50 Commits

Author SHA1 Message Date
Daniil Fukalov
12c1156207
[NFC][AlwaysInliner] Reduce AlwaysInliner memory consumption. (#96958)
Refactored AlwaysInliner to remove some of inlined functions earlier.

Before the change AlwaysInliner walked through all functions in the
module and inlined them into calls where it is appropriate. Removing of
the dead inlined functions was performed only after all of inlining. For
the test case from the issue
[59126](https://github.com/llvm/llvm-project/issues/59126) compiler
consumes all of the memory on 64GB machine, so is killed.

The change checks if just inlined function can be removed from the
module and removes it.
2024-07-02 10:43:49 +02:00
Arthur Eubanks
fa6ea7a419 [AlwaysInliner] Make legacy pass like the new pass
The legacy pass is only used in AMDGPU codegen, which doesn't care about running it in call graph order (it actually has to work around that fact).

Make the legacy pass a module pass and share code with the new pass.

This allows us to remove the legacy inliner infrastructure.

Reviewed By: mtrofin

Differential Revision: https://reviews.llvm.org/D146446
2023-03-21 11:04:22 -07:00
Kazu Hirata
00874c48ea [IPO] Reorder parameters of InlineFunction (NFC)
With the recent addition of new parameter MergeAttributes (D134117),
callers need to specify several default parameters before getting to
specify the new parameter.

This patch reorders the parameters so that callers do not have to
specify as many default parameters.

Differential Revision: https://reviews.llvm.org/D134125
2022-09-20 09:09:38 -07:00
Kazu Hirata
284f0397e2 [Transforms] Merge function attributes within InlineFunction (NFC)
In the past, we've had a bug resulting in a compiler crash after
forgetting to merge function attributes (D105729).

This patch teaches InlineFunction to merge function attributes.  This
way, we minimize the "time" when the IR is valid, but the function
attributes are not.

Differential Revision: https://reviews.llvm.org/D134117
2022-09-17 23:10:23 -07:00
serge-sans-paille
f1985a3f85 Cleanup includes: Transforms/IPO
Preprocessor output diff: -238205 lines
Discourse thread: https://discourse.llvm.org/t/include-what-you-use-include-cleanup
Differential Revision: https://reviews.llvm.org/D122183
2022-03-22 10:06:28 +01:00
Ellis Hoag
f6b5142ac2 [AlwaysInliner] Emit inline remark only when successful
Failures in `InlineFunction()` are caught after D121722, but `emitInlinedIntoBasedOnCost()` should only be called when inlining is successful. This also removes an unnecessary call to `shouldInline()` which always returned `InlineCost::getAlways()`.

Reviewed By: kyulee, nikic

Differential Revision: https://reviews.llvm.org/D121946
2022-03-17 15:40:24 -07:00
Ellis Hoag
84c6689b15 [AlwaysInliner] Check inliner errors even without assserts
When we build clang without asserts we should still check the result of
`InlineFunction()` to be sure there wasn't an error. Otherwise we could
incorrectly merge attributes in the next line.

This also removes a redundent call to `getCaller()`.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D121722
2022-03-17 10:16:23 -07:00
serge-sans-paille
71c3a5519d Cleanup includes: LLVMAnalysis
Number of lines output by preprocessor:
before: 1065940348
after:  1065307662

Discourse thread: https://discourse.llvm.org/t/include-what-you-use-include-cleanup
Differential Revision: https://reviews.llvm.org/D120659
2022-03-01 18:01:54 +01:00
Dávid Bolvanský
1be1fd735d [AlwaysInliner] Check for callsite noinline attribute simplified 2022-02-14 09:33:30 +01:00
Dávid Bolvanský
d828281e78 [AlwaysInliner] Respect noinline call site attribute
```
always_inline foo() { }

bar () {

noinline foo();
}
```

We should prefer call site attribute over attribute on decl. This is fix for AlwaysInliner, similar fix is needed for normal Inliner (follow up).

Related to https://reviews.llvm.org/D119061

Reviewed By: aeubanks

Differential Revision: https://reviews.llvm.org/D119553
2022-02-11 19:23:11 +01:00
Dávid Bolvanský
fe30370b00 Reland "[AlwaysInliner] Enable call site inlining to make flatten attribute working again (#53360)" 2022-01-26 01:11:06 +01:00
Dávid Bolvanský
90f185c964 Revert "[AlwaysInliner] Enable call site inlining to make flatten attribute working again (#53360)"
This reverts commit ceec4383681c42bfd3d06a6913ce7554bea160b0. Clang tests fail.
2022-01-25 23:13:46 +01:00
Dávid Bolvanský
ceec438368 [AlwaysInliner] Enable call site inlining to make flatten attribute working again (#53360)
Problem: Migration to new PM broke flatten attribute.

