[PATCH] D20017: Aggressive choosing best loop top

[David Li via llvm-commits]

davidxl added a comment.

The missing weight fixes can be extracted out separately.

I don't think the change in MBP is the right thing to make  -- we don't any more 'pattern' matching code like this in MBP, which can be very fragile. Please try the cost based loop rotation which is a general  solution. For different targets, there are also tuning parameters JumpInstCost and MisfetchCost that can be tuned in a target dependent way.


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Comment at: lib/CodeGen/AtomicExpandPass.cpp:900
@@ -898,2 +899,3 @@
   BasicBlock *LoopBB = BasicBlock::Create(Ctx, "atomicrmw.start", F, ExitBB);
+  MDNode *BrWeight = MDBuilder(AI->getContext()).createBranchWeights(1, 1);
 
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chandlerc wrote:
> Sink this to where it is used?
please split out change in this file into a different patch.

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Comment at: lib/Target/SystemZ/SystemZISelLowering.cpp:5271
@@ -5270,1 +5270,3 @@
+  const BranchProbability VeryHighProb(999, 1000); // 99.9%
+  const BranchProbability VeryLowProb(1, 1000); // 0.1%
 
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This should also be split out into a different patch.


http://reviews.llvm.org/D20017