Author: Michael Klemm Date: 2025-12-08T18:29:02+01:00 New Revision: 8c8074f0fa516210011c7b3beb63807ffbe5c5f7
URL: https://github.com/llvm/llvm-project/commit/8c8074f0fa516210011c7b3beb63807ffbe5c5f7 DIFF: https://github.com/llvm/llvm-project/commit/8c8074f0fa516210011c7b3beb63807ffbe5c5f7.diff LOG: [Flang][OpenMP] Fix OpenMP static scheduling when trip count is zero (#170863) Code-gen produced incorrect code for cases when the trip count an associated DO loop was zero. The generated code evaluated the trip count of the loop and substracted 1 from it. When this was passed to __kmpc_for_static_init_4u, the value was interpreted as unsigned, which made the upper bound of the worksharing loop 2^32-1 and caused a division by zero in the calculation of the loop bounds for the threads. Added: Modified: clang/test/OpenMP/irbuilder_for_unsigned_static_chunked.c llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp Removed: ################################################################################ diff --git a/clang/test/OpenMP/irbuilder_for_unsigned_static_chunked.c b/clang/test/OpenMP/irbuilder_for_unsigned_static_chunked.c index b937568ca9f11..dfa5e8a6e0943 100644 --- a/clang/test/OpenMP/irbuilder_for_unsigned_static_chunked.c +++ b/clang/test/OpenMP/irbuilder_for_unsigned_static_chunked.c @@ -50,7 +50,9 @@ extern "C" void workshareloop_unsigned_static_chunked(float *a, float *b, float // CHECK: omp_loop.preheader: // CHECK-NEXT: store i32 0, ptr [[P_LOWERBOUND]], align 4 // CHECK-NEXT: [[TMP3:%.*]] = sub i32 [[DOTCOUNT]], 1 -// CHECK-NEXT: store i32 [[TMP3]], ptr [[P_UPPERBOUND]], align 4 +// CHECK-NEXT: [[COUNTCOND:%.*]] = icmp eq i32 [[DOTCOUNT]], 0 +// CHECK-NEXT: [[UPPERSEL:%.*]] = select i1 [[COUNTCOND]], i32 0, i32 [[TMP3]] +// CHECK-NEXT: store i32 [[UPPERSEL]], ptr [[P_UPPERBOUND]], align 4 // CHECK-NEXT: store i32 1, ptr [[P_STRIDE]], align 4 // CHECK-NEXT: [[OMP_GLOBAL_THREAD_NUM:%.*]] = call i32 @__kmpc_global_thread_num(ptr @[[GLOB1:[0-9]+]]) // CHECK-NEXT: call void @__kmpc_for_static_init_4u(ptr @[[GLOB1]], i32 [[OMP_GLOBAL_THREAD_NUM]], i32 33, ptr [[P_LASTITER]], ptr [[P_LOWERBOUND]], ptr [[P_UPPERBOUND]], ptr [[P_STRIDE]], i32 1, i32 5) diff --git a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp index 553333d53a106..9c521828660c2 100644 --- a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp +++ b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp @@ -5140,7 +5140,10 @@ OpenMPIRBuilder::applyStaticChunkedWorkshareLoop( ConstantInt::get(I32Type, static_cast<int>(DistScheduleSchedType)); Builder.CreateStore(Zero, PLowerBound); Value *OrigUpperBound = Builder.CreateSub(CastedTripCount, One); - Builder.CreateStore(OrigUpperBound, PUpperBound); + Value *IsTripCountZero = Builder.CreateICmpEQ(CastedTripCount, Zero); + Value *UpperBound = + Builder.CreateSelect(IsTripCountZero, Zero, OrigUpperBound); + Builder.CreateStore(UpperBound, PUpperBound); Builder.CreateStore(One, PStride); // Call the "init" function and update the trip count of the loop with the _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
