Commit Graph

261 Commits

Author SHA1 Message Date
Sanjoy Das
ca40161d4a [IndVars] Have getInsertPointForUses preserve LCSSA
Summary:
Also add a stricter post-condition for IndVarSimplify.

Fixes PR25578.  Test case by Michael Zolotukhin.

Reviewers: hfinkel, atrick, mzolotukhin

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D15059

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@254977 91177308-0d34-0410-b5e6-96231b3b80d8
2015-12-08 00:13:21 +00:00
Sanjoy Das
51d40aea3b [SCEVExpander] Have hoistIVInc preserve LCSSA
Summary:
(Note: the problematic invocation of hoistIVInc that caused PR24804 came
from IndVarSimplify, not from SCEVExpander itself)

Fixes PR24804.  Test case by David Majnemer.

Reviewers: hfinkel, majnemer, atrick, mzolotukhin

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D15058

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@254976 91177308-0d34-0410-b5e6-96231b3b80d8
2015-12-08 00:13:17 +00:00
Peter Collingbourne
5178bc957a ScalarEvolution: do not set nuw when creating exprs of form <expr> + <all-ones>.
The nuw constraint will not be satisfied unless <expr> == 0.

This bug has been around since r102234 (in 2010!), but was uncovered by
r251052, which introduced more aggressive optimization of nuw scev expressions.

Differential Revision: http://reviews.llvm.org/D14850

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@253627 91177308-0d34-0410-b5e6-96231b3b80d8
2015-11-20 01:26:13 +00:00
Sanjoy Das
edb273f9ae Re-apply r251050 with a for PR25421
The bug: I missed adding break statements in the switch / case.

Original commit message:

[SCEV] Teach SCEV some axioms about non-wrapping arithmetic

Summary:
 - A s<  (A + C)<nsw> if C >  0
 - A s<= (A + C)<nsw> if C >= 0
 - (A + C)<nsw> s<  A if C <  0
 - (A + C)<nsw> s<= A if C <= 0

Right now `C` needs to be a constant, but we can later generalize it to
be a non-constant if needed.

Reviewers: atrick, hfinkel, reames, nlewycky

Subscribers: sanjoy, llvm-commits

Differential Revision: http://reviews.llvm.org/D13686

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252236 91177308-0d34-0410-b5e6-96231b3b80d8
2015-11-05 23:45:38 +00:00
Richard Trieu
59970e6f52 Revert r251050 to fix miscompile when running Clang -O1
See bug for details: https://llvm.org/bugs/show_bug.cgi?id=25421
Some comparisons were incorrectly replaced with a constant value.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@252231 91177308-0d34-0410-b5e6-96231b3b80d8
2015-11-05 23:20:36 +00:00
Silviu Baranga
94652aba1f Fix PR25372 - teach replaceCongruentPHIs to handle cases where SE evaluates a PHI to a SCEVConstant
Summary:
Since now Scalar Evolution can create non-add rec expressions for PHI
nodes, it can also create SCEVConstant expressions. This will confuse
replaceCongruentPHIs, which previously relied on the fact that SCEV
could not produce constants in this case.

We will now replace the node with a constant in these cases - or avoid
processing the Phi in case of a type mismatch.

Reviewers: sanjoy

Subscribers: llvm-commits, majnemer

Differential Revision: http://reviews.llvm.org/D14230

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251938 91177308-0d34-0410-b5e6-96231b3b80d8
2015-11-03 16:27:04 +00:00
Tobias Grosser
0efe7b620e Revert "[IndVarSimplify] Rewrite loop exit values with their initial values from loop preheader"
Commit 251839 triggers miscompiles on some bots:

http://lab.llvm.org:8011/builders/perf-x86_64-penryn-O3-polly-fast/builds/13723

(The commit is listed in 13722, but due to an existing failure introduced in
13721 and reverted in 13723 the failure is only visible in 13723)

