Commit Graph

8516 Commits

Author SHA1 Message Date
Sanjay Patel 63fa690617 [InstSimplify] update stale comment; NFC
Missed this diff with rL361118.

llvm-svn: 361180
2019-05-20 17:52:18 +00:00
Nick Desaulniers 639b29b1b5 [INLINER] allow inlining of blockaddresses if sole uses are callbrs
Summary:
It was supposed that Ref LazyCallGraph::Edge's were being inserted by
inlining, but that doesn't seem to be the case.  Instead, it seems that
there was no test for a blockaddress Constant in an instruction that
referenced the function that contained the instruction. Ex:

```
define void @f() {
  %1 = alloca i8*, align 8
2:
  store i8* blockaddress(@f, %2), i8** %1, align 8
  ret void
}
```

When iterating blockaddresses, do not add the function they refer to
back to the worklist if the blockaddress is referring to the contained
function (as opposed to an external function).

Because blockaddress has sligtly different semantics than GNU C's
address of labels, there are 3 cases that can occur with blockaddress,
where only 1 can happen in GNU C due to C's scoping rules:
* blockaddress is within the function it refers to (possible in GNU C).
* blockaddress is within a different function than the one it refers to
(not possible in GNU C).
* blockaddress is used in to declare a global (not possible in GNU C).

The second case is tested in:

```
$ ./llvm/build/unittests/Analysis/AnalysisTests \
  --gtest_filter=LazyCallGraphTest.HandleBlockAddress
```

This patch adjusts the iteration of blockaddresses in
LazyCallGraph::visitReferences to not revisit the blockaddresses
function in the first case.

The Linux kernel contains code that's not semantically valid at -O0;
specifically code passed to asm goto. It requires that asm goto be
inline-able. This patch conservatively does not attempt to handle the
more general case of inlining blockaddresses that have non-callbr users
(pr/39560).

https://bugs.llvm.org/show_bug.cgi?id=39560
https://bugs.llvm.org/show_bug.cgi?id=40722
https://github.com/ClangBuiltLinux/linux/issues/6
https://reviews.llvm.org/rL212077

Reviewers: jyknight, eli.friedman, chandlerc

Reviewed By: chandlerc

Subscribers: george.burgess.iv, nathanchance, mgorny, craig.topper, mengxu.gatech, void, mehdi_amini, E5ten, chandlerc, efriedma, eraman, hiraditya, haicheng, pirama, llvm-commits, srhines

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58260

llvm-svn: 361173
2019-05-20 16:48:09 +00:00
Cameron McInally 2d2a46db8e [InstSimplify] Teach fsub -0.0, (fneg X) ==> X about unary fneg
Differential Revision: https://reviews.llvm.org/D62077

llvm-svn: 361151
2019-05-20 13:13:35 +00:00
Sanjay Patel 9ef99b4b11 [InstSimplify] fold fcmp (maxnum, X, C1), C2
This is the sibling transform for rL360899 (D61691):

  maxnum(X, GreaterC) == C --> false
  maxnum(X, GreaterC) <= C --> false
  maxnum(X, GreaterC) <  C --> false
  maxnum(X, GreaterC) >= C --> true
  maxnum(X, GreaterC) >  C --> true
  maxnum(X, GreaterC) != C --> true

llvm-svn: 361118
2019-05-19 14:26:39 +00:00
Cameron McInally 067e946859 [InstSimplify] Add unary fneg to `fsub 0.0, (fneg X) ==> X` transform
Differential Revision: https://reviews.llvm.org/D62013

llvm-svn: 361047
2019-05-17 16:47:00 +00:00
Sanjay Patel 152f81fae8 [InstSimplify] fold fcmp (minnum, X, C1), C2
minnum(X, LesserC) == C --> false
   minnum(X, LesserC) >= C --> false
   minnum(X, LesserC) >  C --> false
   minnum(X, LesserC) != C --> true
   minnum(X, LesserC) <= C --> true
   minnum(X, LesserC) <  C --> true

maxnum siblings will follow if there are no problems here.

We should be able to perform some other combines when the constants
are equal or greater-than too, but that would go in instcombine.

We might also generalize this by creating an FP ConstantRange
(similar to what we do for integers).

