[PATCH] Reassociate X == CST1 || X == CST2 if popcount (CST2 - CST1) == 1 into ((X - CST1) & ~(CST2 - CST1)) == 0

["Zhenqiang Chen" <zhenqiang dot chen at arm dot com>]

Hi

The patch reassociates X == CST1 || X == CST2 if popcount (CST2 - CST1) == 1
into ((X - CST1) & ~(CST2 - CST1)) == 0.

Bootstrap on x86-64 and ARM chromebook.
No make check regression on x86-64 and panda board.

For some targets/options, the "(X == CST1 || X == CST2)" might be converted
to "if (x == CST1) else if (x == CST2)" at the beginning. In such case, the
patch will not be executed. It is hard to write a reliable testcase to
detect the transformation. So the testcase does not check the dump logs from
reassoc1 pass. It just checks the runtime result.

Is it OK for trunk?

Thanks!
-Zhenqiang

ChangeLog
2013-08-05  Zhenqiang Chen  <zhenqiang.chen@arm.com>

	* tree-ssa-reassoc.c (optimize_range_tests): Reasociate
	X == CST1 || X == CST2 if popcount (CST2 - CST1) == 1 into
	((X - CST1) & ~(CST2 - CST1)) == 0.

testsuite/ChangeLog
2013-08-05  Zhenqiang Chen  <zhenqiang.chen@arm.com>

	* gcc.dg/reassoc1.c: New testcase.

Attachment: reassociate.patch
Description: Binary data