It is redundant; RegisterCoalescer will do the remat if it can't eliminate
the copy. Collected instruction counts before and after this. A few extra
instructions are generated due to spilling but it is normal to see these kinds
of changes with almost any small codegen change, according to Jakob.
This also fixed rdar://11830760 where xor is expected instead of movi0.
llvm-svn: 160749
LiveIntervals due to the two-addr pass generating bogus MI code.
The crux of the issue was a loop nesting problem. The intent of the code
which attempts to transform instructions before converting them to
two-addr form is to defer and reprocess any transformed instructions as
the second processing is likely to have more opportunities to coalesce
copies, etc. Unfortunately, there was one section of processing that was
not deferred -- the INSERT_SUBREG rewriting. Due to quirks of how this
rewriting proceeded, not only did it occur early, it removed the bits of
information needed for the deferred processing to correctly generate the
necessary two address form (specifically inserting a copy), but didn't
trigger any immediate assertions and produced what appeared to be
already valid two-address from code. Thus, the assertion only fired much
later in the pipeline.
The fix is to hoist the transformation logic up layer to where it can
more firmly defer all further processing, and to teach the normal
processing to handle an edge case previously handled as part of the
transformation logic. This edge case (already matched tied register
operands) needs to *not* defer any steps.
As has been brought up repeatedly in the process: wow does this code
need refactoring. I *may* squeeze in some time to at least bring sanity
to this loop... but wow... =]
Thanks to Jakob for helpful hints on the way here, and the review.
llvm-svn: 160443
The notable fix is to look at any dependencies attached to the kill
instruction (or other instructions between MI nad the kill) where the
dependencies are specific to the register in question.
The old code implicitly handled this by rejecting the transform if *any*
other uses were found within the block, but after the start point. The
new code directly finds the kill, and has to re-use the existing
dependency scan to check for non-kill uses.
This was caught by self-host, but I found the bug via inspection and use
of absurd assert scaffolding to compute the kills in two ways and
compare them. So I have no useful testcase for this other than
"bootstrap". I'd work harder to reduce a test case if this particular
code were likely to live for a long time.
Thanks to Benjamin Kramer for reviewing the fix itself.
llvm-svn: 160228
removes the largest scaling problem in the test cases from PR13225 when
ASan is switched to insert basic blocks in the natural CFG order.
It may also solve some scaling problems for more normal code with large
numbers of basic blocks and variables.
llvm-svn: 160194
When the source register to a 2-addr instruction is undefined, there is
no need to attempt any transformations - simply replace the source
register with the destination register.
This also comes up when lowering IMPLICIT_DEF instructions - make sure
the <undef> flag is moved to the new partial register def operand:
%vreg8<def> = INSERT_SUBREG %vreg9<undef>, %vreg0<kill>, sub_16bit
rewrite undef:
%vreg8<def> = INSERT_SUBREG %vreg8<undef>, %vreg0<kill>, sub_16bit
convert to:
%vreg8:sub_16bit<def,read-undef> = COPY %vreg0<kill>
llvm-svn: 159120
non-profitable commute using outdated info. The test case would still fail
because of poor pre-RA schedule. That will be fixed by MI scheduler.
rdar://11472010
llvm-svn: 157038
The getPointerRegClass() hook can return register classes that depend on
the calling convention of the current function (ptr_rc_tailcall).
So far, we have been able to infer the calling convention from the
subtarget alone, but as we add support for multiple calling conventions
per target, that no longer works.
Patch by Yiannis Tsiouris!
llvm-svn: 156328
to catch cases like:
%reg1024<def> = MOV r1
%reg1025<def> = MOV r0
%reg1026<def> = ADD %reg1024, %reg1025
r0 = MOV %reg1026
By commuting ADD, it let coalescer eliminate all of the copies. However, there
was a bug in the heuristics where it ended up commuting the ADD in:
%reg1024<def> = MOV r0
%reg1025<def> = MOV 0
%reg1026<def> = ADD %reg1024, %reg1025
r0 = MOV %reg1026
That did no benefit but rather ensure the last MOV would not be coalesced.
rdar://11355268
llvm-svn: 156048
The ensures that virtual registers always belong to an allocatable class.
If your target attempts to create a vreg for an operand that has no
allocatable register subclass, you will crash quickly.
This ensures that targets define register classes as intended.
llvm-svn: 156046
This patch restores TwoAddressInstructionPass's pre-r153892 behaviour when
rescheduling instructions in TryInstructionTransform. Hopefully this will fix
PR12493. To refix PR11861, lowering of INSERT_SUBREGS is deferred until after
the copy that unties the operands is emitted (this seems to be a more
appropriate fix for that issue anyway).
llvm-svn: 154338
Creates a configurable regalloc pipeline.