This is one use case why LLVM should support inlining call-site with alwaysinline.  The flatten attribute is nowdays broken, so we should either land patch like this one or remove everything related to  flatten attribute from Clang.

Second use case is something like "per call site inlining intrinsics" to control inlining even more; mentioned in
https://lists.llvm.org/pipermail/cfe-dev/2018-September/059232.html

Fixes https://github.com/llvm/llvm-project/issues/53360

Reviewed By: aeubanks

Differential Revision: https://reviews.llvm.org/D117965
2022-01-25 22:55:30 +01:00
Nikita Popov
c8189da201 [ModuleUtils] Remove dead arg from filterDeadComdatFunctions() (NFC)
The module argument is no longer used.
2022-01-07 09:12:16 +01:00
Arthur Eubanks
4a9db7367d [AlwaysInliner] Invalidate analyses when we delete functions
Fixes PR52292.

Reviewed By: asbirlea

Differential Revision: https://reviews.llvm.org/D112473
2021-10-25 13:36:32 -07:00
Mircea Trofin
7d541eb4d4 [inliner] Mandatory inlining decisions produce remarks
This also removes the need to disable the mandatory inlining phase in
tests.

In a departure from the previous remark, we don't output a 'cost' in
this case, because there's no such thing. We just report that inlining
happened because of the attribute.

Differential Revision: https://reviews.llvm.org/D110891
2021-10-05 14:01:25 -07:00
Xun Li
31e60b9133 [coroutine] should disable inline before calling coro split
This is a rework of D85812, which didn't land.
When callee coroutine function is inlined into caller coroutine function before coro-split pass, llvm will emits "coroutine should have exactly one defining @llvm.coro.begin". It seems that coro-early pass can not handle this quiet well.
So we believe that unsplited coroutine function should not be inlined.
This patch fix such issue by not inlining function if it has attribute "coroutine.presplit" (it means the function has not been splited) to fix this issue
test plan: check-llvm, check-clang

In D85812, there was suggestions on moving the macros to Attributes.td to avoid circular header dependency issue.
I believe it's not worth doing just to be able to use one constant string in one place.
Today, there are already 3 possible attribute values for "coroutine.presplit": c6543cc6b8/llvm/lib/Transforms/Coroutines/CoroInternal.h (L40-L42)
If we move them into Attributes.td, we would be adding 3 new attributes to EnumAttr, just to support this, which I think is an overkill.

Instead, I think the best way to do this is to add an API in Function class that checks whether this function is a coroutine, by checking the attribute by name directly.

Differential Revision: https://reviews.llvm.org/D92706
2020-12-08 08:53:08 -08:00
Guozhi Wei
a20220d25b [AlwaysInliner] Call mergeAttributesForInlining after inlining
Like inlineCallIfPossible and InlinerPass, after inlining mergeAttributesForInlining
should be called to merge callee's attributes to caller. But it is not called in
AlwaysInliner, causes caller's attributes inconsistent with inlined code.

Attached test case demonstrates that attribute "min-legal-vector-width"="512" is
not merged into caller without this patch, and it causes failure in SelectionDAG
when lowering the inlined AVX512 intrinsic.

Differential Revision: https://reviews.llvm.org/D91446
2020-11-13 12:01:35 -08:00
Arthur Eubanks
42f76e193b Reland [AlwaysInliner] Pass callee AAResults to InlineFunction()
Test copied from noalias-calls.ll with small changes.

Reviewed By: asbirlea

Differential Revision: https://reviews.llvm.org/D89609
2020-10-26 20:40:46 -07:00
Arthur Eubanks
4af5ba1726 Revert "[AlwaysInliner] Pass callee AAResults to InlineFunction()"
This reverts commit 504fbec7a61cdfbb5f6e1b25cf14afe5195ccaf6.

Test failure.
2020-10-26 20:23:38 -07:00
Arthur Eubanks
504fbec7a6 [AlwaysInliner] Pass callee AAResults to InlineFunction()
Test copied from noalias-calls.ll with small changes.

