Rather than gating on "isSwitchDense" (resulting in necessesarily
sparse lookup tables even when they were generated), always run
this quite cheap transform.
This transform is useful not just for generating tables.
LowerSwitch also wants this: read LowerSwitch.cpp:257.
Be careful to not generate worse code, by introducing a
SubThreshold heuristic.
Instead of just sorting by signed, generalize the finding of the
best base.
And now that it is run unconditionally, do not replicate its
functionality in SwitchToLookupTable (which could use a Sub
when having a hole is smaller, hence the SubThreshold
heuristic located in a single place).
This simplifies SwitchToLookupTable, and fixes
some ugly corner cases due to the use of signed numbers,
such as a table containing i16 32768 and 32769, of which
32769 would be interpreted as -32768, and now the code thinks
the table is size 65536.
(We still use unconditional subtraction when building a single-register mask,
but I think this whole block should go when the more general sparse
map is added, which doesn't leave empty holes in the table.)
And the reason test4 and test5 did not trigger was documented wrong:
it was because they were not considered sufficiently "dense".
Also, fix generation of invalid LLVM-IR: shl by bit-width.
llvm-svn: 361727
and replace with an equilivent countTrailingZeros.
GCD is much more expensive than this, with repeated division.
This depends on D60823
llvm-svn: 361726
This matches countLeadingOnes() and countTrailingOnes(), and
APInt's countLeadingZeros() and countTrailingZeros().
(as well as __builtin_clzll())
llvm-svn: 361724
Summary:
Preserve MemorySSA in LoopSimplify, in the old pass manager, if the analysis is available.
Do not preserve it in the new pass manager.
Update tests.
Subscribers: nemanjai, jlebar, javed.absar, Prazek, kbarton, zzheng, jsji, llvm-commits, george.burgess.iv, chandlerc
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D60833
llvm-svn: 360270
This reverts r357452 (git commit 21eb771dcb5c11d7500fa6ad551c97a921997f05).
This was causing strange optimization-related test failures on an internal test. Will followup with more details offline.
llvm-svn: 360086
The original commit caused false positives from AddressSanitizer's
use-after-scope checks, which have now been fixed in r358478.
> The code was previously checking that candidates for sinking had exactly
> one use or were a store instruction (which can't have uses). This meant
> we could sink call instructions only if they had a use.
>
> That limitation seemed a bit arbitrary, so this patch changes it to
> "instruction has zero or one use" which seems more natural and removes
> the need to special-case stores.
>
> Differential revision: https://reviews.llvm.org/D59936
llvm-svn: 358483
This revision causes tests to fail under ASAN. Since the cause of the failures
is not clear (could be ASAN, could be a Clang bug, could be a bug in this
revision), the safest course of action seems to be to revert while investigating.
llvm-svn: 357667
The code was previously checking that candidates for sinking had exactly
one use or were a store instruction (which can't have uses). This meant
we could sink call instructions only if they had a use.
That limitation seemed a bit arbitrary, so this patch changes it to
"instruction has zero or one use" which seems more natural and removes
the need to special-case stores.
Differential revision: https://reviews.llvm.org/D59936
llvm-svn: 357452
Fixes bug 38023: https://bugs.llvm.org/show_bug.cgi?id=38023
The SimplifyCFG pass will perform jump threading in some cases where
doing so is trivial and would simplify the CFG. When folding a series
of blocks with redundant conditional branches into an unconditional "critical
edge" block, it does not keep the debug location associated with the previous
conditional branch.
This patch fixes the bug described by copying the debug info from the
old conditional branch to the new unconditional branch instruction, and
adds a regression test for the SimplifyCFG pass that covers this case.
Patch by Stephen Tozer!
Differential Revision: https://reviews.llvm.org/D59206
llvm-svn: 355833
This patch accompanies the RFC posted here:
http://lists.llvm.org/pipermail/llvm-dev/2018-October/127239.html
This patch adds a new CallBr IR instruction to support asm-goto
inline assembly like gcc as used by the linux kernel. This
instruction is both a call instruction and a terminator
instruction with multiple successors. Only inline assembly
usage is supported today.
