[PATCH] tree-scalar-evolution.c: Handle LSHIFT by constant

gcc/:

	PR tree-optimization/65963
	* tree-scalar-evolution.c (interpret_rhs_expr): Try to handle
	LSHIFT_EXPRs as equivalent unsigned MULT_EXPRs.

gcc/testsuite/:

	* gcc.dg/pr68112.c: New.
	* gcc.dg/vect/vect-strided-shift-1.c: New.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@229825 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 17 insertions, 0 deletions

diff --git a/gcc/tree-scalar-evolution.c b/gcc/tree-scalar-evolution.c
index bb27b070dba..5cd7b1522ba 100644
--- a/gcc/tree-scalar-evolution.c
+++ b/gcc/tree-scalar-evolution.c
@@ -1827,6 +1827,23 @@ 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).  */
+	tree uns = unsigned_type_for (type);
+	chrec1 = analyze_scalar_evolution (loop, rhs1);
+	chrec2 = analyze_scalar_evolution (loop, rhs2);
+	chrec1 = chrec_convert (uns, chrec1, at_stmt);
+	chrec1 = instantiate_parameters (loop, chrec1);
+	chrec2 = instantiate_parameters (loop, chrec2);
+
+	tree one = build_int_cst (uns, 1);
+	chrec2 = fold_build2 (LSHIFT_EXPR, uns, one, chrec2);
+	res = chrec_fold_multiply (uns, chrec1, chrec2);
+	res = chrec_convert (type, res, at_stmt);
+      }
+      break;
+
     CASE_CONVERT:
       /* In case we have a truncation of a widened operation that in
          the truncated type has undefined overflow behavior analyze