Commit Graph

316 Commits

Author SHA1 Message Date
Hal Finkel cb9f78e1c3 Make processing @llvm.assume more efficient by using operand bundles
There was an efficiency problem with how we processed @llvm.assume in
ValueTracking (and other places). The AssumptionCache tracked all of the
assumptions in a given function. In order to find assumptions relevant to
computing known bits, etc. we searched every assumption in the function. For
ValueTracking, that means that we did O(#assumes * #values) work in InstCombine
and other passes (with a constant factor that can be quite large because we'd
repeat this search at every level of recursion of the analysis).

Several of us discussed this situation at the last developers' meeting, and
this implements the discussed solution: Make the values that an assume might
affect operands of the assume itself. To avoid exposing this detail to
frontends and passes that need not worry about it, I've used the new
operand-bundle feature to add these extra call "operands" in a way that does
not affect the intrinsic's signature. I think this solution is relatively
clean. InstCombine adds these extra operands based on what ValueTracking, LVI,
etc. will need and then those passes need only search the users of the values
under consideration. This should fix the computational-complexity problem.

At this point, no passes depend on the AssumptionCache, and so I'll remove
that as a follow-up change.

Differential Revision: https://reviews.llvm.org/D27259

llvm-svn: 289755
2016-12-15 02:53:42 +00:00
Sanjay Patel 81ed3499cd [Constants] don't die processing non-ConstantInt GEP indices in isGEPWithNoNotionalOverIndexing() (PR31262)
This should fix:
https://llvm.org/bugs/show_bug.cgi?id=31262

llvm-svn: 289401
2016-12-11 20:07:02 +00:00
Zia Ansari 394cef803a [InstSimplify] Add "X / 1.0" to SimplifyFDivInst.
Differential Revision: https://reviews.llvm.org/D27587

llvm-svn: 289153
2016-12-08 23:27:40 +00:00
Sanjay Patel 2580c95dc1 [InstSimplify] add fdiv x/1.0 test and update checks; NFC
llvm-svn: 289098
2016-12-08 20:23:56 +00:00
Sanjay Patel 5369775a84 [InstSimplify] fixed (?) to not mutate icmps
As Eli noted in the post-commit thread for r288833, the use of
swapOperands() may not be allowed in InstSimplify, so I'm 
removing those calls here pending further review. 

The swap mutates the icmp, and there doesn't appear to be precedent
for instruction mutation in InstSimplify.

I didn't actually have any tests for those cases, so I'm adding
a few here. 

llvm-svn: 288855
2016-12-06 22:09:52 +00:00
Sanjay Patel 9b1b2de348 [InstSimplify] add folds for and-of-icmps with same operands
All of these (and a few more) are already handled by InstCombine,
but we shouldn't have to wait until then to simplify these because
they're cheap to deal with here in InstSimplify.

This is the 'and' sibling of the earlier 'or' patch:
https://reviews.llvm.org/rL288833

llvm-svn: 288841
2016-12-06 19:05:46 +00:00
Sanjay Patel 827414876f [InstSimplify] add tests for and-of-icmps; NFC
llvm-svn: 288837
2016-12-06 18:46:54 +00:00
Sanjay Patel d0ccdb46b9 [InstSimplify] add folds for or-of-icmps with same operands
All of these (and a few more) are already handled by InstCombine,
but we shouldn't have to wait until then to simplify these because
they're cheap to deal with here in InstSimplify.

llvm-svn: 288833
2016-12-06 18:09:37 +00:00
Sanjay Patel 6d4444f931 [InstSimplify] add tests for or-of-icmps; NFC
llvm-svn: 288830
2016-12-06 17:49:10 +00:00
Sanjoy Das 01969218a4 Simplify `x >=u x >> y` and `x >=u x udiv y`
Summary:
Extends InstSimplify to handle both `x >=u x >> y` and `x >=u x udiv y`.

This is a folloup of rL258422 and
https://github.com/rust-lang/rust/pull/30917 where llvm failed to
optimize away the bounds checking in a binary search.

Patch by Arthur Silva!

Reviewers: sanjoy

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D25941

llvm-svn: 285228
2016-10-26 19:18:43 +00:00
Sanjay Patel efd8885772 [InstSimplify] fold negation of sign-bit
0 - X --> X, if X is 0 or the minimum signed value
0 - X --> 0, if X is 0 or the minimum signed value and the sub is NSW

I noticed this pattern might be created in the backend after the change from D25485, 
so we'll want to add a similar fold for the DAG.

The use of computeKnownBits in InstSimplify may be something to investigate if the
compile time of InstSimplify is noticeable. We could replace computeKnownBits with 
specific pattern matchers or limit the recursion.

Differential Revision: https://reviews.llvm.org/D25785

llvm-svn: 284649
2016-10-19 21:23:45 +00:00
Sanjay Patel cf26c27478 [InstSimplify] move one and add more tests for potential negation folds
llvm-svn: 284627
2016-10-19 18:42:12 +00:00
Sanjay Patel 220a8730fb [InstSimplify] allow or-of-icmps folds with vector splat constants
llvm-svn: 282592
2016-09-28 14:27:21 +00:00
Sanjay Patel a8f9e57c74 [InstSimplify] add vector splat tests for or-of-icmps
llvm-svn: 282591
2016-09-28 14:17:35 +00:00
Sanjay Patel 1b312ad42d [InstSimplify] allow and-of-icmps folds with vector splat constants
llvm-svn: 282590
2016-09-28 13:53:13 +00:00
Andrea Di Biagio 7277afeec1 [ConstantFold] Improve the bitcast folding logic for constant vectors.
The constant folder didn't know how to always fold bitcasts of constant integer
vectors. In particular, it was unable to handle the case where a constant vector
had some undef elements, and the resulting (i.e. bitcasted) vector type had more
elements than the original vector type.