This also adds a new INLINEASM_BR opcode to SelectionDAG and
MachineIR to represent an INLINEASM block that is also
considered a terminator instruction.
There will likely be more bug fixes and optimizations to follow
this, but we felt it had reached a point where we would like to
switch to an incremental development model.
Patch by Craig Topper, Alexander Ivchenko, Mikhail Dvoretckii
Differential Revision: https://reviews.llvm.org/D53765
llvm-svn: 353563
This cleans up all LoadInst creation in LLVM to explicitly pass the
value type rather than deriving it from the pointer's element-type.
Differential Revision: https://reviews.llvm.org/D57172
llvm-svn: 352911
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
Following PR39807, the way in which SimplifyCFG hoists common code on
branch paths was fixed in r347782. However this left extra code hanging
around HoistThenElseCodeToIf that wasn't necessary and needlessly
complicated matters -- we no longer need to look up through the 'if'
basic block to find a location for hoisted 'select' insts, we can instead
use the location chosen by applyMergedLocation.
This patch deletes that extra logic, and updates a regression test to
reflect the new logic (selects get the merged location, not a previous
insts location).
Differential Revision: https://reviews.llvm.org/D55272
llvm-svn: 351058
The current llvm.mem.parallel_loop_access metadata has a problem in that
it uses LoopIDs. LoopID unfortunately is not loop identifier. It is
neither unique (there's even a regression test assigning the some LoopID
to multiple loops; can otherwise happen if passes such as LoopVersioning
make copies of entire loops) nor persistent (every time a property is
removed/added from a LoopID's MDNode, it will also receive a new LoopID;
this happens e.g. when calling Loop::setLoopAlreadyUnrolled()).
Since most loop transformation passes change the loop attributes (even
if it just to mark that a loop should not be processed again as
llvm.loop.isvectorized does, for the versioned and unversioned loop),
the parallel access information is lost for any subsequent pass.
This patch unlinks LoopIDs and parallel accesses.
llvm.mem.parallel_loop_access metadata on instruction is replaced by
llvm.access.group metadata. llvm.access.group points to a distinct
MDNode with no operands (avoiding the problem to ever need to add/remove
operands), called "access group". Alternatively, it can point to a list
of access groups. The LoopID then has an attribute
llvm.loop.parallel_accesses with all the access groups that are parallel
(no dependencies carries by this loop).
This intentionally avoid any kind of "ID". Loops that are clones/have
their attributes modifies retain the llvm.loop.parallel_accesses
attribute. Access instructions that a cloned point to the same access
group. It is not necessary for each access to have it's own "ID" MDNode,
but those memory access instructions with the same behavior can be
grouped together.
The behavior of llvm.mem.parallel_loop_access is not changed by this
patch, but should be considered deprecated.
Differential Revision: https://reviews.llvm.org/D52116
llvm-svn: 349725
We were duplicating code around the existing isImpliedCondition() that
checks for a predecessor block/dominating condition, so make that a
wrapper call.
llvm-svn: 348088
In PR39807 we incorrectly handle circumstances where calls are common'd
from conditional blocks into the parent BB. Calls that can be inlined
must always have DebugLocs, however we strip them during commoning, which
the IR verifier asserts on.
Fix this by using applyMergedLocation: it will perform the same DebugLoc
stripping of conditional Locs, but will also generate an unknown location
DebugLoc that satisfies the requirement for inlinable calls to always have
locations.
Some of the prior logic for selecting a DebugLoc is now likely redundant;
I'll generate a follow-up to remove it (involves editing more regression
tests).
Differential Revision: https://reviews.llvm.org/D54997
llvm-svn: 347782
Add methods to BasicBlock which make it easier to efficiently check
whether a block has N (or more) predecessors.
This can be more efficient than using pred_size(), which is a linear
time operation.
We might consider adding similar methods for successors. I haven't done
so in this patch because succ_size() is already O(1).
With this patch applied, I measured a 0.065% compile-time reduction in
user time for running `opt -O3` on the sqlite3 amalgamation (30 trials).
