Seeing how we can't generate any debug intrinsics any more: delete a
variety of codepaths where they're handled. For the most part these are
plain deletions, in others I've tweaked comments to remain coherent, or
added a type to (what was) type-generic-lambdas.
This isn't all the DbgInfoIntrinsic call sites but it's most of the
simple scenarios.
Co-authored-by: Nikita Popov <github@npopov.com>
Having a finite Depth (or recursion limit) for computeKnownBits is very
limiting, but is currently a load-bearing necessity, as all KnownBits
are recomputed on each call and there is no caching. As a prerequisite
for an effort to remove the recursion limit altogether, either using a
clever caching technique, or writing a easily-invalidable KnownBits
analysis, make the Depth argument in APIs in ValueTracking uniformly the
last argument with a default value. This would aid in removing the
argument when the time comes, as many callers that currently pass 0
explicitly are now updated to omit the argument altogether.
This is a helper to avoid writing `getModule()->getDataLayout()`. I
regularly try to use this method only to remember it doesn't exist...
`getModule()->getDataLayout()` is also a common (the most common?)
reason why code has to include the Module.h header.
This reverts commit b5743d4798b250506965e07ebab806a3c2d767cc.
This causes some minor compile-time impact. Revert for now, better
to do the change more gradually.
Last user of DemandedBitsWrapperPass was the BDCE pass. Since
the legacy PM version of BDCE was removed in an earlier commit, this
patch removes the now unused DemandedBitsWrapperPass.
Differential Revision: https://reviews.llvm.org/D148336
This renames the primary methods for creating a zero value to `getZero`
instead of `getNullValue` and renames predicates like `isAllOnesValue`
to simply `isAllOnes`. This achieves two things:
1) This starts standardizing predicates across the LLVM codebase,
following (in this case) ConstantInt. The word "Value" doesn't
convey anything of merit, and is missing in some of the other things.
2) Calling an integer "null" doesn't make any sense. The original sin
here is mine and I've regretted it for years. This moves us to calling
it "zero" instead, which is correct!
APInt is widely used and I don't think anyone is keen to take massive source
breakage on anything so core, at least not all in one go. As such, this
doesn't actually delete any entrypoints, it "soft deprecates" them with a
comment.
Included in this patch are changes to a bunch of the codebase, but there are
more. We should normalize SelectionDAG and other APIs as well, which would
make the API change more mechanical.
Differential Revision: https://reviews.llvm.org/D109483
This adjusts mayHaveSideEffect() to return true for !willReturn()
instructions. Just like other side-effects, non-willreturn calls
(aka "divergence") cannot be removed and cannot be reordered relative
to other side effects. This fixes a number of bugs where
non-willreturn calls are either incorrectly dropped or moved. In
particular, it also fixes the last open problem in
https://bugs.llvm.org/show_bug.cgi?id=50511.
I performed a cursory review of all current mayHaveSideEffect()
uses, which convinced me that these are indeed the desired default
semantics. Places that do not want to consider non-willreturn as a
sideeffect generally do not want mayHaveSideEffect() semantics at
all. I identified two such cases, which are addressed by D106591
and D106742. Finally, there is a use in SCEV for which we don't
really have an appropriate API right now -- what it wants is
basically "would this be considered forward progress". I've just
spelled out the previous semantics there.
Differential Revision: https://reviews.llvm.org/D106749
Add getDemandedBits method for uses so we can query demanded bits for each use. This can help getting better use information. For example, for the code below
define i32 @test_use(i32 %a) {
%1 = and i32 %a, -256
%2 = or i32 %1, 1
%3 = trunc i32 %2 to i8 (didn't optimize this to 1 for illustration purpose)
... some use of %3
ret %2
}
if we look at the demanded bit of %2 (which is all 32 bits because of the return), we would conclude that %a is used regardless of how its return is used. However, if we look at each use separately, we will see that the demanded bit of %2 in trunc only uses the lower 8 bits of %a which is redefined, therefore %a's usage depends on how the function return is used.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D97074
In both ADCE and BDCE (via DemandedBits) we should not remove
instructions that are not guaranteed to return. This issue was
pointed out by fhahn in the recent llvm-dev thread.
