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[PATCH] Allow non-overflow ops in vect_is_simple_reduction_1


Hi,

this patch allows parallelization and vectorization of reduction operators that are guaranteed to not overflow (such as min and max operators), independent of the overflow behaviour of the type.

Bootstrapped and reg-tested on x86_64.

OK for trunk?

Thanks,
- Tom
Allow non-overflow ops in vect_is_simple_reduction_1

2015-07-24  Tom de Vries  <tom@codesourcery.com>

	* tree.c (no_overflow_tree_code): New function.
	* tree.h (no_overflow_tree_code): Declare.
	* tree-vect-loop.c (vect_is_simple_reduction_1): Use
	no_overflow_tree_code.

	* gcc.dg/autopar/reduc-2char.c (init_arrays): Mark with attribute
	optimize ("-ftree-parallelize-loops=0").
	Add successful scans for 2 detected reductions.	 Add xfail scans for 3
	detected reductions.
	* gcc.dg/autopar/reduc-2short.c: Same.
	* gcc.dg/autopar/reduc-8.c  (init_arrays): Mark with attribute
	optimize ("-ftree-parallelize-loops=0").  Add successful scans for 2
	detected reductions.
	* gcc.dg/vect/trapv-vect-reduc-4.c: Expect succesful reductions for min
	and max loops.
---
 gcc/testsuite/gcc.dg/autopar/reduc-2char.c     | 10 +++++++---
 gcc/testsuite/gcc.dg/autopar/reduc-2short.c    | 10 ++++++----
 gcc/testsuite/gcc.dg/autopar/reduc-8.c         |  7 ++++---
 gcc/testsuite/gcc.dg/vect/trapv-vect-reduc-4.c |  2 +-
 gcc/tree-vect-loop.c                           |  3 ++-
 gcc/tree.c                                     | 24 ++++++++++++++++++++++++
 gcc/tree.h                                     |  1 +
 7 files changed, 45 insertions(+), 12 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/autopar/reduc-2char.c b/gcc/testsuite/gcc.dg/autopar/reduc-2char.c
index 14867f3..a2dad44 100644
--- a/gcc/testsuite/gcc.dg/autopar/reduc-2char.c
+++ b/gcc/testsuite/gcc.dg/autopar/reduc-2char.c
@@ -39,8 +39,9 @@ void main1 (signed char x, signed char max_result, signed char min_result)
     abort ();
 }
 
- __attribute__((noinline))
- void init_arrays ()
+void __attribute__((noinline))
+  __attribute__((optimize ("-ftree-parallelize-loops=0")))
+init_arrays ()
  {
    int i;
 
@@ -60,7 +61,10 @@ int main (void)
 }
 
 
-/* { dg-final { scan-tree-dump-times "Detected reduction" 2 "parloops" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump-times "Detected reduction" 2 "parloops" } } */
+/* { dg-final { scan-tree-dump-times "Detected reduction" 3 "parloops" { xfail *-*-* } } } */
+
+/* { dg-final { scan-tree-dump-times "SUCCESS: may be parallelized" 2 "parloops" } } */
 /* { dg-final { scan-tree-dump-times "SUCCESS: may be parallelized" 3 "parloops" { xfail *-*-* } } } */
 
 
diff --git a/gcc/testsuite/gcc.dg/autopar/reduc-2short.c b/gcc/testsuite/gcc.dg/autopar/reduc-2short.c
index 7c19cc5..a50e14f 100644
--- a/gcc/testsuite/gcc.dg/autopar/reduc-2short.c
+++ b/gcc/testsuite/gcc.dg/autopar/reduc-2short.c
@@ -38,8 +38,9 @@ void main1 (short x, short max_result, short min_result)
     abort ();
 }
 
- __attribute__((noinline))
- void init_arrays ()
+void __attribute__((noinline))
+  __attribute__((optimize ("-ftree-parallelize-loops=0")))
+init_arrays ()
  {
    int i;
 
@@ -58,7 +59,8 @@ int main (void)
   return 0;
 }
 
+/* { dg-final { scan-tree-dump-times "Detected reduction" 2 "parloops" } } */
+/* { dg-final { scan-tree-dump-times "Detected reduction" 3 "parloops" { xfail *-*-* } } } */
 