Reviewed By: asbirlea

Differential Revision: https://reviews.llvm.org/D89609
2020-10-26 20:10:09 -07:00
Arthur Eubanks
eb55735073 Reland [AlwaysInliner] Update BFI when inlining
Reviewed By: davidxl

Differential Revision: https://reviews.llvm.org/D88324
2020-10-02 10:46:57 -07:00
Arthur Eubanks
9b8c0b8b46 Revert "[AlwaysInliner] Update BFI when inlining"
This reverts commit b1bf24667fc3ec5dc4b541148d0d722ffa28a6df.
2020-10-02 10:34:51 -07:00
Arthur Eubanks
b1bf24667f [AlwaysInliner] Update BFI when inlining
Reviewed By: davidxl

Differential Revision: https://reviews.llvm.org/D88324
2020-10-02 10:26:34 -07:00
Arthur Eubanks
3bf703fb6d [AlwaysInliner] Emit optimization remarks
To match the normal inliner in preparation for https://reviews.llvm.org/D86988.

Also change a FIXME to an assert.

Reviewed By: davidxl

Differential Revision: https://reviews.llvm.org/D88067
2020-09-21 22:09:28 -07:00
Fangrui Song
44ee9d070a Revert D85812 "[coroutine] should disable inline before calling coro split"
This reverts commit 2e43acfed89b1903de473f682c65878bdebc395a.

LLVMCoroutines (the library which contains Coroutines.h) depends on LLVMipo (the
library which contains SampleProfile.cpp). It is inappropriate for
SampleProfile.cpp to depent on Coroutines.h (circular dependency).

The test inverted dependencies as well:
llvm/test/Transforms/Coroutines/coro-inline.ll uses -sample-profile.
2020-08-24 11:41:05 -07:00
dongAxis
2e43acfed8 [coroutine] should disable inline before calling coro split
summary:
When callee coroutine function is inlined into caller coroutine
function before coro-split pass, llvm will emits "coroutine should
have exactly one defining @llvm.coro.begin". It seems that coro-early
pass can not handle this quiet well.
So we believe that unsplited coroutine function should not be inlined.
This patch fix such issue by not inlining function if it has attribute
"coroutine.presplit" (it means the function has not been splited) to
fix this issue

TestPlan: check-llvm

Reviewed By: wenlei

Differential Revision: https://reviews.llvm.org/D85812
2020-08-24 22:22:08 +08:00
Mircea Trofin
08e2386dee Revert "Revert "[llvm][NFC] Cleanup uses of std::function in Inlining-related APIs""
This reverts commit 454de99a6fec705e76ed7743bf538f7a77296f59.

The problem was that one of the ctor arguments of CallAnalyzer was left
to be const std::function<>&. A function_ref was passed for it, and then
the ctor stored the value in a function_ref field. So a std::function<>
would be created as a temporary, and not survive past the ctor
invocation, while the field would.

Tested locally by following https://github.com/google/sanitizers/wiki/SanitizerBotReproduceBuild

Original Differential Revision: https://reviews.llvm.org/D79917
2020-05-15 12:29:16 -07:00
Mircea Trofin
454de99a6f Revert "[llvm][NFC] Cleanup uses of std::function in Inlining-related APIs"
This reverts commit 767db5be67cab5aa04d81227725765cad9620611.
2020-05-14 22:32:44 -07:00
Mircea Trofin
767db5be67 [llvm][NFC] Cleanup uses of std::function in Inlining-related APIs
Summary:
Replacing uses of std::function pointers or refs, or Optional, to
function_ref, since the usage pattern allows that. If the function is
optional, using a default parameter value (nullptr). This led to a few
parameter reshufles, to push all optionals to the end of the parameter
list.

Reviewers: davidxl, dblaikie

Subscribers: arsenm, jvesely, nhaehnle, eraman, hiraditya, haicheng, kerbowa, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D79917
2020-05-14 22:13:53 -07:00
Mircea Trofin
4aae4e3f48 [llvm][NFC] CallSite removal from inliner-related files
Summary: This removes CallSite from inliner files. Some dependencies where thus affected.

Reviewers: dblaikie, davidxl, craig.topper

Subscribers: arsenm, jvesely, nhaehnle, eraman, hiraditya, aheejin, kerbowa, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D77991
2020-04-13 21:28:58 -07:00
Mircea Trofin
5466597fee [NFC] Refactor InlineResult for readability
Summary:
InlineResult is used both in APIs assessing whether a call site is
inlinable (e.g. llvm::isInlineViable) as well as in the function
inlining utility (llvm::InlineFunction). It means slightly different
things (can/should inlining happen, vs did it happen), and the
implicit casting may introduce ambiguity (casting from 'false' in
InlineFunction will default a message about hight costs,
which is incorrect here).