Differential Revision: https://reviews.llvm.org/D61691

llvm-svn: 360899
2019-05-16 14:03:10 +00:00
Fangrui Song 3e92df3e39 Add Triple::isPPC64()
llvm-svn: 360864
2019-05-16 08:31:22 +00:00
Cameron McInally 0c82d9b5a2 Teach InstSimplify -X + X --> 0.0 about unary FNeg
Differential Revision: https://reviews.llvm.org/D61916

llvm-svn: 360777
2019-05-15 14:31:33 +00:00
Nikita Popov 48c4e4fa80 [LVI][CVP] Add support for abs/nabs select pattern flavor
Based on ConstantRange support added in D61084, we can now handle
abs and nabs select pattern flavors in LVI.

Differential Revision: https://reviews.llvm.org/D61794

llvm-svn: 360700
2019-05-14 18:53:47 +00:00
Kit Barton 37b7922daa Save the induction binary operator in IVDescriptors for non FP induction variables.
Summary:
Currently InductionBinOps are only saved for FP induction variables, the PR extends it with non FP induction variable, so user of IVDescriptors can query the InductionBinOps for integer induction variables.

The changes in hasUnsafeAlgebra() and getUnsafeAlgebraInst() are required for the existing LIT test cases to pass. As described in the comment of the two functions, one of the requirement to return true is it is a FP induction variable. The checks was not needed because InductionBinOp was not set on non FP cases before.

https://reviews.llvm.org/D60565 depends on the patch.

Committed on behalf of @Whitney (Whitney Tsang).

Reviewers: jdoerfert, kbarton, fhahn, hfinkel, dmgreen, Meinersbur

Reviewed By: jdoerfert

Subscribers: mgorny, hiraditya, jsji, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61329

llvm-svn: 360671
2019-05-14 13:26:36 +00:00
Teresa Johnson 37b80122bd [ThinLTO] Auto-hide prevailing linkonce_odr only when all copies eligible
Summary:
We hit undefined references building with ThinLTO when one source file
contained explicit instantiations of a template method (weak_odr) but
there were also implicit instantiations in another file (linkonce_odr),
and the latter was the prevailing copy. In this case the symbol was
marked hidden when the prevailing linkonce_odr copy was promoted to
weak_odr. It led to unsats when the resulting shared library was linked
with other code that contained a reference (expecting to be resolved due
to the explicit instantiation).

Add a CanAutoHide flag to the GV summary to allow the thin link to
identify when all copies are eligible for auto-hiding (because they were
all originally linkonce_odr global unnamed addr), and only do the
auto-hide in that case.

Most of the changes here are due to plumbing the new flag through the
bitcode and llvm assembly, and resulting test changes. I augmented the
existing auto-hide test to check for this situation.

Reviewers: pcc

Subscribers: mehdi_amini, inglorion, eraman, dexonsmith, arphaman, dang, llvm-commits, steven_wu, wmi

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59709

llvm-svn: 360466
2019-05-10 20:08:24 +00:00
Philip Reames 76ea748d2d Compile time tweak for libcall lookup
If we have a large module which is mostly intrinsics, we hammer the lib call lookup path from CodeGenPrepare.  Adding a fastpath reduces compile by 15% for one such example.

The problem is really more general than intrinsics - a module with lots of non-intrinsics non-libcall calls has the same problem - but we might as well avoid an easy case quickly.

llvm-svn: 360391
2019-05-09 23:13:09 +00:00
Warren Ristow d27b0c6247 [SCEV] Suppress hoisting insertion point of binops when unsafe
InsertBinop tries to move insertion-points out of loops for expressions
that are loop-invariant. This patch adds a new parameter, IsSafeToHost,
to guard that hoisting. This allows callers to suppress that hoisting
for unsafe situations, such as divisions that may have a zero
denominator.

This fixes PR38697.

Differential Revision: https://reviews.llvm.org/D55232

llvm-svn: 360280
2019-05-08 18:50:07 +00:00
Alina Sbirlea f31eba6494 [MemorySSA] Teach LoopSimplify to preserve MemorySSA.
Summary:
Preserve MemorySSA in LoopSimplify, in the old pass manager, if the analysis is available.
Do not preserve it in the new pass manager.
Update tests.

