[TableGen] Make OpcodeMappings sort comparator deterministic NFCI

nga888 · nga888 · commit f38b00532118 · 2019-02-26T18:50:49.000Z
The previous sort comparator was not deterministic, i.e. in some situations it would be possible for lhs < rhs && rhs < lhs. This was discovered by an STL assertion in a Windows debug build of llvm-tblgen. Differential Revision: https://reviews.llvm.org/D58687 llvm-svn: 354910
diff --git a/llvm/utils/TableGen/CodeGenSchedule.cpp b/llvm/utils/TableGen/CodeGenSchedule.cpp
@@ -368,24 +368,22 @@ processSTIPredicate(STIPredicateFunction &Fn,
              [&](const OpcodeMapPair &Lhs, const OpcodeMapPair &Rhs) {
                unsigned LhsIdx = Opcode2Index[Lhs.first];
                unsigned RhsIdx = Opcode2Index[Rhs.first];
-               std::pair<APInt, APInt> &LhsMasks = OpcodeMasks[LhsIdx];
-               std::pair<APInt, APInt> &RhsMasks = OpcodeMasks[RhsIdx];
-
-               if (LhsMasks.first != RhsMasks.first) {
-                 if (LhsMasks.first.countPopulation() <
-                     RhsMasks.first.countPopulation())
-                   return true;
-                 return LhsMasks.first.countLeadingZeros() >
-                        RhsMasks.first.countLeadingZeros();
-               }
-
-               if (LhsMasks.second != RhsMasks.second) {
-                 if (LhsMasks.second.countPopulation() <
-                     RhsMasks.second.countPopulation())
-                   return true;
-                 return LhsMasks.second.countLeadingZeros() >
-                        RhsMasks.second.countLeadingZeros();
-               }
+               const std::pair<APInt, APInt> &LhsMasks = OpcodeMasks[LhsIdx];
+               const std::pair<APInt, APInt> &RhsMasks = OpcodeMasks[RhsIdx];
+
+               auto LessThan = [](const APInt &Lhs, const APInt &Rhs) {
+                 unsigned LhsCountPopulation = Lhs.countPopulation();
+                 unsigned RhsCountPopulation = Rhs.countPopulation();
+                 return ((LhsCountPopulation < RhsCountPopulation) ||
+                         ((LhsCountPopulation == RhsCountPopulation) &&
+                          (Lhs.countLeadingZeros() > Rhs.countLeadingZeros())));
+               };
+
+               if (LhsMasks.first != RhsMasks.first)
+                 return LessThan(LhsMasks.first, RhsMasks.first);
+
+               if (LhsMasks.second != RhsMasks.second)
+                 return LessThan(LhsMasks.second, RhsMasks.second);
 
                return LhsIdx < RhsIdx;
              });
