This handles cases where we are comparing a masked value against itself.
The analysis could be further improved by making it recursive but such
expense is not currently justified.
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We were matching against the assume intrinsic in every check. Since we know that it must be an assume, this is just wasted work. Somewhat surprisingly, matching an intrinsic id is actually relatively expensive. It devolves to a string construction and comparison in Function::isIntrinsic.
I originally spotted this because it showed up in a performance profile of my compiler. I've since discovered a separate issue which seems to be the actual root cause, but this is minor perf goodness regardless.
I'm likely to follow up with another change to factor out the comparison matching. There's no need to match the compare instruction in every single one of the tests.
Differential Revision: http://reviews.llvm.org/D6312
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Introduced new target-independent intrinsics in order to support masked vector loads and stores. The loop vectorizer optimizes loops containing conditional memory accesses by generating these intrinsics for existing targets AVX2 and AVX-512. The vectorizer asks the target about availability of masked vector loads and stores.
Added SDNodes for masked operations and lowering patterns for X86 code generator.
Examples:
<16 x i32> @llvm.masked.load.v16i32(i8* %addr, <16 x i32> %passthru, i32 4 /* align */, <16 x i1> %mask)
declare void @llvm.masked.store.v8f64(i8* %addr, <8 x double> %value, i32 4, <8 x i1> %mask)
Scalarizer for other targets (not AVX2/AVX-512) will be done in a separate patch.
http://reviews.llvm.org/D6191
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AliasSetTracker::addUnknown may create an AliasSet devoid of pointers
just to contain an instruction if no suitable AliasSet already exists.
It will then AliasSet::addUnknownInst and we will be done.
However, it's possible for addUnknown to choose an existing AliasSet to
addUnknownInst.
If this were to occur, we are in a bit of a pickle: removing pointers
from the AliasSet can cause the entire AliasSet to become destroyed,
taking our unknown instructions out with them.
Instead, keep track whether or not our AliasSet has any unknown
instructions.
This fixes PR21582.
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This is to be consistent with StringSet and ultimately with the standard
library's associative container insert function.
This lead to updating SmallSet::insert to return pair<iterator, bool>,
and then to update SmallPtrSet::insert to return pair<iterator, bool>,
and then to update all the existing users of those functions...
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SCEVDivision::divide constructed an object of SCEVDivision<Derived>
instead of Derived. divide would call visit which would cast the
SCEVDivision<Derived> to type Derived. As it happens,
SCEVDivision<Derived> and Derived currently have the same layout but
this is fragile and grounds for UB.
Instead, just construct Derived. No functional change intended.
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It turns out that not all users of SCEVDivision want the same
signedness. Let the users determine which operation they'd like by
explicitly choosing SCEVUDivision or SCEVSDivision.
findArrayDimensions and computeAccessFunctions will use SCEVSDivision
while HowFarToZero will use SCEVUDivision.
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Summary:
Several places in DependenceAnalysis assumes both SCEVs in a subscript pair
share the same integer type. For instance, isKnownPredicate calls
SE->getMinusSCEV(X, Y) which asserts X and Y share the same type. However,
DependenceAnalysis fails to ensure this assumption when producing a subscript
pair, causing tests such as NonCanonicalizedSubscript to crash. With this
patch, DependenceAnalysis runs unifySubscriptType before producing any
subscript pair, ensuring the assumption.
Test Plan:
Added NonCanonicalizedSubscript.ll on which DependenceAnalysis before the fix
crashed because subscripts have different types.
Reviewers: spop, sebpop, jingyue
Reviewed By: jingyue
Subscribers: eliben, meheff, llvm-commits
Differential Revision: http://reviews.llvm.org/D6289
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HowFarToZero was supposed to use unsigned division in order to calculate
the backedge taken count. However, SCEVDivision::divide performs signed
division. Unless I am mistaken, no users of SCEVDivision actually want
signed arithmetic: switch to udiv and urem.
This fixes PR21578.
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A few things:
- computeKnownBits is relatively expensive, let's delay its use as long
as we can.
- Don't create two APInt values just to run computeKnownBits on a
ConstantInt, we already know the exact value!
- Avoid creating a temporary APInt value in order to calculate unary
negation.
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Private variables are can be renamed, so it is not reliable to make
decisions on the name.
The name is also dropped by the assembler before getting to the
linker, so using the name causes a disconnect between how llvm makes a
decision (var name) and how the linker makes a decision (section it is
in).
This patch changes one case where we were looking at the variable name to use
the section instead.
Test tuning by Michael Gottesman.
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Let's try this again...
This reverts r219432, plus a bug fix.
Description of the bug in r219432 (by Nick):
The bug was using AllPositive to break out of the loop; if the loop break
condition i != e is changed to i != e && AllPositive then the
test_modulo_analysis_with_global test I've added will fail as the Modulo will
be calculated incorrectly (as the last loop iteration is skipped, so Modulo
isn't updated with its Scale).
