This is done by pushing physical register definitions close to their
use, which happens to handle flag definitions if they're not glued to
the branch. This seems to be generally a good thing though, so I
didn't need to add a target hook yet.
The primary motivation is to generate code closer to what people
expect and rule out missed opportunity from enabling macro-op
fusion. As a side benefit, we get several 2-5% gains on x86
benchmarks. There is one regression:
SingleSource/Benchmarks/Shootout/lists slows down be -10%. But this is
an independent scheduler bug that will be tracked separately.
See rdar://problem/9283108.
Incidentally, pre-RA scheduling is only half the solution. Fixing the
later passes is tracked by:
<rdar://problem/8932804> [pre-RA-sched] on x86, attempt to schedule CMP/TEST adjacent with condition jump
Fixes:
<rdar://problem/9262453> Scheduler unnecessary break of cmp/jump fusion
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129508 91177308-0d34-0410-b5e6-96231b3b80d8
This reverts revision 114633. It was breaking llvm-gcc-i386-linux-selfhost.
It seems there is a downstream bug that is exposed by
-cgp-critical-edge-splitting=0. When that bug is fixed, this patch can go back
in.
Note that the changes to tailcallfp2.ll are not reverted. They were good are
required.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@114859 91177308-0d34-0410-b5e6-96231b3b80d8
Measurements show that it does not speed up coalescing, so there is no reason
the keep the added complexity around.
Also clean out some unused methods and static functions.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106548 91177308-0d34-0410-b5e6-96231b3b80d8
happening.
Enhance scheduling to set the DEAD flag on implicit defs
more aggressively. Before, we'd set an implicit def operand
to dead if it were present in the SDNode corresponding to
the machineinstr but had no use. Now we do it in this case
AND if the implicit def does not exist in the SDNode at all.
This exposes a couple of problems: one is the FIXME, which
causes a live intervals crash on CodeGen/X86/sibcall.ll.
The second is that it makes machinecse and licm more
aggressive (which is a good thing) but also exposes a case
where licm hoists a set0 and then it doesn't get resunk.
Talking to codegen folks about both these issues, but I need
this patch in in the meantime.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@99485 91177308-0d34-0410-b5e6-96231b3b80d8