Example:
  %cast = bitcast <2 x i64><i64 undef, i64 2> to <4 x i32>

On a little endian target, %cast could have been folded to:
  <4 x i32><i32 undef, i32 undef, i32 2, i32 0>

This patch improves the folding logic by teaching how to correctly propagate
undef elements in the folded vector.

Differential Revision: https://reviews.llvm.org/D24301

llvm-svn: 281343
2016-09-13 14:50:47 +00:00
Andrea Di Biagio 3647a96a44 [InstSimplify] Add tests to show missed bitcast folding opportunities.
InstSimplify doesn't always know how to fold a bitcast of a constant vector.
In particular, the logic in InstSimplify doesn't know how to handle the case
where the constant vector in input contains some undef elements, and the
number of elements is smaller than the number of elements of the bitcast
vector type.

llvm-svn: 281332
2016-09-13 13:17:42 +00:00
Dehao Chen ebb715b119 Add unittest for r280760
llvm-svn: 280963
2016-09-08 16:53:40 +00:00
Andrea Di Biagio bdd576dbb0 Regenerate vector bitcast folding tests using update_test_checks.py.
Two tests have been merged together, regenerated and then moved to
a more appropriate directory. No functional change.

llvm-svn: 280814
2016-09-07 14:50:07 +00:00
Andrea Di Biagio 805815f407 [instsimplify] Fix incorrect folding of an ordered fcmp with a vector of all NaN.
This patch fixes a crash caused by an incorrect folding of an ordered comparison
between a packed floating point vector and a splat vector of NaN.

An ordered comparison between a vector and a constant vector of NaN, should
always be folded into a constant vector where each element is i1 false.

Since revision 266175, SimplifyFCmpInst folds the ordered fcmp into a scalar
'false'. Later on, this would cause an assertion failure, since the value type
of the folded value doesn't match the expected value type of the uses of the
original instruction: "Assertion failed: New->getType() == getType() &&
"replaceAllUses of value with new value of different type!".

This patch fixes the issue and adds a test case to the already existing test
InstSimplify/floating-point-compares.ll.

Differential Revision: https://reviews.llvm.org/D24143

llvm-svn: 280488
2016-09-02 14:47:43 +00:00
Sanjay Patel b37145712e [InstCombine] replace divide-by-constant checks with asserts; NFC
These folds already have tests for scalar and vector types, except 
for the vector div-by-0 case, so I'm adding tests for that.

llvm-svn: 280115
2016-08-30 17:31:34 +00:00
Sanjay Patel 6946e2ade3 [InstSimplify] allow icmp with constant folds for splat vectors, part 2
Completes the m_APInt changes for simplifyICmpWithConstant().

Other commits in this series:
https://reviews.llvm.org/rL279492
https://reviews.llvm.org/rL279530
https://reviews.llvm.org/rL279534
https://reviews.llvm.org/rL279538

llvm-svn: 279543
2016-08-23 18:00:51 +00:00
Sanjay Patel 200e3cbfb0 [InstSimplify] allow icmp with constant folds for splat vectors, part 1
llvm-svn: 279538
2016-08-23 17:30:56 +00:00
Sanjay Patel ada2bb3d5d [InstSimplify] add tests to show missing vector icmp folds
llvm-svn: 279534
2016-08-23 17:13:38 +00:00
Sanjay Patel 5c269d0b7a [InstSimplify] move icmp with constant tests to another file; NFC
...because like the corresponding code, this is just too big to keep adding to.
And the next step is to add a vector version of each of these tests to show
missed folds.

Also, auto-generate CHECK lines and add comments for the tests that correspond to
the source code.

llvm-svn: 279530
2016-08-23 16:46:53 +00:00
David Majnemer 5c5df6283a [InstSimplify] Fold gep (gep V, C), (xor V, -1) to C-1
llvm-svn: 278779
2016-08-16 06:13:46 +00:00
David Majnemer d150137f64 [InstSimplify] Fold gep (gep V, C), (sub 0, V) to C
llvm-svn: 277952
2016-08-07 07:58:12 +00:00
David Majnemer dc8767a49a [InstSimplify] Try hard to simplify pointer comparisons
Simplify ptrtoint comparisons involving operands with different source
types.

llvm-svn: 277951
2016-08-07 07:58:10 +00:00
Sanjay Patel 80f2eec4b2 remove FIXME comments (fixed with r277738)
llvm-svn: 277744
2016-08-04 18:14:02 +00:00
Sanjay Patel bcaf6f39dd [InstCombine] use m_APInt to allow icmp eq (op X, Y), C folds for splat constant vectors
I'm removing a misplaced pair of more specific folds from InstCombine in this patch as well,
so we know where those folds are happening in InstSimplify.

llvm-svn: 277738
2016-08-04 17:48:04 +00:00
Sanjay Patel bf82f44e7b add tests for missing vector folds
llvm-svn: 277736
2016-08-04 16:48:30 +00:00
David Majnemer 57b94c8d6a [ConstantFolding] Use ConstantExpr::getWithOperands
ConstantExpr::getWithOperands does much of the hard work that
ConstantFoldInstOperandsImpl tries to do but more completely.

This lets us fold ExtractValue/InsertValue expressions.

llvm-svn: 277100
2016-07-29 03:27:31 +00:00
David Majnemer 19d024b2fd [ConstantFolding] Don't bail on folding if ConstantFoldConstantExpression fails
When folding an expression, we run ConstantFoldConstantExpression on
each operand of that expression.
However, ConstantFoldConstantExpression can fail and retur nullptr.