To verify r251839 is indeed the only change that triggered the buildbot failures
and to ensure the buildbots remain green while investigating I temporarily
revert this commit. At the current state it is unclear if this commit introduced
some miscompile or if it only exposed code to Polly that is subsequently
miscompiled by Polly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251901 91177308-0d34-0410-b5e6-96231b3b80d8
2015-11-03 07:14:39 +00:00
Chen Li
fb81c7b828 [IndVarSimplify] Rewrite loop exit values with their initial values from loop preheader
Summary:
This patch adds support to check if a loop has loop invariant conditions which lead to loop exits. If so, we know that if the exit path is taken, it is at the first loop iteration. If there is an induction variable used in that exit path whose value has not been updated, it will keep its initial value passing from loop preheader. We can therefore rewrite the exit value with
its initial value. This will help remove phis created by LCSSA and enable other optimizations like loop unswitch.


Reviewers: sanjoy

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D13974

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251839 91177308-0d34-0410-b5e6-96231b3b80d8
2015-11-02 22:00:15 +00:00
Sanjoy Das
2b19a08110 [SCEV] Don't create SCEV expressions that break LCSSA
Prevent `createNodeFromSelectLikePHI` from creating SCEV expressions
that break LCSSA.

A better fix for the same issue is to teach SCEVExpander to not break
LCSSA by inserting PHI nodes at appropriate places.  That's planned for
the future.

Fixes PR25360.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251756 91177308-0d34-0410-b5e6-96231b3b80d8
2015-10-31 23:21:40 +00:00
Chen Li
b63862ff47 Revert r251492 "[IndVarSimplify] Rewrite loop exit values with their
initial values from loop preheader", because it broke some bots.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251498 91177308-0d34-0410-b5e6-96231b3b80d8
2015-10-28 05:15:51 +00:00
Chen Li
0c46270ed3 [IndVarSimplify] Rewrite loop exit values with their initial values from loop preheader
Summary:
This patch adds support to check if a loop has loop invariant conditions which lead to loop exits. If so, we know that if the exit path is taken, it is at the first loop iteration. If there is an induction variable used in that exit path whose value has not been updated, it will keep its initial value passing from loop preheader. We can therefore rewrite the exit value with
its initial value. This will help remove phis created by LCSSA and enable other optimizations like loop unswitch.


Reviewers: sanjoy

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D13974

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251492 91177308-0d34-0410-b5e6-96231b3b80d8
2015-10-28 04:45:47 +00:00
Sanjoy Das
221255160a [SCEV] Remove a test case added in r249168
The test case wasn't testing what it was commented to be testing; and
when I tried to fix the test I noticed that SCEV does not support the
simplification that the test was supposed to test.

This change removes the test case to avoid confusion.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251053 91177308-0d34-0410-b5e6-96231b3b80d8
2015-10-22 19:57:41 +00:00
Sanjoy Das
b9d057df5c [SCEV] Opportunistically interpret unsigned constraints as signed
Summary:
An unsigned comparision is equivalent to is corresponding signed version
if both the operands being compared are positive.  Teach SCEV to use
this fact when profitable.

Reviewers: atrick, hfinkel, reames, nlewycky

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D13687

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251051 91177308-0d34-0410-b5e6-96231b3b80d8
2015-10-22 19:57:34 +00:00
Sanjoy Das
47b5845e3b [SCEV] Teach SCEV some axioms about non-wrapping arithmetic
Summary:
 - A s<  (A + C)<nsw> if C >  0
 - A s<= (A + C)<nsw> if C >= 0
 - (A + C)<nsw> s<  A if C <  0
 - (A + C)<nsw> s<= A if C <= 0

Right now `C` needs to be a constant, but we can later generalize it to
be a non-constant if needed.

