Scan the MachineFunction for DBG_VALUE instructions, and replace them with a
data structure similar to LiveIntervals. The live range of a DBG_VALUE is
determined by propagating it down the dominator tree until a new DBG_VALUE is
found. When a DBG_VALUE lives in a register, its live range is confined to the
live range of the register's value.
LiveDebugVariables runs before coalescing, so DBG_VALUEs are not artificially
extended when registers are joined.
The missing half will recreate DBG_VALUE instructions from the intervals when
register allocation is complete.
The pass is disabled by default. It can be enabled with the temporary command
line option -live-debug-variables.
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legalization time. Since at legalization time there is no mapping from
SDNode back to the corresponding LLVM instruction and the return
SDNode is target specific, this requires a target hook to check for
eligibility. Only x86 and ARM support this form of sibcall optimization
right now.
rdar://8707777
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may-aliasing stores that partially overlap with different base
pointers. This implements PR6043 and the non-variable part of
PR8657
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- Use a DenseSet instead of a FoldingSet to cache
canonicalized nodes. This reduces the overhead
of double-hashing.
- Use reference counts in ImutAVLTree to much
more aggressively recover tree nodes that are
no longer usable. We can generate many
transient nodes while using add() and remove()
on ImmutableSet/ImmutableMaps to generate a final
set/map.
For the clang static analyzer (the main client
of these data structures), this results in
a slight speedup (0.5%) when analyzing sqlite3,
but much more importantly results in a 30-60%
reduction in peak memory usage when the analyzer
is analyzing a given function in a file. On
average that's about a ** 44% reduction ** in the
memory footprint of the static analyzer.
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about pairs of AA::Location's instead of looking for MemDep's
"Def" predicate. This is more powerful and general, handling
memset/memcpy/store all uniformly, and implementing PR8701 and
probably obsoleting parts of memcpyoptimizer.
This also fixes an obscure bug with init.trampoline and i8
stores, but I'm not surprised it hasn't been hit yet. Enhancing
init.trampoline to carry the size that it stores would allow
DSE to be much more aggressive about optimizing them.
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unbreaks test/Transforms/InstCombine/invariant.ll which was broken by r120382.
This is a fix-forward to do what I think Chris intended.
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This analysis is going to run immediately after LiveIntervals. It will stay
alive during register allocation and keep track of user variables mentioned in
DBG_VALUE instructions.
When the register allocator is moving values between registers and the stack, it
is very hard to keep track of DBG_VALUE instructions. We usually get it wrong.
This analysis maintains a data structure that makes it easy to update DBG_VALUE
instructions.
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is trivially dead, since these have side effects. This makes the
(misnamed) MemoryUseIntrinsic class dead, so remove it.
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Sometimes std::copy can become a memmove call, and that is not a good idea when
copying relatively few bytes as we are doing. We also get a small win by
changing two loops into one.
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We always disallowed overlapping inserts with different values, and this makes
the insertion code smaller and faster.
If an overwriting insert is needed, it can be added as a separate method that
trims any existing intervals before inserting. The immediate use cases for
IntervalMap don't need this - they only use disjoint insertions.
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These iterators don't point anywhere, and they can't be compared to anything.
They are only good for assigning to.
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