Previously, we would bail on further refining the expression.
Instead, use the original operand and see if we can refine a later
operand.

llvm-svn: 276959
2016-07-28 06:39:48 +00:00
David Majnemer bc36b15253 [ConstantFolding] Correctly handle failures in ConstantFoldConstantExpressionImpl
Failures in ConstantFoldConstantExpressionImpl were ignored causing
crashes down the line.

This fixes PR28725.

llvm-svn: 276827
2016-07-27 02:39:16 +00:00
David Majnemer a90a621d1e Reapply: [InstSimplify] Add support for bitcasts"
This reverts commit r276700 and reapplies r276698.
The relevant clang tests have been updated.

llvm-svn: 276727
2016-07-26 05:52:29 +00:00
David Majnemer 6e06b577cc Revert "[InstSimplify] Add support for bitcasts"
This reverts commit r276698.  Clang has tests which rely on the
optimizer :(

llvm-svn: 276700
2016-07-25 22:24:59 +00:00
David Majnemer 62611fd3f7 [InstSimplify] Add support for bitcasts
BitCasts of BitCasts can be folded away as can BitCasts which don't
change the type of the operand.

llvm-svn: 276698
2016-07-25 22:04:58 +00:00
Sanjay Patel e9fc79bb13 [InstSimplify] don't crash handling a pointer or aggregate type
llvm-svn: 276345
2016-07-21 21:56:00 +00:00
Sanjay Patel a3bfb4e313 [InstSimplify] recognize trunc + icmp sgt/slt variants of select simplifications (PR28466)
rL245171 exposed a hole in InstSimplify that manifested in a strange way in PR28466:
https://llvm.org/bugs/show_bug.cgi?id=28466

It's possible to use trunc + icmp sgt/slt in place of an and + icmp eq/ne, so we need to
recognize that pattern to eliminate selects that are choosing between some value and some
bitmasked version of that value.

Note that there is significant room for improvement (refactoring) and enhancement (more
patterns, possibly in InstCombine rather than here).

Differential Revision: https://reviews.llvm.org/D22537

llvm-svn: 276341
2016-07-21 21:26:45 +00:00
Sanjay Patel 9eec550a2b add vector tests and a simpler version of the negative tests
llvm-svn: 276328
2016-07-21 20:11:08 +00:00
Sanjay Patel 5f3c70307d [InstSimplify][InstCombine] don't crash when folding vector selects of icmp
Differential Revision: https://reviews.llvm.org/D22602

llvm-svn: 276209
2016-07-20 23:40:01 +00:00
Sanjay Patel 47c04f9543 add even more missing tests for simplifySelectBitTest()
llvm-svn: 276024
2016-07-19 20:47:00 +00:00
Sanjay Patel 8b76ebe5b8 add tests related to PR28466
llvm-svn: 275995
2016-07-19 17:07:35 +00:00
Sanjay Patel d2ff6d727f add missing test for simplifySelectBitTest()
llvm-svn: 275990
2016-07-19 16:49:55 +00:00
Sanjay Patel 8a2bf3099f auto-generate checks
llvm-svn: 275899
2016-07-18 20:06:51 +00:00
David Majnemer 17a95aaa7b Simplify llvm.masked.load w/ undef masks
We can always pick the passthru value if the mask is undef: we are
permitted to treat the mask as-if it were filled with zeros.

llvm-svn: 275379
2016-07-14 06:58:37 +00:00
David Majnemer 7f781aba97 [ConstantFolding] Fold masked loads
We can constant fold a masked load if the operands are appropriately
constant.

Differential Revision: http://reviews.llvm.org/D22324

llvm-svn: 275352
2016-07-14 00:29:50 +00:00
David Majnemer f89660aba7 [ConstantFolding] Extend FoldReinterpretLoadFromConstPtr to handle negative offsets
Treat loads which clip before the start of a global initializer the same
way we treat clipping beyond the end of the initializer: use zeros.

llvm-svn: 275345
2016-07-13 23:33:07 +00:00
Hal Finkel 2cac58f604 Pointer-comparison folding should look through returned-argument functions
For functions which are known to return a specific argument, pointer-comparison
folding can look through the function calls as part of its analysis.

Differential Revision: http://reviews.llvm.org/D9387

llvm-svn: 275039
2016-07-11 03:37:59 +00:00
Davide Italiano 16284df8ec [PM] Port InstSimplify to the new pass manager.
llvm-svn: 274796
2016-07-07 21:14:36 +00:00
David Majnemer bb53d23ef8 [InstSimplify] Replace calls to null with undef
Calling null is undefined behavior, we can simplify the resulting value
to undef.

llvm-svn: 273777
2016-06-25 07:37:30 +00:00
Sanjay Patel a06d989552 [ValueTracking] improve ComputeNumSignBits for vector constants
This is similar to the computeKnownBits improvement in rL268479. 
There's probably more we can do for vector logic instructions, but 
this should let us see non-splat constant masking ops that can
become vector selects instead of and/andn/or sequences.

Differential Revision: http://reviews.llvm.org/D21610

llvm-svn: 273459
2016-06-22 19:20:59 +00:00
Sanjay Patel c6cacd6067 [InstSimplify] add ashr tests including vector types
llvm-svn: 273421
2016-06-22 14:18:04 +00:00
Sanjay Patel 21579bb39a [InstSimplify] regenerate checks
llvm-svn: 273419
2016-06-22 14:00:16 +00:00
Sanjay Patel 9ad8fb68f7 [InstSimplify] analyze (optionally casted) icmps to eliminate obviously false logic (PR27869)
By moving this transform to InstSimplify from InstCombine, we sidestep the problem/question
raised by PR27869:
https://llvm.org/bugs/show_bug.cgi?id=27869
...where InstCombine turns an icmp+zext into a shift causing us to miss the fold.