Reviewers: atrick, hfinkel, reames, nlewycky

Subscribers: sanjoy, llvm-commits

Differential Revision: http://reviews.llvm.org/D13686

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@251050 91177308-0d34-0410-b5e6-96231b3b80d8
2015-10-22 19:57:29 +00:00
Sanjoy Das
457377c0d4 [IndVars] Have cloneArithmeticIVUser guess better
Summary:
`cloneArithmeticIVUser` currently trips over expression like `add %iv,
-1` when `%iv` is being zero extended -- it tries to construct the
widened use as `add %iv.zext, zext(-1)` and (correctly) fails to prove
equivalence to `zext(add %iv, -1)` (here the SCEV for `%iv` is
`{1,+,1}`).

This change teaches `IndVars` to try sign extending the non-IV operand
if that makes the newly constructed IV use equivalent to the widened
narrow IV use.

Reviewers: atrick, hfinkel, reames

Subscribers: sanjoy, llvm-commits

Differential Revision: http://reviews.llvm.org/D13717

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@250483 91177308-0d34-0410-b5e6-96231b3b80d8
2015-10-16 01:00:47 +00:00
Sanjoy Das
da2b817d1a [SCEV] Pick backedge values for phi nodes correctly
Summary:
`getConstantEvolutionLoopExitValue` and `ComputeExitCountExhaustively`
assumed all phi nodes in the loop header have the same order of incoming
values.  This is not correct, and this commit changes
`getConstantEvolutionLoopExitValue` and `ComputeExitCountExhaustively`
to lookup the backedge value of a phi node using the loop's latch block.

Unfortunately, there is still some code duplication
`getConstantEvolutionLoopExitValue` and `ComputeExitCountExhaustively`.
At some point in the future we should extract out a helper class /
method that can evolve constant evolution phi nodes across iterations.

Fixes 25060.  Thanks to Mattias Eriksson for the spot-on analysis!

Depends on D13457.

Reviewers: atrick, hfinkel

Subscribers: materi, llvm-commits

Differential Revision: http://reviews.llvm.org/D13458

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249712 91177308-0d34-0410-b5e6-96231b3b80d8
2015-10-08 18:28:36 +00:00
Sanjoy Das
d23e55c402 [IndVars] Preserve LCSSA in eliminateIdentitySCEV
Summary:
After r249211, SCEV can see through some LCSSA phis.  Add a
`replacementPreservesLCSSAForm` check before replacing uses of these phi
nodes with a simplified use of the induction variable to avoid breaking
LCSSA.

Fixes 25047.

Depends on D13460.

Reviewers: atrick, hfinkel

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D13461

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249575 91177308-0d34-0410-b5e6-96231b3b80d8
2015-10-07 17:38:31 +00:00
Sanjoy Das
d15cdb7b13 [IndVars] Don't break dominance in eliminateIdentitySCEV
Summary:
After r249211, `getSCEV(X) == getSCEV(Y)` does not guarantee that X and
Y are related in the dominator tree, even if X is an operand to Y (I've
included a toy example in comments, and a real example as a test case).

This commit changes `SimplifyIndVar` to require a `DominatorTree`.  I
don't think this is a problem because `ScalarEvolution` requires it
anyway.

Fixes PR25051.

Depends on D13459.

Reviewers: atrick, hfinkel

Subscribers: joker.eph, llvm-commits, sanjoy

Differential Revision: http://reviews.llvm.org/D13460

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249471 91177308-0d34-0410-b5e6-96231b3b80d8
2015-10-06 21:44:49 +00:00
Sanjoy Das
8c0c4322dd [SCEV] Try to prove predicates by splitting them
Summary:
This change teaches SCEV that to prove `A u< B` it is sufficient to
prove each of these facts individually:

 - B >= 0
 - A s< B
 - A >= 0

In practice, SCEV sometimes finds it easier to prove these facts
individually than to prove `A u< B` as one atomic step.

