This reverts commit 20f0c68fd83a0147a8ec1722bd2e848180610288.
https://reviews.llvm.org/D153966#4464594 reports an optimization
regression in Rust.
Additionally this change has caused an unexpected 0.3% compile-time
regression.
SpeculativelyExecuteBB(), which converts a branch + phi structure
into a select, currently bails out if the block contains an assume
(because it is not speculatable).
Adjust the fold to ignore ephemeral values (i.e. assumes and values
only used in assumes) for cost modelling purposes, and drop them
when performing the fold.
Theoretically, we could try to preserve the assume information by
generating a assume(br_cond || assume_cond) style assume, but this
is very unlikely to to be useful (because we don't do anything
useful with assumes of this form) and it would make things
substantially more complicated once we take operand bundle assumes
into account (which don't really support a || operation).
I'd prefer not to do that without good motivation.
Differential Revision: https://reviews.llvm.org/D137339
First step after e1133179587dd895962a2fe4d6eb0cb1e63b5ee2,
in these tests, DomTree is valid afterwards, so mark them as such,
so that they don't regress.
In further steps, SimplifyCFG transforms shall taught to preserve DomTree,
in as small steps as possible.
As it's causing some bot failures (and per request from kbarton).
This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.
llvm-svn: 358546
This is the first commit in a series that add an @llvm.assume intrinsic which
can be used to provide the optimizer with a condition it may assume to be true
(when the control flow would hit the intrinsic call). Some basic properties are added here:
- llvm.invariant(true) is dead.
- llvm.invariant(false) is unreachable (this directly corresponds to the
documented behavior of MSVC's __assume(0)), so is llvm.invariant(undef).
The intrinsic is tagged as writing arbitrarily, in order to maintain control
dependencies. BasicAA has been updated, however, to return NoModRef for any
particular location-based query so that we don't unnecessarily block code
motion.
llvm-svn: 213973
