re PR middle-end/61158 (negative shift at fold-const.c:12095)

	PR tree-optimization/61158
	* fold-const.c (fold_binary_loc): If X is zero-extended and
	shiftc >= prec, make sure zerobits is all ones instead of
	invoking undefined behavior.

	* gcc.dg/pr61158.c: New test.

From-SVN: r210467

gcc/ChangeLog

+2014-05-15  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/61158
+	* fold-const.c (fold_binary_loc): If X is zero-extended and
+	shiftc >= prec, make sure zerobits is all ones instead of
+	invoking undefined behavior.
+
 2014-05-15  Zhenqiang Chen  <zhenqiang.chen@linaro.org>
 
 	* regcprop.h: New file.
 	* regcprop.c (skip_debug_insn_p): New decl.
 	(replace_oldest_value_reg): Check skip_debug_insn_p.
-	(copyprop_hardreg_forward_bb_without_debug_insn.): New function.
-	* shrink-wrap.c: include regcprop.h
-	(prepare_shrink_wrap):
-	Call copyprop_hardreg_forward_bb_without_debug_insn.
+	(copyprop_hardreg_forward_bb_without_debug_insn): New function.
+	* shrink-wrap.c: Include regcprop.h.
+	(prepare_shrink_wrap): Call
+	copyprop_hardreg_forward_bb_without_debug_insn.
 
 2014-05-15  Zhenqiang Chen  <zhenqiang.chen@linaro.org>
 

gcc/fold-const.c

@@ -11972,11 +11972,17 @@ fold_binary_loc (location_t loc,
 		      /* See if we can shorten the right shift.  */
 		      if (shiftc < prec)
 			shift_type = inner_type;
+		      /* Otherwise X >> C1 is all zeros, so we'll optimize
+			 it into (X, 0) later on by making sure zerobits
+			 is all ones.  */
 		    }
 		}
 	      zerobits = ~(unsigned HOST_WIDE_INT) 0;
-	      zerobits >>= HOST_BITS_PER_WIDE_INT - shiftc;
-	      zerobits <<= prec - shiftc;
+	      if (shiftc < prec)
+		{
+		  zerobits >>= HOST_BITS_PER_WIDE_INT - shiftc;
+		  zerobits <<= prec - shiftc;
+		}
 	      /* For arithmetic shift if sign bit could be set, zerobits
 		 can contain actually sign bits, so no transformation is
 		 possible, unless MASK masks them all away.  In that
@@ -11994,7 +12000,7 @@ fold_binary_loc (location_t loc,
 	  /* ((X << 16) & 0xff00) is (X, 0).  */
 	  if ((mask & zerobits) == mask)
 	    return omit_one_operand_loc (loc, type,
-				     build_int_cst (type, 0), arg0);
+					 build_int_cst (type, 0), arg0);
 
 	  newmask = mask | zerobits;
 	  if (newmask != mask && (newmask & (newmask + 1)) == 0)

gcc/testsuite/ChangeLog

+2014-05-15  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/61158
+	* gcc.dg/pr61158.c: New test.
+
 2014-05-15  Andreas Schwab  <schwab@suse.de>
 
 	* obj-c++.dg/exceptions-3.mm: Remove check for message no longer

gcc/testsuite/gcc.dg/pr61158.c

+/* PR tree-optimization/61158 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-original" } */
+
+unsigned long long
+foo (unsigned int x)
+{
+  return ((unsigned long long) x & 0x00ff000000000000ULL) >> 40;
+}
+
+/* { dg-final { scan-tree-dump "return 0;" "original" { target { ilp32 || lp64 } } } } */
+/* { dg-final { cleanup-tree-dump "original" } } */