remove all the legacy check related to 32GB KDS

issue reported at #796.

The d1b3998 and related commit
removed KDS's length restriction to 32GB, by 64bit offset.
Thus, GpuCache's extra buffer is also not limited to 32GB, and
length validation checks are not needed any more.

src/gpu_cache.c

@@ -490,14 +490,6 @@ __parseSyncTriggerOptions(int elevel,
 		extra_sz += extra_sz / 4;
 		extra_sz += offsetof(kern_data_extra, data);
 	}
-	if (main_sz >= __KDS_LENGTH_LIMIT || extra_sz >= __KDS_LENGTH_LIMIT)
-	{
-		elog(elevel, "gpucache: max_num_rows = %ld consumes too much GPU device memory (main: %s, extra: %s), so we recommend to reduce 'max_num_rows' configuration",
-			 max_num_rows,
-			 format_bytesz(main_sz),
-			 format_bytesz(extra_sz));
-		return false;
-	}
 
 	/*
 	 * write back to the caller
@@ -1094,9 +1086,6 @@ __resetGpuCacheSharedState(GpuCacheSharedState *gc_sstate)
     gc_sstate->redo_sync_pos = 0;
 	pthreadMutexUnlock(&gc_sstate->redo_mutex);
 
-	/* initial buffer size should be legal */
-	Assert(gc_sstate->kds_head.length <= __KDS_LENGTH_LIMIT &&
-		   gc_sstate->kds_extra_sz    <= __KDS_LENGTH_LIMIT);
 	/* make this GpuCache available again */
 	pg_atomic_write_u32(&gc_sstate->phase, GCACHE_PHASE__IS_EMPTY);
 }
@@ -3509,16 +3498,6 @@ __gpucacheExecCompactionKernel(GpuCacheControlCommand *cmd,
 	if (kds_extra->usage > kds_extra->length)
 	{
 		gcache_extra_size = PAGE_ALIGN(kds_extra->usage * 5 / 4);	/* 25% margin */
-		if (gcache_extra_size >= __KDS_LENGTH_LIMIT)
-		{
-#if 1
-			fprintf(stderr,
-					"GpuCache (%s) extra buffer (%ldMB) exceeds the hard limit\n",
-					gc_sstate->table_name,
-					gcache_extra_size >> 20);
-#endif
-			goto bailout;
-		}
 		cuMemFree(m_kds_extra);
 		m_kds_extra = 0UL;
 		goto retry;

src/xpu_common.h

@@ -754,15 +754,6 @@ struct kern_data_extra
 };
 typedef struct kern_data_extra		kern_data_extra;
 
-/*
- * MEMO: Support of 32GB KDS - KDS with row-, hash- and column-format
- * internally uses 32bit offset value from the head or base address.
- * We have assumption here - any objects pointed by the offset value
- * is always aligned to MAXIMUM_ALIGNOF boundary (64bit).
- * It means we can use 32bit offset to represent up to 32GB range (35bit).
- */
-#define __KDS_LENGTH_LIMIT			(1UL<<35)		//deprecated
-
 /* ----------------------------------------------------------------
  *
  * Definitions of HeapTuple/IndexTuple and related