Credit to David Majnemer for a draft patch of the changes to InstructionSimplify.cpp.

Differential Revision: http://reviews.llvm.org/D21512

llvm-svn: 273200
2016-06-20 20:59:59 +00:00
Sanjay Patel a4b052c7d1 [InstSimplify] add tests for PR27689; regenerate checks
llvm-svn: 273128
2016-06-19 21:40:12 +00:00
Sanjay Patel 23019d1006 [ValueTracking, InstSimplify] extend isKnownNonZero() to handle vector constants
Similar in spirit to D20497 :
If all elements of a constant vector are known non-zero, then we can say that the
whole vector is known non-zero.

It seems like we could extend this to FP scalar/vector too, but isKnownNonZero()
says it only works for integers and pointers for now.

Differential Revision: http://reviews.llvm.org/D20544

llvm-svn: 270562
2016-05-24 14:18:49 +00:00
Sanjay Patel adcaef7238 [InstSimplify] add vector tests for isKnownNonZero
llvm-svn: 270498
2016-05-23 22:09:04 +00:00
Elena Demikhovsky ee004bc0a2 Vector GEP - fixed a crash on InstSimplify Pass.
Vector GEP with mixed (vector and scalar) indices failed on the InstSimplify Pass when all indices are constants.

Differential revision http://reviews.llvm.org/D20149

llvm-svn: 269590
2016-05-15 12:30:25 +00:00
Sanjay Patel 6786bc5390 [InstSimplify] use computeKnownBits on shift amount operands
Do simplifications common to all shift instructions based on the amount shifted:
1. If the shift amount is known larger than the bitwidth, the result is undefined.
2. If the valid bits of the shift amount are all known to be 0, it's a shift by zero, so the shift operand is the result.

Note that we could generalize the shift-by-zero transform into a shift-by-constant if all of the valid bits in the shift
amount are known, but that would have to be done in InstCombine rather than here because it would mean we need to create
a new shift instruction.

Differential Revision: http://reviews.llvm.org/D19874

llvm-svn: 269114
2016-05-10 20:46:54 +00:00
Peter Collingbourne 7dd8dbf486 Introduce llvm.load.relative intrinsic.
This intrinsic takes two arguments, ``%ptr`` and ``%offset``. It loads
a 32-bit value from the address ``%ptr + %offset``, adds ``%ptr`` to that
value and returns it. The constant folder specifically recognizes the form of
this intrinsic and the constant initializers it may load from; if a loaded
constant initializer is known to have the form ``i32 trunc(x - %ptr)``,
the intrinsic call is folded to ``x``.

LLVM provides that the calculation of such a constant initializer will
not overflow at link time under the medium code model if ``x`` is an
``unnamed_addr`` function. However, it does not provide this guarantee for
a constant initializer folded into a function body. This intrinsic can be
used to avoid the possibility of overflows when loading from such a constant.

Differential Revision: http://reviews.llvm.org/D18367

llvm-svn: 267223
2016-04-22 21:18:02 +00:00
Nick Lewycky 762f8a8549 Add optimization for 'icmp slt (or A, B), A' and some related idioms based on knowledge of the sign bit for A and B.
No matter what value you OR in to A, the result of (or A, B) is going to be UGE A. When A and B are positive, it's SGE too. If A is negative, OR'ing a value into it can't make it positive, but can increase its value closer to -1, therefore (or A, B) is SGE A. Working through all possible combinations produces this truth table:

```
A is
+, -, +/-
F  F   F   +    B is
T  F   ?   -
?  F   ?   +/-
```

The related optimizations are flipping the 'slt' for 'sge' which always NOTs the result (if the result is known), and swapping the LHS and RHS while swapping the comparison predicate.

There are more idioms left to implement (aren't there always!) but I've stopped here because any more would risk becoming unreasonable for reviewers.

llvm-svn: 266939
2016-04-21 00:53:14 +00:00
Chad Rosier e30fed70e6 [ValueTracking] Correct lit test comments. NFC.
llvm-svn: 266657
2016-04-18 19:11:45 +00:00
Sanjay Patel 69632447b1 [InstSimplify] regenerate checks using a script
I didn't notice any significant changes in the actual checks here;
all of these tests already used FileCheck, so a script can batch
update them in one shot.

This commit is just to show the value of automating this process: 
We have uniform formatting as opposed to a mish-mash of check
structure that changes based on individual prefs and the current
fashion. This makes it simpler to update when we find a bug or
make an enhancement.

llvm-svn: 264457
2016-03-25 20:12:25 +00:00
Benjamin Kramer 6bb15021b3 [InstSimplify] Restore fsub 0.0, (fsub 0.0, X) ==> X optzn
I accidentally removed this in r262212 but there was no test coverage to
detect it.

llvm-svn: 262215
2016-02-29 12:18:25 +00:00
Benjamin Kramer f5b2a47ac6 [InstSimplify] fsub 0.0, (fsub -0.0, X) ==> X is only safe if signed zeros are ignored.
Only allow fsub -0.0, (fsub -0.0, X) ==> X without nsz. PR26746.

llvm-svn: 262212
2016-02-29 11:12:23 +00:00
Justin Bogner 08154bf3d2 IR: Make the X / undef -> undef fold match the comment
The constant folding for sdiv and udiv has a big discrepancy between the
comments and the code, which looks like a typo. Currently, we're folding
X / undef pretty inconsistently:

  0 / undef -> undef
  C / undef -> 0
  undef / undef -> 0

Whereas the comments state we do X / undef -> undef. The logic that
returns zero is actually commented as doing undef / X -> 0, despite that
the LHS isn't undef in many of the cases that hit it.

llvm-svn: 261813
2016-02-25 01:02:18 +00:00
Jun Bum Lim cd197cfb60 Add a test case to show isKnownNonZero() returns correctly; NFC
Summary:
Added a test case just to make sure that isKnownNonZero() returns false
when we cannot guarantee that a ConstantExpr is a non-zero constant.

