diff options
author | Hans Wennborg <hans@hanshq.net> | 2018-08-13 08:28:30 +0000 |
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committer | Hans Wennborg <hans@hanshq.net> | 2018-08-13 08:28:30 +0000 |
commit | 18c17c4874875bbcfe587a0a65a6bb77e91bb92d (patch) | |
tree | 2a520309866eff032e7dc7f39e8bd4ad7989e6fd /lib/Analysis/MemorySSA.cpp | |
parent | b4d5f64917bf8edf52bcc52434b0752e1ca12994 (diff) |
Merging r339411:
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r339411 | gbiv | 2018-08-10 07:14:43 +0200 (Fri, 10 Aug 2018) | 17 lines
[MemorySSA] "Fix" lifetime intrinsic handling
MemorySSA currently creates MemoryAccesses for lifetime intrinsics, and
sometimes treats them as clobbers. This may/may not be the best way
forward, but while we're doing it, we should consider
MayAlias/PartialAlias to be clobbers.
The ideal fix here is probably to remove all of this reasoning about
lifetimes from MemorySSA + put it into the passes that need to care. But
that's a wayyy broader fix that needs some consensus, and we have
miscompiles + a release branch today, and this should solve the
miscompiles just as well.
differential revision is D43269. Landing without an explicit LGTM (and
without using the special please-autoclose-this syntax) so we can still
use that revision as a place to decide what the right fix here is.
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_70@339545 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Analysis/MemorySSA.cpp')
-rw-r--r-- | lib/Analysis/MemorySSA.cpp | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/lib/Analysis/MemorySSA.cpp b/lib/Analysis/MemorySSA.cpp index f57d490ce96..b38c0c4f143 100644 --- a/lib/Analysis/MemorySSA.cpp +++ b/lib/Analysis/MemorySSA.cpp @@ -258,13 +258,18 @@ static ClobberAlias instructionClobbersQuery(MemoryDef *MD, if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(DefInst)) { // These intrinsics will show up as affecting memory, but they are just - // markers. + // markers, mostly. + // + // FIXME: We probably don't actually want MemorySSA to model these at all + // (including creating MemoryAccesses for them): we just end up inventing + // clobbers where they don't really exist at all. Please see D43269 for + // context. switch (II->getIntrinsicID()) { case Intrinsic::lifetime_start: if (UseCS) return {false, NoAlias}; AR = AA.alias(MemoryLocation(II->getArgOperand(1)), UseLoc); - return {AR == MustAlias, AR}; + return {AR != NoAlias, AR}; case Intrinsic::lifetime_end: case Intrinsic::invariant_start: case Intrinsic::invariant_end: |