Differential Revision: https://reviews.llvm.org/D96993
Add DemandedBits / BDCE support for min/max intrinsics: If the low
bits are not demanded in the result, they also aren't demanded in
the operands.
Differential Revision: https://reviews.llvm.org/D87161
The current demand propagator for addition will mark all input bits at and right of the alive output bit as alive. But carry won't propagate beyond a bit for which both operands are zero (or one/zero in the case of subtraction) so a more accurate answer is possible given known bits.
I derived a propagator by working through truth tables and using a bit-reversed addition to make demand ripple to the right, but I'm not sure how to make a convincing argument for its correctness in the comments yet. Nevertheless, here's a minimal implementation and test to get feedback.
This would help in a situation where, for example, four bytes (<128) packed into an int are added with four others SIMD-style but only one of the four results is actually read.
Known A: 0_______0_______0_______0_______
Known B: 0_______0_______0_______0_______
AOut: 00000000001000000000000000000000
AB, current: 00000000001111111111111111111111
AB, patch: 00000000001111111000000000000000
Committed on behalf of: @rrika (Erika)
Differential Revision: https://reviews.llvm.org/D72423
This file lists every pass in LLVM, and is included by Pass.h, which is
very popular. Every time we add, remove, or rename a pass in LLVM, it
caused lots of recompilation.
I found this fact by looking at this table, which is sorted by the
number of times a file was changed over the last 100,000 git commits
multiplied by the number of object files that depend on it in the
current checkout:
recompiles touches affected_files header
342380 95 3604 llvm/include/llvm/ADT/STLExtras.h
314730 234 1345 llvm/include/llvm/InitializePasses.h
307036 118 2602 llvm/include/llvm/ADT/APInt.h
213049 59 3611 llvm/include/llvm/Support/MathExtras.h
170422 47 3626 llvm/include/llvm/Support/Compiler.h
162225 45 3605 llvm/include/llvm/ADT/Optional.h
158319 63 2513 llvm/include/llvm/ADT/Triple.h
140322 39 3598 llvm/include/llvm/ADT/StringRef.h
137647 59 2333 llvm/include/llvm/Support/Error.h
131619 73 1803 llvm/include/llvm/Support/FileSystem.h
Before this change, touching InitializePasses.h would cause 1345 files
to recompile. After this change, touching it only causes 550 compiles in
an incremental rebuild.
Reviewers: bkramer, asbirlea, bollu, jdoerfert
Differential Revision: https://reviews.llvm.org/D70211
InputIsKnownDead check is shared by all operands. Compute it once.
For non-integer instructions, use Visited.insert(I).second to replace a
find() and an insert().
llvm-svn: 355290
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
DemandedBits currently uses a simple vector for the worklist, which
means that instructions may be inserted multiple times into it.
Especially in combination with the deep lattice, this may cause
instructions too be recomputed very often. To avoid this, switch
to a SetVector.
Reapplying with a smaller number of inline elements in the
SmallSetVector, to avoid running into the SmallDenseMap issue
described in D56455.
Differential Revision: https://reviews.llvm.org/D56362
llvm-svn: 350997
DemandedBits currently uses a simple vector for the worklist, which
means that instructions may be inserted multiple times into it.
Especially in combination with the deep lattice, this may cause
instructions too be recomputed very often. To avoid this, switch
to a SetVector.
Differential Revision: https://reviews.llvm.org/D56362
llvm-svn: 350547
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
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
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 test case has a couple of cases that are not simplified yet. In
particular, we're only looking at uses of instructions right now. I think
it would make sense to also extend this to arguments. Furthermore
DemandedBits doesn't yet know some of the tricks that InstCombine does
for the demanded bits or bitwise or/and/xor in combination with known
bits information.
Differential Revision: https://reviews.llvm.org/D55563
llvm-svn: 349674
DemandedBits and BDCE currently only support scalar integers. This
patch extends them to also handle vector integer operations. In this
case bits are not tracked for individual vector elements, instead a
bit is demanded if it is demanded for any of the elements. This matches
the behavior of computeKnownBits in ValueTracking and
SimplifyDemandedBits in InstCombine.
Unlike the previous iteration of this patch, getDemandedBits() can now
again be called on arbirary (sized) instructions, even if they don't
have integer or vector of integer type. (For vector types the size of the
returned mask will now be the scalar size in bits though.)
