2 Commits

Author	SHA1	Message	Date
Evan Cheng	2ec94dd447	Model inline asm constraint which ties an input to an output register as machine operand TIED_TO constraint. This eliminated the need to pre-allocate registers for these. This also allows register allocator can eliminate the unneeded copies. ... llvm-svn: 67512	2009-03-23 08:01:15 +00:00
Evan Cheng	da55c4ffb7	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. llvm-svn: 61259	2008-12-19 20:58:01 +00:00