Ensure specific llc options do what they say and nothing more: -reglloc=... has no effect other than selecting the allocator pass itself. This patch introduces a new umbrella flag, "-optimize-regalloc", to enable/disable the optimizing regalloc "superpass". This allows for example testing coalscing and scheduling under -O0 or vice-versa.
When a CodeGen pass requires the MachineFunction to have a particular property, we need to explicitly define that property so it can be directly queried rather than naming a specific Pass. For example, to check for SSA, use MRI->isSSA, not addRequired<PHIElimination>.
CodeGen transformation passes are never "required" as an analysis
ProcessImplicitDefs does not require LiveVariables.
We have a plan to massively simplify some of the early passes within the regalloc superpass.
llvm-svn: 150226
A REG_SEQUENCE instruction is lowered into a sequence of partial defs:
%vreg7:ssub_0<def,undef> = COPY %vreg20:ssub_0
%vreg7:ssub_1<def> = COPY %vreg2
%vreg7:ssub_2<def> = COPY %vreg2
%vreg7:ssub_3<def> = COPY %vreg2
The first def needs an <undef> flag to indicate it is the beginning of
the live range, while the other defs are read-modify-write. Previously,
we depended on LiveIntervalAnalysis to notice and fix the missing
<def,undef>, but that solution was never robust, it was causing problems
with ProcessImplicitDefs and the lowering of chained REG_SEQUENCE
instructions.
This fixes PR11841.
llvm-svn: 148879
generator to it. For non-bundle instructions, these behave exactly the same
as the MC layer API.
For properties like mayLoad / mayStore, look into the bundle and if any of the
bundled instructions has the property it would return true.
For properties like isPredicable, only return true if *all* of the bundled
instructions have the property.
For properties like canFoldAsLoad, isCompare, conservatively return false for
bundles.
llvm-svn: 146026
"kill". This looks like a bug upstream. Since that's going to take some time
to understand, loosen the assertion and disable the optimization when
multiple kills are seen.
llvm-svn: 144568
instructions of the two-address operands) in order to avoid inserting copies.
This fixes the few regressions introduced when the two-address hack was
disabled (without regressing the improvements).
rdar://10422688
llvm-svn: 144559
This flag is true from isel to register allocation when the machine
function is required to be in SSA form. The TwoAddressInstructionPass
and PHIElimination passes clear the flag.
The SSA flag wil be used by the machine code verifier to check for SSA
form, and eventually an assertion can enforce it in +Asserts builds.
This will catch the common target error of creating machine code with
multiple defs of a virtual register.
llvm-svn: 136532
sink them into MC layer.
- Added MCInstrInfo, which captures the tablegen generated static data. Chang
TargetInstrInfo so it's based off MCInstrInfo.
llvm-svn: 134021
Instead encode llvm IR level property "HasSideEffects" in an operand (shared
with IsAlignStack). Added MachineInstrs::hasUnmodeledSideEffects() to check
the operand when the instruction is an INLINEASM.
This allows memory instructions to be moved around INLINEASM instructions.
llvm-svn: 123044
alternative register allocator that does not require LiveIntervals by specifying
it on the command-line for a target that has StrongPHIElimination enabled by
default.
These checks are pretty meaningless anyways, since StrongPHIElimination and
PHIElimination are never used at the same time.
llvm-svn: 122176
regB = move RCX
regA = op regB, regC
RAX = move regA
where both regB and regC are killed. If regB is constrainted to non-compatible
physical registers but regC is not constrainted at all, then it's better to
commute the instruction.
movl %edi, %eax
shlq $32, %rcx
leaq (%rcx,%rax), %rax
=>
movl %edi, %eax
shlq $32, %rcx
orq %rcx, %rax
rdar://8762995
llvm-svn: 121793
must be called in the pass's constructor. This function uses static dependency declarations to recursively initialize
the pass's dependencies.
Clients that only create passes through the createFooPass() APIs will require no changes. Clients that want to use the
CommandLine options for passes will need to manually call the appropriate initialization functions in PassInitialization.h
before parsing commandline arguments.
I have tested this with all standard configurations of clang and llvm-gcc on Darwin. It is possible that there are problems
with the static dependencies that will only be visible with non-standard options. If you encounter any crash in pass
registration/creation, please send the testcase to me directly.
llvm-svn: 116820
perform initialization without static constructors AND without explicit initialization
by the client. For the moment, passes are required to initialize both their
(potential) dependencies and any passes they preserve. I hope to be able to relax
the latter requirement in the future.
llvm-svn: 116334
If we are emitting COPY instructions for the REG_SEQUENCE, make sure the kill
flag goes on the last COPY. Otherwise we may be using a killed register.
