It is now possible to coalesce weird skewed sub-register copies by
picking a super-register class larger than both original registers. The
included test case produces code like this:
vld2.32 {d16, d17, d18, d19}, [r0]!
vst2.32 {d18, d19, d20, d21}, [r0]
We still perform interference checking as if it were a normal full copy
join, so this is still quite conservative. In particular, the f1 and f2
functions in the included test case still have remaining copies because
of false interference.
llvm-svn: 156878
It is possible to coalesce two overlapping registers to a common
super-register that it larger than both of the original registers.
The important difference is that it may be necessary to rewrite DstReg
operands as well as SrcReg operands because the sub-register index has
changed.
This behavior is still disabled by CoalescerPair.
llvm-svn: 156869
Now both SrcReg and DstReg can be sub-registers of the final coalesced
register.
CoalescerPair::setRegisters still rejects such copies because
RegisterCoalescer doesn't yet handle them.
llvm-svn: 156848
This feature avoids creating edges in the scheduler's dependence graph
for non-aliasing memory operations according to whichever alias
analysis is available. It has been fully tested in Hexagon. Before
making this default, it needs to be extended to handle multiple
MachineMemOperands, compile time needs more evaluation, and
benchmarking on X86 and ARM is needed.
Patch by Sergei Larin!
llvm-svn: 156842
Many targets always use the same bitwise encoding value for physical
registers in all (or most) instructions. Add this mapping to the
.td files and TableGen'erate the information and expose an accessor
in MCRegisterInfo.
patch by Tom Stellard.
llvm-svn: 156829
Besides the weight, we also want to store up to two root registers per
unit. Most units will have a single root, the leaf register they
represent. Units created for ad hoc aliasing get two roots: The two
aliasing registers.
The root registers can be used to compute the set of overlapping
registers.
llvm-svn: 156792
The purpose of this option is to silence error messages issued by machine
verifier passes and enable them to run to the end. If this option is not
provided, -verify-machineinstrs complains when it discovers there is a
non-terminator instruction (an instruction that is in a delay slot) after the
first terminator in a basic block.
llvm-svn: 156790
so that it can be reused in MemCpyOptimizer. This analysis is needed to remove
an unnecessary memcpy when returning a struct into a local variable.
rdar://11341081
PR12686
llvm-svn: 156776
Returning a temporary BitVector is very expensive. If you must, create
the temporary explicitly: Use BitVector(A).flip() instead of ~A.
llvm-svn: 156768
These operators were crazy slow, calling malloc to return a temporary
result. At the same time, they look very innocent when used in code.
If you need temporary BitVectors to compute your thing, create them
explicitly, and use the inplace logical operators. This makes the high
cost explicit in the code.
llvm-svn: 156767
Register units can be used to compute if two registers overlap:
A overlaps B iff units(A) intersects units(B).
With this change, the above holds true even on targets that use ad hoc
aliasing (currently only ARM). This means that register units can be
used to implement regsOverlap() more efficiently, and the register
allocator can use the concept to model interference.
When there is no ad hoc aliasing, the register units correspond to the
maximal cliques in the register overlap graph. This is optimal, no other
register unit assignment can have fewer units.
With ad hoc aliasing, weird things are possible, and we don't try too
hard to compute the maximal cliques. The current approach is always
correct, and it works very well (probably optimally) as long as the ad
hoc aliasing doesn't have cliques larger than pairs. It seems unlikely
that any target would need more.
llvm-svn: 156763
The ad hoc aliasing specified in the 'Aliases' list in .td files is
currently only used by computeOverlaps(). It will soon be needed to
build accurate register units as well, so build the undirected graph in
CodeGenRegister::buildObjectGraph() instead.
Aliasing is a symmetric relationship with only one direction specified
in the .td files. Make sure both directions are represented in
getExplicitAliases().
llvm-svn: 156762
TableGen creates new register classes and sub-register indices based on
the sub-register structure present in the register bank. So far, it has
been doing that on a per-register basis, but that is not very efficient.
This patch teaches TableGen to compute topological signatures for
registers, and use that to reduce the amount of redundant computation.
Registers get the same TopoSig if they have identical sub-register
structure.
TopoSigs are not currently exposed outside TableGen.
llvm-svn: 156761
