+ /* For unsigned comparisons, A != 0 implies A > 0 and A >= 1. */
+ if (GET_CODE (a) == NE
+ && op1 == const0_rtx)
+ {
+ if ((GET_CODE (b) == GTU
+ && opb1 == const0_rtx)
+ || (GET_CODE (b) == GEU
+ && opb1 == const1_rtx))
+ return rtx_equal_p (op0, opb0);
+ }
+
+ /* A != N is equivalent to A - (N + 1) <u -1. */
+ if (GET_CODE (a) == NE
+ && GET_CODE (op1) == CONST_INT
+ && GET_CODE (b) == LTU
+ && opb1 == constm1_rtx
+ && GET_CODE (opb0) == PLUS
+ && GET_CODE (XEXP (opb0, 1)) == CONST_INT
+ /* Avoid overflows. */
+ && ((unsigned HOST_WIDE_INT) INTVAL (XEXP (opb0, 1))
+ != ((unsigned HOST_WIDE_INT)1
+ << (HOST_BITS_PER_WIDE_INT - 1)) - 1)
+ && INTVAL (XEXP (opb0, 1)) + 1 == -INTVAL (op1))
+ return rtx_equal_p (op0, XEXP (opb0, 0));
+
+ /* Likewise, A != N implies A - N > 0. */
+ if (GET_CODE (a) == NE
+ && GET_CODE (op1) == CONST_INT)
+ {
+ if (GET_CODE (b) == GTU
+ && GET_CODE (opb0) == PLUS
+ && opb1 == const0_rtx
+ && GET_CODE (XEXP (opb0, 1)) == CONST_INT
+ /* Avoid overflows. */
+ && ((unsigned HOST_WIDE_INT) INTVAL (XEXP (opb0, 1))
+ != ((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT - 1)))
+ && rtx_equal_p (XEXP (opb0, 0), op0))
+ return INTVAL (op1) == -INTVAL (XEXP (opb0, 1));
+ if (GET_CODE (b) == GEU
+ && GET_CODE (opb0) == PLUS
+ && opb1 == const1_rtx
+ && GET_CODE (XEXP (opb0, 1)) == CONST_INT
+ /* Avoid overflows. */
+ && ((unsigned HOST_WIDE_INT) INTVAL (XEXP (opb0, 1))
+ != ((unsigned HOST_WIDE_INT) 1 << (HOST_BITS_PER_WIDE_INT - 1)))
+ && rtx_equal_p (XEXP (opb0, 0), op0))
+ return INTVAL (op1) == -INTVAL (XEXP (opb0, 1));
+ }
+
+ /* A >s X, where X is positive, implies A <u Y, if Y is negative. */
+ if ((GET_CODE (a) == GT || GET_CODE (a) == GE)
+ && GET_CODE (op1) == CONST_INT
+ && ((GET_CODE (a) == GT && op1 == constm1_rtx)
+ || INTVAL (op1) >= 0)
+ && GET_CODE (b) == LTU
+ && GET_CODE (opb1) == CONST_INT)
+ return INTVAL (opb1) < 0;
+