The change renames the type to a more generic name, and disables
implicit constructors.

Reviewers: eraman, davidxl

Reviewed By: davidxl

Subscribers: kerbowa, arsenm, jvesely, nhaehnle, eraman, hiraditya, haicheng, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D72744
2020-01-15 13:34:20 -08:00
Reid Kleckner
05da2fe521 Sink all InitializePasses.h includes
This file lists every pass in LLVM, and is included by Pass.h, which is
very popular. Every time we add, remove, or rename a pass in LLVM, it
caused lots of recompilation.

I found this fact by looking at this table, which is sorted by the
number of times a file was changed over the last 100,000 git commits
multiplied by the number of object files that depend on it in the
current checkout:
  recompiles    touches affected_files  header
  342380        95      3604    llvm/include/llvm/ADT/STLExtras.h
  314730        234     1345    llvm/include/llvm/InitializePasses.h
  307036        118     2602    llvm/include/llvm/ADT/APInt.h
  213049        59      3611    llvm/include/llvm/Support/MathExtras.h
  170422        47      3626    llvm/include/llvm/Support/Compiler.h
  162225        45      3605    llvm/include/llvm/ADT/Optional.h
  158319        63      2513    llvm/include/llvm/ADT/Triple.h
  140322        39      3598    llvm/include/llvm/ADT/StringRef.h
  137647        59      2333    llvm/include/llvm/Support/Error.h
  131619        73      1803    llvm/include/llvm/Support/FileSystem.h

Before this change, touching InitializePasses.h would cause 1345 files
to recompile. After this change, touching it only causes 550 compiles in
an incremental rebuild.

Reviewers: bkramer, asbirlea, bollu, jdoerfert

Differential Revision: https://reviews.llvm.org/D70211
2019-11-13 16:34:37 -08:00
Leonard Chan
09f56b51ec [clang][NewPM] Fix broken -O0 test from missing assumptions
Add an AssumptionCache callback to the InlineFuntionInfo used for the
AlwaysInlinerPass to match codegen of the AlwaysInlinerLegacyPass to generate
llvm.assume. This fixes CodeGen/builtin-movdir.c when new PM is enabled by
default.

Differential Revision: https://reviews.llvm.org/D63170

llvm-svn: 363287
2019-06-13 18:18:40 +00:00
Yevgeny Rouban
15b17d0a7c Provide reason messages for unviable inlining
InlineCost's isInlineViable() is changed to return InlineResult
instead of bool. This provides messages for failure reasons and
allows to get more specific messages for cases where callsites
are not viable for inlining.

Reviewed By: xbolva00, anemet

Differential Revision: https://reviews.llvm.org/D57089

llvm-svn: 352849
2019-02-01 10:44:43 +00:00
Chandler Carruth
2946cd7010 Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636
2019-01-19 08:50:56 +00:00
David Bolvansky
c0aa4b75a4 Enrich inline messages
Summary:
This patch improves Inliner to provide causes/reasons for negative inline decisions.
1. It adds one new message field to InlineCost to report causes for Always and Never instances. All Never and Always instantiations must provide a simple message.
2. Several functions that used to return the inlining results as boolean are changed to return InlineResult which carries the cause for negative decision.
3. Changed remark priniting and debug output messages to provide the additional messages and related inline cost.
4. Adjusted tests for changed printing.

Patch by: yrouban (Yevgeny Rouban)


Reviewers: craig.topper, sammccall, sgraenitz, NutshellySima, shchenz, chandlerc, apilipenko, javed.absar, tejohnson, dblaikie, sanjoy, eraman, xbolva00

Reviewed By: tejohnson, xbolva00

Subscribers: xbolva00, llvm-commits, arsenm, mehdi_amini, eraman, haicheng, steven_wu, dexonsmith

Differential Revision: https://reviews.llvm.org/D49412

llvm-svn: 338969
2018-08-05 14:53:08 +00:00
David Bolvansky
fbbb83c782 Revert "Enrich inline messages", tests fail
llvm-svn: 338496
2018-08-01 08:02:40 +00:00
David Bolvansky
7f36cd9d96 Enrich inline messages
Summary:
This patch improves Inliner to provide causes/reasons for negative inline decisions.
1. It adds one new message field to InlineCost to report causes for Always and Never instances. All Never and Always instantiations must provide a simple message.
2. Several functions that used to return the inlining results as boolean are changed to return InlineResult which carries the cause for negative decision.
3. Changed remark priniting and debug output messages to provide the additional messages and related inline cost.
4. Adjusted tests for changed printing.

