From 6f9071656286512360ca22b6668c9c8d823ec907 Mon Sep 17 00:00:00 2001
From: Alan Lawrence <alan.lawrence@arm.com>
Date: Tue, 27 Oct 2015 12:36:55 +0000
Subject: [PATCH] tree-scalar-evolution.c: Handle LSHIFT by constant

gcc/:

	tree-scalar-evolution.c (interpret_rhs_expr): Handle some LSHIFT_EXPRs
	as equivalent MULT_EXPRs.

gcc/testsuite/:

	gcc.dg/vect/vect-strided-shift.c: New.

From-SVN: r229437
---
 gcc/ChangeLog                                 |  6 ++++
 gcc/testsuite/ChangeLog                       |  4 +++
 .../gcc.dg/vect/vect-strided-shift-1.c        | 33 +++++++++++++++++++
 gcc/tree-scalar-evolution.c                   | 14 ++++++++
 4 files changed, 57 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/vect/vect-strided-shift-1.c

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 96af75db414..9bee00f56d3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2015-10-27  Alan Lawrence  <alan.lawrence@arm.com>
+
+	PR tree-optimization/65963
+	* tree-scalar-evolution.c (interpret_rhs_expr): Handle some LSHIFT_EXPRs
+	as equivalent MULT_EXPRs.
+
 2015-10-27  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 
 	PR target/67929
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 612e52f8929..e693063b4ad 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2015-10-27  Alan Lawrence  <alan.lawrence@arm.com>
+
+	* gcc.dg/vect/vect-strided-shift-1.c: New.
+
 2015-10-27  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 
 	PR target/67929
diff --git a/gcc/testsuite/gcc.dg/vect/vect-strided-shift-1.c b/gcc/testsuite/gcc.dg/vect/vect-strided-shift-1.c
new file mode 100644
index 00000000000..b1ce2ece170
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/vect-strided-shift-1.c
@@ -0,0 +1,33 @@
+/* PR tree-optimization/65963.  */
+#include "tree-vect.h"
+
+#define N 512
+
+int in[2*N], out[N];
+
+__attribute__ ((noinline)) void
+loop (void)
+{
+  for (int i = 0; i < N; i++)
+    out[i] = in[i << 1] + 7;
+}
+
+int
+main (int argc, char **argv)
+{
+  check_vect ();
+  for (int i = 0; i < 2*N; i++)
+    {
+      in[i] = i;
+      __asm__ volatile ("" : : : "memory");
+    }
+  loop ();
+  __asm__ volatile ("" : : : "memory");
+  for (int i = 0; i < N; i++)
+    {
+      if (out[i] != i*2 + 7)
+	abort ();
+    }
+  return 0;
+}
+/* { dg-final { scan-tree-dump-times "vectorized 1 loops in function" 1 "vect" { target { vect_strided2 } } } } */
diff --git a/gcc/tree-scalar-evolution.c b/gcc/tree-scalar-evolution.c
index 0753bf3122e..8e95ddd2d6a 100644
--- a/gcc/tree-scalar-evolution.c
+++ b/gcc/tree-scalar-evolution.c
@@ -1840,6 +1840,20 @@ interpret_rhs_expr (struct loop *loop, gimple *at_stmt,
       res = chrec_fold_multiply (type, chrec1, chrec2);
       break;
 
+    case LSHIFT_EXPR:
+      /* Handle A<<B as A * (1<<B).  */
+      chrec1 = analyze_scalar_evolution (loop, rhs1);
+      chrec2 = analyze_scalar_evolution (loop, rhs2);
+      chrec1 = chrec_convert (type, chrec1, at_stmt);
+      chrec1 = instantiate_parameters (loop, chrec1);
+      chrec2 = instantiate_parameters (loop, chrec2);
+
+      chrec2 = fold_build2 (LSHIFT_EXPR, type,
+			    build_int_cst (TREE_TYPE (rhs1), 1),
+			    chrec2);
+      res = chrec_fold_multiply (type, chrec1, chrec2);
+      break;
+
     CASE_CONVERT:
       /* In case we have a truncation of a widened operation that in
          the truncated type has undefined overflow behavior analyze
-- 
2.30.2