<rdar://problem/8287792>
llvm-svn: 110589
ScheduleDAGEmit, TwoAddressLowering, and PHIElimination.
This switches the bulk of register copies to using COPY, but many less used
copyRegToReg calls remain.
llvm-svn: 108050
EXTRACT_SUBREG no longer appears as a machine instruction. Use COPY instead.
Add isCopy() checks in many places using isMoveInstr() and isExtractSubreg().
The isMoveInstr hook will be removed later.
llvm-svn: 107879
INSERT_SUBREG will now only appear in SSA machine instructions.
Fix the handling of partial redefs in ProcessImplicitDefs. This is now relevant
since partial redef COPY instructions appear.
llvm-svn: 107726
- X86 unfolding should check if the instructions being unfolded has memoperands.
If there is no memoperands, then it must assume conservative alignment. If this
would introduce an expensive sse unaligned load / store, then unfoldMemoryOperand
etc. should not unfold the instruction.
llvm-svn: 107509
opportunities. For example, this lets it emit this:
movq (%rax), %rcx
addq %rdx, %rcx
instead of this:
movq %rdx, %rcx
addq (%rax), %rcx
in the case where %rdx has subsequent uses. It's the same number
of instructions, and usually the same encoding size on x86, but
it appears faster, and in general, it may allow better scheduling
for the load.
llvm-svn: 106493
combined to an insert_subreg, i.e., where the destination register is larger
than the source. We need to check that the subregs can be composed for that
case in a symmetrical way to the case when the destination is smaller.
llvm-svn: 106004
replacing the overly conservative checks that I had introduced recently to
deal with correctness issues. This makes a pretty noticable difference
in our testcases where reg_sequences are used. I've updated one test to
check that we no longer emit the unnecessary subreg moves.
llvm-svn: 105991
Check that all the instructions are in the same basic block, that the
EXTRACT_SUBREGs write to the same subregs that are being extracted, and that
the source and destination registers are in the same regclass. Some of
these constraints can be relaxed with a bit more work. Jakob suggested
that the loop that checks for subregs when NewSubIdx != 0 should use the
"nodbg" iterator, so I made that change here, too.
llvm-svn: 105437
instruction defines subregisters.
Any existing subreg indices on the original instruction are preserved or
composed with the new subreg index.
Also substitute multiple operands mentioning the original register by using the
new MachineInstr::substituteRegister() function. This is necessary because there
will soon be <imp-def> operands added to non read-modify-write partial
definitions. This instruction:
%reg1234:foo = FLAP %reg1234<imp-def>
will reMaterialize(%reg3333, bar) like this:
%reg3333:bar-foo = FLAP %reg333:bar<imp-def>
Finally, replace the TargetRegisterInfo pointer argument with a reference to
indicate that it cannot be NULL.
llvm-svn: 105358
that are aliases of the specified register.
- Rename modifiesRegister to definesRegister since it's looking a def of the
specific register or one of its super-registers. It's not looking for def of a
sub-register or alias that could change the specified register.
- Added modifiesRegister to look for defs of aliases.
llvm-svn: 104377
instructions.
e.g.
%reg1026<def> = VLDMQ %reg1025<kill>, 260, pred:14, pred:%reg0
%reg1027<def> = EXTRACT_SUBREG %reg1026, 6
%reg1028<def> = EXTRACT_SUBREG %reg1026<kill>, 5
...
%reg1029<def> = REG_SEQUENCE %reg1028<kill>, 5, %reg1027<kill>, 6, %reg1028, 7, %reg1027, 8, %reg1028, 9, %reg1027, 10, %reg1030<kill>, 11, %reg1032<kill>, 12
After REG_SEQUENCE is eliminated, we are left with:
%reg1026<def> = VLDMQ %reg1025<kill>, 260, pred:14, pred:%reg0
%reg1029:6<def> = EXTRACT_SUBREG %reg1026, 6
%reg1029:5<def> = EXTRACT_SUBREG %reg1026<kill>, 5
The regular coalescer will not be able to coalesce reg1026 and reg1029 because it doesn't
know how to combine sub-register indices 5 and 6. Now 2-address pass will consult the
target whether sub-registers 5 and 6 of reg1026 can be combined to into a larger
sub-register (or combined to be reg1026 itself as is the case here). If it is possible,
it will be able to replace references of reg1026 with reg1029 + the larger sub-register
index.
llvm-svn: 103835
into TargetOpcodes.h. #include the new TargetOpcodes.h
into MachineInstr. Add new inline accessors (like isPHI())
to MachineInstr, and start using them throughout the
codebase.
llvm-svn: 95687
When TwoAddressInstructionPass deletes a dead instruction, make sure that all
register kills are accounted for. The 2-addr register does not get special
treatment.
llvm-svn: 89246
is trivially rematerializable and integrate it into
TargetInstrInfo::isTriviallyReMaterializable. This way, all places that
need to know whether an instruction is rematerializable will get the
same answer.
