[PGO] Fixed non-determinism with DenseSet storing function importing info.

[apazos]

Summary

r296498 introduced a DenseSet to store function importing info.

Using this container causes a test failure in
test/Transform/SampleProfile/import.ll when in Reverse Iteration mode.

This patch orders IDs before iterating through this container.

[danielcdh]

does this change any tests?

lib/IR/MDBuilder.cpp

77

please remove this line

[apazos]

No, no test needs to change.

After r296498 change the compiler was generating:
!35 = !{!"function_entry_count", i64 1, i64 -2012135647395072713, i64 6699318081062747564}

While the test expected:
!35 = !{!"function_entry_count", i64 1, i64 6699318081062747564, i64 -2012135647395072713}

In regular mode, the test passes. But it failed in Reverse Iteration mode.

[apazos]

Removed empty line.

[danielcdh]

The sorting is not a concern as it's only called once perf function, and the list should not be large.

Thanks for fixing the non-determinism in code.

lib/IR/MDBuilder.cpp

 }
 
 MDNode *MDBuilder::createFunctionEntryCount(
     uint64_t Count, const DenseSet<GlobalValue::GUID> *Imports) {
   Type *Int64Ty = Type::getInt64Ty(Context);
   SmallVector<Metadata *, 8> Ops;
   Ops.push_back(createString("function_entry_count"));
   Ops.push_back(createConstant(ConstantInt::get(Int64Ty, Count)));
-  if (Imports)
-    for (auto ID : *Imports)
+  if (Imports) {
+    SmallVector<GlobalValue::GUID, 2> OrderID(Imports->begin(), Imports->end());
+    std::stable_sort(OrderID.begin(), OrderID.end(),
+      [] (GlobalValue::GUID A, GlobalValue::GUID B) {
+        return A < B;});
+    for (auto ID : OrderID) {
       Ops.push_back(createConstant(ConstantInt::get(Int64Ty, ID)));
+    }
+  }
   return MDNode::get(Context, Ops);
 }
 
+
 MDNode *MDBuilder::createFunctionSectionPrefix(StringRef Prefix) {
   return MDNode::get(Context,
                      {createString("function_section_prefix"),
                       createString(Prefix)});
 }
 
 MDNode *MDBuilder::createRange(const APInt &Lo, const APInt &Hi) {
   assert(Lo.getBitWidth() == Hi.getBitWidth() && "Mismatched bitwidths!");