[MLIR][OpenMP][OMPIRBuilder] Lower OpenMP version attributes to LLVM IR

[domada]

Summary

MLIR version attribute should be lowered to LLVM IR module metadata.

The lowering is done by OpenMPIRBuilder.

[kiranchandramohan]

LG.

[domada]

OpenMP standard mentions that if implementation of OpenMP supports preprocessor then macro _OPENMP is defined to have value yyyymm, where yyyy denotes the year and mm denotes the month of OpenMP version release. (OpenMP standard 5.2 section 3.3).
Currently Flang has hard coded value of OpenMP 4.5 (see line: https://github.com/llvm/llvm-project/blob/main/flang/lib/Frontend/CompilerInvocation.cpp#L994 )
Shall I add information about other versions?

mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp

LogicalResult convertFlagsAttr(Operation *op, mlir::omp::FlagsAttr attribute,
   ompBuilder->createGlobalFlag(
       attribute.getAssumeNoThreadState() /*LangOpts().OpenMPNoThreadState*/,
       "__omp_rtl_assume_no_thread_state");
   ompBuilder->createGlobalFlag(
       attribute
           .getAssumeNoNestedParallelism() /*LangOpts().OpenMPNoNestedParallelism*/
       ,
       "__omp_rtl_assume_no_nested_parallelism");
-
+  ompBuilder->M.addModuleFlag(llvm::Module::Max, "openmp-device",
+                              attribute.getOpenmpDeviceVersion());
   return success();
 }
 
 static bool getTargetEntryUniqueInfo(llvm::TargetRegionEntryInfo &targetInfo,
                                      omp::TargetOp targetOp,
                                      llvm::StringRef parentName = "") {
   auto fileLoc = targetOp.getLoc()->findInstanceOf<FileLineColLoc>();
 

 LogicalResult OpenMPDialectLLVMIRTranslationInterface::amendOperation(
     Operation *op, NamedAttribute attribute,
     LLVM::ModuleTranslation &moduleTranslation) const {
 
   return llvm::TypeSwitch<Attribute, LogicalResult>(attribute.getValue())
       .Case([&](mlir::omp::FlagsAttr rtlAttr) {
         return convertFlagsAttr(op, rtlAttr, moduleTranslation);
       })
+      .Case([&](mlir::omp::VersionAttr versionAttr) {
+        llvm::OpenMPIRBuilder *ompBuilder =
+            moduleTranslation.getOpenMPBuilder();
+        ompBuilder->M.addModuleFlag(llvm::Module::Max, "openmp",
+                                    versionAttr.getVersion());
+        return success();
+      })
       .Default([&](Attribute attr) {
         // fall through for omp attributes that do not require lowering and/or
         // have no concrete definition and thus no type to define a case on
         return success();
       });
 
   return failure();
 }

mlir/test/Target/LLVMIR/openmp-llvm.mlir

module attributes {omp.flags = #omp.flags<debug_kind = 1, assume_teams_oversubscription = true,
                                           assume_no_nested_parallelism = true>} {}
 // -----
 
 // CHECK: @__omp_rtl_debug_kind = weak_odr hidden constant i32 0
 // CHECK: @__omp_rtl_assume_teams_oversubscription = weak_odr hidden constant i32 0
 // CHECK: @__omp_rtl_assume_threads_oversubscription = weak_odr hidden constant i32 0
 // CHECK: @__omp_rtl_assume_no_thread_state = weak_odr hidden constant i32 0
 // CHECK: @__omp_rtl_assume_no_nested_parallelism = weak_odr hidden constant i32 0
+// CHECK: [[META0:![0-9]+]] = !{i32 7, !"openmp-device", i32 50}
 module attributes {omp.flags = #omp.flags<>} {}
 
 // -----
 
 // CHECK: @__omp_rtl_debug_kind = weak_odr hidden constant i32 0
 // CHECK: @__omp_rtl_assume_teams_oversubscription = weak_odr hidden constant i32 0
 // CHECK: @__omp_rtl_assume_threads_oversubscription = weak_odr hidden constant i32 0
 // CHECK: @__omp_rtl_assume_no_thread_state = weak_odr hidden constant i32 0
 // CHECK: @__omp_rtl_assume_no_nested_parallelism = weak_odr hidden constant i32 0
+// CHECK: [[META0:![0-9]+]] = !{i32 7, !"openmp-device", i32 51}
+module attributes {omp.flags = #omp.flags<openmp_device_version = 51>} {}
+
+// -----
+
+// CHECK: @__omp_rtl_debug_kind = weak_odr hidden constant i32 0
+// CHECK: @__omp_rtl_assume_teams_oversubscription = weak_odr hidden constant i32 0
+// CHECK: @__omp_rtl_assume_threads_oversubscription = weak_odr hidden constant i32 0
+// CHECK: @__omp_rtl_assume_no_thread_state = weak_odr hidden constant i32 0
+// CHECK: @__omp_rtl_assume_no_nested_parallelism = weak_odr hidden constant i32 0
+// CHECK: [[META0:![0-9]+]] = !{i32 7, !"openmp-device", i32 50}
+// CHECK: [[META0:![0-9]+]] = !{i32 7, !"openmp", i32 50}
+module attributes {omp.version = #omp.version<version = 50>, omp.flags = #omp.flags<>} {}
+
+// -----
+
+// CHECK: [[META0:![0-9]+]] = !{i32 7, !"openmp", i32 51}
+// CHECK-NOT: [[META0:![0-9]+]] = !{i32 7, !"openmp-device", i32 50}
+module attributes {omp.version = #omp.version<version = 51>} {}
+
+// -----
+// CHECK: @__omp_rtl_debug_kind = weak_odr hidden constant i32 0
+// CHECK: @__omp_rtl_assume_teams_oversubscription = weak_odr hidden constant i32 0
+// CHECK: @__omp_rtl_assume_threads_oversubscription = weak_odr hidden constant i32 0
+// CHECK: @__omp_rtl_assume_no_thread_state = weak_odr hidden constant i32 0
+// CHECK: @__omp_rtl_assume_no_nested_parallelism = weak_odr hidden constant i32 0
 module attributes {omp.flags = #omp.flags<debug_kind = 0, assume_teams_oversubscription = false, 
                                           assume_threads_oversubscription = false, assume_no_thread_state = false, 
                                           assume_no_nested_parallelism = false>} {}
 
 // -----
 
 // CHECK: @__omp_rtl_debug_kind = weak_odr hidden constant i32 0
 // CHECK: @__omp_rtl_assume_teams_oversubscription = weak_odr hidden constant i32 1
 // CHECK: @__omp_rtl_assume_threads_oversubscription = weak_odr hidden constant i32 0
 // CHECK: @__omp_rtl_assume_no_thread_state = weak_odr hidden constant i32 1
 // CHECK: @__omp_rtl_assume_no_nested_parallelism = weak_odr hidden constant i32 0
 module attributes {omp.flags = #omp.flags<assume_teams_oversubscription = true, assume_no_thread_state = true>} {}