4 files changed, 478 insertions, 0 deletions
diff --git a/clang/test/Analysis/MPIMock.h b/clang/test/Analysis/MPIMock.h
new file mode 100644
index 00000000000..01d2d42fc58
--- /dev/null
+++ b/clang/test/Analysis/MPIMock.h
@@ -0,0 +1,55 @@
+// Message Passing Interface mock header. Mocks MPI constants and functions, in
+// order to make them available in distinct integration test files.
+
+#define NULL 0
+
+// mock types
+typedef int MPI_Datatype;
+typedef int MPI_Comm;
+typedef int MPI_Request;
+typedef int MPI_Status;
+typedef int MPI_Op;
+typedef int int8_t;
+typedef int uint8_t;
+typedef int uint16_t;
+typedef int int64_t;
+namespace std { template<class T> struct complex { T real; T imag; }; }
+
+// mock constants
+#define MPI_DATATYPE_NULL 0
+#define MPI_CHAR 0
+#define MPI_BYTE 0
+#define MPI_INT 0
+#define MPI_LONG 0
+#define MPI_LONG_DOUBLE 0
+#define MPI_UNSIGNED 0
+#define MPI_INT8_T 0
+#define MPI_UINT8_T 0
+#define MPI_UINT16_T 0
+#define MPI_C_LONG_DOUBLE_COMPLEX 0
+#define MPI_FLOAT 0
+#define MPI_DOUBLE 0
+#define MPI_CXX_BOOL 0
+#define MPI_CXX_FLOAT_COMPLEX 0
+#define MPI_CXX_DOUBLE_COMPLEX 0
+#define MPI_CXX_LONG_DOUBLE_COMPLEX 0
+#define MPI_IN_PLACE 0
+#define MPI_COMM_WORLD 0
+#define MPI_STATUS_IGNORE 0
+#define MPI_STATUSES_IGNORE 0
+#define MPI_SUM 0
+
+// mock functions
+int MPI_Comm_size(MPI_Comm, int *);
+int MPI_Comm_rank(MPI_Comm, int *);
+int MPI_Send(const void *, int, MPI_Datatype, int, int, MPI_Comm);
+int MPI_Recv(void *, int, MPI_Datatype, int, int, MPI_Comm, MPI_Status *);
+int MPI_Isend(const void *, int, MPI_Datatype, int, int, MPI_Comm,
+    MPI_Request *);
+int MPI_Irecv(void *, int, MPI_Datatype, int, int, MPI_Comm, MPI_Request *);
+int MPI_Wait(MPI_Request *, MPI_Status *);
+int MPI_Waitall(int, MPI_Request[], MPI_Status[]);
+int MPI_Reduce(const void *, void *, int, MPI_Datatype, MPI_Op, int, MPI_Comm);
+int MPI_Ireduce(const void *, void *, int, MPI_Datatype, MPI_Op, int, MPI_Comm,
+    MPI_Request *);
+int MPI_Bcast(void *, int count, MPI_Datatype, int, MPI_Comm);
diff --git a/clang/test/Analysis/MemRegion.cpp b/clang/test/Analysis/MemRegion.cpp
new file mode 100644
index 00000000000..992b7f1f976
--- /dev/null
+++ b/clang/test/Analysis/MemRegion.cpp
@@ -0,0 +1,47 @@
+// RUN: %clang_cc1 -analyze -analyzer-checker=optin.mpi.MPI-Checker -verify %s
+
+#include "MPIMock.h"
+
+// Use MPI-Checker to test 'getDescriptiveName', as the checker uses the
+// function for diagnostics.