Reviewers: reames, atrick, nlewycky, hfinkel

Subscribers: sanjoy, llvm-commits

Differential Revision: http://reviews.llvm.org/D13042

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249168 91177308-0d34-0410-b5e6-96231b3b80d8
2015-10-02 18:50:30 +00:00
Sanjoy Das
31d74407b9 [SCEV] Don't crash on pointer comparisons
`ScalarEvolution::isImpliedCondOperandsViaNoOverflow` tries to cast the
operand type of the comparison it is given to an `IntegerType`.  This is
incorrect because it could actually be simplifying a comparison between
two pointers.  Switch it to using `getTypeSizeInBits` instead, which
does the right thing for both pointers and integers.

Fixed PR24956.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248743 91177308-0d34-0410-b5e6-96231b3b80d8
2015-09-28 21:14:32 +00:00
Sanjoy Das
d8387ead1e [SCEV] identical instructions don't compute equal values
Before this change `HasSameValue` would return true for distinct
`alloca` instructions if they happened to be allocating the same
type (`alloca` instructions are not specified as reading memory).  This
change adds an explicit whitelist of instruction types for which
"identical" instructions compute the same value.

Fixes PR24952.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248690 91177308-0d34-0410-b5e6-96231b3b80d8
2015-09-27 21:09:48 +00:00
Sanjoy Das
fe14a332e4 [SCEV] Reapply 'Teach isLoopBackedgeGuardedByCond to exploit trip counts'
Summary:
If the trip count of a specific backedge is `N`, then we know that
backedge is effectively guarded by the condition `{0,+,1} u< N`.  This
change teaches SCEV to use this condition to prove things in
`isLoopBackedgeGuardedByCond`.

Depends on D12948
Depends on D12949

The original checkin, r248608 had to be backed out due to an issue with
a ObjCXX unit test.  That issue is now fixed, so re-landing.

Reviewers: atrick, reames, majnemer, hfinkel

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D12950

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248638 91177308-0d34-0410-b5e6-96231b3b80d8
2015-09-25 23:53:50 +00:00
Sanjoy Das
f0841dc648 [SCEV] Reapply 'Exploit A < B => (A+K) < (B+K) when possible'
Summary:

This change teaches SCEV's `isImpliedCond` two new identities:

  A u< B u< -C          =>  (A + C) u< (B + C)
  A s< B s< INT_MIN - C =>  (A + C) s< (B + C)

While these are useful on their own, they're really intended to support
D12950.

The original checkin, r248606 had to be backed out due to an issue with
a ObjCXX unit test.  That issue is now fixed, so re-landing.

Reviewers: atrick, reames, majnemer, nlewycky, hfinkel

Subscribers: aadg, sanjoy, llvm-commits

Differential Revision: http://reviews.llvm.org/D12948

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248637 91177308-0d34-0410-b5e6-96231b3b80d8
2015-09-25 23:53:45 +00:00
Sanjoy Das
34fd05d8b5 Revert two SCEV changes that caused test failures in clang.
r248606: "[SCEV] Exploit A < B => (A+K) < (B+K) when possible"
r248608: "[SCEV] Teach isLoopBackedgeGuardedByCond to exploit trip counts."

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248614 91177308-0d34-0410-b5e6-96231b3b80d8
2015-09-25 21:16:50 +00:00
Sanjoy Das
9026ca15f4 [SCEV] Teach isLoopBackedgeGuardedByCond to exploit trip counts.
Summary:
If the trip count of a specific backedge is `N`, then we know that
backedge is effectively guarded by the condition `{0,+,1} u< N`.  This
change teaches SCEV to use this condition to prove things in
`isLoopBackedgeGuardedByCond`.

Depends on D12948
Depends on D12949

Reviewers: atrick, reames, majnemer, hfinkel

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D12950

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248608 91177308-0d34-0410-b5e6-96231b3b80d8
2015-09-25 19:59:57 +00:00
Sanjoy Das
dab86b5a2b [SCEV] Exploit A < B => (A+K) < (B+K) when possible
Summary:

This change teaches SCEV's `isImpliedCond` two new identities:

  A u< B u< -C          =>  (A + C) u< (B + C)
  A s< B s< INT_MIN - C =>  (A + C) s< (B + C)

While these are useful on their own, they're really intended to support
D12950.

