Add a bit more logic into the 'FalseLaneZeros' tracking to enable
horizontal reductions and also make the VADDV variants
validForTailPredication.
Differential Revision: https://reviews.llvm.org/D76708
Given that some instructions generate wider result elements than
their inputs, flag them as being able to generate non zeros in the
false lanes.
Differential Revision: https://reviews.llvm.org/D76766
When decided whether to generate a post-inc load/store, look at the
other memory nodes that use the same base address and, if any proceed
the current node, then don't do the combine.
The change only seems to be affecting the Arm backend, which I was
surprised at, but it appears to fix a lot of our issues around MVE
masked load/stores having to store a temporary address after an early
post-increment on a shared base address.
Differential Revision: https://reviews.llvm.org/D75847
Iterate through the loop and check that the observable values
produced are the same whether tail predication happens or not.
We want to find out if the tail-predicated version of this loop will
produce the same values as the loop in its original form. For this to
be true, the newly inserted implicit predication must not change the
the (observable) results.
We're doing this because many instructions in the loop will not be
predicated and so the conversion from VPT predication to tail
predication can result in different values being produced, because of
falsely predicated lanes not being updated in the converted form.
A masked load, whether through VPT or tail predication, will write
zeros to any of the falsely predicated bytes. So, from the loads, we
know that the false lanes are zeroed and here we're trying to track
that those false lanes remain zero, or where they change, the
differences are masked away by their user(s).
All MVE loads and stores have to be predicated, so we know that any
load operands, or stored results are equivalent already. Other
explicitly predicated instructions will perform the same operation in
the original loop and the tail-predicated form too. Because of this,
we can insert loads, stores and other predicated instructions into
our KnownFalseZeros set and build from there.
Differential Revision: https://reviews.llvm.org/D75452
Use MIOperand in collectLocalKilledOperands to make the search
global, as we already have to search for global uses too. This
allows us to delete more dead code when tail predicating.
Differential Revision: https://reviews.llvm.org/D75167
One of the checks has been removed as it seem invalid.
The LoopStep size is always almost a 32-bit.
Differential Revision: https://reviews.llvm.org/D75079
This addes extra patterns for the VMLAS MVE instruction, which performs
Qda = Qda * Qn + Rm, a similar pattern to the existing VMLA. The sinking
of splat(Rm) into the loop is already performed, meaning we just need
extra Pat's in tablegen.
Differential Revision: https://reviews.llvm.org/D75115
Ensure that we're recording implicit defs, as well as visiting implicit
uses and implicit defs when we're walking through operands.
Differential Revision: https://reviews.llvm.org/D75185
This adds infrastructure to print and parse MIR MachineOperand comments.
The motivation for the ARM backend is to print condition code names instead of
magic constants that are difficult to read (for human beings). For example,
instead of this:
dead renamable $r2, $cpsr = tEOR killed renamable $r2, renamable $r1, 14, $noreg
t2Bcc %bb.4, 0, killed $cpsr
we now print this:
dead renamable $r2, $cpsr = tEOR killed renamable $r2, renamable $r1, 14 /* CC::always */, $noreg
t2Bcc %bb.4, 0 /* CC:eq */, killed $cpsr
This shows that MachineOperand comments are enclosed between /* and */. In this
example, the EOR instruction is not conditionally executed (i.e. it is "always
executed"), which is encoded by the 14 immediate machine operand. Thus, now
this machine operand has /* CC::always */ as a comment. The 0 on the next
conditional branch instruction represents the equal condition code, thus now
this operand has /* CC:eq */ as a comment.
As it is a comment, the MI lexer/parser completely ignores it. The benefit is
that this keeps the change in the lexer extremely minimal and no target
specific parsing needs to be done. The changes on the MIPrinter side are also
minimal, as there is only one target hooks that is used to create the machine
operand comments.
Differential Revision: https://reviews.llvm.org/D74306
Change the way that we remove the redundant iteration count code in
the presence of IT blocks. collectLocalKilledOperands has been
introduced to scan an instructions operands, collecting the killed
instructions and then visiting them too. This is used to delete the
code in the preheader which calculates the iteration count. We also
track any IT blocks within the preheader and, if we remove all the
instructions from the IT block, we also remove the IT instruction.
isSafeToRemove is used to remove any redundant uses of the iteration
count within the loop body.
Differential Revision: https://reviews.llvm.org/D74975
Check that no Q-regs are live out of the loop, unless the instruction
within the loop is predicated on the vctp.
Differential Revision: https://reviews.llvm.org/D72713
A small IR change in calculating the active lanes resulted in no longer
recognising tail-predication. Now recognise both an 'add' and 'or' in
the expression that calculates the active lanes.
Differential Revision: https://reviews.llvm.org/D74394
Printing floating point number in decimal is inconvenient for humans.
Verbose asm output will print out floating point values in comments, it
helps.
But in lots of cases, users still need additional work to covert the
decimal back to hex or binary to check the bit patterns,
especially when there are small precision difference.
Hexadecimal form is one of the supported form in LLVM IR, and easier for
debugging.
This patch try to print all FP constant in hex form instead.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D73566
Once we have created a tail-predicated hardware-loop, and thus know the number
of elements that are processed, we want to clean-up the iteration count
expression of that loop. In D73682, we bailed the analysis on conditionally
executed instructions. This adds support for IT-blocks, so that we can handle
these cases again. The restriction is that we only support IT blocks containing
1 statement, but that seems to cover most cases and forms of the iteration
count expression.
Differential Revision: https://reviews.llvm.org/D73947
Checking that the use-def chain that performs the loop count
isSafeToRemove is not sufficient because it means that we can
remove register copies that we need to restore lr to its correct
value. This change now prevents the transform from kicking in for the
'remove-elem-moves' test which needs to addressed later on.