Subscribers: nemanjai, jlebar, javed.absar, Prazek, kbarton, zzheng, jsji, llvm-commits, george.burgess.iv, chandlerc

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60833

llvm-svn: 360270
2019-05-08 17:05:36 +00:00
Nikita Popov 9fd02a71a3 Revert "[ValueTracking] Improve isKnowNonZero for Ints"
This reverts commit 3b137a4956.

As reported in https://reviews.llvm.org/D60846, this is causing
miscompiles.

llvm-svn: 360260
2019-05-08 14:50:01 +00:00
Dan Robertson 3b137a4956 [ValueTracking] Improve isKnowNonZero for Ints
Improve isKnownNonZero for integers in order to improve cttz
optimizations.

Differential Revision: https://reviews.llvm.org/D60846

llvm-svn: 360222
2019-05-08 02:25:08 +00:00
Sanjay Patel e088d03b9c [ValueTracking] add logic for known-never-nan with minnum/maxnum
From the LangRef: "Returns NaN only if both operands are NaN."

llvm-svn: 360206
2019-05-07 22:58:31 +00:00
Keno Fischer a1a4adf4b9 [SCEV] Add explicit representations of umin/smin
Summary:
Currently we express umin as `~umax(~x, ~y)`. However, this becomes
a problem for operands in non-integral pointer spaces, because `~x`
is not something we can compute for `x` non-integral. However, since
comparisons are generally still allowed, we are actually able to
express `umin(x, y)` directly as long as we don't try to express is
as a umax. Support this by adding an explicit umin/smin representation
to SCEV. We do this by factoring the existing getUMax/getSMax functions
into a new function that does all four. The previous two functions were
largely identical.

Reviewed By: sanjoy
Differential Revision: https://reviews.llvm.org/D50167

llvm-svn: 360159
2019-05-07 15:28:47 +00:00
Cameron McInally c3167696bc Add FNeg support to InstructionSimplify
Differential Revision: https://reviews.llvm.org/D61573

llvm-svn: 360053
2019-05-06 16:05:10 +00:00
Cameron McInally 1d0c845d9d Add FNeg IR constant folding support
llvm-svn: 359982
2019-05-05 16:07:09 +00:00
Alina Sbirlea 0363c3b8bb [MemorySSA] Check that block is reachable when adding phis.
Summary:
Originally the insertDef method was only used when building MemorySSA, and was limiting the number of Phi nodes that it created.
Now it's used for updates as well, and it can create additional Phis needed for correctness.
Make sure no Phis are created in unreachable blocks (condition met during MSSA build), otherwise the renamePass will find a null DTNode.

Resolves PR41640.

Reviewers: george.burgess.iv

Subscribers: jlebar, Prazek, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61410

llvm-svn: 359845
2019-05-02 23:41:58 +00:00
Alina Sbirlea 151ab4844a [MemorySSA] Refactor removing multiple trivial phis [NFC].
Summary: Create a method to clean up multiple potentially trivial phis, since we will need this often.

Reviewers: george.burgess.iv

Subscribers: jlebar, Prazek, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61471

llvm-svn: 359842
2019-05-02 23:12:49 +00:00
Keno Fischer a3e4b3bd33 [SCEV] Use isKnownViaNonRecursiveReasoning for smax simplification
Summary:
Commit
	rL331949: SCEV] Do not use induction in isKnownPredicate for simplification umax

changed the codepath for umax from isKnownPredicate to
isKnownViaNonRecursiveReasoning to avoid compile time blow up (and as
I found out also stack overflows). However, there is an exact copy of
the code for umax that was lacking this change. In D50167 I want to unify
these codepaths, but to avoid that being a behavior change for the smax
case, pull this independent bit out of it.

Reviewed By: sanjoy
Differential Revision: https://reviews.llvm.org/D61166

llvm-svn: 359693
2019-05-01 15:58:24 +00:00
Keno Fischer d8f856d265 [LoopInfo] Faster implementation of setLoopID. NFC.
Summary:
This change was part of D46460. However, in the meantime rL341926 fixed the
correctness issue here. What remained was the performance issue in setLoopID
where it would iterate through all blocks in the loop and their successors,
rather than just the predecessor of the header (the later presumably being
much faster). We already have the `getLoopLatches` to compute precisely these
basic blocks in an efficient manner, so just use it (as the original commit
did for `getLoopID`).

Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D61215

llvm-svn: 359684
2019-05-01 14:39:11 +00:00
Alina Sbirlea b468320313 [MemorySSA] Invalidate MemorySSA if AA or DT are invalidated.
Summary:
MemorySSA keeps internal pointers of AA and DT.
If these get invalidated, so should MemorySSA.

Reviewers: george.burgess.iv, chandlerc

Subscribers: jlebar, Prazek, llvm-commits

Tags: LLVM

Differential Revision: https://reviews.llvm.org/D61043

llvm-svn: 359627
2019-04-30 22:43:55 +00:00
Alina Sbirlea ba48a2c5e8 [AliasAnalysis/NewPassManager] Invalidate AAManager less often.
Summary:
This is a redo of D60914.

The objective is to not invalidate AAManager, which is stateless, unless
there is an explicit invalidate in one of the AAResults.

To achieve this, this patch adds an API to PAC, to check precisely this:
is this analysis not invalidated explicitly == is this analysis not abandoned == is this analysis stateless, so preserved without explicitly being marked as preserved by everyone

Reviewers: chandlerc

Subscribers: mehdi_amini, jlebar, george.burgess.iv, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61284

llvm-svn: 359622
2019-04-30 22:15:47 +00:00
Fedor Sergeev eeae45dc77 [NFC][InlineCost] cleanup - comments, overflow handling.
Reviewed By: apilipenko
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D60751

llvm-svn: 359609
2019-04-30 20:44:53 +00:00
Simon Pilgrim f5e8f222d6 Revert rL359519 : [MemorySSA] Invalidate MemorySSA if AA or DT are invalidated.
Summary:
MemorySSA keeps internal pointers of AA and DT.
If these get invalidated, so should MemorySSA.

Reviewers: george.burgess.iv, chandlerc

Subscribers: jlebar, Prazek, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61043
........
This was causing windows build bot failures

llvm-svn: 359555
2019-04-30 12:34:21 +00:00
Sjoerd Meijer ea31ddb36f [ARM] Implement TTI::getMemcpyCost
This implements TargetTransformInfo method getMemcpyCost, which estimates the
number of instructions to which a memcpy instruction expands to.

Differential Revision: https://reviews.llvm.org/D59787

llvm-svn: 359547
2019-04-30 10:28:50 +00:00
Alina Sbirlea 9a1edd14a2 [MemorySSA] Invalidate MemorySSA if AA or DT are invalidated.
Summary:
MemorySSA keeps internal pointers of AA and DT.
If these get invalidated, so should MemorySSA.

Reviewers: george.burgess.iv, chandlerc

Subscribers: jlebar, Prazek, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61043

llvm-svn: 359519
2019-04-29 23:53:04 +00:00
Nikita Popov 7a94795b2b [ConstantRange] Add makeExactNoWrapRegion()
I got confused on the terminology, and the change in D60598 was not
correct. I was thinking of "exact" in terms of the result being
non-approximate. However, the relevant distinction here is whether
the result is

 * Largest range such that:
   Forall Y in Other: Forall X in Result: X BinOp Y does not wrap.
   (makeGuaranteedNoWrapRegion)
 * Smallest range such that:
   Forall Y in Other: Forall X not in Result: X BinOp Y wraps.
   (A hypothetical makeAllowedNoWrapRegion)
 * Both. (makeExactNoWrapRegion)

I'm adding a separate makeExactNoWrapRegion method accepting a
single APInt (same as makeExactICmpRegion) and using it in the
places where the guarantee is relevant.

Differential Revision: https://reviews.llvm.org/D60960

llvm-svn: 359402
2019-04-28 15:40:56 +00:00
Philip Reames 88cd69b56f Consolidate existing utilities for interpreting vector predicate maskes [NFC]
llvm-svn: 359163
2019-04-25 02:30:17 +00:00
Xinliang David Li 499c80b890 Add optional arg to profile count getters to filter
synthetic profile count.

Differential Revision: http://reviews.llvm.org/D61025

llvm-svn: 359131
2019-04-24 19:51:16 +00:00
Bjorn Pettersson 71e8c6f20f Add "const" in GetUnderlyingObjects. NFC
Summary:
Both the input Value pointer and the returned Value
pointers in GetUnderlyingObjects are now declared as
const.