-/* { dg-final { scan-tree-dump-times "Detected reduction" 2 "parloops" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump-times "SUCCESS: may be parallelized" 2 "parloops" } } */
 /* { dg-final { scan-tree-dump-times "SUCCESS: may be parallelized" 3 "parloops" { xfail *-*-* } } } */
-
diff --git a/gcc/testsuite/gcc.dg/autopar/reduc-8.c b/gcc/testsuite/gcc.dg/autopar/reduc-8.c
index 1d05c48..18ba03d 100644
--- a/gcc/testsuite/gcc.dg/autopar/reduc-8.c
+++ b/gcc/testsuite/gcc.dg/autopar/reduc-8.c
@@ -40,7 +40,8 @@ testmin (const T *c, T init, T result)
     abort ();
 }
 
-int main (void)
+int __attribute__((optimize ("-ftree-parallelize-loops=0")))
+main (void)
 { 
   static signed char A[N] = {
     0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
@@ -84,5 +85,5 @@ int main (void)
 }
 
 
-/* { dg-final { scan-tree-dump-times "Detected reduction" 2 "parloops" { xfail *-*-* } } } */
-/* { dg-final { scan-tree-dump-times "SUCCESS: may be parallelized" 3 "parloops" { xfail *-*-* } } } */
+/* { dg-final { scan-tree-dump-times "Detected reduction" 2 "parloops" } } */
+/* { dg-final { scan-tree-dump-times "SUCCESS: may be parallelized" 2 "parloops" } } */
diff --git a/gcc/testsuite/gcc.dg/vect/trapv-vect-reduc-4.c b/gcc/testsuite/gcc.dg/vect/trapv-vect-reduc-4.c
index 2129717..86f9b90 100644
--- a/gcc/testsuite/gcc.dg/vect/trapv-vect-reduc-4.c
+++ b/gcc/testsuite/gcc.dg/vect/trapv-vect-reduc-4.c
@@ -46,4 +46,4 @@ int main (void)
   return 0;
 }
 
-/* { dg-final { scan-tree-dump-times "vectorized 0 loops" 1 "vect" } } */
+/* { dg-final { scan-tree-dump-times "vectorized 2 loops" 1 "vect" } } */
diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
index c31bfbd..42ba5f8 100644
--- a/gcc/tree-vect-loop.c
+++ b/gcc/tree-vect-loop.c
@@ -2613,7 +2613,8 @@ vect_is_simple_reduction_1 (loop_vec_info loop_info, gimple phi,
 			"reduction: unsafe fp math optimization: ");
       return NULL;
     }
-  else if (INTEGRAL_TYPE_P (type) && check_reduction)
+  else if (INTEGRAL_TYPE_P (type) && check_reduction
+	   && !no_overflow_tree_code (code, type))
     {
       if (TYPE_OVERFLOW_TRAPS (type))
 	{
diff --git a/gcc/tree.c b/gcc/tree.c
index 94263af..5b8dd1a 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -7541,6 +7541,30 @@ associative_tree_code (enum tree_code code)
   return false;
 }
 
+/* Return true if CODE represents an tree code that cannot overflow, given
+   operand type OP_TYPE.  Otherwise return false.  */
+bool
+no_overflow_tree_code (enum tree_code code, tree op_type)
+{
+  /* For now, just handle associative tree codes.  */
+  switch (code)
+    {
+    case BIT_IOR_EXPR:
+    case BIT_AND_EXPR:
+    case BIT_XOR_EXPR:
+      return true;
+
+    case MIN_EXPR:
+    case MAX_EXPR:
+      return (ANY_INTEGRAL_TYPE_P (op_type)
+	      && TREE_CODE (op_type) != COMPLEX_TYPE);
+
+    default:
+      break;
+    }
+  return false;
+}
+
 /* Return true if CODE represents a commutative tree code.  Otherwise
    return false.  */
 bool
diff --git a/gcc/tree.h b/gcc/tree.h
index 6df2217..360d13e 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -4367,6 +4367,7 @@ extern tree get_file_function_name (const char *);
 extern tree get_callee_fndecl (const_tree);
 extern int type_num_arguments (const_tree);
 extern bool associative_tree_code (enum tree_code);
+extern bool no_overflow_tree_code (enum tree_code, tree);
 extern bool commutative_tree_code (enum tree_code);
 extern bool commutative_ternary_tree_code (enum tree_code);
 extern tree upper_bound_in_type (tree, tree);
-- 
1.9.1


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