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LLVM backend for 6502
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Jakob Stoklund Olesen ded2e3b0d0 LowerSubregsInstructionPass::LowerExtract should not extend the live range of registers. 
When LowerExtract eliminates an EXTRACT_SUBREG with a kill flag, it moves the
kill flag to the place where the sub-register is killed. This can accidentally
overlap with the use of a sibling sub-register, and we have trouble.

In the test case we have this code:

Live Ins: %R0 %R1 %R2
	%R2L<def> = EXTRACT_SUBREG %R2<kill>, 1
	%R2H<def> = LOAD16fi <fi#-1>, 0, Mem:LD(2,4) [FixedStack-1 + 0]
	%R1L<def> = EXTRACT_SUBREG %R1<kill>, 1
	%R0L<def> = EXTRACT_SUBREG %R0<kill>, 1
	%R0H<def> = ADD16 %R2H<kill>, %R2L<kill>, %AZ<imp-def>, %AN<imp-def>, %AC0<imp-def>, %V<imp-def>, %VS<imp-def>

subreg: CONVERTING: %R2L<def> = EXTRACT_SUBREG %R2<kill>, 1
subreg: eliminated!
subreg: killed here: %R0H<def> = ADD16 %R2H, %R2L, %R2<imp-use,kill>, %AZ<imp-def>, %AN<imp-def>, %AC0<imp-def>, %V<imp-def>, %VS<imp-def>

The kill flag on %R2 is moved to the last instruction, and the live range overlaps with the definition of %R2H:

*** Bad machine code: Redefining a live physical register ***
- function:    f
- basic block:  0x18358c0 (#0)
- instruction: %R2H<def> = LOAD16fi <fi#-1>, 0, Mem:LD(2,4) [FixedStack-1 + 0]
Register R2H was defined but already live.

The fix is to replace EXTRACT_SUBREG with IMPLICIT_DEF instead of eliminating
it completely:

subreg: CONVERTING: %R2L<def> = EXTRACT_SUBREG %R2<kill>, 1
subreg: replace by: %R2L<def> = IMPLICIT_DEF %R2<kill>

Note that these IMPLICIT_DEF instructions survive to the asm output. It is
necessary to fix the stack-color-with-reg test case because of that.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78093 91177308-0d34-0410-b5e6-96231b3b80d8
2009-08-04 20:01:11 +00:00
autoconf Build Blackfin target with autoconf and cmake. 2009-08-02 17:32:37 +00:00
bindings Reorder the "Metadata" entry to match the C bindings. 2009-07-21 21:52:57 +00:00
cmake CMake configuration: find mkdtemp, mkstemp, mktemp. 2009-07-27 18:23:41 +00:00
docs Minor www site formating improvements. 2009-08-04 05:24:28 +00:00
examples Move a few more APIs back to 2.5 forms. The only remaining ones left to change back are 2009-07-31 20:28:14 +00:00
include Add some type traits that are used for Clang's statically-checked 2009-08-04 17:04:52 +00:00
lib LowerSubregsInstructionPass::LowerExtract should not extend the live range of registers. 2009-08-04 20:01:11 +00:00
projects remove dead makefile flags. 2009-06-24 05:29:56 +00:00
runtime
test LowerSubregsInstructionPass::LowerExtract should not extend the live range of registers. 2009-08-04 20:01:11 +00:00
tools No really, it's unused. 2009-08-04 04:08:40 +00:00
unittests Remove now empty unit test directory. 2009-08-01 19:07:29 +00:00
utils * Use "svn export" instead of "svn co" and avoid cleaning up .svn dirs 2009-08-04 15:47:18 +00:00
website
win32 Revert the ConstantInt constructors back to their 2.5 forms where possible, thanks to contexts-on-types. More to come. 2009-07-24 23:12:02 +00:00
Xcode Remove the IA-64 backend. 2009-07-24 00:30:09 +00:00
build-for-llvm-top.sh
CMakeLists.txt Build Blackfin target with autoconf and cmake. 2009-08-02 17:32:37 +00:00
configure Build Blackfin target with autoconf and cmake. 2009-08-02 17:32:37 +00:00
CREDITS.TXT Added myself to the blame list. 2009-07-15 13:01:49 +00:00
LICENSE.TXT one fewer license, yay. :) 2009-08-01 22:54:39 +00:00
llvm.spec.in
Makefile Introduce new headers whose inclusion forces linking and 2009-06-16 20:12:29 +00:00
Makefile.common
Makefile.config.in LLVMC can be now compiled w/o dynamic plugin support. 2009-07-04 03:55:25 +00:00
Makefile.rules Makefile rules for generating assembly matcher. 2009-07-13 18:35:35 +00:00
ModuleInfo.txt
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