instructions.
e.g.
%reg1026<def> = VLDMQ %reg1025<kill>, 260, pred:14, pred:%reg0
%reg1027<def> = EXTRACT_SUBREG %reg1026, 6
%reg1028<def> = EXTRACT_SUBREG %reg1026<kill>, 5
...
%reg1029<def> = REG_SEQUENCE %reg1028<kill>, 5, %reg1027<kill>, 6, %reg1028, 7, %reg1027, 8, %reg1028, 9, %reg1027, 10, %reg1030<kill>, 11, %reg1032<kill>, 12
After REG_SEQUENCE is eliminated, we are left with:
%reg1026<def> = VLDMQ %reg1025<kill>, 260, pred:14, pred:%reg0
%reg1029:6<def> = EXTRACT_SUBREG %reg1026, 6
%reg1029:5<def> = EXTRACT_SUBREG %reg1026<kill>, 5
The regular coalescer will not be able to coalesce reg1026 and reg1029 because it doesn't
know how to combine sub-register indices 5 and 6. Now 2-address pass will consult the
target whether sub-registers 5 and 6 of reg1026 can be combined to into a larger
sub-register (or combined to be reg1026 itself as is the case here). If it is possible,
it will be able to replace references of reg1026 with reg1029 + the larger sub-register
index.
llvm-svn: 103835
v1024 = REG_SEQUENCE ...
v1025 = EXTRACT_SUBREG v1024, 5
v1026 = EXTRACR_SUBREG v1024, 6
= VSTxx <addr>, v1025, v1026
The REG_SEQUENCE ensures the sources that feed into the VST instruction
are getting the right register allocation so they form a large super-
register. The extract_subreg will be coalesced away all would just work:
v1024 = REG_SEQUENCE ...
= VSTxx <addr>, v1024:5, v1024:6
The problem is if the coalescer isn't run, the extract_subreg instructions
would stick around and there is no assurance v1025 and v1026 will get the
right registers.
As a short term workaround, teach the NEON pre-allocation pass to transfer
the sub-register indices over. An alternative would be do it 2addr pass
when reg_sequence's are eliminated. But that *seems* wrong and require
updating liveness information.
Another alternative is to do this in the scheduler when the instructions are
created. But that would mean somehow the scheduler this has to be done for
correctness reason. That's yucky as well. So for now, we are leaving this
in the target specific pass.
llvm-svn: 103540
with changes to add a separate optional register update argument. Change all
the NEON instructions with address register writeback to use it.
llvm-svn: 99095
load/stores with address register writeback, and use "odd" suffix to distinguish
instructions to access odd numbered registers (instead of "a" and "b").
No functional changes.
llvm-svn: 99066
that have that constraint. This is currently just assigning a fixed set of
registers, and it only handles VLDn for n=2,3,4 with DPR registers.
I'm going to expand it to handle more operations next; we can make it smarter
once everything is working correctly.
llvm-svn: 78256