Patch by: yrouban (Yevgeny Rouban)


Reviewers: craig.topper, sammccall, sgraenitz, NutshellySima, shchenz, chandlerc, apilipenko, javed.absar, tejohnson, dblaikie, sanjoy, eraman, xbolva00

Reviewed By: tejohnson, xbolva00

Subscribers: xbolva00, llvm-commits, arsenm, mehdi_amini, eraman, haicheng, steven_wu, dexonsmith

Differential Revision: https://reviews.llvm.org/D49412

llvm-svn: 338494
2018-08-01 07:37:16 +00:00
David Bolvansky
ab79414f7b Revert Enrich inline messages
llvm-svn: 338389
2018-07-31 14:47:22 +00:00
David Bolvansky
b562dbabda Enrich inline messages
Summary:
This patch improves Inliner to provide causes/reasons for negative inline decisions.
1. It adds one new message field to InlineCost to report causes for Always and Never instances. All Never and Always instantiations must provide a simple message.
2. Several functions that used to return the inlining results as boolean are changed to return InlineResult which carries the cause for negative decision.
3. Changed remark priniting and debug output messages to provide the additional messages and related inline cost.
4. Adjusted tests for changed printing.

Patch by: yrouban (Yevgeny Rouban)


Reviewers: craig.topper, sammccall, sgraenitz, NutshellySima, shchenz, chandlerc, apilipenko, javed.absar, tejohnson, dblaikie, sanjoy, eraman, xbolva00

Reviewed By: tejohnson, xbolva00

Subscribers: xbolva00, llvm-commits, arsenm, mehdi_amini, eraman, haicheng, steven_wu, dexonsmith

Differential Revision: https://reviews.llvm.org/D49412

llvm-svn: 338387
2018-07-31 14:25:24 +00:00
Adrian Prantl
5f8f34e459 Remove \brief commands from doxygen comments.
We've been running doxygen with the autobrief option for a couple of
years now. This makes the \brief markers into our comments
redundant. Since they are a visual distraction and we don't want to
encourage more \brief markers in new code either, this patch removes
them all.

Patch produced by

  for i in $(git grep -l '\\brief'); do perl -pi -e 's/\\brief //g' $i & done

Differential Revision: https://reviews.llvm.org/D46290

llvm-svn: 331272
2018-05-01 15:54:18 +00:00
Justin Bogner
6f6846fc9d AlwaysInliner: Alow setting InsertLifetime in the new-style pass
llvm-svn: 322033
2018-01-08 22:07:42 +00:00
Michael Zolotukhin
6af4f232b5 Remove redundant includes from lib/Transforms.
llvm-svn: 320628
2017-12-13 21:31:01 +00:00
Chandler Carruth
6e9bb7e064 [PM] Teach the always inliner in the new pass manager to support
removing fully-dead comdats without removing dead entries in comdats
with live members.

This factors the core logic out of the current inliner's internals to
a reusable utility and leverages that in both places. The factored out
code should also be (minorly) more efficient in cases where we have very
few dead functions or dead comdats to consider.

I've added a test case to cover this behavior of the always inliner.
This is the last significant bug in the new PM's always inliner I've
found (so far).

llvm-svn: 290557
2016-12-26 23:43:27 +00:00
Chandler Carruth
4eaff12ba2 [PM] Teach the always inlining test case to be much more strict about
whether functions are removed, and fix the new PM's always inliner to
actually pass this test.

Without this, the new PM's always inliner leaves all the functions
kicking around which won't work out very well given the semantics of
always inline.

Doing this really highlights how frustrating the current alwaysinline
semantic contract is though -- why can we put it on *external*
functions, etc?

Also I've added a number of tricky and interesting test cases for
removing functions with the always inliner. There is one remaining case
not handled -- fully removing comdats -- and I've left a FIXME about
this.

llvm-svn: 290457
2016-12-23 23:33:35 +00:00
Chandler Carruth
1d96311447 [PM] Provide an initial, minimal port of the inliner to the new pass manager.
This doesn't implement *every* feature of the existing inliner, but
tries to implement the most important ones for building a functional
optimization pipeline and beginning to sort out bugs, regressions, and
other problems.