+void testGetDescriptiveName() {
+  int rank = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  MPI_Request sendReq1;
+  MPI_Wait(&sendReq1, MPI_STATUS_IGNORE); // expected-warning{{Request 'sendReq1' has no matching nonblocking call.}}
+}
+
+void testGetDescriptiveName2() {
+  int rank = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  MPI_Request sendReq1[10][10][10];
+  MPI_Wait(&sendReq1[1][7][9], MPI_STATUS_IGNORE); // expected-warning{{Request 'sendReq1[1][7][9]' has no matching nonblocking call.}}
+}
+
+void testGetDescriptiveName3() {
+  int rank = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  typedef struct { MPI_Request req; } ReqStruct;
+  ReqStruct rs;
+  MPI_Request *r = &rs.req;
+  MPI_Wait(r, MPI_STATUS_IGNORE); // expected-warning{{Request 'rs.req' has no matching nonblocking call.}}
+}
+
+void testGetDescriptiveName4() {
+  int rank = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  typedef struct { MPI_Request req[2][2]; } ReqStruct;
+  ReqStruct rs;
+  MPI_Request *r = &rs.req[0][1];
+  MPI_Wait(r, MPI_STATUS_IGNORE); // expected-warning{{Request 'rs.req[0][1]' has no matching nonblocking call.}}
+}
+
+void testGetDescriptiveName5() {
+  int rank = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  typedef struct { MPI_Request req; } ReqStructInner;
+  typedef struct  { ReqStructInner req; } ReqStruct;
+  ReqStruct rs;
+  MPI_Request *r = &rs.req.req;
+  MPI_Wait(r, MPI_STATUS_IGNORE); // expected-warning{{Request 'rs.req.req' has no matching nonblocking call.}}
+}
diff --git a/clang/test/Analysis/mpichecker.cpp b/clang/test/Analysis/mpichecker.cpp
new file mode 100644
index 00000000000..a7f1763855a
--- /dev/null
+++ b/clang/test/Analysis/mpichecker.cpp
@@ -0,0 +1,342 @@
+// RUN: %clang_cc1 -analyze -analyzer-checker=optin.mpi.MPI-Checker -verify %s
+
+#include "MPIMock.h"
+
+void matchedWait1() {
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  if (rank >= 0) {
+    MPI_Request sendReq1, recvReq1;
+    MPI_Isend(&buf, 1, MPI_DOUBLE, rank + 1, 0, MPI_COMM_WORLD, &sendReq1);
+    MPI_Irecv(&buf, 1, MPI_DOUBLE, rank - 1, 0, MPI_COMM_WORLD, &recvReq1);
+
+    MPI_Wait(&sendReq1, MPI_STATUS_IGNORE);
+    MPI_Wait(&recvReq1, MPI_STATUS_IGNORE);
+  }
+} // no error
+
+void matchedWait2() {
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  if (rank >= 0) {
+    MPI_Request sendReq1, recvReq1;
+    MPI_Isend(&buf, 1, MPI_DOUBLE, rank + 1, 0, MPI_COMM_WORLD, &sendReq1);
+    MPI_Irecv(&buf, 1, MPI_DOUBLE, rank - 1, 0, MPI_COMM_WORLD, &recvReq1);
+    MPI_Wait(&sendReq1, MPI_STATUS_IGNORE);
+    MPI_Wait(&recvReq1, MPI_STATUS_IGNORE);
+  }
+} // no error
+
+void matchedWait3() {
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  if (rank >= 0) {
+    MPI_Request sendReq1, recvReq1;
+    MPI_Isend(&buf, 1, MPI_DOUBLE, rank + 1, 0, MPI_COMM_WORLD, &sendReq1);
+    MPI_Irecv(&buf, 1, MPI_DOUBLE, rank - 1, 0, MPI_COMM_WORLD, &recvReq1);
+
+    if (rank > 1000) {
+      MPI_Wait(&sendReq1, MPI_STATUS_IGNORE);
+      MPI_Wait(&recvReq1, MPI_STATUS_IGNORE);
+    } else {
+      MPI_Wait(&sendReq1, MPI_STATUS_IGNORE);
+      MPI_Wait(&recvReq1, MPI_STATUS_IGNORE);
+    }
+  }
+} // no error
+
+void missingWait1() { // Check missing wait for dead region.
