Add debug counter for loop array prefetching.

	* dbgcnt.def (prefetch): New debug counter.
	* tree-ssa-loop-prefetch.c (dbgcnt.h): New include.
	(schedule_prefetches): Stop issueing prefetches if debug counter
	tripped.

Change-Id: Ia6160364735a889fb6d2370be21d98f87c0fe962

From-SVN: r248924

gcc/ChangeLog

+2017-06-06  Maxim Kuvyrkov  <maxim.kuvyrkov@linaro.org>
+
+        * dbgcnt.def (prefetch): New debug counter.
+        * tree-ssa-loop-prefetch.c (dbgcnt.h): New include.
+        (schedule_prefetches): Stop issueing prefetches if debug counter
+        tripped.
+
 2017-06-06  Tom de Vries  <tom@codesourcery.com>
 
 	* doc/sourcebuild.texi (Testsuites, C Language Testsuites,

gcc/dbgcnt.def

@@ -174,6 +174,7 @@ DEBUG_COUNTER (merged_ipa_icf)
 DEBUG_COUNTER (postreload_cse)
 DEBUG_COUNTER (pre)
 DEBUG_COUNTER (pre_insn)
+DEBUG_COUNTER (prefetch)
 DEBUG_COUNTER (registered_jump_thread)
 DEBUG_COUNTER (sched2_func)
 DEBUG_COUNTER (sched_block)

gcc/tree-ssa-loop-prefetch.c

@@ -48,6 +48,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-inline.h"
 #include "tree-data-ref.h"
 #include "diagnostic-core.h"
+#include "dbgcnt.h"
 
 /* This pass inserts prefetch instructions to optimize cache usage during
    accesses to arrays in loops.  It processes loops sequentially and:
@@ -1058,6 +1059,10 @@ schedule_prefetches (struct mem_ref_group *groups, unsigned unroll_factor,
 	if (2 * remaining_prefetch_slots < prefetch_slots)
 	  continue;
 
+	/* Stop prefetching if debug counter is activated.  */
+	if (!dbg_cnt (prefetch))
+	  continue;
+
 	ref->issue_prefetch_p = true;
 
 	if (remaining_prefetch_slots <= prefetch_slots)