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Backport fixes for JumpThreading/assume bug #106

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@dotdash @alexcrichton @bmrzycki
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dotdash commented Feb 27, 2018

This fixes the original cause for rust-lang/rust#48116 which was worked around by removing an assume() intrinsic call. We could still hit the bug, as we're still using assume() intrinsics in other places.

bmrzycki added some commits Jan 12, 2018

@bmrzycki @dotdash
[JumpThreading] Preservation of DT and LVI across the pass 
Summary:
See D37528 for a previous (non-deferred) version of this
patch and its description.

Preserves dominance in a deferred manner using a new class
DeferredDominance. This reduces the performance impact of
updating the DominatorTree at every edge insertion and
deletion. A user may call DDT->flush() within JumpThreading
for an up-to-date DT. This patch currently has one flush()
at the end of runImpl() to ensure DT is preserved across
the pass.

LVI is also preserved to help subsequent passes such as
CorrelatedValuePropagation. LVI is simpler to maintain and
is done immediately (not deferred). The code to perform the
preversation was minimally altered and simply marked as
preserved for the PassManager to be informed.

This extends the analysis available to JumpThreading for
future enhancements such as threading across loop headers.

Reviewers: dberlin, kuhar, sebpop

Reviewed By: kuhar, sebpop

Subscribers: mgorny, dmgreen, kuba, rnk, rsmith, hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D40146



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@322401 91177308-0d34-0410-b5e6-96231b3b80d8
90f447e
@bmrzycki @dotdash
[JumpThreading] PR36133 enable/disable DominatorTree for LVI analysis 
Summary:
The LazyValueInfo pass caches a copy of the DominatorTree when available.
Whenever there are pending DominatorTree updates within JumpThreading's
DeferredDominance object we cannot use the cached DT for LVI analysis.
This commit adds the new methods enableDT() and disableDT() to LVI.
JumpThreading also sets the appropriate usage model before calling LVI
analysis methods.

Fixes https://bugs.llvm.org/show_bug.cgi?id=36133

Reviewers: sebpop, dberlin, kuhar

Reviewed by: sebpop, kuhar

Subscribers: uabelho, llvm-commits, aprantl, hiraditya, a.elovikov

Differential Revision: https://reviews.llvm.org/D42717



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@325356 91177308-0d34-0410-b5e6-96231b3b80d8
3dd7de0

@dotdash dotdash assigned alexcrichton Feb 27, 2018

@alexcrichton alexcrichton merged commit 5c6b7fe into rust-lang:rust-llvm-release-6-0-0 Feb 27, 2018

@glandium glandium referenced this pull request Jul 26, 2018

Closed

Miscompilation while working on PR #50882 #52694

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