This enables the useful parts of the aggressive-remat option by
default -- using AliasAnalysis to determine whether a memory location
is invariant, and removes the questionable parts -- rematting operations
with virtual register inputs that may not be live everywhere.
llvm-svn: 83687
for the complicated case where one register is tied to multiple destinations.
This avoids the extra scan of instruction operands that was introduced by
my recent change. I also pulled some code out into a separate
TryInstructionTransform method, added more comments, and renamed some
variables.
Besides all those changes, this takes care of a FIXME in the code regarding
an assumption about there being a single tied use of a register when
converting to a 3-address form. I'm not aware of cases where that assumption
is violated, but the code now only attempts to transform an instruction,
either by commuting its operands or by converting to a 3-address form,
for the simple case where there is a single pair of tied operands.
llvm-svn: 80945
tied to different source registers, the TwoAddressInstructionPass needs to
be smarter. Change it to check before replacing a source register whether
that source register is tied to a different destination register, and if so,
defer handling it until a subsequent iteration.
llvm-svn: 80654
- Some clients which used DOUT have moved to DEBUG. We are deprecating the
"magic" DOUT behavior which avoided calling printing functions when the
statement was disabled. In addition to being unnecessary magic, it had the
downside of leaving code in -Asserts builds, and of hiding potentially
unnecessary computations.
llvm-svn: 77019
with SUBREG_TO_REG, teach SimpleRegisterCoalescing to coalesce
SUBREG_TO_REG instructions (which are similar to INSERT_SUBREG
instructions), and teach the DAGCombiner to take advantage of this on
targets which support it. This eliminates many redundant
zero-extension operations on x86-64.
This adds a new TargetLowering hook, isZExtFree. It's similar to
isTruncateFree, except it only applies to actual definitions, and not
no-op truncates which may not zero the high bits.
Also, this adds a new optimization to SimplifyDemandedBits: transform
operations like x+y into (zext (add (trunc x), (trunc y))) on targets
where all the casts are no-ops. In contexts where the high part of the
add is explicitly masked off, this allows the mask operation to be
eliminated. Fix the DAGCombiner to avoid undoing these transformations
to eliminate casts on targets where the casts are no-ops.
Also, this adds a new two-address lowering heuristic. Since
two-address lowering runs before coalescing, it helps to be able to
look through copies when deciding whether commuting and/or
three-address conversion are profitable.
Also, fix a bug in LiveInterval::MergeInClobberRanges. It didn't handle
the case that a clobber range extended both before and beyond an
existing live range. In that case, multiple live ranges need to be
added. This was exposed by the new subreg coalescing code.
Remove 2008-05-06-SpillerBug.ll. It was bugpoint-reduced, and the
spiller behavior it was looking for no longer occurrs with the new
instruction selection.
llvm-svn: 68576
e.g.
%reg1024<def> = MOV r1
%reg1025<def> = ADD %reg1024, %reg1026
r0 = MOV %reg1025
If it's not possible / profitable to commute ADD, then turning ADD into a LEA saves a copy.
llvm-svn: 68065
%reg1028<def> = EXTRACT_SUBREG %reg1027<kill>, 1
%reg1029<def> = MOV8rr %reg1028
%reg1029<def> = SHR8ri %reg1029, 7, %EFLAGS<imp-def,dead>
insert => %reg1030<def> = MOV8rr %reg1028
%reg1030<def> = ADD8rr %reg1028<kill>, %reg1029<kill>, %EFLAGS<imp-def,dead>
In this case, it might not be possible to coalesce the second MOV8rr
instruction if the first one is coalesced. So it would be profitable to
commute it:
%reg1028<def> = EXTRACT_SUBREG %reg1027<kill>, 1
%reg1029<def> = MOV8rr %reg1028
%reg1029<def> = SHR8ri %reg1029, 7, %EFLAGS<imp-def,dead>
insert => %reg1030<def> = MOV8rr %reg1029
%reg1030<def> = ADD8rr %reg1029<kill>, %reg1028<kill>, %EFLAGS<imp-def,dead>
llvm-svn: 62954
