to be more general and understand more varieties of loops.
Teach CodePlacementOpt to reorganize the basic blocks of a loop so that
they are contiguous. This also includes a fair amount of logic for preserving
fall-through edges while doing so. This fixes a BranchFolding-ism where blocks
which can't be made to use a fall-through edge and don't conveniently fit
anywhere nearby get tossed out to the end of the function.
llvm-svn: 84295
variable increment / decrement slighter high priority.
This has major impact on some micro-benchmarks. On MultiSource/Applications
and spec tests, it's a minor win. It also reduce 256.bzip instruction count
by 8%, 55 on 164.gzip on i386 / Darwin.
llvm-svn: 82485
%reg1498<def> = MOV32rm %reg1024, 1, %reg0, 12, %reg0, Mem:LD(4,4) [sunkaddr39 + 0]
%reg1506<def> = MOV32rm %reg1024, 1, %reg0, 8, %reg0, Mem:LD(4,4) [sunkaddr42 + 0]
%reg1486<def> = MOV32rr %reg1506
%reg1486<def> = XOR32rr %reg1486, %reg1498, %EFLAGS<imp-def,dead>
%reg1510<def> = MOV32rm %reg1024, 1, %reg0, 4, %reg0, Mem:LD(4,4) [sunkaddr45 + 0]
=>
%reg1498<def> = MOV32rm %reg2036, 1, %reg0, 12, %reg0, Mem:LD(4,4) [sunkaddr39 + 0]
%reg1506<def> = MOV32rm %reg2037, 1, %reg0, 8, %reg0, Mem:LD(4,4) [sunkaddr42 + 0]
%reg1486<def> = MOV32rr %reg1506
%reg1486<def> = XOR32rr %reg1486, %reg1498, %EFLAGS<imp-def,dead>
%reg1510<def> = MOV32rm %reg2038, 1, %reg0, 4, %reg0, Mem:LD(4,4) [sunkaddr45 + 0]
From linearscan's point of view, each of reg2036, 2037, and 2038 are separate registers, each is "killed" after a single use. The reloaded register is available and it's often clobbered right away. e.g. In thise case reg1498 is allocated EAX while reg2036 is allocated RAX. This means we end up with multiple reloads from the same stack slot in the same basic block.
Now linearscan recognize there are other reloads from same SS in the same BB. So it'll "downgrade" RAX (and its aliases) after reg2036 is allocated until the next reload (reg2037) is done. This greatly increase the likihood reloads from SS are reused.
This speeds up sha1 from OpenSSL by 5.8%. It is also an across the board win for SPEC2000 and 2006.
llvm-svn: 69585