Reviewers: atrick, reames, majnemer, nlewycky, hfinkel

Subscribers: aadg, sanjoy, llvm-commits

Differential Revision: http://reviews.llvm.org/D12948

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248606 91177308-0d34-0410-b5e6-96231b3b80d8
2015-09-25 19:59:49 +00:00
Sanjoy Das
8ba782a30c [IndVars] Fix a bug in r248045.
Because -indvars widens induction variables through arithmetic,
`NeverNegative` cannot be a property of the `WidenIV` (a `WidenIV`
manages information for all transitive uses of an IV being widened,
including uses of `-1 * IV`).  Instead it must live on `NarrowIVDefUse`
which manages information for a specific def-use edge in the transitive
use list of an induction variable.

This change also adds a test case that demonstrates the problem with
r248045.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248107 91177308-0d34-0410-b5e6-96231b3b80d8
2015-09-20 01:52:18 +00:00
Sanjoy Das
9025a1f860 [IndVars] Widen more comparisons for non-negative induction vars
Summary:
If an induction variable is provably non-negative, its sign extension is
equal to its zero extension.  This means narrow uses like

  icmp slt iNarrow %indvar, %rhs

can be widened into

  icmp slt iWide zext(%indvar), sext(%rhs)

Reviewers: atrick, mcrosier, hfinkel

Subscribers: hfinkel, reames, llvm-commits

Differential Revision: http://reviews.llvm.org/D12745

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248045 91177308-0d34-0410-b5e6-96231b3b80d8
2015-09-18 21:21:02 +00:00
Sanjoy Das
e1269fa6d7 [IndVars] Fix PR24783.
In `IndVarSimplify::ExpandSCEVIfNeeded`,
`SCEVExpander::findExistingExpansion` may return an `llvm::Value` that
differs in type from the SCEV it was asked to find an expansion for (but
computes the same value).  In such cases, we fall back on
`expandCodeFor`; and rely on LLVM to CSE the two equivalent
expressions (different only by a no-op cast) into a single computation.

I tried a few other approaches to fixing PR24783, all of which turned
out to be more complex than this current version:

 1. Move the `ExpandSCEVIfNeeded` logic into `expandCodeFor`.  This got
    problematic because currently we do not pass in the `Loop *` into
    `expandCodeFor`.  Changing the interface to do this is a more
    invasive change, and really does not make much semantic sense unless
    the SCEV being passed in is an add recurrence.

    There is also the problem of `expandCodeFor` being used in places
    other than `indvars` -- there may be performance / correctness
    issues elsewhere if `expandCodeFor` is moved from always generating
    IR from scratch to cache-like model.

 2. Have `findExistingExpansion` only return expression with the correct
    type.  This would make `isHighCostExpansionHelper` and thus
    `isHighCostExpansion` more conservative than necessary.

 3. Insert casts on the value returned by `findExistingExpansion` if
    needed using `InsertNoopCastOfTo`.  This is complicated because
    `InsertNoopCastOfTo` depends on internal state of its
    `SCEVExpander` (specifically `Builder.GetInserPoint()`), and this
    may not be set up when `ExpandSCEVIfNeeded` is called.

 4. Manually insert casts on the value returned by
    `findExistingExpansion` if needed using `InsertNoopCastOfTo` via
    `CastInst::Create`.  This is probably workable, but figuring out the
    location where the cast instruction needs to be inserted has enough
    edge cases (arguments, constants, invokes, LCSSA must be preserved)
    makes me feel what I have right now is simplest solution.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@247749 91177308-0d34-0410-b5e6-96231b3b80d8
2015-09-15 23:45:39 +00:00
Hal Finkel
25fa0d406c Make ScalarEvolution::isKnownPredicate a little smarter
Here we make ScalarEvolution::isKnownPredicate, indirectly, a little smarter.
Given some relational comparison operator OP, and two AddRec SCEVs, {I,+,S} OP
{J,+,T}, we can reduce this to the comparison I OP J when S == T, both AddRecs
are for the same loop, and both are known not to wrap.

