This is part of an effort to remove ConstantExpr based
representations of `vscale` so that its LangRef definiton can
be relaxed to accommodate a less strict definition of constant.
Differential Revision: https://reviews.llvm.org/D144891
LSR can include Regs of AddRec SCEVs from different loops, which do not combine
well when added in Scalar Evolution. As they should never produce constant
differences so we can just guard against trying to create them.
Fixes#60927
NarrowSearchSpaceByPickingWinnerRegs has an aggressive filtering method to
reduce the complexity of the search space down by picking a best formula with
the highest number of reuses and assuming it will yield profitable reuse. In
certain cases we can find a best formula like {X+30,+,1} and later check a
formula like {X,+,1} with the same number of Uses. On some architectures it
can be better to pick {X,+,1}, especially if an offset of 30 can be used as a
legal addressing mode, but -30 cannot. That happens under Thumb1 code, which
has fairly limited addressing modes. This patch adds a check to see if it can
pick the simpler formula, if it looks more profitable.
Differential Revision: https://reviews.llvm.org/D144014
Original code will cause crash when the load/store memory type is structure because isIndexedLoadLegal/isIndexedStore doesn't support struct type.
So we limit the load/store memory type to integer.
Origin commit message:
When the latch block is different from header block, IVInc will be expanded in the latch loop. We can't generate the post index load/store this case.
But if the IVInc only used in the loop, actually we still can use the post index load/store because when exit loop we don't care the last IVInc value.
So, trying to hoist IVInc to help backend to generate more post index load/store.
Fix#53625
Reviewed By: eopXD
Differential Revision: https://reviews.llvm.org/D138636
There's no need to require the start value to come directly from the loop predecessor. This was sometimes covering up a latent miscompile in this off-by-default option, but the miscompile needs fixed anyways and the issue has been raised on the original review.
Differential Revision: https://reviews.llvm.org/D142240
Reapply with checks for instructions in unreachable blocks. A test
case for this was added in 1ee4a93b15bb.
-----
This is a recurring pattern: We want to find the nearest common
dominator (instruction) for two instructions, but currently only
provide an API for the nearest common dominator of two basic blocks.
Add an overload that accepts and return instructions.
When the latch block is different from header block, IVInc will be expanded in the latch loop. We can't generate the post index load/store this case.
But if the IVInc only used in the loop, actually we still can use the post index load/store because when exit loop we don't care the last IVInc value.
So, trying to hoist IVInc to help backend to generate more post index load/store.
Fix#53625
Reviewed By: eopXD
Differential Revision: https://reviews.llvm.org/D138636
This reverts commit 7f0de9573f758f5f9108795850337a5acbd17eef.
This is missing handling for !isReachableFromEntry() blocks, which
may be relevant for some callers. Revert for now.
This is a recurring pattern: We want to find the nearest common
dominator (instruction) for two instructions, but currently only
provide an API for the nearest common dominator of two basic blocks.
Add an overload that accepts and return instructions.
value() has undesired exception checking semantics and calls
__throw_bad_optional_access in libc++. Moreover, the API is unavailable without
_LIBCPP_NO_EXCEPTIONS on older Mach-O platforms (see
_LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS).
Use a consistent type for the operands() methods of different SCEV
types. Also make the API consistent by only providing operands(),
rather than also providin op_begin() and op_end() for some of them.
This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated. The intent is to reduce
the amount of manual work required in migrating from Optional to
std::optional.
This is part of an effort to migrate from llvm::Optional to
std::optional:
https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716
According to report by @JojoR, the assertion error was hit hence we need
to have this check before the actual transformation.
Reviewed By: Meinersbur, #loopoptwg
Differential Revision: https://reviews.llvm.org/D136415
The LSR may suggest less profitable transformation to the loop. This
patch adds check to prevent LSR from generating worse code than what
we already have.
Since LSR affects nearly all targets, the patch is guarded by the
option 'lsr-drop-solution' and default as disable for now.
The next step should be extending an TTI interface to allow target(s)
to enable this enhancememnt.
