[OpenMPIRBuilder] Don't drop debug info for target region. (#80692)

When an outlined function is generated for omp target region, a
corresponding DISubprogram was not being generated. This resulted in all
the debug information for the target region being dropped.

This commit adds DISubprogram for the outlined function if there is one
available for the parent function. It also updates the current debug
location so that the right scope is used for the entries in the outlined
function.

There are places in the OpenMPIRBuilder which changes insertion point but
don't update the debug location accordingly. They cause issue when debug info
is enabled. I have fixed a few that I observed to cause issue. But there may be
more and a systematic cleanup may be required.

With this change in place, I can set source line breakpoint in target
region and run to them in debugger.

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/unittests/Frontend/OpenMPIRBuilderTest.cpp b/llvm/unittests/Frontend/OpenMPIRBuilderTest.cpp
index 6207792..c92a3ff 100644
--- a/llvm/unittests/Frontend/OpenMPIRBuilderTest.cpp
+++ b/llvm/unittests/Frontend/OpenMPIRBuilderTest.cpp
@@ -6006,6 +6006,10 @@ TEST_F(OpenMPIRBuilderTest, TargetRegion) {
   BasicBlock *FallbackBlock = Branch->getSuccessor(0);
   Iter = FallbackBlock->rbegin();
   CallInst *FCall = dyn_cast<CallInst>(&*(++Iter));
+  // 'F' has a dummy DISubprogram which causes OutlinedFunc to also
+  // have a DISubprogram. In this case, the call to OutlinedFunc needs
+  // to have a debug loc, otherwise verifier will complain.
+  FCall->setDebugLoc(DL);
   EXPECT_NE(FCall, nullptr);
 
   // Check that the correct aguments are passed in