+  double buf = 0;
+  MPI_Request sendReq1;
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD, &sendReq1);
+} // expected-warning{{Request 'sendReq1' has no matching wait.}}
+
+void missingWait2() {
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  if (rank == 0) {
+  } else {
+    MPI_Request sendReq1, recvReq1;
+
+    MPI_Isend(&buf, 1, MPI_DOUBLE, rank + 1, 0, MPI_COMM_WORLD, &sendReq1);
+    MPI_Irecv(&buf, 1, MPI_DOUBLE, rank - 1, 0, MPI_COMM_WORLD, &recvReq1); // expected-warning{{Request 'sendReq1' has no matching wait.}}
+    MPI_Wait(&recvReq1, MPI_STATUS_IGNORE);
+  }
+}
+
+void doubleNonblocking() {
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  if (rank == 1) {
+  } else {
+    MPI_Request sendReq1;
+
+    MPI_Isend(&buf, 1, MPI_DOUBLE, rank + 1, 0, MPI_COMM_WORLD, &sendReq1);
+    MPI_Irecv(&buf, 1, MPI_DOUBLE, rank - 1, 0, MPI_COMM_WORLD, &sendReq1); // expected-warning{{Double nonblocking on request 'sendReq1'.}}
+    MPI_Wait(&sendReq1, MPI_STATUS_IGNORE);
+  }
+}
+
+void doubleNonblocking2() {
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+
+  MPI_Request req;
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD, &req);
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD, &req); // expected-warning{{Double nonblocking on request 'req'.}}
+  MPI_Wait(&req, MPI_STATUS_IGNORE);
+}
+
+void doubleNonblocking3() {
+  typedef struct { MPI_Request req; } ReqStruct;
+
+  ReqStruct rs;
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD, &rs.req);
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD, &rs.req); // expected-warning{{Double nonblocking on request 'rs.req'.}}
+  MPI_Wait(&rs.req, MPI_STATUS_IGNORE);
+}
+
+void doubleNonblocking4() {
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+
+  MPI_Request req;
+  for (int i = 0; i < 2; ++i) {
+    MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD, &req); // expected-warning{{Double nonblocking on request 'req'.}}
+  }
+  MPI_Wait(&req, MPI_STATUS_IGNORE);
+}
+
+void tripleNonblocking() {
+  double buf = 0;
+  MPI_Request sendReq;
+  MPI_Isend(&buf, 1, MPI_DOUBLE, 0, 0, MPI_COMM_WORLD, &sendReq); 
+  MPI_Irecv(&buf, 1, MPI_DOUBLE, 0, 0, MPI_COMM_WORLD, &sendReq); // expected-warning{{Double nonblocking on request 'sendReq'.}}
+  MPI_Isend(&buf, 1, MPI_DOUBLE, 0, 0, MPI_COMM_WORLD, &sendReq); // expected-warning{{Double nonblocking on request 'sendReq'.}}
+  MPI_Wait(&sendReq, MPI_STATUS_IGNORE);
+}
+
+void missingNonBlocking() {
+  int rank = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  MPI_Request sendReq1[10][10][10];
+  MPI_Wait(&sendReq1[1][7][9], MPI_STATUS_IGNORE); // expected-warning{{Request 'sendReq1[1][7][9]' has no matching nonblocking call.}}
+}
+
+void missingNonBlocking2() {
+  int rank = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  typedef struct { MPI_Request req[2][2]; } ReqStruct;
+  ReqStruct rs;
+  MPI_Request *r = &rs.req[0][1];
+  MPI_Wait(r, MPI_STATUS_IGNORE); // expected-warning{{Request 'rs.req[0][1]' has no matching nonblocking call.}}
+}
+
+void missingNonBlocking3() {
+  int rank = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  MPI_Request sendReq;
+  MPI_Wait(&sendReq, MPI_STATUS_IGNORE); // expected-warning{{Request 'sendReq' has no matching nonblocking call.}}
+}
+
+void missingNonBlockingMultiple() {
+  int rank = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  MPI_Request sendReq[4];
+  for (int i = 0; i < 4; ++i) {
+    MPI_Wait(&sendReq[i], MPI_STATUS_IGNORE); // expected-warning-re 1+{{Request {{.*}} has no matching nonblocking call.}}
+  }
+}
+
+void missingNonBlockingWaitall() {
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  MPI_Request req[4];
+
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+      &req[0]);
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+      &req[1]);
