Add an nneg flag to the zext instruction, which specifies that the
argument is non-negative. Otherwise, the result is a poison value.
The primary use-case for the flag is to preserve information when sext
gets replaced with zext due to range-based canonicalization. The nneg
flag allows us to convert the zext back into an sext later. This is
useful for some optimizations (e.g. a signed icmp can fold with sext but
not zext), as well as some targets (e.g. RISCV prefers sext over zext).
Discourse thread: https://discourse.llvm.org/t/rfc-add-zext-nneg-flag/73914
This patch is based on https://reviews.llvm.org/D156444 by
@Panagiotis156, with some implementation simplifications and additional
tests.
---------
Co-authored-by: Panagiotis K <karouzakispan@gmail.com>
This reverts commit 96ea48ff5dcba46af350f5300eafd7f7394ba606.
The change may cause Verifier.cpp error
"musttail call must precede a ret with an optional bitcast"
Based ontop of D104598, which is a NFCI-ish refactoring.
Here, a restriction, that only empty blocks can be merged, is lifted.
Reviewed By: rnk
Differential Revision: https://reviews.llvm.org/D104597
And that exposes that a number of tests don't *actually* manage to
maintain DomTree validity, which is inline with my observations.
Once again, SimlifyCFG pass currently does not require/preserve DomTree
by default, so this is effectively NFC.
... so just ensure that we pass DomTreeUpdater it into it.
Fixes DomTree preservation for a large number of tests,
all of which are marked as such so that they do not regress.
SimplifyCFG's options should always be overridden by command line flags,
but they mistakenly weren't in the default constructor.
Reviewed By: ychen
Differential Revision: https://reviews.llvm.org/D87718
Common code sinking is already guarded with a (with default-off!) flag,
so add a flag for hoisting, too.
D84108 will hopefully make hoisting off-by-default too.
This is another step towards having FMF apply only to FP values
rather than those + fcmp. See PR38086 for one of the original
discussions/motivations:
https://bugs.llvm.org/show_bug.cgi?id=38086
And the test here is derived from PR39535:
https://bugs.llvm.org/show_bug.cgi?id=39535
Currently, we lose FMF when converting any phi to select in
SimplifyCFG. There are a small number of similar changes needed
to correct within SimplifyCFG, so it should be quick to patch
this pass up.
FMF was extended to select and phi with:
D61917
D67564
Differential Revision: https://reviews.llvm.org/D70208
As it's causing some bot failures (and per request from kbarton).
This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.
llvm-svn: 358546
