When dependence analysis encounters a non-constant distance between
memory accesses it aborts the analysis and falls back to run-time checks
only. In this case we weren't resetting the array of dependences.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237574 91177308-0d34-0410-b5e6-96231b3b80d8
"Store to invariant address..." is moved as the last line. This is not
the prime result of the analysis. Plus it simplifies some of the tests.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237573 91177308-0d34-0410-b5e6-96231b3b80d8
Specifically, if a pointer accesses different underlying objects in each
iteration, don't look through the phi node defining the pointer.
The motivating case is the underlyling-objects-2.ll testcase. Consider
the loop nest:
int **A;
for (i)
for (j)
A[i][j] = A[i-1][j] * B[j]
This loop is transformed by Load-PRE to stash away A[i] for the next
iteration of the outer loop:
Curr = A[0]; // Prev_0
for (i: 1..N) {
Prev = Curr; // Prev = PHI (Prev_0, Curr)
Curr = A[i];
for (j: 0..N)
Curr[j] = Prev[j] * B[j]
}
Since A[i] and A[i-1] are likely to be independent pointers,
getUnderlyingObjects should not assume that Curr and Prev share the same
underlying object in the inner loop.
If it did we would try to dependence-analyze Curr and Prev and the
analysis of the corresponding SCEVs would fail with non-constant
distance.
To fix this, the getUnderlyingObjects API is extended with an optional
LoopInfo parameter. This is effectively what controls whether we want
the above behavior or the original. Currently, I only changed to use
this approach for LoopAccessAnalysis.
The other testcase is to guard the opposite case where we do want to
look through the loop PHI. If we step through an array by incrementing
a pointer, the underlying object is the incoming value of the phi as the
loop is entered.
Fixes rdar://problem/19566729
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235634 91177308-0d34-0410-b5e6-96231b3b80d8
Fix oversight in -analyze output. PtrRtCheck contains the pointers that
need to be checked against each other and not whether memchecks are
necessary.
For instance in the testcase PtrRtCheck has four elements but all
no-alias so no checking is necessary.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234833 91177308-0d34-0410-b5e6-96231b3b80d8
(Re-apply r234361 with a fix and a testcase for PR23157)
Both run-time pointer checking and the dependence analysis are capable
of dealing with uniform addresses. I.e. it's really just an orthogonal
property of the loop that the analysis computes.
Run-time pointer checking will only try to reason about SCEVAddRec
pointers or else gives up. If the uniform pointer turns out the be a
SCEVAddRec in an outer loop, the run-time checks generated will be
correct (start and end bounds would be equal).
In case of the dependence analysis, we work again with SCEVs. When
compared against a loop-dependent address of the same underlying object,
the difference of the two SCEVs won't be constant. This will result in
returning an Unknown dependence for the pair.
When compared against another uniform access, the difference would be
constant and we should return the right type of dependence
(forward/backward/etc).
The changes also adds support to query this property of the loop and
modify the vectorizer to use this.
Patch by Ashutosh Nema!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234424 91177308-0d34-0410-b5e6-96231b3b80d8
Both run-time pointer checking and the dependence analysis are capable
of dealing with uniform addresses. I.e. it's really just an orthogonal
property of the loop that the analysis computes.
Run-time pointer checking will only try to reason about SCEVAddRec
pointers or else gives up. If the uniform pointer turns out the be a
SCEVAddRec in an outer loop, the run-time checks generated will be
correct (start and end bounds would be equal).
In case of the dependence analysis, we work again with SCEVs. When
compared against a loop-dependent address of the same underlying object,
the difference of the two SCEVs won't be constant. This will result in
returning an Unknown dependence for the pair.
When compared against another uniform access, the difference would be
constant and we should return the right type of dependence
(forward/backward/etc).
The changes also adds support to query this property of the loop and
modify the vectorizer to use this.
Patch by Ashutosh Nema!
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234361 91177308-0d34-0410-b5e6-96231b3b80d8
The debug message was pretty confusing here. It only reported the
situation with memchecks without the result of the dependence analysis.
Now it prints whether the loop is safe from the POV of the dependence
analysis and if yes, whether we need memchecks.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231854 91177308-0d34-0410-b5e6-96231b3b80d8
This is the final patch that actually introduces the new parameter of
partition mapping to RuntimePointerCheck::needsChecking.
Another API (LAI::getInstructionsForAccess) is also exposed that helps
to map pointers to instructions because ultimately we partition
instructions.
