs.
My investigation was on an older version of LLVM, (source from October this year). What it looks like was occurring is the following, and the assembly from the latest pull of llvm in December seems to confirm this might still be an issue; however, I have not witnessed the crash on more recent builds. Of course the asm in question is generated from the host compiler on that Windows box (not clang), but it hints that we might want to consider how we access the BlockRPONumber map in this conditional (line 2197, listed above). In any case, I don't think the host compiler is wrong, rather I think it is pointing out a possibly latent bug in llvm.
1) There is no sequence point for the `>=` operation.
2) A call to a `DenseMapBase::operator[]` can have the side effect of the map reallocating a larger store (more Buckets, via a call to `DenseMap::grow`).
3) It seems perfectly legal for a host compiler to generate assembly that stores the result of a call to `operator[]` on the stack (that's what my host compile of GVN.cpp is doing) . A second call to `operator[]` //might// encourage the map to 'grow' thus making any pointers to the map's store invalid. The `>=` compares the first and second values. If the first happens to be a pointer produced from operator[], it could be invalid when dereferenced at the time of comparison.
The assembly generated from the Window's host compiler does show the result of the first access to the map via `operator[]` produces a pointer to an unsigned int. And that pointer is being stored on the stack. If a second call to the map (which does occur) causes the map to grow, that address (on the stack) is now invalid.
Reviewers: t.p.northover, efriedma
Reviewed By: efriedma
Subscribers: efriedma, llvm-commits
Differential Revision: https://reviews.llvm.org/D55974
llvm-svn: 350880
Summary:
Step 2 in using MemorySSA in LICM:
Use MemorySSA in LICM to do sinking and hoisting, all under "EnableMSSALoopDependency" flag.
Promotion is disabled.
Enable flag in LICM sink/hoist tests to test correctness of this change. Moved one test which
relied on promotion, in order to test all sinking tests.
Reviewers: sanjoy, davide, gberry, george.burgess.iv
Subscribers: llvm-commits, Prazek
Differential Revision: https://reviews.llvm.org/D40375
llvm-svn: 350879
That is, remove many of the calls to Type::getNumContainedTypes(),
Type::subtypes(), and Type::getContainedType(N).
I'm not intending to remove these accessors -- they are
useful/necessary in some cases. However, removing the pointee type
from pointers would potentially break some uses, and reducing the
number of calls makes it easier to audit.
llvm-svn: 350835
Current strategy of dropping `InstructionPrecedenceTracking` cache is to
invalidate the entire basic block whenever we change its contents. In fact,
`InstructionPrecedenceTracking` has 2 internal strictures: `OrderedInstructions`
that is needed to be invalidated whenever the contents changes, and the map
with first special instructions in block. This second map does not need an
update if we add/remove a non-special instuction because it cannot
affect the contents of this map.
This patch changes API of `InstructionPrecedenceTracking` so that it now
accounts for reasons under which we invalidate blocks. This should lead
to much less recalculations of the map and should save us some compile time
because in practice we don't typically add/remove special instructions.
Differential Revision: https://reviews.llvm.org/D54462
Reviewed By: efriedma
llvm-svn: 350694
minted `CallBase` class instead of the `CallSite` wrapper.
This moves the largest interwoven collection of APIs that traffic in
`CallSite`s. While a handful of these could have been migrated with
a minorly more shallow migration by converting from a `CallSite` to
a `CallBase`, it hardly seemed worth it. Most of the APIs needed to
migrate together because of the complex interplay of AA APIs and the
fact that converting from a `CallBase` to a `CallSite` isn't free in its
current implementation.
Out of tree users of these APIs can fairly reliably migrate with some
combination of `.getInstruction()` on the `CallSite` instance and
casting the resulting pointer. The most generic form will look like `CS`
-> `cast_or_null<CallBase>(CS.getInstruction())` but in most cases there
is a more elegant migration. Hopefully, this migrates enough APIs for
users to fully move from `CallSite` to the base class. All of the
in-tree users were easily migrated in that fashion.
Thanks for the review from Saleem!
Differential Revision: https://reviews.llvm.org/D55641
llvm-svn: 350503
In addition to finding dead uses of instructions, also find dead uses
of function arguments, and replace them with zero as well.