Nick also adds this comment:
ComputeSignBit is safe to use in loops as it takes into account phi nodes, and
the == EK_ZeroEx check is safe in loops as, no matter how the variable changes
between iterations, zero-extensions will always guarantee a zero sign bit. The
isValueEqualInPotentialCycles check is therefore definitely not needed as all
the variable analysis holds no matter how the variables change between loop
iterations.
And this patch also adds another enhancement to GetLinearExpression - basically
to convert ConstantInts to Offsets (see test_const_eval and
test_const_eval_scaled for the situations this improves).
Original commit message:
This reverts r218944, which reverted r218714, plus a bug fix.
Description of the bug in r218714 (by Nick):
The original patch forgot to check if the Scale in VariableGEPIndex flipped the
sign of the variable. The BasicAA pass iterates over the instructions in the
order they appear in the function, and so BasicAliasAnalysis::aliasGEP is
called with the variable it first comes across as parameter GEP1. Adding a
%reorder label puts the definition of %a after %b so aliasGEP is called with %b
as the first parameter and %a as the second. aliasGEP later calculates that %a
== %b + 1 - %idxprom where %idxprom >= 0 (if %a was passed as the first
parameter it would calculate %b == %a - 1 + %idxprom where %idxprom >= 0) -
ignoring that %idxprom is scaled by -1 here lead the patch to incorrectly
conclude that %a > %b.
Revised patch by Nick White, thanks! Thanks to Lang to isolating the bug.
Slightly modified by me to add an early exit from the loop and avoid
unnecessary, but expensive, function calls.
Original commit message:
Two related things:
1. Fixes a bug when calculating the offset in GetLinearExpression. The code
previously used zext to extend the offset, so negative offsets were converted
to large positive ones.
2. Enhance aliasGEP to deduce that, if the difference between two GEP
allocations is positive and all the variables that govern the offset are also
positive (i.e. the offset is strictly after the higher base pointer), then
locations that fit in the gap between the two base pointers are NoAlias.
Patch by Nick White!
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If x is known to have the range [a, b), in a loop predicated by (icmp
ne x, a) its range can be sharpened to [a + 1, b). Get
ScalarEvolution and hence IndVars to exploit this fact.
This change triggers an optimization to widen-loop-comp.ll, so it had
to be edited to get it to pass.
This change was originally landed in r219834 but had a bug and broke
ASan. It was reverted in r219878, and is now being re-landed after
fixing the original bug.
phabricator: http://reviews.llvm.org/D5639
reviewed by: atrick
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Make the handling of calls to intrinsics in CGSCC consistent:
they are not treated like regular function calls because they
are never lowered to function calls.
Without this patch, we can get dangling pointer asserts from
the subsequent loop that processes callsites because it already
ignores intrinsics.
See http://llvm.org/bugs/show_bug.cgi?id=21403 for more details / discussion.
Differential Revision: http://reviews.llvm.org/D6124
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Instead, we're going to separate metadata from the Value hierarchy. See
PR21532.
This reverts commit r221375.
This reverts commit r221373.
This reverts commit r221359.
This reverts commit r221167.
This reverts commit r221027.
This reverts commit r221024.
This reverts commit r221023.
This reverts commit r220995.
This reverts commit r220994.
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This commit adds a new pass that can inject checks before indirect calls to
make sure that these calls target known locations. It supports three types of
checks and, at compile time, it can take the name of a custom function to call
when an indirect call check fails. The default failure function ignores the
error and continues.
This pass incidentally moves the function JumpInstrTables::transformType from
private to public and makes it static (with a new argument that specifies the
table type to use); this is so that the CFI code can transform function types
at call sites to determine which jump-instruction table to use for the check at
that site.
Also, this removes support for jumptables in ARM, pending further performance
analysis and discussion.
Review: http://reviews.llvm.org/D4167
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Exact shifts may not shift out any non-zero bits. Use computeKnownBits
to determine when this occurs and just return the left hand side.
This fixes PR21477.
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Divides and remainder operations do not behave like other operations
when they are given poison: they turn into undefined behavior.
It's really hard to know if the operands going into a div are or are not
poison. Because of this, we should only choose to speculate if there
are constant operands which we can easily reason about.
This fixes PR21412.
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LoadCombine can be smarter about aborting when a writing instruction is
encountered, instead of aborting upon encountering any writing instruction, use
an AliasSetTracker, and only abort when encountering some write that might
alias with the loads that could potentially be combined.
This was originally motivated by comments made (and a test case provided) by
David Majnemer in response to PR21448. It turned out that LoadCombine was not
responsible for that PR, but LoadCombine should also be improved so that
unrelated stores (and @llvm.assume) don't interrupt load combining.
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Change `Instruction::getMetadata()` to return `Value` as part of
PR21433.
Update most callers to use `Instruction::getMDNode()`, which wraps the
result in a `cast_or_null<MDNode>`.
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In a case where we have a no {un,}signed wrap flag on the increment, if
RHS - Start is constant then we can avoid inserting a max operation bewteen
the two, since we can statically determine which is greater.
This allows us to unroll loops such as:
void testcase3(int v) {
for (int i=v; i<=v+1; ++i)
f(i);
}
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If we load from a location with range metadata, we can use information about the ranges of the loaded value for optimization purposes. This helps to remove redundant checks and canonicalize checks for other optimization passes. This particular patch checks whether a value is known to be non-zero from the range metadata.
