1. LiveIntervals now implement a 4 slot per instruction model. Load,
Use, Def and a Store slot. This is required in order to correctly
represent caller saved register clobbering on function calls,
register reuse in the same instruction (def resues last use) and
also spill code added later by the allocator. The previous
representation (2 slots per instruction) was insufficient and as a
result was causing subtle bugs.
2. Fixes in spill code generation. This was the major cause of
failures in the test suite.
3. Linear scan now has core support for folding memory operands. This
is untested and not enabled (the live interval update function does
not attempt to fold loads/stores in instructions).
4. Lots of improvements in the debugging output of both live intervals
and linear scan. Give it a try... it is beautiful :-)
In summary the above fixes all the issues with the recent reserved
register elimination changes and get the allocator very close to the
next big step: folding memory operands.
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MachineBasicBlock. Also change opcode to a short and numImplicitRefs
to an unsigned char so that overall MachineInstr's size stays the
same.
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ilist of MachineInstr objects. This allows constant time removal and
insertion of MachineInstr instances from anywhere in each
MachineBasicBlock. It also allows for constant time splicing of
MachineInstrs into or out of MachineBasicBlocks.
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methods which have strangely different semantics in different backends,
and noone knew what any did.
Getting rid of these ALSO allows the dependence of MachineInstr.h on
MRegisterInfo.h to be removed, which makes me much happier, and probably
alkis too. :)
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Simplification of LiveIntervals::Interval::overlaps() and addition of
examples to overlaps() and liveAt() to make them clearer.
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when joining we need to check if we overlap with the second interval
or any of its aliases.
Also make joining intervals the default.
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is a move between two registers, at least one of the registers is
virtual and the two live intervals do not overlap.
This results in about 40% reduction in intervals, 30% decrease in the
register allocators running time and a 20% increase in peephole
optimizations (mainly move eliminations).
The option can be enabled by passing -join-liveintervals where
appropriate.
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LiveVariables::HandlePhysRegDef private they use information that is
not in memory when LiveVariables finishes the analysis.
Also update the TwoAddressInstructionPass to not use this interface.
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which denotes the register we would like to be assigned to (virtual or
physical). In register allocation, if this hint exists and we can map
it to a physical register (it is either a physical register or it is a
virtual register that already got assigned to a physical one) we use
that register if it is available instead of a random one in the free
pool.
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provides for future extensibility, might help the LLVA project avoid having to
hack their own LLI, and provides support required for the experimental Venus
project.
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