From 1938f2eb9832978952f6a6397a5ad40c6338ed6e Mon Sep 17 00:00:00 2001
From: Cong Hou <congh@google.com>
Date: Tue, 24 Nov 2015 08:51:23 +0000
Subject: Let SelectionDAG start to use probability-based interface to add
 successors.

The patch in http://reviews.llvm.org/D13745 is broken into four parts:

1. New interfaces without functional changes.
2. Use new interfaces in SelectionDAG, while in other passes treat probabilities
as weights.
3. Use new interfaces in all other passes.
4. Remove old interfaces.

This the second patch above. In this patch SelectionDAG starts to use
probability-based interfaces in MBB to add successors but other MC passes are
still using weight-based interfaces. Therefore, we need to maintain correct
weight list in MBB even when probability-based interfaces are used. This is
done by updating weight list in probability-based interfaces by treating the
numerator of probabilities as weights. This change affects many test cases
that check successor weight values. I will update those test cases once this
patch looks good to you.


Differential revision: http://reviews.llvm.org/D14361

llvm-svn: 253965
---
 llvm/lib/CodeGen/MachineBasicBlock.cpp | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

(limited to 'llvm/lib/CodeGen/MachineBasicBlock.cpp')

diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index 80e5d82b9a9..602b75182fc 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -528,8 +528,13 @@ void MachineBasicBlock::addSuccessor(MachineBasicBlock *Succ,
                                      BranchProbability Prob) {
   // Probability list is either empty (if successor list isn't empty, this means
   // disabled optimization) or has the same size as successor list.
-  if (!(Probs.empty() && !Successors.empty()))
+  if (!(Probs.empty() && !Successors.empty())) {
     Probs.push_back(Prob);
+    // FIXME: Temporarily use the numerator of the probability to represent edge
+    // weight. This will be removed once all weight-version interfaces in MBB
+    // are replaced with probability-version interfaces.
+    Weights.push_back(Prob.getNumerator());
+  }
   Successors.push_back(Succ);
   Succ->addPredecessor(this);
 }
@@ -539,6 +544,7 @@ void MachineBasicBlock::addSuccessorWithoutProb(MachineBasicBlock *Succ) {
   // of successor list. When this function is called, we can safely delete all
   // probability in the list.
   Probs.clear();
+  Weights.clear();
   Successors.push_back(Succ);
   Succ->addPredecessor(this);
 }
@@ -558,12 +564,17 @@ MachineBasicBlock::removeSuccessor(succ_iterator I) {
     Weights.erase(WI);
   }
 
+  // FIXME: Temporarily comment the following code as probabilities are now only
+  // used during instruction lowering, but this interface is called in later
+  // passes. Uncomment it once all edge weights are replaced with probabilities.
+#if 0
   // If probability list is empty it means we don't use it (disabled
   // optimization).
   if (!Probs.empty()) {
     probability_iterator WI = getProbabilityIterator(I);
     Probs.erase(WI);
   }
+#endif
 
   (*I)->removePredecessor(this);
   return Successors.erase(I);
@@ -603,10 +614,14 @@ void MachineBasicBlock::replaceSuccessor(MachineBasicBlock *Old,
   // Update its weight instead of adding a duplicate edge.
   if (!Weights.empty())
     *getWeightIterator(NewI) += *getWeightIterator(OldI);
+  // FIXME: Temporarily comment the following code as probabilities are now only
+  // used during instruction lowering, but this interface is called in later
+  // passes. Uncomment it once all edge weights are replaced with probabilities.
+#if 0
   // Update its probability instead of adding a duplicate edge.
   if (!Probs.empty())
     *getProbabilityIterator(NewI) += *getProbabilityIterator(OldI);
-
+#endif
   removeSuccessor(OldI);
 }
 
@@ -1165,9 +1180,13 @@ void MachineBasicBlock::setSuccWeight(succ_iterator I, uint32_t Weight) {
 void MachineBasicBlock::setSuccProbability(succ_iterator I,
                                            BranchProbability Prob) {
   assert(!Prob.isUnknown());
-  if (Probs.empty())
+  if (Probs.empty() || Weights.empty())
     return;
   *getProbabilityIterator(I) = Prob;
+  // FIXME: Temporarily use the numerator of the probability to represent edge
+  // weight. This will be removed once all weight-version interfaces in MBB
+  // are replaces with probability-version interfaces.
+  *getWeightIterator(I) = Prob.getNumerator();
 }
 
 /// Return wight iterator corresonding to the I successor iterator.
-- 
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