The change in mergeStoreIntoSuccessor alone saves 45 million linked list
iterations in a stage2 Release build of llc.
See llvm.org/PR39702 for a harder but more general way of achieving
similar results.
Differential Revision: https://reviews.llvm.org/D54686
llvm-svn: 347256
In SimplifyCFG when given a conditional branch that goes to BB1 and BB2, the hoisted common terminator instruction in the two blocks, caused debug line records associated with subsequent select instructions to become ambiguous. It causes the debugger to display unreachable source lines.
Differential Revision: https://reviews.llvm.org/D53390
llvm-svn: 346481
When SimplifyCFG changes the PHI node into a select instruction, the debug line records becomes ambiguous. It causes the debugger to display unreachable source lines.
Differential Revision: https://reviews.llvm.org/D53287
llvm-svn: 345250
by `getTerminator()` calls instead be declared as `Instruction`.
This is the biggest remaining chunk of the usage of `getTerminator()`
that insists on the narrow type and so is an easy batch of updates.
Several files saw more extensive updates where this would cascade to
requiring API updates within the file to use `Instruction` instead of
`TerminatorInst`. All of these were trivial in nature (pervasively using
`Instruction` instead just worked).
llvm-svn: 344502
When SimplifyCFG changes the PHI node into a select instruction, the debug line records becomes ambiguous. It causes the debugger to display unreachable source lines.
Differential Revision: https://reviews.llvm.org/D52887
llvm-svn: 344120
Summary:
At some point in the past the recursion in DominatesMergePoint used to pass null for AggressiveInsts as part of the recursion. It no longer does this. So there is no way for AggressiveInsts to be null.
This passes it by reference and removes the null check to make this explicit.
Reviewers: efriedma, reames
Reviewed By: efriedma
Subscribers: xbolva00, llvm-commits
Differential Revision: https://reviews.llvm.org/D52575
llvm-svn: 343828
Summary:
The llvm::SimplifyCFG function creates a SimplifyCFGOpt object and calls run on it. There were numerous places reached from this run function that called back out llvm::SimplifyCFG which would create another SimplifyCFGOpt object. This is an inefficient use of stack space at minimum. We are also not passing along the LoopHeaders pointer passed into the outer llvm::SimplifyCFG call. So if its not null we lose it on the first recursion and get nullptr from there on.
This patch adds an outer loop around the main BasicBlock simplifying code and adds a flag to the SimplifyCFGOpt class that can be set by to request another iteration. I don't think we can iterate based just on the change flag alone since some of the simplifications delete a basic block entirely leaving nothing to iterate on.
Reviewers: bogner, eli.friedman, reames
Reviewed By: reames
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D52760
llvm-svn: 343816
getNumUses is linear in the number of uses. Since we're looking for a specific use count, we can use hasNUses which will stop as soon as it determines there are more than N uses instead of walking all of them.
llvm-svn: 343550
When SimplifyCFG changes the PHI node into a select instruction, the debug information becomes ambiguous. It causes the debugger to display wrong variable value.
Differential Revision: https://reviews.llvm.org/D51976
llvm-svn: 342527
Previously the alignment on the newly created switch table data was not set,
meaning that DataLayout::getPreferredAlignment was free to overalign it to 16
bytes. This causes unnecessary code bloat.
Differential Revision: https://reviews.llvm.org/D51800
llvm-svn: 342039
This reverts commit r340997.
This change turned out not to be NFC after all, but e.g. causes
clang to crash when building the linux kernel for aarch64.
llvm-svn: 341031
The cost modeling was not accounting for the fact we were duplicating the instruction once per predecessor. With a default threshold of 1, this meant we were actually creating #pred copies.
Adding to the fun, there is *absolutely no* test coverage for this. Simply bailing for more than one predecessor passes all checked in tests.
llvm-svn: 341001
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
`isExceptionalTermiantor` and implement it for opcodes as well following
the common pattern in `Instruction`.
