[mlir][OpenMP] Don't allow firstprivate for simd (#146734)

This is not allowed by the openmp standard.

Author: tblah

mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp

@@ -15,11 +15,13 @@
 #include "mlir/Dialect/Func/IR/FuncOps.h"
 #include "mlir/Dialect/LLVMIR/LLVMTypes.h"
 #include "mlir/Dialect/OpenACCMPCommon/Interfaces/AtomicInterfaces.h"
+#include "mlir/Dialect/OpenMP/OpenMPClauseOperands.h"
 #include "mlir/IR/Attributes.h"
 #include "mlir/IR/BuiltinAttributes.h"
 #include "mlir/IR/DialectImplementation.h"
 #include "mlir/IR/OpImplementation.h"
 #include "mlir/IR/OperationSupport.h"
+#include "mlir/IR/SymbolTable.h"
 #include "mlir/Interfaces/FoldInterfaces.h"
 
 #include "llvm/ADT/ArrayRef.h"
@@ -2640,6 +2642,23 @@ LogicalResult SimdOp::verify() {
     return emitError()
            << "'omp.composite' attribute present in non-composite wrapper";
 
+  // Firstprivate is not allowed for SIMD in the standard. Check that none of
+  // the private decls are for firstprivate.
+  std::optional<ArrayAttr> privateSyms = getPrivateSyms();
+  if (privateSyms) {
+    for (const Attribute &sym : *privateSyms) {
+      auto symRef = cast<SymbolRefAttr>(sym);
+      omp::PrivateClauseOp privatizer =
+          SymbolTable::lookupNearestSymbolFrom<omp::PrivateClauseOp>(
+              getOperation(), symRef);
+      if (!privatizer)
+        return emitError() << "Cannot find privatizer '" << symRef << "'";
+      if (privatizer.getDataSharingType() ==
+          DataSharingClauseType::FirstPrivate)
+        return emitError() << "FIRSTPRIVATE cannot be used with SIMD";
+    }
+  }
+
   return success();
 }
 

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

@@ -2899,7 +2899,8 @@ convertOmpSimd(Operation &opInst, llvm::IRBuilderBase &builder,
           .failed())
     return failure();
 
-  // TODO: no call to copyFirstPrivateVars?
+  // No call to copyFirstPrivateVars because FIRSTPRIVATE is not allowed for
+  // SIMD.
 
   assert(afterAllocas.get()->getSinglePredecessor());
   if (failed(initReductionVars(simdOp, reductionArgs, builder,

mlir/test/Dialect/OpenMP/invalid.mlir

@@ -480,6 +480,39 @@ func.func @omp_simd_pretty_simdlen_safelen(%lb : index, %ub : index, %step : ind
 
 // -----
 
+func.func @omp_simd_bad_privatizer(%lb : index, %ub : index, %step : index) {
+  %0 = llvm.mlir.constant(1 : i64) : i64
+  %1 = llvm.alloca %0 x i32 : (i64) -> !llvm.ptr
+  // expected-error @below {{Cannot find privatizer '@not_defined'}}
+  omp.simd private(@not_defined %1 -> %arg0 : !llvm.ptr) {
+    omp.loop_nest (%arg2) : index = (%lb) to (%ub) inclusive step (%step) {
+      omp.yield
+    }
+  }
+}
+
+// -----
+
+omp.private {type = firstprivate} @_QFEp_firstprivate_i32 : i32 copy {
+^bb0(%arg0: !llvm.ptr, %arg1: !llvm.ptr):
+  %0 = llvm.load %arg0 : !llvm.ptr -> i32
+  llvm.store %0, %arg1 : i32, !llvm.ptr
+  omp.yield(%arg1 : !llvm.ptr)
+}
+func.func @omp_simd_firstprivate(%lb : index, %ub : index, %step : index) {
+  %0 = llvm.mlir.constant(1 : i64) : i64
+  %1 = llvm.alloca %0 x i32 : (i64) -> !llvm.ptr
+  // expected-error @below {{FIRSTPRIVATE cannot be used with SIMD}}
+  omp.simd private(@_QFEp_firstprivate_i32 %1 -> %arg0 : !llvm.ptr) {
+    omp.loop_nest (%arg2) : index = (%lb) to (%ub) inclusive step (%step) {
+      omp.yield
+    }
+  }
+  llvm.return
+}
+
+// -----
+
 // expected-error @below {{op expects alloc region to yield a value of the reduction type}}
 omp.declare_reduction @add_f32 : f32
 alloc {