Subzero: Deterministically sort local var stack offsets.

src/IceTargetLowering.cpp

 //===- subzero/src/IceTargetLowering.cpp - Basic lowering implementation --===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 719 matching lines @@
   }
 }
 
 void TargetLowering::sortVarsByAlignment(VarList &Dest,
                                          const VarList &Source) const {
   Dest = Source;
   // Instead of std::sort, we could do a bucket sort with log2(alignment) as
   // the buckets, if performance is an issue.
   std::sort(Dest.begin(), Dest.end(),
             [this](const Variable *V1, const Variable *V2) {
-              return typeWidthInBytesOnStack(V1->getType()) >
-                     typeWidthInBytesOnStack(V2->getType());
+              const size_t WidthV1 = typeWidthInBytesOnStack(V1->getType());
+              const size_t WidthV2 = typeWidthInBytesOnStack(V2->getType());
+              if (WidthV1 == WidthV2)
+                return V1->getIndex() < V2->getIndex();
+              return WidthV1 > WidthV2;
             });
 }
 
 void TargetLowering::getVarStackSlotParams(
     VarList &SortedSpilledVariables, SmallBitVector &RegsUsed,
     size_t *GlobalsSize, size_t *SpillAreaSizeBytes,
     uint32_t *SpillAreaAlignmentBytes, uint32_t *LocalsSlotsAlignmentBytes,
     std::function<bool(Variable *)> TargetVarHook) {
   const VariablesMetadata *VMetadata = Func->getVMetadata();
   BitVector IsVarReferenced(Func->getNumVariables());
@@ skipping 336 matching lines @@
   case TARGET_LOWERING_CLASS_FOR(X):                                           \
     return ::X::createTargetHeaderLowering(Ctx);
 #include "SZTargets.def"
 #undef SUBZERO_TARGET
   }
 }
 
 TargetHeaderLowering::~TargetHeaderLowering() = default;
 
 } // end of namespace Ice