The check for complexity compares the number of polyhedra in a set,
which are combined by disjunctions (union, "OR"),
not conjunctions (intersection, "AND").
llvm-svn: 268223
For debugging it is often convenient to not abort at the very first memory
management error. This option allows to control this behavior at run-time.
llvm-svn: 268030
It does not suffice to take a global assumptions for unsigned comparisons but
we also need to adjust the invalid domain of the statements guarded by such
an assumption. To this end we allow to specialize the getPwAff call now in
order to indicate unsigned interpretation.
llvm-svn: 268025
Assumptions and restrictions can both be simplified with the domain of a
statement but not the same way. After this patch we will correctly
distinguish them.
llvm-svn: 267885
If the base pointer of an invariant load is is loaded conditionally, that
condition needs to hold for the invariant load too. The structure of the
program will imply this for domain constraints but not for imprecisions in
the modeling. To this end we will propagate the execution context of base
pointers during code generation and thus ensure the derived pointer does
not access an invalid base pointer.
llvm-svn: 267707
With this patch we will optimistically assume that the result of an unsigned
comparison is the same as the result of the same comparison interpreted as
signed.
llvm-svn: 267559
Before, we checked all GEPs in a statement in order to derive
out-of-bound assumptions. However, this can not only introduce new
parameters but it is also not clear what we can learn from GEPs that
are not immediately used in a memory accesses inside the SCoP. As this
case is very rare, no actual change in the behaviour is expected.
llvm-svn: 267442
Before, assumptions derived from llvm.assume could reference new
parameters that were not known to the SCoP before. These were neither
beneficial to the representation nor to the user that reads the
emitted remark. Now we project them out and keep only user assumptions
on known parameters. Nevertheless, the new parameters are still part
of the SCoPs parameter space as the SCEVAffinator currently adds them
on demand.
llvm-svn: 267441
The new handling is consistent with the remaining code, e.g., we do
not create a new parameter id for each lookup call but copy an
existing one. Additionally, we now use the implicit order defined by
the Parameters set instead of an explicit one defined in a map.
llvm-svn: 267423
A zero-extended value can be interpreted as a piecewise defined signed
value. If the value was non-negative it stays the same, otherwise it
is the sum of the original value and 2^n where n is the bit-width of
the original (or operand) type. Examples:
zext i8 127 to i32 -> { [127] }
zext i8 -1 to i32 -> { [256 + (-1)] } = { [255] }
zext i8 %v to i32 -> [v] -> { [v] | v >= 0; [256 + v] | v < 0 }
However, LLVM/Scalar Evolution uses zero-extend (potentially lead by a
truncate) to represent some forms of modulo computation. The left-hand side
of the condition in the code below would result in the SCEV
"zext i1 <false, +, true>for.body" which is just another description
of the C expression "i & 1 != 0" or, equivalently, "i % 2 != 0".
for (i = 0; i < N; i++)
if (i & 1 != 0 /* == i % 2 */)
/* do something */
If we do not make the modulo explicit but only use the mechanism described
above we will get the very restrictive assumption "N < 3", because for all
values of N >= 3 the SCEVAddRecExpr operand of the zero-extend would wrap.
Alternatively, we can make the modulo in the operand explicit in the
resulting piecewise function and thereby avoid the assumption on N. For the
example this would result in the following piecewise affine function:
{ [i0] -> [(1)] : 2*floor((-1 + i0)/2) = -1 + i0;
[i0] -> [(0)] : 2*floor((i0)/2) = i0 }
To this end we can first determine if the (immediate) operand of the
zero-extend can wrap and, in case it might, we will use explicit modulo
semantic to compute the result instead of emitting non-wrapping assumptions.
Note that operands with large bit-widths are less likely to be negative
because it would result in a very large access offset or loop bound after the
zero-extend. To this end one can optimistically assume the operand to be
positive and avoid the piecewise definition if the bit-width is bigger than
some threshold (here MaxZextSmallBitWidth).
We choose to go with a hybrid solution of all modeling techniques described
above. For small bit-widths (up to MaxZextSmallBitWidth) we will model the
wrapping explicitly and use a piecewise defined function. However, if the
bit-width is bigger than MaxZextSmallBitWidth we will employ overflow
assumptions and assume the "former negative" piece will not exist.
llvm-svn: 267408
Memory accesses can have non-precisely modeled access functions that
would cause us to build incorrect execution context for hoisted loads.
This is the same issue that occurred during the domain construction for
statements and it is dealt with the same way.
llvm-svn: 267289
The SCEVAffinator will now produce not only the isl representaiton of
a SCEV but also the domain under which it is invalid. This is used to
record possible overflows that can happen in the statement domains in
the statements invalid domain. The result is that invalid loads have
an accurate execution contexts with regards to the validity of their
statements domain. While the SCEVAffinator currently is only taking
"no-wrapping" assumptions, we can add more withouth worrying about the
execution context of loads that are optimistically hoisted.
llvm-svn: 267288
The invalid context is not enough to describe the parameter constraints under
which a statement is not modeled precisely. The reason is that during the
domain construction the bounds on the induction variables are not known but
needed to check if e.g., an overflow can actually happen. To this end we
replace the invalid context of a statement with an invalid domain. It is
initialized during domain construction and intersected with the domain once
it was completely build. Later this invalid domain allows to eliminate
falsely assumed wrapping cases and other falsely assumed mismatches in the
modeling.
llvm-svn: 267286
We used checks to minimize the number of remarks we present to a user
but these checks can become expensive, especially since all wrapping
assumptions are emitted separately. Because there is not benefit for a
"headless" run we put these checks under a command line flag. Thus, if
the flag is not given we will emit "non-effective" remarks, e.g.,
duplicates and revert to the old behaviour if it is given. As this
also changes the internal representation of some sets we set the flag
by default for our unit tests.
llvm-svn: 266087
Utilizing the record option for assumptions we can simplify the wrapping
assumption generation a lot. Additionally, we can now report locations
together with wrapping assumptions, though they might not be accurate yet.
llvm-svn: 266069
There are three reasons why we want to record assumptions first before we
add them to the assumed/invalid context:
1) If the SCoP is not profitable or otherwise invalid without the
assumed/invalid context we do not have to compute it.
