This adjusts mayHaveSideEffect() to return true for !willReturn()
instructions. Just like other side-effects, non-willreturn calls
(aka "divergence") cannot be removed and cannot be reordered relative
to other side effects. This fixes a number of bugs where
non-willreturn calls are either incorrectly dropped or moved. In
particular, it also fixes the last open problem in
https://bugs.llvm.org/show_bug.cgi?id=50511.
I performed a cursory review of all current mayHaveSideEffect()
uses, which convinced me that these are indeed the desired default
semantics. Places that do not want to consider non-willreturn as a
sideeffect generally do not want mayHaveSideEffect() semantics at
all. I identified two such cases, which are addressed by D106591
and D106742. Finally, there is a use in SCEV for which we don't
really have an appropriate API right now -- what it wants is
basically "would this be considered forward progress". I've just
spelled out the previous semantics there.
Differential Revision: https://reviews.llvm.org/D106749
... 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.
From C11 and C++11 onwards, a forward-progress requirement has been
introduced for both languages. In the case of C, loops with non-constant
conditionals that do not have any observable side-effects (as defined by
6.8.5p6) can be assumed by the implementation to terminate, and in the
case of C++, this assumption extends to all functions. The clang
frontend will emit the `mustprogress` function attribute for C++
functions (D86233, D85393, D86841) and emit the loop metadata
`llvm.loop.mustprogress` for every loop in C11 or later that has a
non-constant conditional.
This patch modifies LoopDeletion so that only loops with
the `llvm.loop.mustprogress` metadata or loops contained in functions
that are required to make progress (`mustprogress` or `willreturn`) are
checked for observable side-effects. If these loops do not have an
observable side-effect, then we delete them.
Loops without observable side-effects that do not satisfy the above
conditions will not be deleted.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D86844
As it's causing some bot failures (and per request from kbarton).
This reverts commit r358543/ab70da07286e618016e78247e4a24fcb84077fda.
llvm-svn: 358546
I'm not sure if the `!isa<CallInst>(Inst) &&
!isa<TerminatorInst>(Inst))` bit is correct either, but this fixes the
case we know is broken.
llvm-svn: 279647
Upgrade to use new Tcl exec based test harness. This exposes 3 bugs that
were previously not being reported:
test/Transforms/GlobalDCE/2002-08-17-FunctionDGE.ll
test/Transforms/GlobalOpt/memset.ll
test/Transforms/IndVarsSimplify/exit_value_tests.llx
llvm-svn: 36065
Nikita Popov