2 Commits

Author	SHA1	Message	Date
Evan Cheng	c2f95b56db	Minor optimization: ... Look for situations like this: %reg1024<def> = MOV r1 %reg1025<def> = MOV r0 %reg1026<def> = ADD %reg1024, %reg1025 r0 = MOV %reg1026 Commute the ADD to hopefully eliminate an otherwise unavoidable copy. llvm-svn: 65752	2009-03-01 02:03:43 +00:00
Evan Cheng	abda665f5f	Teach 2addr pass to be do more commuting. If both uses of a two-address instruction are killed, but the first operand has a use before and after the def, commute if the second operand does not suffer from the same issue. ... %reg1028<def> = EXTRACT_SUBREG %reg1027<kill>, 1 %reg1029<def> = MOV8rr %reg1028 %reg1029<def> = SHR8ri %reg1029, 7, %EFLAGS<imp-def,dead> insert => %reg1030<def> = MOV8rr %reg1028 %reg1030<def> = ADD8rr %reg1028<kill>, %reg1029<kill>, %EFLAGS<imp-def,dead> In this case, it might not be possible to coalesce the second MOV8rr instruction if the first one is coalesced. So it would be profitable to commute it: %reg1028<def> = EXTRACT_SUBREG %reg1027<kill>, 1 %reg1029<def> = MOV8rr %reg1028 %reg1029<def> = SHR8ri %reg1029, 7, %EFLAGS<imp-def,dead> insert => %reg1030<def> = MOV8rr %reg1029 %reg1030<def> = ADD8rr %reg1029<kill>, %reg1028<kill>, %EFLAGS<imp-def,dead> llvm-svn: 62954	2009-01-25 03:53:59 +00:00