The WIP version of the Loop Distribution pass in D6930 has been adapted
to use all this. See for example, how
InstrPartitionContainer::computePartitionSetForPointers sets up the
partitions using the above API and then calls to LAI::addRuntimeCheck
with the pointer partitions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231818 91177308-0d34-0410-b5e6-96231b3b80d8
Now the analysis won't "fail" if the memchecks exceed the threshold. It
is the transform pass' responsibility to perform the check.
This allows the transform pass to further analyze/eliminate the
memchecks. E.g. in Loop distribution we only need to check pointers
that end up in different partitions.
Note that there is a slight change of functionality here. The logic in
analyzeLoop is that if dependence checking fails due to non-constant
distance between the pointers, another attempt is made to prove safety
of the dependences purely using run-time checks.
Before this patch we could fail the loop due to exceeding the memcheck
threshold after the first step, now we only check the threshold in the
client after the full analysis. There is no measurable compile-time
effect but I wanted to record this here.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231817 91177308-0d34-0410-b5e6-96231b3b80d8
The check for the number of memchecks will be moved to the client of
this analysis. Besides allowing for transform-specific thresholds, this
also lets Loop Distribution post-process the memchecks; Loop
Distribution only needs memchecks between pointers of different
partitions.
The motivation for this first patch is to untangle the CanDoRT check
from the NumComparison check before moving the NumComparison part.
CanDoRT means that we couldn't determine the bounds for the pointer.
Note that NumComparison is set independent of this flag.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231816 91177308-0d34-0410-b5e6-96231b3b80d8
The dependences are now expose through the new getInterestingDependences
API so we can use that with -analyze too and fix the FIXME.
This lets us remove the test that relied on -debug to check the
dependences.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231807 91177308-0d34-0410-b5e6-96231b3b80d8
Gather an array of interesting dependences rather than just failing
after the first unsafe one and regarding the loop unsafe. Loop
Distribution needs to be able to collect all dependences in order to
isolate the dependence cycles into their own partition.
Since the dependence checking algorithm is quadratic in terms of
accesses sharing the same underlying pointer, I am applying a cut-off
threshold (MaxInterestingDependence). Exceeding that, the logic reverts
back to the original approach deeming the loop unsafe upon encountering
the first unsafe dependence.
The main idea of the patch is to split isDepedent from directly
answering the question whether the dep is safe for vectorization to
return a dependence type which then gets mapped to old boolean result
using Dependence::isSafeForVectorization.
Tested that this was compile-time neutral on SpecINT2006 LTO bitcode
inputs. No assembly change on the testsuite including external.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231806 91177308-0d34-0410-b5e6-96231b3b80d8
LoopDistribution needs to query various results of the dependence
analysis. This series will expose some more APIs and state of the
dependence checker.
This patch is a simple one to just expose the DepChecker instance. The
set is compile-time neutral measured with LTO bitcode files of
SpecINT2006. Also there is no assembly change on the testsuite.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231805 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
Now that the DataLayout is a mandatory part of the module, let's start
cleaning the codebase. This patch is a first attempt at doing that.
This patch is not exactly NFC as for instance some places were passing
a nullptr instead of the DataLayout, possibly just because there was a
default value on the DataLayout argument to many functions in the API.
Even though it is not purely NFC, there is no change in the
validation.
I turned as many pointer to DataLayout to references, this helped
figuring out all the places where a nullptr could come up.
I had initially a local version of this patch broken into over 30
independant, commits but some later commit were cleaning the API and
touching part of the code modified in the previous commits, so it
seemed cleaner without the intermediate state.
Test Plan:
Reviewers: echristo
Subscribers: llvm-commits
From: Mehdi Amini <mehdi.amini@apple.com>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231740 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
DataLayout keeps the string used for its creation.
As a side effect it is no longer needed in the Module.
This is "almost" NFC, the string is no longer
canonicalized, you can't rely on two "equals" DataLayout
having the same string returned by getStringRepresentation().
Get rid of DataLayoutPass: the DataLayout is in the Module
The DataLayout is "per-module", let's enforce this by not
duplicating it more than necessary.
One more step toward non-optionality of the DataLayout in the
module.
Make DataLayout Non-Optional in the Module
Module->getDataLayout() will never returns nullptr anymore.
Reviewers: echristo
Subscribers: resistor, llvm-commits, jholewinski
Differential Revision: http://reviews.llvm.org/D7992
From: Mehdi Amini <mehdi.amini@apple.com>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231270 91177308-0d34-0410-b5e6-96231b3b80d8
accesses are via different types
Noticed this while generalizing the code for loop distribution.
I confirmed with Arnold that this was indeed a bug and managed to create
a testcase.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230647 91177308-0d34-0410-b5e6-96231b3b80d8
Adam Nemet
Benjamin Kramer
Michael Zolotukhin
David Majnemer
Mehdi Amini