Reviewers: sanjoy, majnemer, mcrosier, nlewycky

Subscribers: nlewycky, mssimpso, mcrosier, llvm-commits

Differential Revision: http://reviews.llvm.org/D16908

llvm-svn: 260544
2016-02-11 17:11:49 +00:00
David Majnemer 3af5bf30e3 [InstCombine] Simplify (x >> y) <= x
This commit extends the patterns recognised by InstSimplify to also handle (x >> y) <= x in the same way as (x /u y) <= x.

The missing optimisation was found investigating why LLVM did not optimise away bound checks in a binary search: https://github.com/rust-lang/rust/pull/30917

Patch by Andrea Canciani!

Differential Revision: http://reviews.llvm.org/D16402

llvm-svn: 258422
2016-01-21 18:55:54 +00:00
Fiona Glaser db7824f0c1 CannotBeOrderedLessThanZero: add some missing cases
llvm-svn: 257542
2016-01-12 23:37:30 +00:00
Philip Reames 2466719e44 [MemoryBuiltins] Remove isOperatorNewLike by consolidating non-null inference handling
This patch removes the isOperatorNewLike predicate since it was only being used to establish a non-null return value and we have attributes specifically for that purpose with generic handling. To keep approximate the same behaviour for existing frontends, I added the various operator new like (i.e. instances of operator new) to InferFunctionAttrs. It's not really clear to me why this isn't handled in Clang, but I didn't want to break existing code and any subtle assumptions it might have.

Once this patch is in, I'm going to start separating the isAllocLike family of predicates. These appear to be being used for a mixture of things which should be more clearly separated and documented. Today, they're being used to indicate (at least) aliasing facts, CSE-ability, and default values from an allocation site.

Differential Revision: http://reviews.llvm.org/D15820

llvm-svn: 256787
2016-01-04 22:49:23 +00:00
Sanjoy Das 925681053d [ValueTracking] Teach isImpliedCondition a new bitwise trick
Summary:
This change teaches isImpliedCondition to prove things like

  (A | 15) < L  ==>  (A | 14) < L

if the low 4 bits of A are known to be zero.

Depends on D14391

Reviewers: majnemer, reames, hfinkel

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D14392

llvm-svn: 252673
2015-11-10 23:56:20 +00:00
Philip Reames 2d858747df [ValueTracking] Recognize that and(x, add (x, -1)) clears the low bit
This is a cleaned up version of a patch by John Regehr with permission. Originally found via the souper tool.

If we add an odd number to x, then bitwise-and the result with x, we know that the low bit of the result must be zero. Either it was zero in x originally, or the add cleared it in the temporary value. As a result, one of the two values anded together must have the bit cleared.

Differential Revision: http://reviews.llvm.org/D14315

llvm-svn: 252629
2015-11-10 18:46:14 +00:00
Sanjoy Das c01b4d2b28 [ValueTracking] De-pessimize isImpliedCondition around unsigned compares
Summary:
Currently `isImpliedCondition` will optimize "I +_nuw C < L ==> I < L"
only if C is positive.  This is an unnecessary restriction -- the
implication holds even if `C` is negative.

Reviewers: reames, majnemer

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D14369

llvm-svn: 252332
2015-11-06 19:01:03 +00:00
Sanjoy Das 9349dcc74a [ValueTracking] Add a framework for encoding implication rules
Summary:
This change adds a framework for adding more smarts to
`isImpliedCondition` around inequalities.  Informally,
`isImpliedCondition` will now try to prove "A < B ==> C < D" by proving
"C <= A && B <= D", since then it follows "C <= A < B <= D".

While this change is in principle NFC, I could not think of a way to not
handle cases like "i +_nsw 1 < L ==> i < L +_nsw 1" (that ValueTracking
did not handle before) while keeping the change understandable.  I've
added tests for these cases.

Reviewers: reames, majnemer, hfinkel

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D14368

llvm-svn: 252331
2015-11-06 19:00:57 +00:00
Philip Reames dbbd77921d [InstSimplify] sgt on i1s also encodes implication
Follow on to http://reviews.llvm.org/D13074, implementing something pointed out by Sanjoy. His truth table from his comment on that bug summarizes things well:
LHS | RHS | LHS >=s RHS | LHS implies RHS
0 | 0 | 1 (0 >= 0) | 1
0 | 1 | 1 (0 >= -1) | 1
1 | 0 | 0 (-1 >= 0) | 0
1 | 1 | 1 (-1 >= -1) | 1

The key point is that an "i1 1" is the value "-1", not "1".

Differential Revision: http://reviews.llvm.org/D13756

llvm-svn: 251597
2015-10-29 03:19:10 +00:00
Hal Finkel f2199b2178 Handle non-constant shifts in computeKnownBits, and use computeKnownBits for constant folding in InstCombine/Simplify
First, the motivation: LLVM currently does not realize that:

  ((2072 >> (L == 0)) >> 7) & 1 == 0

where L is some arbitrary value. Whether you right-shift 2072 by 7 or by 8, the
lowest-order bit is always zero. There are obviously several ways to go about
fixing this, but the generic solution pursued in this patch is to teach
computeKnownBits something about shifts by a non-constant amount. Previously,
we would give up completely on these. Instead, in cases where we know something
about the low-order bits of the shift-amount operand, we can combine (and
together) the associated restrictions for all shift amounts consistent with
that knowledge. As a further generalization, I refactored all of the logic for
all three kinds of shifts to have this capability. This works well in the above
case, for example, because the dynamic shift amount can only be 0 or 1, and
thus we can say a lot about the known bits of the result.

