On 10/15/13 02:12, Jakub Jelinek wrote:
On Tue, Oct 15, 2013 at 03:57:23PM +0800, Zhenqiang Chen wrote:
Is it OK?
Ok, except two comments apparently still need updating.
+/* Optimize X == CST1 || X == CST2
+ if popcount (CST1 ^ CST2) == 1 into
+ (X & ~(CST1 ^ CST2)) == (CST1 & ~(CST1 ^ CST2)).
+ Similarly for ranges. E.g.
+ X != 2 && X != 3 && X != 10 && X != 11
+ will be transformed by the previous optimization into
+ (X - 2U) <= 1U && (X - 10U) <= 1U
+ and this loop can transform that into
+ ((X & ~8) - 2U) <= 1U. */
Here the example is using != and &&, so it is transformed into:
!((X - 2U) <= 1U || (X - 10U) <= 1U)
(everything is negated at the end, and note || instead of &&,
with && it could fold into !(0))
and finally into:
!(((X & ~8) - 2U) <= 1U)
Or alternatively change the first expression into:
X == 2 || X == 3 || X == 10 || X == 11
and the second to:
(X - 2U) <= 1U || (X - 10U) <= 1U
and the third keep as is.
+/* Optimize X == CST1 || X == CST2
+ if popcount (CST2 - CST1) == 1 into
+ ((X - CST1) & ~(CST2 - CST1)) == 0.
+ Similarly for ranges. E.g.
+ X == 43 || X == 76 || X == 44 || X == 78 || X == 77 || X == 46
+ || X == 75 || X == 45
+ will be transformed by the previous optimization into
+ (X - 43U) <= 3U && (X - 75U) <= 3U
+ and this loop can transform that into
+ ((X - 43U) & ~(75U - 43U)) <= 3U. */
Here the example is using == and ||, so the only wrong thing in there
is that the second expression should be
(X - 43U) <= 3U || (X - 75U) <= 3U
Ok with those changes.
I fixed up the comments & ChangeLog entry and committed on Zhenqiang's
behalf.
jeff
