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LLVM backend for 6502
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cea8688ee4
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Chris Lattner cea8688ee4 Teach the local spiller to turn stack slot loads into register-register copies 
when possible, avoiding the load (and avoiding the copy if the value is already
in the right register).

This patch came about when I noticed code like the following being generated:

  store R17 -> [SS1]
  ...blah...
  R4 = load [SS1]

This was causing an LSU reject on the G5.  This problem was due to the register
allocator folding spill code into a reg-reg copy (producing the load), which
prevented the spiller from being able to rewrite the load into a copy, despite
the fact that the value was already available in a register.  In the case
above, we now rip out the R4 load and replace it with a R4 = R17 copy.

This speeds up several programs on X86 (which spills a lot :) ), e.g.
smg2k from 22.39->20.60s, povray from 12.93->12.66s, 168.wupwise from
68.54->53.83s (!), 197.parser from 7.33->6.62s (!), etc.  This may have a larger
impact in some cases on the G5 (by avoiding LSU rejects), though it probably
won't trigger as often (less spilling in general).

Targets that implement folding of loads/stores into copies should implement
the isLoadFromStackSlot hook to get this.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23388 91177308-0d34-0410-b5e6-96231b3b80d8
2005-09-19 06:56:21 +00:00
autoconf For PR619: 2005-08-24 10:43:10 +00:00
docs new expression type 2005-09-08 18:47:21 +00:00
examples For PR616: 2005-08-24 10:07:20 +00:00
include/llvm add a new callback 2005-09-17 01:02:45 +00:00
lib Teach the local spiller to turn stack slot loads into register-register copies 2005-09-19 06:56:21 +00:00
projects Implement PR614: 2005-08-27 18:50:39 +00:00
runtime Remove trailing whitespace 2005-04-21 23:48:37 +00:00
test new testcase 2005-09-18 05:10:39 +00:00
tools Add help support for -mcpu and -mattr. 2005-09-02 19:27:43 +00:00
utils Fix a minor bug, add comments 2005-09-16 00:29:46 +00:00
win32 Fix more Visual Studio build problems. 2005-09-10 02:33:17 +00:00
Xcode Added targets to speed up build of llc. 2005-09-09 17:50:20 +00:00
.cvsignore Ignore the configure.out file generated by "make reconfigure" 2005-06-18 23:01:25 +00:00
configure For PR616: 2005-08-24 10:07:20 +00:00
CREDITS.TXT Add a note, people are responsible for requesting that they be added to the 2005-08-02 22:10:21 +00:00
LICENSE.TXT Remove extraneous colons after program names for consistency 2005-05-12 21:39:01 +00:00
llvm.spec Onward to LLVM-1.6 and beyond! 2005-05-18 20:23:20 +00:00
llvm.spec.in Onward to LLVM-1.6 and beyond! 2005-05-18 20:23:20 +00:00
Makefile For PR614: 2005-08-25 04:59:49 +00:00
Makefile.common Update comments to reflect new variable names. Patch contributed by 2005-02-14 16:02:19 +00:00
Makefile.config.in Two changes: 2005-04-22 17:14:14 +00:00
Makefile.rules allow for a target to ask for a dag isel 2005-09-03 01:15:25 +00:00
README.txt Make the text of this file a little more useful. 2004-09-02 22:49:27 +00:00

README.txt 

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

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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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