This brings us to the second part of this change: Even when we know all of the
bits of a value via computeKnownBits, nothing used to constant-fold the result.
This introduces the necessary code into InstCombine and InstSimplify. I've
added it into both because:

  1. InstCombine won't automatically pick up the associated logic in
     InstSimplify (InstCombine uses InstSimplify, but not via the API that
     passes in the original instruction).

  2. Putting the logic in InstCombine allows the resulting simplifications to become
     part of the iterative worklist

  3. Putting the logic in InstSimplify allows the resulting simplifications to be
     used by everywhere else that calls SimplifyInstruction (inlining, unrolling,
     and many others).

And this requires a small change to our definition of an ephemeral value so
that we don't break the rest case from r246696 (where the icmp feeding the
@llvm.assume, is also feeding a br). Under the old definition, the icmp would
not be considered ephemeral (because it is used by the br), but this causes the
assume to remove itself (in addition to simplifying the branch structure), and
it seems more-useful to prevent that from happening.

llvm-svn: 251146
2015-10-23 20:37:08 +00:00
Philip Reames 675418ebc0 Extend known bits to understand @llvm.bswap
This is a cleaned up patch from the one written by John Regehr based on the findings of the Souper superoptimizer.

When writing tests, I was surprised to find that instsimplify apparently doesn't know how to collapse bit test sequences based purely on known bits. This required me to split my tests across both instsimplify and instcombine.

Differential Revision: http://reviews.llvm.org/D13250

llvm-svn: 249453
2015-10-06 20:20:45 +00:00
Philip Reames 600a91580f Fix pr25040 - Handle vectors of i1s in recently added implication code
As mentioned in the bug, I'd missed the presence of a getScalarType in the caller of the new implies method. As a result, when we ended up with a implication over two vectors, we'd trip an assert and crash.

Differential Revision: http://reviews.llvm.org/D13441

llvm-svn: 249442
2015-10-06 19:00:02 +00:00
Philip Reames 13f023c09d [InstSimplify] Fold simple known implications to true
This was split off of http://reviews.llvm.org/D13040 to make it easier to test the correctness of the implication logic. For the moment, this only handles a single easy case which shows up when eliminating and combining range checks. In the (near) future, I plan to extend this for other cases which show up in range checks, but I wanted to make those changes incrementally once the framework was in place.

At the moment, the implication logic will be used by three places. One in InstSimplify (this review) and two in SimplifyCFG (http://reviews.llvm.org/D13040 & http://reviews.llvm.org/D13070). Can anyone think of other locations this style of reasoning would make sense?

Differential Revision: http://reviews.llvm.org/D13074

llvm-svn: 248719
2015-09-28 17:14:24 +00:00
Benjamin Kramer c3c183554b Merge or combine tests and convert to FileCheck.
- Move tests only exercising instsimplify to instsimplify's apint-or.ll
- Actually test the CHECK lines in instsimplify's apint-or.ll
- Merge the remaining tests in apint-or1.ll and apint-or2.ll, use FileCheck

llvm-svn: 247045
2015-09-08 18:36:56 +00:00
Hans Wennborg 4a61370b8f Fix CHECK directives that weren't checking.
llvm-svn: 246485
2015-08-31 21:10:35 +00:00
David Majnemer 2df38cd0c4 [InstSimplify] add nuw %x, C2 must be at least C2
Use the fact that add nuw always creates a larger bit pattern when
trying to simplify comparisons.

llvm-svn: 245638
2015-08-20 23:01:41 +00:00
David Majnemer c6bb0e2a51 [InstSimplify] Don't assume getAggregateElement will succeed
It isn't always possible to get a value from getAggregateElement.
This fixes PR24488.

llvm-svn: 245365
2015-08-18 22:07:25 +00:00
Jonathan Roelofs 49e46ce8e2 Fix a bunch of trivial cases of 'CHECK[^:]*$' in the tests. NFCI
I looked into adding a warning / error for this to FileCheck, but there doesn't
seem to be a good way to avoid it triggering on the instances of it in RUN lines.

llvm-svn: 244481
2015-08-10 19:01:27 +00:00
David Majnemer 599ca4426c [InstSimplify] Teach InstSimplify how to simplify extractelement
llvm-svn: 242008
2015-07-13 01:15:53 +00:00
David Majnemer 25a796e148 [InstSimplify] Teach InstSimplify how to simplify extractvalue
llvm-svn: 242007
2015-07-13 01:15:46 +00:00
Benjamin Kramer f4ebfa3ae1 [InstSimplify] Fold away ord/uno fcmps when nnan is present.
This is important to fold away the slow case of complex multiplies
emitted by clang.

llvm-svn: 241911
2015-07-10 14:02:02 +00:00
David Majnemer 7fddeccb8b Move the personality function from LandingPadInst to Function
The personality routine currently lives in the LandingPadInst.

This isn't desirable because:
- All LandingPadInsts in the same function must have the same
  personality routine.  This means that each LandingPadInst beyond the
  first has an operand which produces no additional information.

- There is ongoing work to introduce EH IR constructs other than
  LandingPadInst.  Moving the personality routine off of any one
  particular Instruction and onto the parent function seems a lot better
  than have N different places a personality function can sneak onto an
  exceptional function.

