mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2025-01-31 20:51:52 +01:00
d746d62b1a
Summary: It is pretty common to assume that something is not zero. Even optimizer itself sometimes emits such assumptions (e.g. `addAssumeNonNull()` in `PromoteMemoryToRegister.cpp`). But we currently don't deal with such assumptions :) The only way `isKnownNonZero()` handles assumptions is by calling `computeKnownBits()` which calls `computeKnownBitsFromAssume()`. But `x != 0` does not tell us anything about set bits, it only says that there are *some* set bits. So naturally, `KnownBits` does not get populated, and we fail to make use of this assumption. I propose to deal with this special case by special-casing it via adding a `isKnownNonZeroFromAssume()` that returns boolean when there is an applicable assumption. While there, we also deal with other predicates, mainly if the comparison is with constant. Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=43267 | PR43267 ]]. Differential Revision: https://reviews.llvm.org/D71660