It turned out that all current (in-tree) uses of
GetUnderlyingObjects were trivial to update, being
satisfied with have those Value pointers declared
as const. Actually, in the past several of the users
had to use const_cast, just because of ValueTracking
not providing a version of GetUnderlyingObjects with
"const" Value pointers. With this patch we get rid
of those const casts.

Reviewers: hfinkel, materi, jkorous

Reviewed By: jkorous

Subscribers: dexonsmith, jkorous, jholewinski, sdardis, eraman, hiraditya, jrtc27, atanasyan, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61038

llvm-svn: 359072
2019-04-24 06:55:50 +00:00
Alina Sbirlea b341efce31 Revert [AliasAnalysis] AAResults preserves AAManager.
Triggers use-after-free.

llvm-svn: 359055
2019-04-24 00:28:29 +00:00
Josh Stone 27924c3a3c [Lint] Permit aliasing noalias readonly arguments
Summary:
If two arguments are both readonly, then they have no memory dependency
that would violate noalias, even if they do actually overlap.

Reviewers: hfinkel, efriedma

Reviewed By: efriedma

Subscribers: efriedma, hiraditya, llvm-commits, tstellar

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60239

llvm-svn: 359047
2019-04-23 23:43:47 +00:00
Alina Sbirlea 4fd1f266b1 [MemorySSA] LCSSA preserves MemorySSA.
Summary:
Enabling MemorySSA in the old pass manager leads to MemorySSA being run
twice due to the fact that LCSSA and LoopSimplify do not preserve
MemorySSA. This is the first step to address that: target LCSSA.

LCSSA does not make any changes that invalidate MemorySSA, so it
preserves it by design. It must preserve AA as well, for this to hold.

After this patch, MemorySSA is still run twice in the old pass manager.
Step two follows: target LoopSimplify.

Subscribers: mehdi_amini, jlebar, Prazek, llvm-commits, george.burgess.iv, chandlerc

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60832

llvm-svn: 359032
2019-04-23 20:59:44 +00:00
Alina Sbirlea a809e8e5e7 [AliasAnalysis] AAResults preserves AAManager.
Summary:
AAResults should not invalidate AAManager.
Update tests.

Reviewers: chandlerc

Subscribers: mehdi_amini, jlebar, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60914

llvm-svn: 359014
2019-04-23 17:21:18 +00:00
Fangrui Song efd94c56ba Use llvm::stable_sort
While touching the code, simplify if feasible.

llvm-svn: 358996
2019-04-23 14:51:27 +00:00
Fedor Sergeev 652168a99b [CallSite removal] move InlineCost to CallBase usage
Converting InlineCost interface and its internals into CallBase usage.
Inliners themselves are still not converted.

Reviewed By: reames
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D60636

llvm-svn: 358982
2019-04-23 12:43:27 +00:00
Philip Reames d8d9b7b20e [InstSimplify] Move masked.gather w/no active lanes handling to InstSimplify from InstCombine
In the process, use the existing masked.load combine which is slightly stronger, and handles a mix of zero and undef elements in the mask.  

llvm-svn: 358913
2019-04-22 19:30:01 +00:00
Nikita Popov 5aacc7a573 Revert "[ConstantRange] Rename make{Guaranteed -> Exact}NoWrapRegion() NFC"
This reverts commit 7bf4d7c07f2fac862ef34c82ad0fef6513452445.

After thinking about this more, this isn't right, the range is not exact
in the same sense as makeExactICmpRegion(). This needs a separate
function.

llvm-svn: 358876
2019-04-22 09:01:38 +00:00
Nikita Popov 5299e25f50 [ConstantRange] Rename make{Guaranteed -> Exact}NoWrapRegion() NFC
Following D60632 makeGuaranteedNoWrapRegion() always returns an
exact nowrap region. Rename the function accordingly. This is in
line with the naming of makeExactICmpRegion().

llvm-svn: 358875
2019-04-22 08:36:05 +00:00
Nikita Popov dbc3fbafe7 [ConstantRange] Add getNonEmpty() constructor
ConstantRanges have an annoying special case: If upper and lower are
the same, it can be either an empty or a full set. When constructing
constant ranges nearly always a full set is intended, but this still
requires an explicit check in many places.

This revision adds a getNonEmpty() constructor that disambiguates this
case: If upper and lower are the same, a full set is created.