Currently, these tests are against InstCombine. In theory, all of these should be InstSimplify since we're not inserting any new instructions. Moving the code may follow in a separate change.
Reviewed by: Hal
Differential Revision: http://reviews.llvm.org/D5947
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ConstantFolding crashes when trying to InstSimplify the following load:
@a = private unnamed_addr constant %mst {
i8* inttoptr (i64 -1 to i8*),
i8* inttoptr (i64 -1 to i8*)
}, align 8
%x = load <2 x i8*>* bitcast (%mst* @a to <2 x i8*>*), align 8
This patch fix this by adding support to this type of folding:
%x = load <2 x i8*>* bitcast (%mst* @a to <2 x i8*>*), align 8
==> gets folded to:
%x = <2 x i8*> <i8* inttoptr (i64 -1 to i8*), i8* inttoptr (i64 -1 to i8*)>
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These are named following the IEEE-754 names for these
functions, rather than the libm fmin / fmax to avoid
possible ambiguities. Some languages may implement something
resembling fmin / fmax which return NaN if either operand is
to propagate errors. These implement the IEEE-754 semantics
of returning the other operand if either is a NaN representing
missing data.
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inttoptr or ptrtoint cast provided there is datalayout available.
Eventually, the datalayout can just be required but in practice it will
always be there today.
To go with the ability to expose available values requiring a ptrtoint
or inttoptr cast, helpers are added to perform one of these three casts.
These smarts are necessary to finish canonicalizing loads and stores to
the operational type requirements without regressing fundamental
combines.
I've added some test cases. These should actually improve as the load
combining and store combining improves, but they may fundamentally be
highlighting some missing combines for select in addition to exercising
the specific added logic to load analysis.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220277 91177308-0d34-0410-b5e6-96231b3b80d8
Our metadata scheme lazily assigns IDs to string metadata, but we have a mechanism to preassign them as well. Using a preassigned ID is helpful since we get compile time type checking, and avoid some (minimal) string construction and comparison. This change adds enum value for three existing metadata types:
+ MD_nontemporal = 9, // "nontemporal"
+ MD_mem_parallel_loop_access = 10, // "llvm.mem.parallel_loop_access"
+ MD_nonnull = 11 // "nonnull"
I went through an updated various uses as well. I made no attempt to get all uses; I focused on the ones which were easily grepable and easily to translate. For example, there were several items in LoopInfo.cpp I chose not to update.
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The newly introduced 'nonnull' metadata is analogous to existing 'nonnull' attributes, but applies to load instructions rather than call arguments or returns. Long term, it would be nice to combine these into a single construct. The value of the load is allowed to vary between successive loads, but null is not a valid value to be loaded by any load marked nonnull.
Reviewed by: Hal Finkel
Differential Revision: http://reviews.llvm.org/D5220
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The original code had an implicit assumption that if the test for
allocas or globals was reached, the two pointers were not equal. With my
changes to make the pointer analysis more powerful here, I also had to
guard against circumstances where the results weren't useful. That in
turn violated the assumption and gave rise to a circumstance in which we
could have a store with both the queried pointer and stored pointer
rooted at *the same* alloca. Clearly, we cannot ignore such a store.
There are other things we might do in this code to better handle the
case of both pointers ending up at the same alloca or global, but it
seems best to at least make the test explicit in what it intends to
check.
I've added tests for both the alloca and global case here.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220190 91177308-0d34-0410-b5e6-96231b3b80d8
logic to look through pointer casts, making them trivially stronger in
the face of loads and stores with intervening pointer casts.
I've included a few test cases that demonstrate the kind of folding
instcombine can do without pointer casts and then variations which
obfuscate the logic through bitcasts. Without this patch, the variations
all fail to optimize fully.
This is more important now than it has been in the past as I've started
moving the load canonicialization to more closely follow the value type
requirements rather than the pointer type requirements and thus this
needs to be prepared for more pointer casts. When I made the same change
to stores several test cases regressed without logic along these lines
so I wanted to systematically improve matters first.
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up to where it actually works as intended. The problem is that
a GlobalAlias isa GlobalValue and so the prior block handled all of the
cases.
This allows us to constant fold based on the actual constant expression
in the global alias. As an example, see the last function in the newly
added test case which explicitly aligns an unaligned pointer using
constant expression math. Without this change, we fail to see that and
fold an alignment test to zero.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220164 91177308-0d34-0410-b5e6-96231b3b80d8
by my refactoring of this code.
The method isSafeToLoadUnconditionally assumes that the load will
proceed with the preferred type alignment. Given that, it has to ensure
that the alloca or global is at least that aligned. It has always done
this historically when a datalayout is present, but has never checked it
when the datalayout is absent. When I refactored the code in r220156,
I exposed this path when datalayout was present and that turned the
latent bug into a patent bug.
This fixes the issue by just removing the special case which allows
folding things without datalayout. This isn't worth the complexity of
trying to tease apart when it is or isn't safe without actually knowing
the preferred alignment.
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