[PATCH] D39995: [SelectionDAG] Make sorting predicate stronger to remove non-deterministic ordering
Mandeep Singh Grang via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Mon Nov 20 10:46:31 PST 2017
This revision was automatically updated to reflect the committed changes.
Closed by commit rL318680: [SelectionDAG] Make sorting predicate stronger to remove non-deterministic… (authored by mgrang).
Changed prior to commit:
https://reviews.llvm.org/D39995?vs=123545&id=123622#toc
Repository:
rL LLVM
https://reviews.llvm.org/D39995
Files:
llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
Index: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -9350,10 +9350,12 @@
BitTestInfo BTI;
std::sort(CBV.begin(), CBV.end(), [](const CaseBits &a, const CaseBits &b) {
- // Sort by probability first, number of bits second.
+ // Sort by probability first, number of bits second, bit mask third.
if (a.ExtraProb != b.ExtraProb)
return a.ExtraProb > b.ExtraProb;
- return a.Bits > b.Bits;
+ if (a.Bits != b.Bits)
+ return a.Bits > b.Bits;
+ return a.Mask < b.Mask;
});
for (auto &CB : CBV) {
@@ -9542,10 +9544,13 @@
}
if (TM.getOptLevel() != CodeGenOpt::None) {
- // Order cases by probability so the most likely case will be checked first.
+ // Here, we order cases by probability so the most likely case will be
+ // checked first. However, two clusters can have the same probability in
+ // which case their relative ordering is non-deterministic. So we use Low
+ // as a tie-breaker as clusters are guaranteed to never overlap.
std::sort(W.FirstCluster, W.LastCluster + 1,
[](const CaseCluster &a, const CaseCluster &b) {
- return a.Prob > b.Prob;
+ return a.Prob != b.Prob ? a.Prob > b.Prob : a.Low < b.Low;
});
// Rearrange the case blocks so that the last one falls through if possible
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