Differential Revision: https://reviews.llvm.org/D60947

llvm-svn: 358854
2019-04-21 15:22:54 +00:00
Chandler Carruth ce3f75df1f [CallSite removal] Move the legacy PM, call graph, and some inliner
code to `CallBase`.

This patch focuses on the legacy PM, call graph, and some of inliner and legacy
passes interacting with those APIs from `CallSite` to the new `CallBase` class.
No interesting changes.

Differential Revision: https://reviews.llvm.org/D60412

llvm-svn: 358739
2019-04-19 05:59:42 +00:00
Nicolai Haehnle 523f90a2ba [SDA] Bug fix: Use IPD outside the loop as divergence bound
Summary:
The immediate post dominator of the loop header may be part of the divergent loop.
Since this /was/ the divergence propagation bound the SDA would not detect joins of divergent paths outside the loop.

Reviewers: nhaehnle

Reviewed By: nhaehnle

Subscribers: mmasten, arsenm, jvesely, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59042

llvm-svn: 358681
2019-04-18 16:17:35 +00:00
Philip Reames b2c9fc02d5 Fix a bug in SCEV's isSafeToExpand around speculation safety
isSafeToExpand was making a common, but dangerously wrong, mistake in assuming that if any instruction within a basic block executes, that all instructions within that block must execute.  This can be trivially shown to be false by considering the following small example:
bb:
  add x, y  <-- InsertionPoint
  call @throws()
  udiv x, y <-- SCEV* S
  br ...

It's clearly not legal to expand S above the throwing call, but the previous logic would do so since S dominates (but not properlyDominates) the block containing the InsertionPoint.

Since iterating instructions w/in a block is expensive, this change special cases two cases: 1) S is an operand of InsertionPoint, and 2) InsertionPoint is the terminator of it's block.  These two together are enough to keep all current optimizations triggering while fixing the latent correctness issue.

As best I can tell, this is a silent bug in current ToT.  Given that, there's no tests with this change.  It was noticed in an upcoming optimization change (D60093), and was reviewed as part of that.  That change will include the test which caused me to notice the issue.  I'm submitting this seperately so that anyone bisecting a problem gets a clear explanation.

llvm-svn: 358680
2019-04-18 16:10:21 +00:00
Nikita Popov 2039581002 [LVI][CVP] Constrain values in with.overflow branches
If a branch is conditional on extractvalue(op.with.overflow(%x, C), 1)
then we can constrain the value of %x inside the branch based on
makeGuaranteedNoWrapRegion(). We do this by extending the edge-value
handling in LVI. This allows CVP to then fold comparisons against %x,
as illustrated in the tests.

Differential Revision: https://reviews.llvm.org/D60650

llvm-svn: 358597
2019-04-17 16:57:42 +00:00
Nikita Popov 79dffc67b5 [IR] Add WithOverflowInst class
This adds a WithOverflowInst class with a few helper methods to get
the underlying binop, signedness and nowrap type and makes use of it
where sensible. There will be two more uses in D60650/D60656.

The refactorings are all NFC, though I left some TODOs where things
could be improved. In particular we have two places where add/sub are
handled but mul isn't.

Differential Revision: https://reviews.llvm.org/D60668

llvm-svn: 358512
2019-04-16 18:55:16 +00:00
Alina Sbirlea f9f073a861 [MemorySSA] Add previous def to cache when found, even if trivial.
Summary:
When inserting a new Def, MemorySSA may be have non-minimal number of Phis.
While inserting, the walk to find the previous definition may cleanup minimal Phis.
When the last definition is trivial to obtain, we do not cache it.

It is possible while getting the previous definition for a Def to get two different answers:
- one that was straight-forward to find when walking the first path (a trivial phi in this case), and
- another that follows a cleanup of the trivial phi, it determines it may need additional Phi nodes, it inserts them and returns a new phi in the same position as the former trivial one.
While the Phis added for the second path are all redundant, they are not complete (the walk is only done upwards), and they are not properly cleaned up afterwards.

A way to fix this problem is to cache the straight-forward answer we got on the first walk.
The caching is only kept for the duration of a getPreviousDef call, and for Phis we use TrackingVH, so removing the trivial phi will lead to replacing it with the next dominating phi in the cache.
Resolves PR40749.

Reviewers: george.burgess.iv

Subscribers: jlebar, Prazek, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60634

llvm-svn: 358313
2019-04-12 21:58:52 +00:00