Differential Revision: http://reviews.llvm.org/D10429

llvm-svn: 239940
2015-06-17 20:52:32 +00:00
Benjamin Kramer 1ee59cba5d [InstSimplify] Allow folding of fdiv X, X with just NaNs ignored
Any combination of +-inf/+-inf is NaN so it's already ignored with
nnan and we can skip checking for ninf. Also rephrase logic in comments
a bit.

llvm-svn: 239821
2015-06-16 14:57:29 +00:00
Benjamin Kramer 228680ded8 [InstSimplify] fsub nnan x, x -> 0.0 is valid without ninf
Both inf - inf and (-inf) - (-inf) are NaN, so it's already covered by
nnan.

llvm-svn: 239702
2015-06-14 21:01:20 +00:00
Benjamin Kramer 4f0524614e [InstSimplify] Add self-fdiv identities for -ffinite-math-only.
When NaNs and Infs are ignored we can fold
 X /  X -> 1.0
-X /  X -> -1.0
 X / -X -> -1.0

llvm-svn: 239701
2015-06-14 18:53:58 +00:00
David Majnemer 1503258157 [InstSimplify] Handle some overflow intrinsics in InstSimplify
This change does a few things:
- Move some InstCombine transforms to InstSimplify
- Run SimplifyCall from within InstCombine::visitCallInst
- Teach InstSimplify to fold [us]mul_with_overflow(X, undef) to 0.

llvm-svn: 237995
2015-05-22 03:56:46 +00:00
David Blaikie 23af64846f [opaque pointer type] Add textual IR support for explicit type parameter to the call instruction
See r230786 and r230794 for similar changes to gep and load
respectively.

Call is a bit different because it often doesn't have a single explicit
type - usually the type is deduced from the arguments, and just the
return type is explicit. In those cases there's no need to change the
IR.

When that's not the case, the IR usually contains the pointer type of
the first operand - but since typed pointers are going away, that
representation is insufficient so I'm just stripping the "pointerness"
of the explicit type away.

This does make the IR a bit weird - it /sort of/ reads like the type of
the first operand: "call void () %x(" but %x is actually of type "void
()*" and will eventually be just of type "ptr". But this seems not too
bad and I don't think it would benefit from repeating the type
("void (), void () * %x(" and then eventually "void (), ptr %x(") as has
been done with gep and load.

This also has a side benefit: since the explicit type is no longer a
pointer, there's no ambiguity between an explicit type and a function
that returns a function pointer. Previously this case needed an explicit
type (eg: a function returning a void() function was written as
"call void () () * @x(" rather than "call void () * @x(" because of the
ambiguity between a function returning a pointer to a void() function
and a function returning void).

No ambiguity means even function pointer return types can just be
written alone, without writing the whole function's type.

This leaves /only/ the varargs case where the explicit type is required.

Given the special type syntax in call instructions, the regex-fu used
for migration was a bit more involved in its own unique way (as every
one of these is) so here it is. Use it in conjunction with the apply.sh
script and associated find/xargs commands I've provided in rr230786 to
migrate your out of tree tests. Do let me know if any of this doesn't
cover your cases & we can iterate on a more general script/regexes to
help others with out of tree tests.

About 9 test cases couldn't be automatically migrated - half of those
were functions returning function pointers, where I just had to manually
delete the function argument types now that we didn't need an explicit
function type there. The other half were typedefs of function types used
in calls - just had to manually drop the * from those.

import fileinput
import sys
import re

pat = re.compile(r'((?:=|:|^|\s)call\s(?:[^@]*?))(\s*$|\s*(?:(?:\[\[[a-zA-Z0-9_]+\]\]|[@%](?:(")?[\\\?@a-zA-Z0-9_.]*?(?(3)"|)|{{.*}}))(?:\(|$)|undef|inttoptr|bitcast|null|asm).*$)')
addrspace_end = re.compile(r"addrspace\(\d+\)\s*\*$")
func_end = re.compile("(?:void.*|\)\s*)\*$")

def conv(match, line):
  if not match or re.search(addrspace_end, match.group(1)) or not re.search(func_end, match.group(1)):
    return line
  return line[:match.start()] + match.group(1)[:match.group(1).rfind('*')].rstrip() + match.group(2) + line[match.end():]

for line in sys.stdin:
  sys.stdout.write(conv(re.search(pat, line), line))

llvm-svn: 235145
2015-04-16 23:24:18 +00:00
Ahmed Bougacha 082c5c707a Add a bunch of CHECK missing colons in tests. NFC.
Some wouldn't pass;  fixed most, the rest will be fixed separately.

llvm-svn: 232239
2015-03-14 01:43:57 +00:00
David Blaikie f72d05bc7b [opaque pointer type] Add textual IR support for explicit type parameter to gep operator
Similar to gep (r230786) and load (r230794) changes.

Similar migration script can be used to update test cases, which
successfully migrated all of LLVM and Polly, but about 4 test cases
needed manually changes in Clang.

(this script will read the contents of stdin and massage it into stdout
- wrap it in the 'apply.sh' script shown in previous commits + xargs to
apply it over a large set of test cases)

import fileinput
import sys
import re

rep = re.compile(r"(getelementptr(?:\s+inbounds)?\s*\()((<\d*\s+x\s+)?([^@]*?)(|\s*addrspace\(\d+\))\s*\*(?(3)>)\s*)(?=$|%|@|null|undef|blockaddress|getelementptr|addrspacecast|bitcast|inttoptr|zeroinitializer|<|\[\[[a-zA-Z]|\{\{)", re.MULTILINE | re.DOTALL)

def conv(match):
  line = match.group(1)
  line += match.group(4)
  line += ", "
  line += match.group(2)
  return line

line = sys.stdin.read()
off = 0
for match in re.finditer(rep, line):
  sys.stdout.write(line[off:match.start()])
  sys.stdout.write(conv(match))
  off = match.end()
sys.stdout.write(line[off:])

llvm-svn: 232184
2015-03-13 18:20:45 +00:00
David Blaikie a79ac14fa6 [opaque pointer type] Add textual IR support for explicit type parameter to load instruction
Essentially the same as the GEP change in r230786.

