Simplify the spill weight calculation a bit by bypassing
getApproximateInstructionCount() and using LiveInterval::getSize() directly.
This changes the computed spill weights, but only by a constant factor in each
function. It should not affect how spill weights compare against each other, and
so it shouldn't affect code generation.
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This is a lot easier than trying to get kill flags right during live range
splitting and rematerialization.
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After uses of a live range are removed, recompute the live range to only cover
the remaining uses. This is necessary after rematerializing the value before
some (but not all) uses.
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A live range cannot be split everywhere in a basic block. A split must go before
the first terminator, and if the variable is live into a landing pad, the split
must happen before the call that can throw.
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These functions not longer assert when passed 0, but simply return false instead.
No functional change intended.
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Print virtual registers numbered from 0 instead of the arbitrary
FirstVirtualRegister. The first virtual register is printed as %vreg0.
TRI::NoRegister is printed as %noreg.
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Always spill the full representative register at any point where any subregister
is live.
This fixes PR8620 which caused the old logic to get confused and not spill
anything at all.
The fundamental problem here is that the coalescer is too aggressive about
physical register coalescing. It sometimes makes it impossible to allocate
registers without these emergency spills.
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The live range of a register defined by an early clobber starts at the use slot,
not the def slot.
Except when it is an early clobber tied to a use operand. Then it starts at the
def slot like a standard def.
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benchmarks hitting an assertion.
Adds LiveIntervalUnion::collectInterferingVRegs.
Fixes "late spilling" by checking for any unspillable live vregs among
all physReg aliases.
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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.
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When the normalizeSpillWeights function was introduced, I forgot to remove this
normalization.
This change could affect register allocation. Hopefully for the better.
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inserted in a MBB, and return an already inserted MI.
This target API change is necessary to allow foldMemoryOperand to call
storeToStackSlot and loadFromStackSlot when folding a COPY to a stack slot
reference in a target independent way.
The foldMemoryOperandImpl hook is going to change in the same way, but I'll wait
until COPY folding is actually implemented. Most targets only fold copies and
won't need to specialize this hook at all.
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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.
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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.
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This code is transitional, it will soon be possible to eliminate
isExtractSubreg, isInsertSubreg, and isMoveInstr in most places.
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The VNInfo.kills vector was almost unused except for all the code keeping it
updated. The few places using it were easily rewritten to check for interval
ends instead.
The two new methods LiveInterval::killedAt and killedInRange are replacements.
This brings us down to 3 independent data structures tracking kills.
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This method was always a bit too simplistic for the real world. It didn't really
deal with subregisters and such.
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This code path has never really been used, and we are going to be handling
spilling through the Spiller interface in the future.
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CoalescerPair can determine if a copy can be coalesced, and which register gets
merged away. The old logic in SimpleRegisterCoalescing had evolved into
something a bit too convoluted.
This second attempt fixes some crashes that only occurred Linux.
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In this case it is essential that the kill is real because the spiller will
decide to omit a spill if it thinks there is a later kill.
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CoalescerPair can determine if a copy can be coalesced, and which register gets
merged away. The old logic in SimpleRegisterCoalescing had evolved into
something a bit too convoluted.
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instructions, but it doesn't really understand live ranges, so the first
INSERT_SUBREG uses an implicitly defined register.
Fix it in LiveVariableAnalysis by adding the <undef> flag.
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LiveVariableAnalysis was a bit picky about a register only being redefined once,
but that really isn't necessary.
Here is an example of chained INSERT_SUBREGs that we can handle now:
68 %reg1040<def> = INSERT_SUBREG %reg1040, %reg1028<kill>, 14
register: %reg1040 +[70,134:0)
76 %reg1040<def> = INSERT_SUBREG %reg1040, %reg1029<kill>, 13
register: %reg1040 replace range with [70,78:1) RESULT: %reg1040,0.000000e+00 = [70,78:1)[78,134:0) 0@78-(134) 1@70-(78)
84 %reg1040<def> = INSERT_SUBREG %reg1040, %reg1030<kill>, 12
register: %reg1040 replace range with [78,86:2) RESULT: %reg1040,0.000000e+00 = [70,78:1)[78,86:2)[86,134:0) 0@86-(134) 1@70-(78) 2@78-(86)
92 %reg1040<def> = INSERT_SUBREG %reg1040, %reg1031<kill>, 11
register: %reg1040 replace range with [86,94:3) RESULT: %reg1040,0.000000e+00 = [70,78:1)[78,86:2)[86,94:3)[94,134:0) 0@94-(134) 1@70-(78) 2@78-(86) 3@86-(94)
rdar://problem/8096390
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spills and reloads.
This means that a partial define of a register causes a reload so the other
parts of the register are preserved.
The reload can be prevented by adding an <imp-def> operand for the full
register. This is already done by the coalescer and live interval analysis where
relevant.
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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.
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<imp-def> operand for the full register. This ensures that the full physical
register is marked live after register allocation.
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