Process only valid shift ranges.

When shifting outside the valid range of [0, precision-1], we can
choose to process just the valid ones since the rest is undefined.
this allows us to produce results for x << [0,2][+INF, +INF] by discarding
the invalid ranges and processing just [0,2].

	gcc/
	PR tree-optimization/93781
	* range-op.cc (get_shift_range): Rename from
	undefined_shift_range_check and now return valid shift ranges.
	(operator_lshift::fold_range): Use result from get_shift_range.
	(operator_rshift::fold_range): Ditto.
	gcc/testsuite/
	* gcc.dg/tree-ssa/pr93781-1.c: New.
	* gcc.dg/tree-ssa/pr93781-2.c: New.
	* gcc.dg/tree-ssa/pr93781-3.c: New.

3 files changed, 56 insertions, 0 deletions

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr93781-1.c b/gcc/testsuite/gcc.dg/tree-ssa/pr93781-1.c
new file mode 100644
index 0000000..5ebd805
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr93781-1.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-evrp" } */
+
+void kill (void);
+
+void foo (unsigned int arg)
+{
+  int a = arg - 3;
+  unsigned int b = 4;
+  int x = 0x1 << arg;
+
+  if (a < 0)
+    b = x;
+
+  /* In the fullness of time, we will delete this call.  */
+  if (b >=  5)
+    kill ();;
+}
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr93781-2.c b/gcc/testsuite/gcc.dg/tree-ssa/pr93781-2.c
new file mode 100644
index 0000000..c9b2878
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr93781-2.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-evrp" } */
+
+void kill (void);
+
+void foo (unsigned int arg)
+{
+  unsigned int C000003FE = 4;
+
+  if (arg + 1 < 4)  // work for if (arg < 3)
+     C000003FE = 0x1 << arg;
+
+  if (C000003FE >= 5)
+    kill ();
+}
+
+/* { dg-final { scan-tree-dump-not "kill" "evrp" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr93781-3.c b/gcc/testsuite/gcc.dg/tree-ssa/pr93781-3.c
new file mode 100644
index 0000000..e1d2be0
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr93781-3.c
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-evrp" } */
+
+void kill (void);
+
+void foo (unsigned int arg)
+{
+  int a = arg - 3;
+  unsigned int b = 4;
+
+  if (a < 0)
+    {
+      int x = 0x1 << arg;
+      b = x;
+    }
+
+  if (b >=  5)
+   kill ();
+}
+
+/* { dg-final { scan-tree-dump-not "kill" "evrp" } } */