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+      &req[3]);
+
+  MPI_Waitall(4, req, MPI_STATUSES_IGNORE); // expected-warning{{Request 'req[2]' has no matching nonblocking call.}}
+}
+
+void missingNonBlockingWaitall2() {
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  MPI_Request req[4];
+
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+      &req[0]);
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+      &req[3]);
+
+  MPI_Waitall(4, req, MPI_STATUSES_IGNORE); // expected-warning-re 2{{Request '{{(.*)[[1-2]](.*)}}' has no matching nonblocking call.}}
+}
+
+void missingNonBlockingWaitall3() {
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  MPI_Request req[4];
+
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+      &req[0]);
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+      &req[2]);
+
+  MPI_Waitall(4, req, MPI_STATUSES_IGNORE); // expected-warning-re 2{{Request '{{(.*)[[1,3]](.*)}}' has no matching nonblocking call.}}
+}
+
+void missingNonBlockingWaitall4() {
+  int rank = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  MPI_Request req[4];
+  MPI_Waitall(4, req, MPI_STATUSES_IGNORE); // expected-warning-re 4{{Request '{{(.*)[[0-3]](.*)}}' has no matching nonblocking call.}}
+}
+
+void noDoubleRequestUsage() {
+  typedef struct {
+    MPI_Request req;
+    MPI_Request req2;
+  } ReqStruct;
+
+  ReqStruct rs;
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+              &rs.req);
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+              &rs.req2);
+  MPI_Wait(&rs.req, MPI_STATUS_IGNORE);
+  MPI_Wait(&rs.req2, MPI_STATUS_IGNORE);
+} // no error
+
+void noDoubleRequestUsage2() {
+  typedef struct {
+    MPI_Request req[2];
+    MPI_Request req2;
+  } ReqStruct;
+
+  ReqStruct rs;
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+              &rs.req[0]);
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+              &rs.req[1]);
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+              &rs.req2);
+  MPI_Wait(&rs.req[0], MPI_STATUS_IGNORE);
+  MPI_Wait(&rs.req[1], MPI_STATUS_IGNORE);
+  MPI_Wait(&rs.req2, MPI_STATUS_IGNORE);
+} // no error
+
+void nestedRequest() {
+  typedef struct {
+    MPI_Request req[2];
+    MPI_Request req2;
+  } ReqStruct;
+
+  ReqStruct rs;
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+              &rs.req[0]);
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+              &rs.req[1]);
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+              &rs.req2);
+  MPI_Waitall(2, rs.req, MPI_STATUSES_IGNORE);
+  MPI_Wait(&rs.req2, MPI_STATUS_IGNORE);
+} // no error
+
+void singleRequestInWaitall() {
+  MPI_Request r;
+  int rank = 0;
+  double buf = 0;
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+              &r);
+  MPI_Waitall(1, &r, MPI_STATUSES_IGNORE);
+} // no error
+
+void multiRequestUsage() {
+  double buf = 0;
+  MPI_Request req;
+
+  MPI_Isend(&buf, 1, MPI_DOUBLE, 1, 0, MPI_COMM_WORLD, &req);
+  MPI_Wait(&req, MPI_STATUS_IGNORE);
+
+  MPI_Irecv(&buf, 1, MPI_DOUBLE, 1, 0, MPI_COMM_WORLD, &req);
+  MPI_Wait(&req, MPI_STATUS_IGNORE);
+} // no error
+
+void multiRequestUsage2() {
+  double buf = 0;
+  MPI_Request req;
+
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+              &req);
+  MPI_Wait(&req, MPI_STATUS_IGNORE);
+
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+              &req);
+  MPI_Wait(&req, MPI_STATUS_IGNORE);
+} // no error
+
+// wrapper function 
+void callNonblocking(MPI_Request *req) {
+  double buf = 0;
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+             req);
+}
+
+// wrapper function
+void callWait(MPI_Request *req) {
+  MPI_Wait(req, MPI_STATUS_IGNORE);
+} 
+
+// Call nonblocking, wait wrapper functions.
