Evan Cheng b990a2f249 Teach two-address pass to do some coalescing while eliminating REG_SEQUENCE
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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103835 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-14 23:21:14 +00:00
2010-02-23 15:11:17 +00:00
2010-04-16 13:32:55 +00:00
2010-02-23 19:15:24 +00:00
2010-04-30 23:36:47 +00:00

Low Level Virtual Machine (LLVM)
================================

This directory and its subdirectories contain source code for the Low Level
Virtual Machine, a toolkit for the construction of highly optimized compilers,
optimizers, and runtime environments.

LLVM is open source software. You may freely distribute it under the terms of
the license agreement found in LICENSE.txt.

Please see the HTML documentation provided in docs/index.html for further
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LLVM backend for 6502
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