tryLatency compares two sched candidates. For the top zone it prefers
the one with lesser depth, but only if that depth is greater than the
total latency of the instructions we've already scheduled -- otherwise
its latency would be hidden and there would be no stall.
Unfortunately it only tests the depth of one of the candidates. This can
lead to situations where the TopDepthReduce heuristic does not kick in,
but a lower priority heuristic chooses the other candidate, whose depth
*is* greater than the already scheduled latency, which causes a stall.
The fix is to apply the heuristic if the depth of *either* candidate is
greater than the already scheduled latency.
All this also applies to the BotHeightReduce heuristic in the bottom
zone.
Differential Revision: https://reviews.llvm.org/D72392
Summary:
I'm not planning to check this in at the moment, but feedback is very welcome, in particular how this affects performance.
The feedback obtains here will guide the next steps towards enabling this.
This patch enables the use of MemorySSA in the loop pass manager.
Passes that currently use MemorySSA:
- EarlyCSE
Passes that use MemorySSA after this patch:
- EarlyCSE
- LICM
- SimpleLoopUnswitch
Loop passes that update MemorySSA (and do not use it yet, but could use it after this patch):
- LoopInstSimplify
- LoopSimplifyCFG
- LoopUnswitch
- LoopRotate
- LoopSimplify
- LCSSA
Loop passes that do *not* update MemorySSA:
- IndVarSimplify
- LoopDelete
- LoopIdiom
- LoopSink
- LoopUnroll
- LoopInterchange
- LoopUnrollAndJam
- LoopVectorize
- LoopReroll
- IRCE
Reviewers: chandlerc, george.burgess.iv, davide, sanjoy, gberry
Subscribers: jlebar, Prazek, dmgreen, jdoerfert, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D58311
llvm-svn: 370384
Summary:
Problem exposed in PowerPC functional testing.
We did not consider Anti dependence for nodes in same cycle,
so we may end up generating bad machine code.
eg: the reduced test won't verify.
*** Bad machine code: Using an undefined physical register ***
- function: lame_encode_buffer_interleaved
- basic block: %bb.4 (0x4bde4e12928)
- instruction: %29:gprc = ADDZE %27:gprc, implicit-def dead $carry, implicit $carry
- operand 3: implicit $carry
Reviewers: bcahoon, kparzysz, hfinkel
Subscribers: MaskRay, wuzish, nemanjai, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D64192
llvm-svn: 365859
Jay Foad