Part of removing `TerminatorInst` from the `Instruction` type hierarchy
to make it easier to share logic and interfaces between instructions
that are both terminators and not terminators.
llvm-svn: 340699
The core get and set routines move to the `Instruction` class. These
routines are only valid to call on instructions which are terminators.
The iterator and *generic* range based access move to `CFG.h` where all
the other generic successor and predecessor access lives. While moving
the iterator here, simplify it using the iterator utilities LLVM
provides and updates coding style as much as reasonable. The APIs remain
pointer-heavy when they could better use references, and retain the odd
behavior of `operator*` and `operator->` that is common in LLVM
iterators. Adjusting this API, if desired, should be a follow-up step.
Non-generic range iteration is added for the two instructions where
there is an especially easy mechanism and where there was code
attempting to use the range accessor from a specific subclass:
`indirectbr` and `br`. In both cases, the successors are contiguous
operands and can be easily iterated via the operand list.
This is the first major patch in removing the `TerminatorInst` type from
the IR's instruction type hierarchy. This change was discussed in an RFC
here and was pretty clearly positive:
http://lists.llvm.org/pipermail/llvm-dev/2018-May/123407.html
There will be a series of much more mechanical changes following this
one to complete this move.
Differential Revision: https://reviews.llvm.org/D47467
llvm-svn: 340698
This patch makes the DoesKMove argument non-optional, to force people
to think about it. Most cases where it is false are either code hoisting
or code sinking, where we pick one instruction from a set of
equal instructions among different code paths.
Reviewers: dberlin, nlopes, efriedma, davide
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D47475
llvm-svn: 340606
Summary:
Previously, `eraseFromParent()` calls `delete` which invalidates the value of the pointer. Copying the value of the pointer later is undefined behavior in C++11 and implementation-defined (which may cause a segfault on implementations having strict pointer safety) in C++14.
This patch removes the BasicBlock pointer from related SmallPtrSet before `delete` invalidates it in the SimplifyCFG pass.
Reviewers: kuhar, dmgreen, davide, trentxintong
Reviewed By: kuhar, dmgreen
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D50717
llvm-svn: 339773
Summary:
Support for this option is needed for building Linux kernel.
This is a very frequently requested feature by kernel developers.
More details : https://lkml.org/lkml/2018/4/4/601
GCC option description for -fdelete-null-pointer-checks:
This Assume that programs cannot safely dereference null pointers,
and that no code or data element resides at address zero.
-fno-delete-null-pointer-checks is the inverse of this implying that
null pointer dereferencing is not undefined.
This feature is implemented in LLVM IR in this CL as the function attribute
"null-pointer-is-valid"="true" in IR (Under review at D47894).
The CL updates several passes that assumed null pointer dereferencing is
undefined to not optimize when the "null-pointer-is-valid"="true"
attribute is present.
Reviewers: t.p.northover, efriedma, jyknight, chandlerc, rnk, srhines, void, george.burgess.iv
Reviewed By: efriedma, george.burgess.iv
Subscribers: eraman, haicheng, george.burgess.iv, drinkcat, theraven, reames, sanjoy, xbolva00, llvm-commits
Differential Revision: https://reviews.llvm.org/D47895
llvm-svn: 336613
Currently SmallSet<PointerTy> inherits from SmallPtrSet<PointerTy>. This
patch replaces such types with SmallPtrSet, because IMO it is slightly
clearer and allows us to get rid of unnecessarily including SmallSet.h
Reviewers: dblaikie, craig.topper
Reviewed By: dblaikie
Differential Revision: https://reviews.llvm.org/D47836
llvm-svn: 334492
SmallSet forwards to SmallPtrSet for pointer types. SmallPtrSet supports iteration, but a normal SmallSet doesn't. So if it wasn't for the forwarding, this wouldn't work.
These places were found by hiding the begin/end methods in the SmallSet forwarding
llvm-svn: 334343
Review feedback from r328165. Split out just the one function from the
file that's used by Analysis. (As chandlerc pointed out, the original
change only moved the header and not the implementation anyway - which
was fine for the one function that was used (since it's a
template/inlined in the header) but not in general)
llvm-svn: 333954