I'm changing the way the known bits are computed here to remove the
coupling between the transfer function and the algorithm. It previously
relied on the first op being visited first and computing known bits --
unless the first op is not an instruction, in which case they're computed
on the second op. I could have adjusted this to check for "instruction
or argument", but I think it's better to avoid the repeated calculation
with an explicit flag.
Differential Revision: https://reviews.llvm.org/D56247
llvm-svn: 350435
In some cases the order that we hoist instructions in means that when rehoisting
(which uses the same order as hoisting) we can rehoist to a block A, then a
block B, then block A again. This currently causes an assertion failure as it
expects that when changing the hoist point it only ever moves to a block that
dominates the hoist point being moved from.
Fix this by moving the re-hoist point when it doesn't dominate the dominator of
hoisted instruction, or in other words when it wouldn't dominate the uses of
the instruction being rehoisted.
Differential Revision: https://reviews.llvm.org/D55266
llvm-svn: 350408
If an instruction has no demanded bits, remove it directly during BDCE,
instead of leaving it for something else to clean up.
Differential Revision: https://reviews.llvm.org/D56185
llvm-svn: 350257
This (mostly) fixes https://bugs.llvm.org/show_bug.cgi?id=39771.
BDCE currently detects instructions that don't have any demanded bits
and replaces their uses with zero. However, if an instruction has
multiple uses, then some of the uses may be dead (have no demanded bits)
even though the instruction itself is still live. This patch extends
DemandedBits/BDCE to detect such uses and replace them with zero.
While this will not immediately render any instructions dead, it may
lead to simplifications (in the motivating case, by converting a rotate
into a simple shift), break dependencies, etc.
The implementation tries to strike a balance between analysis power and
complexity/memory usage. Originally I wanted to track demanded bits on
a per-use level, but ultimately we're only really interested in whether
a use is entirely dead or not. I'm using an extra set to track which uses
are dead. However, as initially all uses are dead, I'm not storing uses
those user is also dead. This case is checked separately instead.
The previous attempt to land this lead to miscompiles, because cases
where uses were initially dead but were later found to be live during
further analysis were not always correctly removed from the DeadUses
set. This is fixed now and the added test case demanstrates such an
instance.
Differential Revision: https://reviews.llvm.org/D55563
llvm-svn: 350188
Deletion of dead blocks in arbitrary order may lead to failure
of assertion in `DeleteDeadBlock` that requires that we have
deleted all predecessors before we can delete the current block.
We should instead delete them in RPO order.
llvm-svn: 350116
Summary:
Existing LIR recognizes CTLZ where shifting input variable right until it is zero. (Shift-Until-Zero idiom)
This commit:
1. Augments Shift-Until-Zero idiom to recognize CTTZ where input variable is shifted left.
2. Prepare for BitScan idiom recognition.
Patch by Yuanfang Chen (tabloid.adroit)
Reviewers: craig.topper, evstupac
Reviewed By: craig.topper
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D55876
llvm-svn: 350074
This patch teaches LoopSimplifyCFG to remove dead exiting edges
from loops.
Differential Revision: https://reviews.llvm.org/D54025
Reviewed By: fedor.sergeev
llvm-svn: 350049
Both of these places reference memset-like loops. Memset is precise.
Trying to keep these patches super small so they're easily post-commit
verifiable, as requested in D44748.
llvm-svn: 350044
Trying to keep these patches super small so they're easily post-commit
verifiable, as requested in D44748.
srcSize is derived from the size of an alloca, and we quit out if the
size of that is > the size of the thing we're copying to. Hence, we
should always copy everything over, so these sizes are precise.
Don't make srcSize itself a LocationSize, since optionality isn't
helpful, and we do some comparisons against other sizes elsewhere in
that function.
llvm-svn: 350019
Instruction::isLifetimeStartOrEnd() checks whether an Instruction is an
llvm.lifetime.start or an llvm.lifetime.end intrinsic.
This was suggested as a cleanup in D55967.
Differential Revision: https://reviews.llvm.org/D56019
llvm-svn: 349964
Alina Sbirlea