A similar migration script can be used to update test cases, though a few more
test case improvements/changes were required this time around: (r229269-r229278)

import fileinput
import sys
import re

pat = re.compile(r"((?:=|:|^)\s*load (?:atomic )?(?:volatile )?(.*?))(| addrspace\(\d+\) *)\*($| *(?:%|@|null|undef|blockaddress|getelementptr|addrspacecast|bitcast|inttoptr|\[\[[a-zA-Z]|\{\{).*$)")

for line in sys.stdin:
  sys.stdout.write(re.sub(pat, r"\1, \2\3*\4", line))

Reviewers: rafael, dexonsmith, grosser

Differential Revision: http://reviews.llvm.org/D7649

llvm-svn: 230794
2015-02-27 21:17:42 +00:00
David Blaikie 79e6c74981 [opaque pointer type] Add textual IR support for explicit type parameter to getelementptr instruction
One of several parallel first steps to remove the target type of pointers,
replacing them with a single opaque pointer type.

This adds an explicit type parameter to the gep instruction so that when the
first parameter becomes an opaque pointer type, the type to gep through is
still available to the instructions.

* This doesn't modify gep operators, only instructions (operators will be
  handled separately)

* Textual IR changes only. Bitcode (including upgrade) and changing the
  in-memory representation will be in separate changes.

* geps of vectors are transformed as:
    getelementptr <4 x float*> %x, ...
  ->getelementptr float, <4 x float*> %x, ...
  Then, once the opaque pointer type is introduced, this will ultimately look
  like:
    getelementptr float, <4 x ptr> %x
  with the unambiguous interpretation that it is a vector of pointers to float.

* address spaces remain on the pointer, not the type:
    getelementptr float addrspace(1)* %x
  ->getelementptr float, float addrspace(1)* %x
  Then, eventually:
    getelementptr float, ptr addrspace(1) %x

Importantly, the massive amount of test case churn has been automated by
same crappy python code. I had to manually update a few test cases that
wouldn't fit the script's model (r228970,r229196,r229197,r229198). The
python script just massages stdin and writes the result to stdout, I
then wrapped that in a shell script to handle replacing files, then
using the usual find+xargs to migrate all the files.

update.py:
import fileinput
import sys
import re

ibrep = re.compile(r"(^.*?[^%\w]getelementptr inbounds )(((?:<\d* x )?)(.*?)(| addrspace\(\d\)) *\*(|>)(?:$| *(?:%|@|null|undef|blockaddress|getelementptr|addrspacecast|bitcast|inttoptr|\[\[[a-zA-Z]|\{\{).*$))")
normrep = re.compile(       r"(^.*?[^%\w]getelementptr )(((?:<\d* x )?)(.*?)(| addrspace\(\d\)) *\*(|>)(?:$| *(?:%|@|null|undef|blockaddress|getelementptr|addrspacecast|bitcast|inttoptr|\[\[[a-zA-Z]|\{\{).*$))")

def conv(match, line):
  if not match:
    return line
  line = match.groups()[0]
  if len(match.groups()[5]) == 0:
    line += match.groups()[2]
  line += match.groups()[3]
  line += ", "
  line += match.groups()[1]
  line += "\n"
  return line

for line in sys.stdin:
  if line.find("getelementptr ") == line.find("getelementptr inbounds"):
    if line.find("getelementptr inbounds") != line.find("getelementptr inbounds ("):
      line = conv(re.match(ibrep, line), line)
  elif line.find("getelementptr ") != line.find("getelementptr ("):
    line = conv(re.match(normrep, line), line)
  sys.stdout.write(line)

apply.sh:
for name in "$@"
do
  python3 `dirname "$0"`/update.py < "$name" > "$name.tmp" && mv "$name.tmp" "$name"
  rm -f "$name.tmp"
done

The actual commands:
From llvm/src:
find test/ -name *.ll | xargs ./apply.sh
From llvm/src/tools/clang:
find test/ -name *.mm -o -name *.m -o -name *.cpp -o -name *.c | xargs -I '{}' ../../apply.sh "{}"
From llvm/src/tools/polly:
find test/ -name *.ll | xargs ./apply.sh

After that, check-all (with llvm, clang, clang-tools-extra, lld,
compiler-rt, and polly all checked out).

The extra 'rm' in the apply.sh script is due to a few files in clang's test
suite using interesting unicode stuff that my python script was throwing
exceptions on. None of those files needed to be migrated, so it seemed
sufficient to ignore those cases.

Reviewers: rafael, dexonsmith, grosser

Differential Revision: http://reviews.llvm.org/D7636

llvm-svn: 230786
2015-02-27 19:29:02 +00:00
Sanjay Patel 40eaa8df99 Fix really obscure bug in CannotBeNegativeZero() (PR22688)
With a diabolically crafted test case, we could recurse
through this code and return true instead of false.

The larger engineering crime is the use of magic numbers. 
Added FIXME comments for those.

llvm-svn: 230515
2015-02-25 18:00:15 +00:00
Mehdi Amini cd3ca6f7dd InstSimplify: simplify 0 / X if nnan and nsz
From: Fiona Glaser <fglaser@apple.com>
llvm-svn: 230238
2015-02-23 18:30:25 +00:00