As it turns out, because of the way that backedge-guard expressions can be
leveraged when computing known predicates, this allows indvars to simplify the
if-statement comparison in this loop:

  void foo (int *a, int *b, int n) {
    for (int i = 0; i < n; ++i) {
      if (i > n)
        a[i] = b[i] + 1;
    }
  }

which, somewhat surprisingly, we were not previously optimizing away.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@245400 91177308-0d34-0410-b5e6-96231b3b80d8
2015-08-19 01:51:51 +00:00
Sanjoy Das
93011351ea [IndVars] Fix PR24356.
Unsigned predicates increase or decrease agnostic of the signs of their
increments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@244265 91177308-0d34-0410-b5e6-96231b3b80d8
2015-08-06 20:43:41 +00:00
Sanjoy Das
d9408bca26 FileCheck'ify some wc/grep based tests; NFCI.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243378 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-28 03:50:09 +00:00
Sanjoy Das
39d6da003d [IndVars] Make loop varying predicates loop invariant.
Summary:
Was D9784: "Remove loop variant range check when induction variable is
strictly increasing"

This change re-implements D9784 with the two differences:

 1. It does not use SCEVExpander and does not generate new
    instructions.  Instead, it does a quick local search for existing
    `llvm::Value`s that it needs when modifying the `icmp`
    instruction.

 2. It is more general -- it deals with both increasing and decreasing
    induction variables.

I've added all of the tests included with D9784, and two more.

As an example on what this change does (copied from D9784):

Given C code:

```
for (int i = M; i < N; i++) // i is known not to overflow
  if (i < 0) break;
  a[i] = 0;
}
```

This transformation produces:

```
for (int i = M; i < N; i++)
  if (M < 0) break;
  a[i] = 0;
}
```

Which can be unswitched into:

```
if (!(M < 0))
  for (int i = M; i < N; i++)
    a[i] = 0;
}
```

I went back and forth on whether the top level logic should live in
`SimplifyIndvar::eliminateIVComparison` or be put into its own
routine.  Right now I've put it under `eliminateIVComparison` because
even though the `icmp` is not *eliminated*, it no longer is an IV
comparison.  I'm open to putting it in its own helper routine if you
think that is better.

Reviewers: reames, nicholas, atrick

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D11278

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@243331 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-27 21:42:49 +00:00
Sanjoy Das
4db527032a [IndVars] Try to use existing values in RewriteLoopExitValues.
Summary:
In RewriteLoopExitValues, before expanding out an SCEV expression using
SCEVExpander, try to see if an existing LLVM IR expression already
computes the value we're interested in.  If so use that existing
expression.

Apart from reducing IndVars' reliance on the rest of the compilation
pipeline, this also prevents IndVars from concluding some expressions as
"high cost" when they're not.  For instance,
`InductiveRangeCheckElimination` often emits code of the following form:

```
len = umin(len_A, len_B)

loop:
  ...
  if (i++ < len)
    goto loop

outside_loop:
    use(i)
```

`SCEVExpander` refuses to rewrite the use of `i` in `outside_loop`,
since it thinks the value of `i` on loop exit, `len`, is a high cost
expansion since it contains an `umax` in it.  With this change,
`IndVars` can see that it can re-use `len` instead of creating a new
expression to compute `umin(len_A, len_B)`.

I considered putting this cleverness in `SCEVExpander`, but I was
worried that it may then have a deterimental effect on other passes
that use it.  So I decided it was better to just do this in the one
place where it seems like an obviously good idea, with the intent of
generalizing later if needed.