The added LoopVectorize test case shows a case which triggered an
assertion failure with the previous attempt, because getDemandedBits()
was called on a pointer-typed instruction.
Differential Revision: https://reviews.llvm.org/D55297
llvm-svn: 348602
DemandedBits and BDCE currently only support scalar integers. This
patch extends them to also handle vector integer operations. In this
case bits are not tracked for individual vector elements, instead a
bit is demanded if it is demanded for any of the elements. This matches
the behavior of computeKnownBits in ValueTracking and
SimplifyDemandedBits in InstCombine.
The getDemandedBits() method can now only be called on instructions that
have integer or vector of integer type. Previously it could be called on
any sized instruction (even if it was not particularly useful). The size
of the return value is now always the scalar size in bits (while
previously it was the type size in bits).
Differential Revision: https://reviews.llvm.org/D55297
llvm-svn: 348549
Add support for funnel shifts to the DemandedBits analysis. The
demanded bits of the first two operands can be determined if the
shift amount is constant. The demanded bits of the third operand
(shift amount) can be determined if the bitwidth is a power of two.
This is basically the same functionality as implemented in D54869
and D54478, but for DemandedBits rather than InstCombine.
Differential Revision: https://reviews.llvm.org/D54876
llvm-svn: 347561
This is a bit awkward in a handful of places where we didn't even have
an instruction and now we have to see if we can build one. But on the
whole, this seems like a win and at worst a reasonable cost for removing
`TerminatorInst`.
All of this is part of the removal of `TerminatorInst` from the
`Instruction` type hierarchy.
llvm-svn: 340701
The DEBUG() macro is very generic so it might clash with other projects.
The renaming was done as follows:
- git grep -l 'DEBUG' | xargs sed -i 's/\bDEBUG\s\?(/LLVM_DEBUG(/g'
- git diff -U0 master | ../clang/tools/clang-format/clang-format-diff.py -i -p1 -style LLVM
- Manual change to APInt
- Manually chage DOCS as regex doesn't match it.
In the transition period the DEBUG() macro is still present and aliased
to the LLVM_DEBUG() one.
Differential Revision: https://reviews.llvm.org/D43624
llvm-svn: 332240
This patch adds min/max population count, leading/trailing zero/one bit counting methods.
The min methods return answers based on bits that are known without considering unknown bits. The max methods give answers taking into account the largest count that unknown bits could give.
Differential Revision: https://reviews.llvm.org/D32931
llvm-svn: 302925
This patch introduces a new KnownBits struct that wraps the two APInt used by computeKnownBits. This allows us to treat them as more of a unit.
Initially I've just altered the signatures of computeKnownBits and InstCombine's simplifyDemandedBits to pass a KnownBits reference instead of two separate APInt references. I'll do similar to the SelectionDAG version of computeKnownBits/simplifyDemandedBits as a separate patch.
I've added a constructor that allows initializing both APInts to the same bit width with a starting value of 0. This reduces the repeated pattern of initializing both APInts. Once place default constructed the APInts so I added a default constructor for those cases.
Going forward I would like to add more methods that will work on the pairs. For example trunc, zext, and sext occur on both APInts together in several places. We should probably add a clear method that can be used to clear both pieces. Maybe a method to check for conflicting information. A method to return (Zero|One) so we don't write it out everywhere. Maybe a method for (Zero|One).isAllOnesValue() to determine if all bits are known. I'm sure there are many other methods we can come up with.
Differential Revision: https://reviews.llvm.org/D32376
llvm-svn: 301432
Summary:
* Add a bitreverse case in the demanded bits analysis pass.
* Add tests for the bitreverse (and bswap) intrinsic in the
demanded bits pass.
* Add a test case to the BDCE tests: that manipulations to
high-order bits are eliminated once the bits are reversed
and then right-shifted.
Reviewers: mkuper, jmolloy, hfinkel, trentxintong
Reviewed By: jmolloy
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D31857
llvm-svn: 300215
After r289755, the AssumptionCache is no longer needed. Variables affected by
assumptions are now found by using the new operand-bundle-based scheme. This
new scheme is more computationally efficient, and also we need much less
code...
llvm-svn: 289756
