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LLVM backend for 6502
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Evan Cheng 5379f412bc Fix PR3149. If an early clobber def is a physical register and it is tied to an input operand, it effectively extends the live range of the physical register. Currently we do not have a good way to represent this. 
172     %ECX<def> = MOV32rr %reg1039<kill>
180     INLINEASM <es:subl $5,$1
        sbbl $3,$0>, 10, %EAX<def>, 14, %ECX<earlyclobber,def>, 9, %EAX<kill>,
36, <fi#0>, 1, %reg0, 0, 9, %ECX<kill>, 36, <fi#1>, 1, %reg0, 0
188     %EAX<def> = MOV32rr %EAX<kill>
196     %ECX<def> = MOV32rr %ECX<kill>
204     %ECX<def> = MOV32rr %ECX<kill>
212     %EAX<def> = MOV32rr %EAX<kill>
220     %EAX<def> = MOV32rr %EAX
228     %reg1039<def> = MOV32rr %ECX<kill>

The early clobber operand ties ECX input to the ECX def.

The live interval of ECX is represented as this:
%reg20,inf = [46,47:1)[174,230:0)  0@174-(230) 1@46-(47)

The right way to represent this is something like
%reg20,inf = [46,47:2)[174,182:1)[181:230:0)  0@174-(182) 1@181-230 @2@46-(47)

Of course that won't work since that means overlapping live ranges defined by two val#.

The workaround for now is to add a bit to val# which says the val# is redefined by a early clobber def somewhere. This prevents the move at 228 from being optimized away by SimpleRegisterCoalescing::AdjustCopiesBackFrom.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61259 91177308-0d34-0410-b5e6-96231b3b80d8
2008-12-19 20:58:01 +00:00
autoconf Revert accidental last patch 2008-11-20 04:28:08 +00:00
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cmake Fix a link issue I ran into trying compiling LLVM on MinGW with CMake. 2008-11-30 02:42:05 +00:00
docs Resubmit support for the 'nocapture' attribute. 2008-12-19 06:39:12 +00:00
examples reapply Sanjiv's patch to genericize memcpy/memset/memmove to take an 2008-11-21 16:42:48 +00:00
include Fix PR3149. If an early clobber def is a physical register and it is tied to an input operand, it effectively extends the live range of the physical register. Currently we do not have a good way to represent this. 2008-12-19 20:58:01 +00:00
lib Fix PR3149. If an early clobber def is a physical register and it is tied to an input operand, it effectively extends the live range of the physical register. Currently we do not have a good way to represent this. 2008-12-19 20:58:01 +00:00
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test Fix PR3149. If an early clobber def is a physical register and it is tied to an input operand, it effectively extends the live range of the physical register. Currently we do not have a good way to represent this. 2008-12-19 20:58:01 +00:00
tools Some enhancements for the 'case' expression. 2008-12-17 02:47:01 +00:00
utils Use dyn_cast intead of isa + cast in the generated DAGISel code. This 2008-12-19 18:13:39 +00:00
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