+void callWrapperFunctions() {
+  MPI_Request req;
+  callNonblocking(&req);
+  callWait(&req);
+} // no error
+
+void externFunctions1() {
+  double buf = 0;
+  MPI_Request req;
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD,
+              &req);
+  void callWaitExtern(MPI_Request *req); 
+  callWaitExtern(&req); 
+} // expected-warning{{Request 'req' has no matching wait.}}
+
+void externFunctions2() {
+  MPI_Request req;
+  void callNonblockingExtern(MPI_Request *req); 
+  callNonblockingExtern(&req); 
+}
diff --git a/clang/test/Analysis/mpicheckernotes.cpp b/clang/test/Analysis/mpicheckernotes.cpp
new file mode 100644
index 00000000000..be312fdf5fd
--- /dev/null
+++ b/clang/test/Analysis/mpicheckernotes.cpp
@@ -0,0 +1,34 @@
+// RUN: %clang_cc1 -analyze -analyzer-checker=optin.mpi.MPI-Checker -analyzer-output=text -verify %s
+
+// MPI-Checker test file to test note diagnostics.
+
+#include "MPIMock.h"
+
+void doubleNonblocking() {
+  double buf = 0;
+  MPI_Request sendReq;
+  MPI_Isend(&buf, 1, MPI_DOUBLE, 0, 0, MPI_COMM_WORLD, &sendReq); // expected-note{{Request is previously used by nonblocking call here.}}
+  MPI_Irecv(&buf, 1, MPI_DOUBLE, 0, 0, MPI_COMM_WORLD, &sendReq); // expected-warning{{Double nonblocking on request 'sendReq'.}} expected-note{{Double nonblocking on request 'sendReq'.}}
+  MPI_Wait(&sendReq, MPI_STATUS_IGNORE);
+}
+
+void missingWait() {
+  double buf = 0;
+  MPI_Request sendReq;
+  MPI_Ireduce(MPI_IN_PLACE, &buf, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD, &sendReq); // expected-note{{Request is previously used by nonblocking call here.}}
+} // expected-warning{{Request 'sendReq' has no matching wait.}} expected-note{{Request 'sendReq' has no matching wait.}}
+
+// If more than 2 nonblocking calls are using a request in a sequence, they all
+// point to the first call as the 'previous' call. This is because the
+// BugReporterVisitor only checks for differences in state or existence of an
+// entity.
+void tripleNonblocking() {
+  double buf = 0;
+  MPI_Request sendReq;
+  MPI_Isend(&buf, 1, MPI_DOUBLE, 0, 0, MPI_COMM_WORLD, &sendReq); // expected-note 2{{Request is previously used by nonblocking call here.}}
+  MPI_Irecv(&buf, 1, MPI_DOUBLE, 0, 0, MPI_COMM_WORLD, &sendReq); // expected-warning{{Double nonblocking on request 'sendReq'.}} expected-note{{Double nonblocking on request 'sendReq'.}}
+
+  MPI_Isend(&buf, 1, MPI_DOUBLE, 0, 0, MPI_COMM_WORLD, &sendReq); // expected-warning{{Double nonblocking on request 'sendReq'.}} expected-note{{Double nonblocking on request 'sendReq'.}}
+
+  MPI_Wait(&sendReq, MPI_STATUS_IGNORE);
+}