[GPUJIT] Make max managed pointers an environment variable

[bollu]

Summary

This was originally a #define, but it is much easier to play around with
this variable when we run on large programs.

[grosser]

LGTM.

tools/GPURuntime/GPUJIT.c

 #include <CL/cl.h>
 #endif /* __APPLE__ */
 #endif /* HAS_LIBOPENCL */
 
 #include <assert.h>
 #include <dlfcn.h>
 #include <stdarg.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 
 static int DebugMode;
 static int CacheMode;
 #define max(x, y) ((x) > (y) ? (x) : (y))
 
 static PollyGPURuntime Runtime = RUNTIME_NONE;
Res =
                            SharedMemBytes, Stream, Parameters, Extra);
   if (Res != CUDA_SUCCESS) {
     fprintf(stderr, "Launching CUDA kernel failed.\n");
     exit(-1);
   }
 }
 
 // Maximum number of managed memory pointers.
-#define MAX_POINTERS 4000
+#define DEFAULT_MAX_POINTERS 4000
 // For the rationale behing a list of free pointers, see `polly_freeManaged`.
-void *g_managedptrs[MAX_POINTERS];
-int g_nmanagedptrs = 0;
+void **g_managedptrs;
+unsigned long long g_nmanagedptrs = 0;
+unsigned long long g_maxmanagedptrs = 0;
+
+__attribute__((constructor)) static void initManagedPtrsBuffer() {
+  g_maxmanagedptrs = DEFAULT_MAX_POINTERS;
+  const char *maxManagedPointersString = getenv("POLLY_MAX_MANAGED_POINTERS");
+  if (maxManagedPointersString)
+    g_maxmanagedptrs = atoll(maxManagedPointersString);
+
+  g_managedptrs = (void **)malloc(sizeof(void *) * g_maxmanagedptrs);
+}
 
 // Add a pointer as being allocated by cuMallocManaged
 void addManagedPtr(void *mem) {
-  assert(g_nmanagedptrs < MAX_POINTERS && "We have hit the maximum number of "
-                                          "managed pointers allowed. Increase "
-                                          "MAX_POINTERS");
+  assert(g_maxmanagedptrs > 0 && "g_maxmanagedptrs was set to 0!");
+  assert(g_nmanagedptrs < g_maxmanagedptrs &&
+         "We have hit the maximum number of "
+         "managed pointers allowed. Set the "
+         "POLLY_MAX_MANAGED_POINTERS environment variable. ");
   g_managedptrs[g_nmanagedptrs++] = mem;
 }
 
 int isManagedPtr(void *mem) {
-  for (int i = 0; i < g_nmanagedptrs; i++) {
+  for (unsigned long long i = 0; i < g_nmanagedptrs; i++) {
     if (g_managedptrs[i] == mem)
       return 1;
   }
   return 0;
 }
 
 void polly_freeManaged(void *mem) {
   dump_function();