4 Commits

Author	SHA1	Message	Date
Craig Topper	5b173f2bb3	[InstCombine] Add range metadata to cttz/ctlz/ctpop intrinsic calls based on known bits ... Summary: I noticed that passing known bits across these intrinsics isn't great at capturing the information we really know. Turning known bits of the input into known bits of a count output isn't able to convey a lot of what we really know. This patch adds range metadata to these intrinsics based on the known bits. Currently the patch punts if we already have range metadata present. Reviewers: spatel, RKSimon, davide, majnemer Reviewed By: RKSimon Subscribers: sanjoy, hfinkel, llvm-commits Differential Revision: https://reviews.llvm.org/D32582 llvm-svn: 305927	2017-06-21 16:32:35 +00:00
Craig Topper	4cec434a1b	[InstCombine] Add test cases to show missed opportunities to remove compare instructions after cttz/ctlz/ctpop where some bits of the input is known. ... llvm-svn: 304224	2017-05-30 17:47:59 +00:00
Craig Topper	dfd27dd107	[InstCombine] Use update_test_checks to regenerate the ctpop test. NFC ... llvm-svn: 303659	2017-05-23 17:20:18 +00:00
Philip Reames	ddcf6b35a2	Tighten known bits for ctpop based on zero input bits ... This is a cleaned up patch from the one written by John Regehr based on the findings of the Souper superoptimizer. The basic idea here is that input bits that are known zero reduce the maximum count that the intrinsic could return. We know that the number of bits required to represent a particular count is at most log2(N)+1. Differential Revision: http://reviews.llvm.org/D13253 llvm-svn: 250338	2015-10-14 22:42:12 +00:00