[OpenMPIRBuilder] Put the barrier in the exit block in createWorkshapeLoop

[ftynse]

Summary

The original code was inserting the barrier at the location given by the
caller. Make sure it is always inserted at the end of the loop exit block
instead.

[Meinersbur]

LGTM

[ftynse]

Rebase on main

[ftynse]

Rebase

llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp

CanonicalLoopInfo *OpenMPIRBuilder::createStaticWorkshareLoop(
 
   // In the "exit" block, call the "fini" function.
   Builder.SetInsertPoint(CLI->getExit(),
                          CLI->getExit()->getTerminator()->getIterator());
   Builder.CreateCall(StaticFini, {SrcLoc, ThreadNum});
 
   // Add the barrier if requested.
   if (NeedsBarrier)
-    createBarrier(Loc, omp::Directive::OMPD_for, /* ForceSimpleCall */ false,
+    createBarrier(LocationDescription(Builder.saveIP(), Loc.DL),
+                  omp::Directive::OMPD_for, /* ForceSimpleCall */ false,
                   /* CheckCancelFlag */ false);
 
   CLI->assertOK();
   return CLI;
 }
 
 void CanonicalLoopInfo::eraseFromParent() {
   assert(IsValid && "can only erase previously valid loop cfg");

llvm/unittests/Frontend/OpenMPIRBuilderTest.cpp

TEST_F(OpenMPIRBuilderTest, StaticWorkShareLoop) {
   auto *LoadedUpperBound = dyn_cast<LoadInst>(Difference->getOperand(0));
   ASSERT_NE(LoadedUpperBound, nullptr);
   EXPECT_EQ(LoadedUpperBound->getPointerOperand(), PUpperBound);
 
   // The original loop iterator should only be used in the condition, in the
   // increment and in the statement that adds the lower bound to it.
   Value *IV = CLI->getIndVar();
   EXPECT_EQ(std::distance(IV->use_begin(), IV->use_end()), 3);
+
+  // The exit block should contain the "fini" call and the barrier call,
+  // plus the call to obtain the thread ID.
+  BasicBlock *ExitBlock = CLI->getExit();
+  size_t NumCallsInExitBlock =
+      count_if(*ExitBlock, [](Instruction &I) { return isa<CallInst>(I); });
+  EXPECT_EQ(NumCallsInExitBlock, 3u);
 }
 
 TEST_F(OpenMPIRBuilderTest, MasterDirective) {
   using InsertPointTy = OpenMPIRBuilder::InsertPointTy;
   OpenMPIRBuilder OMPBuilder(*M);
   OMPBuilder.initialize();
   F->setName("func");
   IRBuilder<> Builder(BB);