[OPENMP]Fix PR48740: OpenMP declare reduction in C does not require an initializer

If no initializer-clause is specified, the private variables will be
initialized following the rules for initialization of objects with static
storage duration.

Need to adjust the implementation to the current version of the
standard.

Differential Revision: https://reviews.llvm.org/D99539

clang/lib/CodeGen/CGOpenMPRuntime.cpp

@@ -655,9 +655,13 @@ static void emitInitWithReductionInitializer(CodeGenFunction &CGF,
       InitRVal =
           RValue::getComplex(CGF.EmitLoadOfComplex(LV, DRD->getLocation()));
       break;
-    case TEK_Aggregate:
-      InitRVal = RValue::getAggregate(LV.getAddress(CGF));
-      break;
+    case TEK_Aggregate: {
+      OpaqueValueExpr OVE(DRD->getLocation(), Ty, VK_LValue);
+      CodeGenFunction::OpaqueValueMapping OpaqueMap(CGF, &OVE, LV);
+      CGF.EmitAnyExprToMem(&OVE, Private, Ty.getQualifiers(),
+                           /*IsInitializer=*/false);
+      return;
+    }
     }
     OpaqueValueExpr OVE(DRD->getLocation(), Ty, VK_RValue);
     CodeGenFunction::OpaqueValueMapping OpaqueMap(CGF, &OVE, InitRVal);

clang/lib/Sema/SemaOpenMP.cpp

@@ -16567,8 +16567,7 @@ static bool actOnOMPReductionKindClause(
     }
     if (RHSVD->isInvalidDecl())
       continue;
-    if (!RHSVD->hasInit() &&
-        (DeclareReductionRef.isUnset() || !S.LangOpts.CPlusPlus)) {
+    if (!RHSVD->hasInit() && DeclareReductionRef.isUnset()) {
       S.Diag(ELoc, diag::err_omp_reduction_id_not_compatible)
           << Type << ReductionIdRange;
       bool IsDecl = !VD || VD->isThisDeclarationADefinition(Context) ==

clang/test/OpenMP/declare_reduction_ast_print.c

@@ -47,13 +47,18 @@ int main() {
                               : omp_out = omp_out > omp_in ? omp_in : omp_out) \
     initializer(omp_priv = 2147483647)
 
+#pragma omp declare reduction(mymin        \
+                              : struct SSS \
+                              : omp_out = omp_out.field > omp_in.field ? omp_in : omp_out)
+
 int foo(int argc, char **argv) {
   int x;
-#pragma omp parallel for reduction(mymin : x)
+  struct SSS ss;
+#pragma omp parallel for reduction(mymin : x, ss)
   for (int i = 0; i < 1000; i++)
     ;
   return 0;
 }
 
-// CHECK: #pragma omp parallel for reduction(mymin: x)
+// CHECK: #pragma omp parallel for reduction(mymin: x,ss)
 #endif

clang/test/OpenMP/declare_reduction_codegen.c

@@ -17,6 +17,9 @@
 // CHECK: [[SSS_INT:.+]] = type { i32 }
 // CHECK-LOAD: [[SSS_INT:.+]] = type { i32 }
 
+// CHECK-DAG: [[SSS_INIT:@.+]] = private constant %struct.SSS zeroinitializer
+// CHECK-DAG: [[INT_INIT:@.+]] = private constant i32 0
+
 #pragma omp declare reduction(+ : int, char : omp_out *= omp_in)
 // CHECK: define internal {{.*}}void @{{[^(]+}}(i32* noalias %0, i32* noalias %1)
 // CHECK: [[MUL:%.+]] = mul nsw i32
@@ -163,4 +166,27 @@ int main() {
 // OMP45-LOAD-NEXT: store i8 [[TRUNC]], i8*
 // OMP45-LOAD-NEXT: ret void
 // OMP45-LOAD-NEXT: }
+
+// CHECK-LABEL: bar
+struct SSS ss;
+int in;
+void bar() {
+  // CHECK: [[SS_PRIV:%.+]] = alloca %struct.SSS,
+  // CHECK: [[IN_PRIV:%.+]] = alloca i32,
+  // CHECK: [[BC:%.+]] = bitcast %struct.SSS* [[SS_PRIV]] to i8*
+  // CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 4 [[BC]], i8* align 4 bitcast (%struct.SSS* [[SSS_INIT]] to i8*), i64 4, i1 false)
+  // CHECK: [[IN_VAL:%.+]] = load i32, i32* [[INT_INIT]],
+  // CHECK: store i32 [[IN_VAL]], i32* [[IN_PRIV]],
+  // CHECK: call void @__kmpc_for_static_init_4(
+#pragma omp declare reduction(+            \
+                              : struct SSS \
+                              : omp_out = omp_in)
+#pragma omp declare reduction(+     \
+                              : int \
+                              : omp_out = omp_in)
+#pragma omp for reduction(+ \
+                          : ss, in)
+  for (int i = 0; i < 10; ++i)
+    ;
+}
 #endif

clang/test/OpenMP/declare_reduction_messages.c

@@ -49,9 +49,9 @@ struct S {
 #pragma omp declare reduction(|: struct S: omp_out.s += omp_in.s) initializer(omp_priv = { 0 })
 
 int fun(int arg) {
-  struct S s;// expected-note {{'s' defined here}}
+  struct S s;
   s.s = 0;
-#pragma omp parallel for reduction(+ : s) // expected-error {{list item of type 'struct S' is not valid for specified reduction operation: unable to provide default initialization value}}
+#pragma omp parallel for reduction(+ : s)
   for (arg = 0; arg < 10; ++arg)
     s.s += arg;
 #pragma omp declare reduction(red : int : omp_out++)