Reviewers: atrick, reames

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D10782

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241838 91177308-0d34-0410-b5e6-96231b3b80d8
2015-07-09 18:46:12 +00:00
David Majnemer
cc714e2142 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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239940 91177308-0d34-0410-b5e6-96231b3b80d8
2015-06-17 20:52:32 +00:00
Wei Mi
61897e8564 Enable exitValue rewrite only when the cost of expansion is low.
The patch evaluates the expansion cost of exitValue in indVarSimplify pass, and only does the rewriting when the expansion cost is low or loop can be deleted with the rewriting. It provides an option "-replexitval=" to control the default aggressiveness of the exitvalue rewriting. It also fixes some missing cases in SCEVExpander::isHighCostExpansionHelper to enhance the evaluation of SCEV expansion cost.

Differential Revision: http://reviews.llvm.org/D9800


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238507 91177308-0d34-0410-b5e6-96231b3b80d8
2015-05-28 21:49:07 +00:00
David Blaikie
32b845d223 [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))

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235145 91177308-0d34-0410-b5e6-96231b3b80d8
2015-04-16 23:24:18 +00:00
Sanjoy Das
17e08f50b9 [SCEV] Strengthen SCEVExpander::isHighCostExpansion.
Summary:

Teach `isHighCostExpansion` to consider divisions by power-of-two
constants as cheap and add a test case.  This change is needed for a new
user of `isHighCostExpansion` that will be added in a subsequent change.

Depends on D8995.

Reviewers: atrick

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D8993

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234845 91177308-0d34-0410-b5e6-96231b3b80d8
2015-04-14 03:20:32 +00:00
Duncan P. N. Exon Smith
de89228dfb Verifier: Call verifyModule() from llc and opt
Change `llc` and `opt` to run `verifyModule()`.  This ensures that we
check the full module before `FunctionPass::doInitialization()` ever
gets called (I was getting crashes in `DwarfDebug` instead of verifier
failures when testing a WIP patch that checks operands of compile
units).  In `opt`, also move up debug-info-stripping so that it still
runs before verification.

There was a fair bit of broken code that was sitting in tree.
Interestingly, some were cases of a `select` that referred to itself in
`-instcombine` tests (apparently an intermediate result).  I split them
off to `*-noverify.ll` tests with RUN lines like this:

    opt < %s -S -disable-verify -instcombine | opt -S | FileCheck %s

This avoids verifying the input file (so we can get the broken code into
`-instcombine), but still verifies the output with a second call to
`opt` (to verify that `-instcombine` will clean it up like it should).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233432 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-27 22:04:28 +00:00
David Blaikie
5a70dd1d82 [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:])

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232184 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-13 18:20:45 +00:00
Mehdi Amini
c94da20917 Make DataLayout Non-Optional in the Module
Summary:
DataLayout keeps the string used for its creation.

As a side effect it is no longer needed in the Module.
This is "almost" NFC, the string is no longer
canonicalized, you can't rely on two "equals" DataLayout
having the same string returned by getStringRepresentation().

Get rid of DataLayoutPass: the DataLayout is in the Module

The DataLayout is "per-module", let's enforce this by not
duplicating it more than necessary.
One more step toward non-optionality of the DataLayout in the
module.

Make DataLayout Non-Optional in the Module

Module->getDataLayout() will never returns nullptr anymore.

Reviewers: echristo

Subscribers: resistor, llvm-commits, jholewinski

Differential Revision: http://reviews.llvm.org/D7992

From: Mehdi Amini <mehdi.amini@apple.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231270 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-04 18:43:29 +00:00
Sanjoy Das
caee94bbb4 Revert some changes that were made to fix PR20680.
This re-lands change r230921.  r230921 was reverted because it broke a
clang test; a checkin fixing the clang test will be commited shortly.

Summary:
As far as I can tell, the real bug causing the issue was fixed in
r230533.  SCEVExpander should mark an increment operation as nuw or nsw
only if it can *prove* that the operation does not overflow.  There
shouldn't be any situation where we have to do something different
because of no-wrap flags generated by SCEVExpander.

Revert "IndVarSimplify: Allow LFTR to fire more often"

This reverts commit 1ade0f0faa (SVN: 222213).