2) Information about the context are gathered rather late in the SCoP
construction (basically after we know all parameters), thus the user
might see overly complicated assumptions to be taken while they would
have been simplified later on.
3) Currently we cannot take assumptions at any point but have to wait,
e.g., for the domain generation to finish. This makes wrapping
assumptions much more complicated as they need to be and it will
have a similar effect on "signed-unsigned" assumptions later.
llvm-svn: 266068
Collect the error domain contexts (formerly in the ErrorDomainCtxMap)
for each statement in the new InvalidContext member variable. While
this commit is basically a [NFC] it is a first step to make hoisting
sound by allowing a more fine grained record of invalid contexts,
e.g., here on statement level.
llvm-svn: 266053
Allow overflow of indices into the next higher dimension if it has
constant size. E.g.
float A[32][2];
((float*)A)[5];
is effectively the same as
A[2][1];
This can happen since r265379 as a side effect if ScopDetection
recognizes an access as affine, but ScopInfo rejects the GetElementPtr.
Differential Revision: http://reviews.llvm.org/D18878
llvm-svn: 265942
MSVC warns with:
warning C4239: nonstandard extension used: 'initializing': conversion from 'llvm::DebugLoc' to 'llvm::DebugLoc &'
note: A non-const reference may only be bound to an lvalue
Change the reference to a const reference.
llvm-svn: 265937
The way to get the elements size with getPrimitiveSizeInBits() is not
the same as used in other parts of Polly which should use
DataLayout::getTypeAllocSize(). Its use only queries the size of the
pointer and getPrimitiveSizeInBits returns 0 for types that require a
DataLayout object such as pointers.
Together with r265379, this should fix PR27195.
llvm-svn: 265795
If we build the domains for error blocks and later remove them we lose
the information that they are not executed. Thus, in the SCoP it looks
like the control will always reach the statement S:
for (i = 0 ... N)
if (*valid == 0)
doSth(&ptr);
S: A[i] = *ptr;
Consequently, we would have assumed "ptr" to be always accessed and
preloaded it unconditionally. However, only if "*valid != 0" we would
execute the optimized version of the SCoP. Nevertheless, we would have
hoisted and accessed "ptr"regardless of "*valid". This changes the
semantic of the program as the value of "*valid" can cause a change of
"ptr" and control if it is executed or not.
To fix this problem we adjust the execution context of hoisted loads
wrt. error domains. To this end we introduce an ErrorDomainCtxMap that
maps each basic block to the error context under which it might be
executed. Thus, to the context under which it is executed but an error
block would have been executed to. To fill this map one traversal of
the blocks in the SCoP suffices. During this traversal we do also
"remove" error statements and those that are only reachable via error
statements. This was previously done by the removeErrorBlockDomains
function which is therefor not needed anymore.
This fixes bug PR26683 and thereby several SPEC miscompiles.
Differential Revision: http://reviews.llvm.org/D18822
llvm-svn: 265778
The findValues() function did not look through div & srem instructions
that were part of the argument SCEV. However, in different other
places we already look through it. This mismatch caused us to preload
values in the wrong order.
llvm-svn: 265775
If all exiting blocks of a SCoP are error blocks and therefor not
represented we will not generate accesses and consequently no SAI
objects for exit PHIs. However, they are needed in the code generation
to generate the merge PHIs between the original and optimized region.
With this patch we enusre that the SAI objects for exit PHIs exist
even if all exiting blocks turn out to be eror blocks.
This fixes the crash reported in PR27207.
llvm-svn: 265393
We currently only consider the first GEP when delinearizing access functions,
which makes us loose information about additional index expression offsets,
which results in our SCoP model to be incorrect. With this patch we now
compare the base pointers used to ensure we do not miss any additional offsets.
This fixes llvm.org/PR27195.
We may consider supporting nested GEP in our delinearization heuristics in
the future.
llvm-svn: 265379
Even before we build the domain the branch condition can become very
complex, especially if we have to build the complement of a lot of
equality constraints. With this patch we bail if the branch condition
has a lot of basic sets and parameters.
After this patch we now successfully compile
External/SPEC/CINT2000/186_crafty/186_crafty
with "-polly-process-unprofitable -polly-position=before-vectorizer".
llvm-svn: 265286
As a CFG is often structured we can simplify the steps performed during
domain generation. When we push domain information we can utilize the
information from a block A to build the domain of a block B, if A dominates B
and there is no loop backede on a path from A to B. When we pull domain
information we can use information from a block A to build the domain of a
block B if B post-dominates A. This patch implements both ideas and thereby
simplifies domains that were not simplified by isl. For the FINAL basic block
in test/ScopInfo/complex-successor-structure-3.ll we used to build a universe
set with 81 basic sets. Now it actually is represented as universe set.
While the initial idea to utilize the graph structure depended on the
dominator and post-dominator tree we can use the available region
information as a coarse grained replacement. To this end we push the
region entry domain to the region exit and pull it from the region
entry for the region exit if applicable.
With this patch we now successfully compile
External/SPEC/CINT2006/400_perlbench/400_perlbench
and
SingleSource/Benchmarks/Adobe-C++/loop_unroll.
Differential Revision: http://reviews.llvm.org/D18450
llvm-svn: 265285
Michael Kruse