HomePhabricator

Add @llvm.assume, lowering, and some basic properties

Description

Add @llvm.assume, lowering, and some basic properties

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.

Details

Committed
hfinkelJul 25 2014, 2:13 PM
Parents
rL213972: Now that PIC generation on PPC32 is supported, hook up linking support
Branches
Unknown
Tags
Unknown

Event Timeline