- Walking over pred_begin/pred_end is an expensive operation.
- PHINodes contain a value for each predecessor anyway.
- While it may look like we used to save a few iterations with the set,
be aware that getIncomingValueForBlock does a linear search on
the values of the phi node.
- Another -5% on ARMDisassembler.cpp (Release build). This was the last
entry in the profile that was obviously wasting time.
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recent discussions. Poison can't make every value that depends on
it act in maximally undefined ways, because the optimizer may still
hoist code following the usual rules for undef. Make Poison invoke
its full undefined behavior only when it reaches an instruction with
externally visible side effects.
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It's always good to prune early, but formulae that are unsatisfactory
in their own right need to be removed before running any other pruning
heuristics. We easily avoid generating such formulae, but we need them
as an intermediate basis for forming other good formulae.
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The new register allocator is much more able to split back up ranges too constrained by register classes.
Fixes <rdar://problem/10466609>
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Previously, all ARM::CONSTPOOL_ENTRY instructions had a hardwired
alignment of 4 bytes emitted by ARMAsmPrinter. Now the same alignment
is set on the basic block.
This is in preparation of supporting ARM constant pool islands with
different alignments.
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This was actually a bit of a mess. TLI.setPrefLoopAlignment was clearly
documented as taking log2(bytes) units, but the x86 target would still
set a preferred loop alignment of '16'.
CodePlacementOpt passed this number on to the basic block, and
AsmPrinter interpreted it as bytes.
Now both MachineFunction and MachineBasicBlock use logarithmic
alignments.
Obviously, MachineConstantPool still measures alignments in bytes, so we
can emulate the thrill of using as.
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Whether a fixup needs relaxation for the associated instruction is a
target-specific function, as the FIXME indicated. Create a hook for that
and use it.
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don't do this now, but add a test case to prevent this from happening in the
future.
Additional test for rdar://9892684
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Not right yet, as the rules for when to relax in the MCAssembler aren't
(yet) correct for ARM. This is a step in the proper direction, though.
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memory fences) in statistics registration, which works the same way that
ManagedStatic registration does.
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where this would be bad as the backend shouldn't have a problem inlining small
memcpys.
rdar://10510150
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