re PR rtl-optimization/49799 (gcc arm generates illegal sbfx instruction)

	PR rtl-optimization/49799

	* combine.c (make_compound_operation): Check if the bit field is valid
	before change it to bit field extraction.

	* gcc.dg/pr49799.c: New test case.

From-SVN: r176911

gcc/ChangeLog

+2011-07-29  Wei Guozhi  <carrot@google.com>
+
+	PR rtl-optimization/49799
+	* combine.c (make_compound_operation): Check if the bit field is valid
+	before change it to bit field extraction.
+
 2011-07-29  Bernd Schmidt  <bernds@codesourcery.com>
 
 	PR rtl-optimization/49891

gcc/combine.c

@@ -7787,6 +7787,7 @@ make_compound_operation (rtx x, enum rtx_code in_code)
 	  && GET_CODE (lhs) == ASHIFT
 	  && CONST_INT_P (XEXP (lhs, 1))
 	  && INTVAL (rhs) >= INTVAL (XEXP (lhs, 1))
+	  && INTVAL (XEXP (lhs, 1)) >= 0
 	  && INTVAL (rhs) < mode_width)
 	{
 	  new_rtx = make_compound_operation (XEXP (lhs, 0), next_code);

gcc/testsuite/ChangeLog

+2011-07-29  Wei Guozhi  <carrot@google.com>
+
+	PR rtl-optimization/49799
+	* gcc.dg/pr49799.c: New test case.
+
 2011-07-22  Sebastian Pop  <sebastian.pop@amd.com>
 
 	PR middle-end/48648

gcc/testsuite/gcc.dg/pr49799.c

+/* PR rtl-optimization/49799 */
+/* { dg-do assemble } */
+/* { dg-options "-O2 -w" } */
+
+static __inline int bar(int a)
+{
+    int tmp;
+
+    if (a <= 0) a ^= 0xFFFFFFFF;
+
+    return tmp - 1;
+}
+
+void foo(short *K)
+{
+    short tmp;
+    short *pptr, P[14];
+
+    pptr = P;
+    tmp = bar(*K);
+    *pptr = (*K << tmp) >> 16;
+
+    if (*P < tmp)
+        *K++ = 0;
+}