Revert "IndVarSimplify: Don't let LFTR compare against a poison value"

This reverts commit c0f2b8b528 (SVN: 217102).

Reviewers: majnemer, atrick, spatel

Differential Revision: http://reviews.llvm.org/D7979

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231018 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-02 21:41:07 +00:00
NAKAMURA Takumi
6cad61163a Revert r230921, "Revert some changes that were made to fix PR20680.", for now.
It caused a failure on clang/test/Misc/backend-optimization-failure.cpp .

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230929 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-02 01:14:03 +00:00
Sanjoy Das
008dd56706 Revert some changes that were made to fix PR20680.
Summary:
As far as I can tell, the real bug causing the issue was fixed in
r230533.  SCEVExpander should mark an increment operation as nuw or nsw
only if it can *prove* that the operation does not overflow.  There
shouldn't be any situation where we have to do something different
because of no-wrap flags generated by SCEVExpander.

Revert "IndVarSimplify: Allow LFTR to fire more often"

This reverts commit 1ade0f0faa (SVN: 222213).

Revert "IndVarSimplify: Don't let LFTR compare against a poison value"

This reverts commit c0f2b8b528 (SVN: 217102).

Reviewers: majnemer, atrick, spatel

Differential Revision: http://reviews.llvm.org/D7979

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230921 91177308-0d34-0410-b5e6-96231b3b80d8
2015-03-01 23:36:26 +00:00
David Blaikie
7c9c6ed761 [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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230794 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-27 21:17:42 +00:00
David Blaikie
198d8baafb [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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230786 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-27 19:29:02 +00:00
Sanjoy Das
a0a0b40aa3 Bugfix: SCEVExpander incorrectly marks increment operations as no-wrap
(The change was landed in r230280 and caused the regression PR22674.
This version contains a fix and a test-case for PR22674).
    
When emitting the increment operation, SCEVExpander marks the
operation as nuw or nsw based on the flags on the preincrement SCEV.
This is incorrect because, for instance, it is possible that {-6,+,1}
is <nuw> while {-6,+,1}+1 = {-5,+,1} is not.
    
This change teaches SCEV to mark the increment as nuw/nsw only if it
can explicitly prove that the increment operation won't overflow.
    
Apart from the attached test case, another (more realistic)
manifestation of the bug can be seen in
Transforms/IndVarSimplify/pr20680.ll.

Differential Revision: http://reviews.llvm.org/D7778



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230533 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-25 20:02:59 +00:00
Hans Wennborg
b499b73e30 Revert r230280: "Bugfix: SCEVExpander incorrectly marks increment operations as no-wrap"
This caused PR22674, failing this assert:

Instructions.h:2281: llvm::Value* llvm::PHINode::getOperand(unsigned int) const: Assertion `i_nocapture < OperandTraits<PHINode>::operands(this) && "getOperand() out of range!"' failed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230341 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-24 16:19:29 +00:00
Sanjoy Das
8d16a81c33 Bugfix: SCEVExpander incorrectly marks increment operations as no-wrap
When emitting the increment operation, SCEVExpander marks the
operation as nuw or nsw based on the flags on the preincrement SCEV.
This is incorrect because, for instance, it is possible that {-6,+,1}
is <nuw> while {-6,+,1}+1 = {-5,+,1} is not.

This change teaches SCEV to mark the increment as nuw/nsw only if it
can explicitly prove that the increment operation won't overflow.

Apart from the attached test case, another (more realistic) manifestation
of the bug can be seen in Transforms/IndVarSimplify/pr20680.ll.

NOTE: this change was landed with an incorrect commit message in
rL230275 and was reverted for that reason in rL230279.  This commit
message is the correct one.

Differential Revision: http://reviews.llvm.org/D7778



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230280 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-23 23:22:58 +00:00
Sanjoy Das
69048edf8a Revert 230275.
230275 got committed with an incorrect commit message due to a mixup
on my side.  Will re-land in a few moments with the correct commit
message.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230279 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-23 23:13:22 +00:00