https://github.com/mjklemm updated https://github.com/llvm/llvm-project/pull/170863
>From 5bd0974817c7e6f2f1964acf1d5e1b372a00535c Mon Sep 17 00:00:00 2001 From: Michael Klemm <[email protected]> Date: Fri, 5 Dec 2025 14:27:57 +0100 Subject: [PATCH 1/2] [Flang][OpenMP] Fix OpenMP static scheduling when trip count is zero 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. --- llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp index fff9a815e5368..694b98225f8c5 100644 --- a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp +++ b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp @@ -4829,7 +4829,10 @@ OpenMPIRBuilder::applyStaticChunkedWorkshareLoop(DebugLoc DL, I32Type, static_cast<int>(OMPScheduleType::UnorderedStaticChunked)); 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 >From b3bcd07d31cef4a49763d8f5d6fa435e073ceb79 Mon Sep 17 00:00:00 2001 From: Michael Klemm <[email protected]> Date: Fri, 5 Dec 2025 16:52:13 +0100 Subject: [PATCH 2/2] Update test case --- clang/test/OpenMP/irbuilder_for_unsigned_static_chunked.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) 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) _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
