As it's causing some bot failures (and per request from kbarton).
This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.
llvm-svn: 358546
The cttz/ctlz intrinsics have a parameter specifying whether the
result is undefined for zero. cttz(x, false) can be relaxed to
cttz(x, true) if x is known non-zero, and in fact such an optimization
is already performed. However, this currently doesn't work if x is
non-zero as a result of a select rather than an explicit branch.
This patch adds handling for this case, thus allowing
x != 0 ? cttz(x, false) : y to simplify to x != 0 ? cttz(x, true) : y.
Differential Revision: https://reviews.llvm.org/D55786
llvm-svn: 350463
Not sure why this restriction existed, but it seems like we should support any size Constant here.
The particular pattern in the tests is not the only use of this matcher in the tree. There's one in CodeGenPrepare and one in InstSimplify as well.
Differential Revision: https://reviews.llvm.org/D34666
llvm-svn: 306417
This patch fixes a problem I accidentally introduced in an instruction combine
on select instructions added at r227197. That revision taught the instruction
combiner how to fold a cttz/ctlz followed by a icmp plus select into a single
cttz/ctlz with flag 'is_zero_undef' cleared.
However, the new rule added at r227197 would have produced wrong results in the
case where a cttz/ctlz with flag 'is_zero_undef' cleared was follwed by a
zero-extend or truncate. In that case, the folded instruction would have
been inserted in a wrong location thus leaving the CFG in an inconsistent
state.
This patch fixes the problem and add two reproducible test cases to
existing test 'InstCombine/select-cmp-cttz-ctlz.ll'.
llvm-svn: 229124
This patch teaches the Instruction Combiner how to fold a cttz/ctlz followed by
a icmp plus select into a single cttz/ctlz with flag 'is_zero_undef' cleared.
Added test InstCombine/select-cmp-cttz-ctlz.ll.
llvm-svn: 227197
Eric Christopher