Notable, but intentional omissions:
- No alloca merging support. Why? Because it isn't clear we want to do
  this at all. Active discussion and investigation is going on to remove
  it, so for simplicity I omitted it.
- No support for trying to iterate on "internally" devirtualized calls.
  Why? Because it adds what I suspect is inappropriate coupling for
  little or no benefit. We will have an outer iteration system that
  tracks devirtualization including that from function passes and
  iterates already. We should improve that rather than approximate it
  here.
- Optimization remarks. Why? Purely to make the patch smaller, no other
  reason at all.

The last one I'll probably work on almost immediately. But I wanted to
skip it in the initial patch to try to focus the change as much as
possible as there is already a lot of code moving around and both of
these *could* be skipped without really disrupting the core logic.

A summary of the different things happening here:

1) Adding the usual new PM class and rigging.

2) Fixing minor underlying assumptions in the inline cost analysis or
   inline logic that don't generally hold in the new PM world.

3) Adding the core pass logic which is in essence a loop over the calls
   in the nodes in the call graph. This is a bit duplicated from the old
   inliner, but only a handful of lines could realistically be shared.
   (I tried at first, and it really didn't help anything.) All told,
   this is only about 100 lines of code, and most of that is the
   mechanics of wiring up analyses from the new PM world.

4) Updating the LazyCallGraph (in the new PM) based on the *newly
   inlined* calls and references. This is very minimal because we cannot
   form cycles.

5) When inlining removes the last use of a function, eagerly nuking the
   body of the function so that any "one use remaining" inline cost
   heuristics are immediately refined, and queuing these functions to be
   completely deleted once inlining is complete and the call graph
   updated to reflect that they have become dead.

6) After all the inlining for a particular function, updating the
   LazyCallGraph and the CGSCC pass manager to reflect the
   function-local simplifications that are done immediately and
   internally by the inline utilties. These are the exact same
   fundamental set of CG updates done by arbitrary function passes.

7) Adding a bunch of test cases to specifically target CGSCC and other
   subtle aspects in the new PM world.

Many thanks to the careful review from Easwaran and Sanjoy and others!

Differential Revision: https://reviews.llvm.org/D24226

llvm-svn: 290161
2016-12-20 03:15:32 +00:00
Daniel Jasper
aec2fa352f Revert @llvm.assume with operator bundles (r289755-r289757)
This creates non-linear behavior in the inliner (see more details in
r289755's commit thread).

llvm-svn: 290086
2016-12-19 08:22:17 +00:00
Hal Finkel
3ca4a6bcf1 Remove the AssumptionCache
After r289755, the AssumptionCache is no longer needed. Variables affected by
assumptions are now found by using the new operand-bundle-based scheme. This
new scheme is more computationally efficient, and also we need much less
code...

llvm-svn: 289756
2016-12-15 03:02:15 +00:00
Chandler Carruth
67fc52f067 [PM] Port the always inliner to the new pass manager in a much more
minimal and boring form than the old pass manager's version.

This pass does the very minimal amount of work necessary to inline
functions declared as always-inline. It doesn't support a wide array of
things that the legacy pass manager did support, but is alse ... about
20 lines of code. So it has that going for it. Notably things this
doesn't support:

- Array alloca merging
  - To support the above, bottom-up inlining with careful history
    tracking and call graph updates
- DCE of the functions that become dead after this inlining.
- Inlining through call instructions with the always_inline attribute.
  Instead, it focuses on inlining functions with that attribute.

The first I've omitted because I'm hoping to just turn it off for the
primary pass manager. If that doesn't pan out, I can add it here but it
will be reasonably expensive to do so.

The second should really be handled by running global-dce after the
inliner. I don't want to re-implement the non-trivial logic necessary to
do comdat-correct DCE of functions. This means the -O0 pipeline will
have to be at least 'always-inline,global-dce', but that seems
reasonable to me. If others are seriously worried about this I'd like to
hear about it and understand why. Again, this is all solveable by
factoring that logic into a utility and calling it here, but I'd like to
wait to do that until there is a clear reason why the existing
pass-based factoring won't work.

The final point is a serious one. I can fairly easily add support for
this, but it seems both costly and a confusing construct for the use
case of the always inliner running at -O0. This attribute can of course
still impact the normal inliner easily (although I find that
a questionable re-use of the same attribute). I've started a discussion
to sort out what semantics we want here and based on that can figure out
if it makes sense ta have this complexity at O0 or not.

One other advantage of this design is that it should be quite a bit
faster due to checking for whether the function is a viable candidate
for inlining exactly once per function instead of doing it for each call
site.

Anyways, hopefully a reasonable starting point for this pass.

Differential Revision: https://reviews.llvm.org/D23299

llvm-svn: 278896
2016-08-17 02:56:20 +00:00