[OpenACC] Prototype OpenMP extension: omp_get_mapped_hostptr

`omp_get_mapped_hostptr` is an original OpenMP extension for the sake
of supporting OpenACC's `acc_hostptr`, which will be implemented in a
following commit.  For now, all testing of `omp_get_mapped_hostptr`
will be via testing for `acc_hostptr`.  That is,
`omp_get_mapped_hostptr` is not well tested outside of Clacc's OpenACC
runtime, so it is not yet recommended for general use in OpenMP code.

Author: jdenny-ornl

openmp/libomptarget/include/omptarget.h

@@ -154,6 +154,7 @@ int omp_target_associate_ptr(void *host_ptr, void *device_ptr, size_t size,
     size_t device_offset, int device_num);
 int omp_target_disassociate_ptr(void *host_ptr, int device_num);
 void *omp_get_mapped_ptr(const void *ptr, int device_num);
+void *omp_get_mapped_hostptr(const void *ptr, int device_num);
 size_t omp_get_accessible_buffer(const void *ptr, size_t size, int device_num,
                                  void **buffer_host, void **buffer_device);
 void *omp_target_map_to(void *ptr, size_t size, int device_num);

openmp/libomptarget/src/api.cpp

@@ -290,8 +290,8 @@ EXTERN void *omp_get_mapped_ptr(const void *ptr, int device_num) {
   if (device_num == omp_get_initial_device()) {
     DP("Call to omp_get_mapped_ptr on host, returning host pointer\n");
     // OpenMP 5.1, sec. 3.8.11 "omp_get_mapped_ptr", p. 431, L10-12:
-    // Otherwise it returns the device pointer, which is ptr if device_num is
-    // the value returned by omp_get_initial_device().
+    // "Otherwise it returns the device pointer, which is ptr if device_num is
+    // the value returned by omp_get_initial_device()."
     //
     // That is, the spec actually requires us to cast away const.
     return const_cast<void *>(ptr);
@@ -316,7 +316,7 @@ EXTERN void *omp_get_mapped_ptr(const void *ptr, int device_num) {
   // TODO: This seems to be implied by the named "mapped" instead of
   // "accessible".  Or should we return the host pointer?  That is, is this
   // supposed to be like omp_target_is_present or omp_target_is_accessible?
-  // OpenMP 5.1 doesn't seem clear.
+  // OpenMP 5.1 doesn't seem clear.  Keep omp_get_mapped_hostptr in sync.
   if (IsHostPtr) {
     DP("Call to omp_get_mapped_ptr for unified shared memory, returning "
        "NULL\n");
@@ -326,6 +326,41 @@ EXTERN void *omp_get_mapped_ptr(const void *ptr, int device_num) {
   return TgtPtr;
 }
 
+EXTERN void *omp_get_mapped_hostptr(const void *ptr, int device_num) {
+  DP("Call to omp_get_mapped_hostptr for device %d and address " DPxMOD "\n",
+     device_num, DPxPTR(ptr));
+
+  if (!ptr) {
+    DP("Call to omp_get_mapped_hostptr with NULL ptr, returning NULL\n");
+    return NULL;
+  }
+
+  if (device_num == omp_get_initial_device()) {
+    DP("Call to omp_get_mapped_hostptr for host, returning device pointer\n");
+    // For consistency with OpenMP 5.1, sec. 3.8.11 "omp_get_mapped_ptr", p.
+    // 431, L10-12:
+    // "Otherwise it returns the device pointer, which is ptr if device_num is
+    // the value returned by omp_get_initial_device()."
+    return const_cast<void *>(ptr);
+  }
+
+  RTLsMtx->lock();
+  size_t Devices_size = Devices.size();
+  RTLsMtx->unlock();
+  if (Devices_size <= (size_t)device_num) {
+    DP("Call to omp_get_mapped_hostptr with invalid device ID, returning "
+       "NULL\n");
+    return NULL;
+  }
+
+  DeviceTy &Device = Devices[device_num];
+  // TODO: This returns nullptr in the case of unified shared memory.  This is
+  // for consistency with the current omp_get_mapped_ptr implementation.
+  void *HostPtr = Device.lookupHostPtr(const_cast<void *>(ptr));
+  DP("Call to omp_get_mapped_hostptr returns " DPxMOD "\n", DPxPTR(HostPtr));
+  return HostPtr;
+}
+
 EXTERN size_t omp_get_accessible_buffer(
   const void *ptr, size_t size, int device_num, void **buffer_host,
   void **buffer_device) {

openmp/libomptarget/src/device.cpp

@@ -14,6 +14,7 @@
 #include "private.h"
 #include "rtl.h"
 
+#include <algorithm>
 #include <cassert>
 #include <climits>
 #include <string>
@@ -164,6 +165,33 @@ LookupResult DeviceTy::lookupMapping(void *HstPtrBegin, int64_t Size) {
   return lr;
 }
 