Differential Revision: https://reviews.llvm.org/D74037
While validating each MVE instruction, check that all instructions
that touch memory are somehow predicated upon the VCTP.
Differential Revision: https://reviews.llvm.org/D73616
We had support for runtime trip count values, but not constants, and this adds
supports for that.
And added a minor optimisation while I was add it: don't invoke Cleanup when
there's nothing to clean up.
Differential Revision: https://reviews.llvm.org/D73198
When expanding the LoopStart, we try to remove the iteration count
calculation. However, if part of the calculation was also used to
calculate the number of elements we could end up deleting
instructions that were required to feed DLSTP/WLSTP.
Differential Revision: https://reviews.llvm.org/D73275
The hasSideEffect parameter is usually automatically inferred from
instruction patterns. For some of our MVE instructions, we do not have
patterns though, such as for the pre/post inc loads and stores. This
instead specifies the flag manually on the base MVE_VLDRSTR_base
tablegen class, making sure we get this correct.
This can help with scheduling multiple loads more optimally. Here I've
added a unittest as a more direct form of testing.
Differential Revision: https://reviews.llvm.org/D73117
This patch uses helper function rewriteLoopExitValues that is refactored in
D72602 to rematerialise the iteration count in exit blocks, so that we can
clean-up loop update expressions inside the hardware-loops later in
ARMLowOverheadLoops, which is necessary to get actual performance gains for
tail-predicated loops.
Differential Revision: https://reviews.llvm.org/D72714
We were previously not necessarily favouring postinc for the MVE loads
and stores, leading to extra code prior to the loop to set up the
preinc. MVE in general can benefit from postinc (as we don't have
unrolled loops), and certain instructions like the VLD2's only post-inc
versions are available.
Differential Revision: https://reviews.llvm.org/D70790
Introduce a method to walk through use-def chains to decide whether
it's possible to remove a given instruction and its users. These
instructions are then stored in a set until the end of the transform
when they're erased. This is now used to perform checks on the
iteration count (LoopDec chain), element count (VCTP chain) and the
possibly redundant iteration count.
As well as being able to remove chains of instructions, we know also
check that the sub feeding the vctp is producing the expected value.
Differential Revision: https://reviews.llvm.org/D71837
Recommitting e93e0d413f after reverting due to test failures, which
will hopefully now be fixed. Original commit message:
After expanding the pseudo instructions, update the liveness info.
We do this in a post-order traversal of the loop, including its
exit blocks and preheader(s).
Differential Revision: https://reviews.llvm.org/D72131
We have a whitelist of instructions that we allow when tail
predicating, since these are trivial ones that we've deemed need no
special handling. Now change ARMLowOverheadLoops to allow the
non-trivial instructions if they're contained within a valid VPT
block. Since a valid block is one that is predicated upon the VCTP so
we know that these non-trivial instructions will still behave as
expected once the implicit predication is used instead.
This also fixes a previous test failure.
Differential Revision: https://reviews.llvm.org/D72509
Use the already provided helper function to get the operand type so
that we can detect whether the vpr is being used as a predicate or
not. Also use existing helpers to get the predicate indices when we
converting the vpt blocks. This enables us to support both types of
vpr predicate operand.
Differential Revision: https://reviews.llvm.org/D72504
Due to the current way that we collect predicated instructions, we
can't easily handle vpsel in tail predicated loops. There are a
couple of issues:
1) It will use the VPR as a predicate operand, but doesn't have to be
instead a VPT block, which means we can assert while building up
the VPT block because we don't find another VPST to being a new
one.
2) VPSEL still requires a VPR operand even after tail predicating,
which means we can't remove it unless there is another
instruction, such as vcmp, that can provide the VPR def.
The first issue should be a relatively simple fix in the logic of the
LowOverheadLoops pass, whereas the second will require us to
represent the 'implicit' tail predication with an explicit value.
Differential Revision: https://reviews.llvm.org/D72629
Architecturally, it's allowed to have MVE-I without an FPU, thus
-mfpu=none should not disable MVE-I, or moves to/from FP-registers.
This patch removes `+/-fpregs` from features unconditionally added to
target feature list, depending on FPU and moves the logic to Clang
driver, where the negative form (`-fpregs`) is conditionally added to
the target features list for the cases of `-mfloat-abi=soft`, or
`-mfpu=none` without either `+mve` or `+mve.fp`. Only the negative
form is added by the driver, the positive one is derived from other
features in the backend.
Differential Revision: https://reviews.llvm.org/D71843
After expanding the pseudo instructions, update the liveness info.
We do this in a post-order traversal of the loop, including its
exit blocks and preheader(s).
Differential Revision: https://reviews.llvm.org/D72131
While we do manage to fold integer-typed IR in middle-end,
we can't do that for the main motivational case of pointers.
There is @llvm.ptrmask() intrinsic which may or may not be helpful,
but i'm not sure it is fully considered canonical yet,
not everything is fully aware of it likely.
Name: PR44448 ptr - (ptr & C) -> ptr & (~C)
%bias = and i32 %ptr, C
%r = sub i32 %ptr, %bias
=>
%r = and i32 %ptr, ~C
See
https://bugs.llvm.org/show_bug.cgi?id=44448https://reviews.llvm.org/D71499
This adds ICmp to the list of instructions that we sink a splat to in a
loop, allowing the register forms of instructions to be selected more
often. It does not add FCmp yet as the results look a little odd, trying
to keep the register in an float reg and having to move it back to a GPR.
Differential Revision: https://reviews.llvm.org/D70997
David Green