combine.c (simplify_comparison): Do not commute a AND into a paradoxical SUBREG…

combine.c (simplify_comparison): Do not commute a AND into a paradoxical SUBREG if not WORD_REGISTER_OPERATIONS.

	* combine.c (simplify_comparison): Do not commute a AND into
	a paradoxical SUBREG if not WORD_REGISTER_OPERATIONS.

From-SVN: r20934

gcc/ChangeLog

 Sun Jul  5 23:58:19 1998  Jeffrey A Law  (law@cygnus.com)
 
+	* combine.c (simplify_comparison): Do not commute a AND into
+	a paradoxical SUBREG if not WORD_REGISTER_OPERATIONS.
+
 	* i386/freebsd-elf.h (ASM_OUTPUT_MAX_SKIP_ALIGN): Protect with
 	HAVE_GAS_MAX_SKIP_P2ALIGN.
 	* i386/linux.h: Likewise.

gcc/combine.c

@@ -10154,6 +10154,16 @@ simplify_comparison (code, pop0, pop1)
 		  || subreg_lowpart_p (XEXP (op0, 0))
 #endif
 		  )
+#ifndef WORD_REGISTER_OPERATIONS
+	      /* It is unsafe to commute the AND into the SUBREG if the SUBREG
+		 is paradoxical and WORD_REGISTER_OPERATIONS is not defined.
+		 As originally written the upper bits have a defined value
+		 due to the AND operation.  However, if we commute the AND
+		 inside the SUBREG then they no longer have defined values
+		 and the meaning of the code has been changed.  */
+	      && (GET_MODE_SIZE (GET_MODE (XEXP (op0, 0)))
+		  <= GET_MODE_SIZE (GET_MODE (SUBREG_REG (XEXP (op0, 0)))))
+#endif
 	      && GET_CODE (XEXP (op0, 1)) == CONST_INT
 	      && mode_width <= HOST_BITS_PER_WIDE_INT
 	      && (GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (XEXP (op0, 0))))