[OPENMP]Do not crash for const firstprivates.

If the variable is a firstprivate variable and it was not emitted beause
this a constant variable with the constant initializer, we can use the
initial value instead of the variable itself. It also fixes the problem
with the compiler crash in this case.

llvm-svn: 361564

2 files changed, 24 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CGStmtOpenMP.cpp b/clang/lib/CodeGen/CGStmtOpenMP.cpp
index 01194e3a60f..6a973cdb57e 100644
--- a/clang/lib/CodeGen/CGStmtOpenMP.cpp
+++ b/clang/lib/CodeGen/CGStmtOpenMP.cpp
@@ -758,7 +758,25 @@ bool CodeGenFunction::EmitOMPFirstprivateClause(const OMPExecutableDirective &D,
         DeclRefExpr DRE(getContext(), const_cast<VarDecl *>(OrigVD),
                         /*RefersToEnclosingVariableOrCapture=*/FD != nullptr,
                         (*IRef)->getType(), VK_LValue, (*IRef)->getExprLoc());
-        LValue OriginalLVal = EmitLValue(&DRE);
+        LValue OriginalLVal;
+        if (!FD) {
+          // Check if the firstprivate variable is just a constant value.
+          ConstantEmission CE = tryEmitAsConstant(&DRE);
+          if (CE && !CE.isReference()) {
+            // Constant value, no need to create a copy.
+            ++IRef;
+            ++InitsRef;
+            continue;
+          }
+          if (CE && CE.isReference()) {
+            OriginalLVal = CE.getReferenceLValue(*this, &DRE);
+          } else {
+            assert(!CE && "Expected non-constant firstprivate.");
+            OriginalLVal = EmitLValue(&DRE);
+          }
+        } else {
+          OriginalLVal = EmitLValue(&DRE);
+        }
         QualType Type = VD->getType();
         if (Type->isArrayType()) {
           // Emit VarDecl with copy init for arrays.
diff --git a/clang/test/OpenMP/parallel_firstprivate_codegen.cpp b/clang/test/OpenMP/parallel_firstprivate_codegen.cpp
index 8aa64668f05..2a306d1272f 100644
--- a/clang/test/OpenMP/parallel_firstprivate_codegen.cpp
+++ b/clang/test/OpenMP/parallel_firstprivate_codegen.cpp
@@ -335,8 +335,9 @@ int main() {
     s_arr[0] = var;
     sivar = 2;
   }
-#pragma omp parallel allocate(omp_default_mem_alloc: t_var) firstprivate(t_var)
-  {}
+  const int a = 0;
+#pragma omp parallel allocate(omp_default_mem_alloc: t_var) firstprivate(t_var, a)
+  { t_var = a; }
   return tmain<int>();
 #endif
 }
@@ -346,6 +347,7 @@ int main() {
 // CHECK: [[T_VAR:%.+]] = alloca i32,
 // CHECK: [[T_VARCAST:%.+]] = alloca [[iz:i64|i32]],
 // CHECK: [[SIVARCAST:%.+]] = alloca [[iz]],
+// CHECK: [[A:%.+]] = alloca i32,
 // CHECK: [[T_VARCAST1:%.+]] = alloca [[iz:i64|i32]],
 // CHECK: call {{.*}} [[S_FLOAT_TY_DEF_CONSTR:@.+]]([[S_FLOAT_TY]]* [[TEST]])
 // CHECK: [[T_VARVAL:%.+]] = load i32, i32* [[T_VAR]],
@@ -420,6 +422,7 @@ int main() {
 // CHECK-32: [[T_VAR_VAL:%.+]] = load i32, i32* [[T_VAR_ADDR]],
 // CHECK-64: [[T_VAR_VAL:%.+]] = load i32, i32* [[BC]],
 // CHECK:    store i32 [[T_VAR_VAL]], i32* [[T_VAR_PRIV]],
+// CHECK:    store i32 0, i32* [[T_VAR_PRIV]],
 // CHECK:    call void @__kmpc_free(i32 [[GTID]], i8* [[T_VAR_VOID_PTR]], i8* inttoptr ([[iz]] 1 to i8*))
 // CHECK:    ret void