5 Commits

Author	SHA1	Message	Date
Gerolf Hoflehner	ec6217c929	[InstCombine] Re-commit of r218721 (Optimize icmp-select-icmp sequence) ... Fixes the self-host fail. Note that this commit activates dominator analysis in the combiner by default (like the original commit did). llvm-svn: 222590	2014-11-21 23:36:44 +00:00
Justin Bogner	894eff7a9f	Revert "[InstCombine] re-commit r218721 with fix for pr21199" ... This seems to cause a miscompile when building clang, which causes a bootstrapped clang to fail or crash in several of its tests. See: http://lab.llvm.org:8013/builders/clang-x86_64-darwin11-RA/builds/1184 http://bb.pgr.jp/builders/clang-3stage-x86_64-linux/builds/7813 This reverts commit r219282. llvm-svn: 219317	2014-10-08 16:30:22 +00:00
Gerolf Hoflehner	e2ff5b9223	[InstCombine] re-commit r218721 with fix for pr21199 ... The icmp-select-icmp optimization targets select-icmp.eq only. This is now ensured by testing the branch predicate explictly. This commit also includes the test case for pr21199. llvm-svn: 219282	2014-10-08 06:42:19 +00:00
Evgeniy Stepanov	815f2869ad	Revert r218721, r218735. ... Failing bootstrap on Linux (arm, x86). http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux/builds/13139/steps/bootstrap%20clang/logs/stdio http://lab.llvm.org:8011/builders/clang-cmake-armv7-a15-selfhost/builds/470 http://lab.llvm.org:8011/builders/clang-native-arm-lnt/builds/8518 llvm-svn: 218752	2014-10-01 10:07:28 +00:00
Gerolf Hoflehner	08cc4b950c	[InstCombine] Optimize icmp-select-icmp ... In special cases select instructions can be eliminated by replacing them with a cheaper bitwise operation even when the select result is used outside its home block. The instances implemented are patterns like %x=icmp.eq %y=select %x,%r, null %z=icmp.eq|neq %y, null br %z,true, false ==> %x=icmp.ne %y=icmp.eq %r,null %z=or %x,%y br %z,true,false The optimization is integrated into the instruction combiner and performed only when all uses of the select result can be replaced by the select operand proper. For this dominator information is used and dominance is now a required analysis pass in the combiner. The optimization itself is iterative. The critical step is to replace the select result with the non-constant select operand. So the select becomes local and the combiner iteratively works out simpler code pattern and eventually eliminates the select. rdar://17853760 llvm-svn: 218721	2014-10-01 00:13:22 +00:00