tree-vectorizer.h (struct _loop_vec_info): Add no_data_dependencies field.

	* tree-vectorizer.h (struct _loop_vec_info): Add no_data_dependencies
	field.
	(LOOP_VINFO_NO_DATA_DEPENDENCIES): Define.
	* tree-vect-data-refs.c (vect_analyze_data_ref_dependence): Clear it
	when not giving up or versioning for alias only because of
	loop->safelen.
	(vect_analyze_data_ref_dependences): Set to true.
	* tree-vect-stmts.c (hoist_defs_of_uses): Return false if def_stmt
	is a GIMPLE_PHI.
	(vectorizable_load): Use LOOP_VINFO_NO_DATA_DEPENDENCIES instead of
	LOOP_REQUIRES_VERSIONING_FOR_ALIAS, add && !nested_in_vect_loop
	to the condition.

From-SVN: r206687

1 files changed, 20 insertions, 0 deletions

diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h
index 935aab9..51367ea 100644
--- a/gcc/tree-vectorizer.h
+++ b/gcc/tree-vectorizer.h
@@ -347,6 +347,25 @@ typedef struct _loop_vec_info {
      fix it up.  */
   bool operands_swapped;
 
+  /* True if there are no loop carried data dependencies in the loop.
+     If loop->safelen <= 1, then this is always true, either the loop
+     didn't have any loop carried data dependencies, or the loop is being
+     vectorized guarded with some runtime alias checks, or couldn't
+     be vectorized at all, but then this field shouldn't be used.
+     For loop->safelen >= 2, the user has asserted that there are no
+     backward dependencies, but there still could be loop carried forward
+     dependencies in such loops.  This flag will be false if normal
+     vectorizer data dependency analysis would fail or require versioning
+     for alias, but because of loop->safelen >= 2 it has been vectorized
+     even without versioning for alias.  E.g. in:
+     #pragma omp simd
+     for (int i = 0; i < m; i++)
+       a[i] = a[i + k] * c;
+     (or #pragma simd or #pragma ivdep) we can vectorize this and it will
+     DTRT even for k > 0 && k < m, but without safelen we would not
+     vectorize this, so this field would be false.  */
+  bool no_data_dependencies;
+
   /* If if-conversion versioned this loop before conversion, this is the
      loop version without if-conversion.  */
   struct loop *scalar_loop;
@@ -385,6 +404,7 @@ typedef struct _loop_vec_info {
 #define LOOP_VINFO_PEELING_FOR_GAPS(L)     (L)->peeling_for_gaps
 #define LOOP_VINFO_OPERANDS_SWAPPED(L)     (L)->operands_swapped
 #define LOOP_VINFO_PEELING_FOR_NITER(L)    (L)->peeling_for_niter
+#define LOOP_VINFO_NO_DATA_DEPENDENCIES(L) (L)->no_data_dependencies
 #define LOOP_VINFO_SCALAR_LOOP(L)	   (L)->scalar_loop
 
 #define LOOP_REQUIRES_VERSIONING_FOR_ALIGNMENT(L) \