[flang][OpenMP] Support multi-block reduction combiner regions on the GPU (#156837)

Fixes a bug related to insertion points when inlining multi-block
combiner reduction regions. The IP at the end of the inlined region was
not used resulting in emitting BBs with multiple terminators.

PR stack:
- https://github.com/llvm/llvm-project/pull/155754
- https://github.com/llvm/llvm-project/pull/155987
- https://github.com/llvm/llvm-project/pull/155992
- https://github.com/llvm/llvm-project/pull/155993
- https://github.com/llvm/llvm-project/pull/157638
- https://github.com/llvm/llvm-project/pull/156610
- https://github.com/llvm/llvm-project/pull/156837 ◀️

1 files changed, 3 insertions, 0 deletions

diff --git a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
index 220eee3cb8b0..6d948f184392 100644
--- a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
+++ b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
@@ -3507,6 +3507,8 @@ Expected<Function *> OpenMPIRBuilder::createReductionFunction(
         return AfterIP.takeError();
       if (!Builder.GetInsertBlock())
         return ReductionFunc;
+
+      Builder.restoreIP(*AfterIP);
       Builder.CreateStore(Reduced, LHSPtr);
     }
   }
@@ -3751,6 +3753,7 @@ OpenMPIRBuilder::InsertPointOrErrorTy OpenMPIRBuilder::createReductionsGPU(
           RI.ReductionGen(Builder.saveIP(), RHSValue, LHSValue, Reduced);
       if (!AfterIP)
         return AfterIP.takeError();
+      Builder.restoreIP(*AfterIP);
       Builder.CreateStore(Reduced, LHS, false);
     }
   }