reassoc: Test rank biasing

Add both positive and negative tests.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/reassoc-46.c: New test.
	* gcc.dg/tree-ssa/reassoc-46.h: Common code for new tests.
	* gcc.dg/tree-ssa/reassoc-47.c: New test.
	* gcc.dg/tree-ssa/reassoc-48.c: New test.
	* gcc.dg/tree-ssa/reassoc-49.c: New test.
	* gcc.dg/tree-ssa/reassoc-50.c: New test.
	* gcc.dg/tree-ssa/reassoc-51.c: New test.

gcc/testsuite/gcc.dg/tree-ssa/reassoc-46.c

@@ -0,0 +1,7 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized -ftree-vectorize" } */
+
+#include "reassoc-46.h"
+
+/* Check that the loop accumulator is added last.  */
+/* { dg-final { scan-tree-dump-times {(?:vect_)?sum_[\d._]+ = (?:(?:vect_)?_[\d._]+ \+ (?:vect_)?sum_[\d._]+|(?:vect_)?sum_[\d._]+ \+ (?:vect_)?_[\d._]+)} 1 "optimized" } } */

gcc/testsuite/gcc.dg/tree-ssa/reassoc-46.h

@@ -0,0 +1,33 @@
+#define M 1024
+unsigned int arr1[M];
+unsigned int arr2[M];
+volatile unsigned int sink;
+
+unsigned int
+test (void)
+{
+  unsigned int sum = 0;
+  for (int i = 0; i < M; i++)
+    {
+#ifdef MODIFY
+      /* Modify the loop accumulator using a chain of operations - this should
+         not affect its rank biasing.  */
+      sum |= 1;
+      sum ^= 2;
+#endif
+#ifdef STORE
+      /* Save the loop accumulator into a global variable - this should not
+         affect its rank biasing.  */
+      sink = sum;
+#endif
+#ifdef USE
+      /* Add a tricky use of the loop accumulator - this should prevent its
+         rank biasing.  */
+      i = (i + sum) % M;
+#endif
+      /* Use addends with different ranks.  */
+      sum += arr1[i];
+      sum += arr2[((i ^ 1) + 1) % M];
+    }
+  return sum;
+}

gcc/testsuite/gcc.dg/tree-ssa/reassoc-47.c

@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized -ftree-vectorize" } */
+
+#define MODIFY
+#include "reassoc-46.h"
+
+/* Check that if the loop accumulator is saved into a global variable, it's
+   still added last.  */
+/* { dg-final { scan-tree-dump-times {(?:vect_)?sum_[\d._]+ = (?:(?:vect_)?_[\d._]+ \+ (?:vect_)?sum_[\d._]+|(?:vect_)?sum_[\d._]+ \+ (?:vect_)?_[\d._]+)} 1 "optimized" } } */

gcc/testsuite/gcc.dg/tree-ssa/reassoc-48.c

@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized -ftree-vectorize" } */
+
+#define STORE
+#include "reassoc-46.h"
+
+/* Check that if the loop accumulator is modified using a chain of operations
+   other than addition, its new value is still added last.  */
+/* { dg-final { scan-tree-dump-times {(?:vect_)?sum_[\d._]+ = (?:(?:vect_)?_[\d._]+ \+ (?:vect_)?sum_[\d._]+|(?:vect_)?sum_[\d._]+ \+ (?:vect_)?_[\d._]+)} 1 "optimized" } } */

gcc/testsuite/gcc.dg/tree-ssa/reassoc-49.c

@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized -ftree-vectorize" } */
+
+#define MODIFY
+#define STORE
+#include "reassoc-46.h"
+
+/* Check that if the loop accumulator is both modified using a chain of
+   operations other than addition and stored into a global variable, its new
+   value is still added last.  */
+/* { dg-final { scan-tree-dump-times {(?:vect_)?sum_[\d._]+ = (?:(?:vect_)?_[\d._]+ \+ (?:vect_)?sum_[\d._]+|(?:vect_)?sum_[\d._]+ \+ (?:vect_)?_[\d._]+)} 1 "optimized" } } */

gcc/testsuite/gcc.dg/tree-ssa/reassoc-50.c

@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized -ftree-vectorize" } */
+
+#define MODIFY
+#define USE
+#include "reassoc-46.h"
+
+/* Check that if the loop accumulator has multiple uses inside the loop, it's
+   not forced to the end of the reassociation chain.  */
+/* { dg-final { scan-tree-dump-times {(?:vect_)?sum_[\d._]+ = (?:(?:vect_)?_[\d._]+ \+ (?:vect_)?sum_[\d._]+|(?:vect_)?sum_[\d._]+ \+ (?:vect_)?_[\d._]+)} 2 "optimized" } } */

gcc/testsuite/gcc.dg/tree-ssa/reassoc-51.c

@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized -ftree-vectorize" } */
+
+#define MODIFY
+#define STORE
+#define USE
+#include "reassoc-46.h"
+
+/* Check that if the loop accumulator has multiple uses inside the loop, it's
+   not forced to the end of the reassociation chain.  */
+/* { dg-final { scan-tree-dump-times {(?:vect_)?sum_[\d._]+ = (?:(?:vect_)?_[\d._]+ \+ (?:vect_)?sum_[\d._]+|(?:vect_)?sum_[\d._]+ \+ (?:vect_)?_[\d._]+)} 2 "optimized" } } */