+void *DeviceTy::lookupHostPtr(void *TgtPtr) {
+  uintptr_t Tp = (uintptr_t)TgtPtr;
+  DP("Looking up mapping for TgtPtr=" DPxMOD "...\n", DPxPTR(Tp));
+  DataMapMtx.lock();
+
+  HostDataToTargetListTy::iterator Itr = std::find_if(
+      HostDataToTargetMap.begin(), HostDataToTargetMap.end(),
+      [Tp](const HostDataToTargetTy &Entry) {
+        uintptr_t Size = Entry.HstPtrEnd - Entry.HstPtrBegin;
+        return Entry.TgtPtrBegin <= Tp && Tp < Entry.TgtPtrBegin + Size;
+      });
+
+  void *HostPtr;
+  if (Itr == HostDataToTargetMap.end()) {
+    DP("Mapping does not exist\n");
+    HostPtr = NULL;
+  } else {
+    uintptr_t Offset = Tp - Itr->TgtPtrBegin;
+    uintptr_t Hp = Itr->HstPtrBegin + Offset;
+    DP("Mapping exists with HstPtr=" DPxMOD "\n", DPxPTR(Hp));
+    HostPtr = (void *)Hp;
+  }
+
+  DataMapMtx.unlock();
+  return HostPtr;
+}
+
 size_t DeviceTy::getAccessibleBuffer(void *Ptr, int64_t Size, void **BufferHost,
                                      void **BufferDevice) {
   size_t BufferSize;

openmp/libomptarget/src/device.h

@@ -218,6 +218,7 @@ struct DeviceTy {
 
   uint64_t getMapEntryRefCnt(void *HstPtrBegin);
   LookupResult lookupMapping(void *HstPtrBegin, int64_t Size);
+  void *lookupHostPtr(void *TgtPtr);
   size_t getAccessibleBuffer(void *Ptr, int64_t Size, void **BufferHost,
                              void **BufferDevice);
   void *getOrAllocTgtPtr(void *HstPtrBegin, void *HstPtrBase, int64_t Size,

openmp/libomptarget/src/exports

@@ -36,6 +36,7 @@ VERS1.0 {
     omp_target_associate_ptr;
     omp_target_disassociate_ptr;
     omp_get_mapped_ptr;
+    omp_get_mapped_hostptr;
     omp_get_accessible_buffer;
     omp_target_map_to;
     omp_target_map_from;

openmp/runtime/src/include/omp.h.var

@@ -217,6 +217,11 @@
     extern void __KAI_KMPC_CONVENTION omp_target_map_release(void *ptr, size_t size, int device_num);
     extern void __KAI_KMPC_CONVENTION omp_target_map_delete(void *ptr, size_t size, int device_num);
 
+    // The reverse of omp_get_mapped_ptr.  The implementation is inefficient, so
+    // it shouldn't be used in production code, but it might be useful for
+    // debugging.
+    extern void *__KAI_KMPC_CONVENTION omp_get_mapped_hostptr(const void *ptr, int device_num);
+
     /* kmp API functions */
     extern int    __KAI_KMPC_CONVENTION  kmp_get_stacksize          (void);
     extern void   __KAI_KMPC_CONVENTION  kmp_set_stacksize          (int);

openmp/runtime/src/kmp_ftn_entry.h

@@ -1019,6 +1019,10 @@ void *FTN_STDCALL FTN_GET_MAPPED_PTR(const void *ptr, int device_num) {
   return NULL;
 }
 
+void *FTN_STDCALL FTN_GET_MAPPED_HOSTPTR(const void *ptr, int device_num) {
+  return NULL;
+}
+
 size_t FTN_STDCALL FTN_GET_ACCESSIBLE_BUFFER(const void *ptr, size_t size,
                                              int device_num, void **buffer_host,
                                              void **buffer_device) {

openmp/runtime/src/kmp_ftn_os.h

@@ -120,6 +120,7 @@
 #define FTN_TARGET_ASSOCIATE_PTR omp_target_associate_ptr
 #define FTN_TARGET_DISASSOCIATE_PTR omp_target_disassociate_ptr
 #define FTN_GET_MAPPED_PTR omp_get_mapped_ptr
+#define FTN_GET_MAPPED_HOSTPTR omp_get_mapped_hostptr
 #define FTN_GET_ACCESSIBLE_BUFFER omp_get_accessible_buffer
 #endif
 
@@ -245,6 +246,7 @@
 #define FTN_TARGET_ASSOCIATE_PTR omp_target_associate_ptr_
 #define FTN_TARGET_DISASSOCIATE_PTR omp_target_disassociate_ptr_
 #define FTN_GET_MAPPED_PTR omp_get_mapped_ptr_
+#define FTN_GET_MAPPED_HOSTPTR omp_get_mapped_hostptr_
 #define FTN_GET_ACCESSIBLE_BUFFER omp_get_accessible_buffer_
 #endif
 
@@ -372,6 +374,7 @@
 #define FTN_TARGET_ASSOCIATE_PTR OMP_TARGET_ASSOCIATE_PTR
 #define FTN_TARGET_DISASSOCIATE_PTR OMP_TARGET_DISASSOCIATE_PTR
 #define FTN_GET_MAPPED_PTR OMP_GET_MAPPED_PTR
+#define FTN_GET_MAPPED_HOSTPTR OMP_GET_MAPPED_HOSTPTR
 #define FTN_GET_ACCESSIBLE_BUFFER OMP_GET_ACCESSIBLE_BUFFER
 #endif
 
@@ -497,6 +500,7 @@
 #define FTN_TARGET_ASSOCIATE_PTR OMP_TARGET_ASSOCIATE_PTR_
 #define FTN_TARGET_DISASSOCIATE_PTR OMP_TARGET_DISASSOCIATE_PTR_
 #define FTN_GET_MAPPED_PTR OMP_GET_MAPPED_PTR_
+#define FTN_GET_MAPPED_HOSTPTR OMP_GET_MAPPED_HOSTPTR_
 #define FTN_GET_ACCESSIBLE_BUFFER OMP_GET_ACCESSIBLE_BUFFER_
 #endif