[Openmp-commits] [clang] [openmp] [OpenMP 6.0 ]Codegen for Reduction over private variables with reduction clause (PR #134709)

[Alexey Bataev via Openmp-commits]

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@@ -4898,6 +4898,266 @@ void CGOpenMPRuntime::emitSingleReductionCombiner(CodeGenFunction &CGF,
   }
 }
 
+void CGOpenMPRuntime::emitPrivateReduction(
+    CodeGenFunction &CGF, SourceLocation Loc, const Expr *Privates,
+    const Expr *LHSExprs, const Expr *RHSExprs, const Expr *ReductionOps) {
+
+  //  Create a shared global variable (__shared_reduction_var) to accumulate the
+  //  final result.
+  //
+  //  Call __kmpc_barrier to synchronize threads before initialization.
+  //
+  //  The master thread (thread_id == 0) initializes __shared_reduction_var
+  //    with the identity value or initializer.
+  //
+  //  Call __kmpc_barrier to synchronize before combining.
+  //  For each i:
+  //    - Thread enters critical section.
+  //    - Reads its private value from LHSExprs[i].
+  //    - Updates __shared_reduction_var[i] = RedOp_i(__shared_reduction_var[i],
+  //    LHSExprs[i]).
+  //    - Exits critical section.
+  //
+  //  Call __kmpc_barrier after combining.
+  //
+  //  Each thread copies __shared_reduction_var[i] back to LHSExprs[i].
+  //
+  //  Final __kmpc_barrier to synchronize after broadcasting
+  QualType PrivateType = Privates->getType();
+  llvm::Type *LLVMType = CGF.ConvertTypeForMem(PrivateType);
+
+  llvm::Constant *InitVal = nullptr;
+  const OMPDeclareReductionDecl *UDR = getReductionInit(ReductionOps);
+  // Determine the initial value for the shared reduction variable
+  if (!UDR) {
+    InitVal = llvm::Constant::getNullValue(LLVMType);
+    if (const auto *DRE = dyn_cast<DeclRefExpr>(Privates)) {
+      if (const auto *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
+        const Expr *InitExpr = VD->getInit();
+        if (InitExpr && !PrivateType->isAggregateType() &&
+            !PrivateType->isAnyComplexType()) {
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alexey-bataev wrote:

Add at least a runtime test with complex types, if possible

https://github.com/llvm/llvm-project/pull/134709