Debug log is added to remind user of such choice to skip the LSR
solution.
Reviewed By: Meinersbur, #loopoptwg
Differential Revision: https://reviews.llvm.org/D126043
When the IV is only used by the terminating condition (say IV-A) and the loop
has a predictable back-edge count and we have another IV (say IV-B) that is an
affine add recursion, we will be able to calculate the terminating value of
IV-B in the loop pre-header. This patch adds attempts to replace IV-B as the
new terminating condition and remove IV-A. It is safe to do so since IV-A is
only used as the terminating condition.
This transformation is suitable to be appended after LSR as it may optimize the
loop into the situation mentioned above. The transformation can reduce number of
IV-s in the loop by one.
A cli option `lsr-term-fold` is added and default disabled.
Reviewed By: mcberg2021, craig.topper
Differential Revision: https://reviews.llvm.org/D132443
Changes since initial commit:
* Wrapping a pointer in an SCEV unknown hides the base, and SCEV is only able to compute a subtraction when the bases are known to be equal. This results in a SCEVCouldNotCompute flowing forward and triggering asserts. Test case added in d767b392.
* isLoopInvariant returns true for instructions outside the loop, but not necessarily *above* the loop. Since this code is allowed to visit uses of an IV outside of a loop, we have to make sure the operands of the compare are both invariant and dominating the header. Test case added in 2aed3cdb.
Original commit message follows...
The ICmpZero matching is checking to see if the expression is loop invariant per SCEV and expandable. This allows expressions inside the loop which can be made loop invariant to be seamlessly expanded, but is overly conservative for expressions which already *are* loop invariant.
As a simple justification for why this is correct, consider a loop invariant urem as RHS vs an alternate function with that same urem wrapped inside a helper call. Why would it be legal to match the later, but not the former?
Differential Revision: https://reviews.llvm.org/D129793
The ICmpZero matching is checking to see if the expression is loop invariant per SCEV and expandable. This allows expressions inside the loop which can be made loop invariant to be seamlessly expanded, but is overly conservative for expressions which already *are* loop invariant.
As a simple justification for why this is correct, consider a loop invariant urem as RHS vs an alternate function with that same urem wrapped inside a helper call. Why would it be legal to match the later, but not the former?
Differential Revision: https://reviews.llvm.org/D129793
This is a followup to D129630, which switches LSR to the member
isSafeToExpand() variant, and removes the freestanding function.
This is done by creating the SCEVExpander early (already during the
analysis phase). Because the SCEVExpander is now available for the
whole lifetime of LSRInstance, I've also made it into a member
variable, rather than passing it around in even more places.
Differential Revision: https://reviews.llvm.org/D129769
isSafeToExpand() for addrecs depends on whether the SCEVExpander
will be used in CanonicalMode. At least one caller currently gets
this wrong, resulting in PR50506.
Fix this by a) making the CanonicalMode argument on the freestanding
functions required and b) adding member functions on SCEVExpander
that automatically take the SCEVExpander mode into account. We can
use the latter variant nearly everywhere, and thus make sure that
there is no chance of CanonicalMode mismatch.
Fixes https://github.com/llvm/llvm-project/issues/50506.
Differential Revision: https://reviews.llvm.org/D129630
Scale reg should never be zero, so when the quotient is zero, we
cannot assign it there. Limit this transform to avoid this situation.
Differential Revision: https://reviews.llvm.org/D128339
Reviewed By: eopXD
This patch does not effect any behavior of the current code.
The codebase implicitly implies that `Cost::RateFormula` is only called
when the `Cost` is not in losing status, or else there may be possible
to trigger the assertion of `Cost::isValid`.
The intention here is to prevent mis-use where future development
allow `Cost` that is already loser to call `Cost::RateFormula` - Early
exit when `Cost` is already losing.
Reviewed By: Meinersbur, #loopoptwg
Differential Revision: https://reviews.llvm.org/D125670
Reland 3f2b76ec90b5f108272a3072a1345ba55d8ec75b with the test corrected
to require x86-registered-target.
Differential Revision: https://reviews.llvm.org/D120169
