8266798: C1: More types of instruction can also apply LoopInvariantCodeMotion #3965

y1yang0 · 2021-05-11T02:26:04Z

C1 only applies LoopInvariantCodeMotion for instructions whose types are Constant/ArithmeticOp/LoadField/ArrayLength/LoadIndexed. We are possible to apply this optimization for more types of instruction.

Candidates: NegateOp,Convert.

Due to the lack of verification at IR level, it is difficult to write jtreg to check if it transformed, so I can only demonstrate it with a simple program:

// run with -XX:+PrintValueNumbering
static int foo10(int t){
    int sum=12;
    for(int i=0;i<100;i++){
        sum += 12;
        sum += -t;
        sum += (long)t;
    }
    return sum;
}

Before:

[...]
* loop invariant code motion for short loop B1
processing block B1
Value Numbering: insert Constant i10  (size 11, entries 3, nesting 2)
Instruction i10 is loop invariant
processing block B2
Value Numbering: Constant i12 equal to i5  (size 11, entries 3, nesting-diff 1)
substitution for 12 set to 5
Instruction i12 is loop invariant   // only 12 is recongized
Value Numbering: insert Constant i20  (size 11, entries 4, nesting 2)
Instruction i20 is loop invariant
** loop successfully optimized
[...]

After:

[...]
** loop invariant code motion for short loop B1
processing block B1
Value Numbering: insert Constant i10  (size 11, entries 3, nesting 2)
Instruction i10 is loop invariant
  6    0    i10    100
processing block B2
Value Numbering: Constant i12 equal to i5  (size 11, entries 3, nesting-diff 1)
substitution for i12 set to 105
Instruction i12 is loop invariant
  11   0    i12    12
Instruction i14 is loop invariant
. 16   0    i14    -i4
Value Numbering: insert Convert l17  (size 11, entries 4, nesting 2)
Instruction l17 is loop invariant
. 22   0    l17    i2l(i4)
Value Numbering: insert Constant i20  (size 11, entries 5, nesting 2)
Instruction i20 is loop invariant
  26   0    i20    1
[...]

Progress

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Issue

JDK-8266798: C1: More types of instruction can also apply LoopInvariantCodeMotion

Reviewers

Tobias Hartmann (@TobiHartmann - Reviewer)
Nils Eliasson (@neliasso - Reviewer)

Reviewing

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Update a local copy of the PR:
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$ git pull https://git.openjdk.java.net/jdk pull/3965/head

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$ git pr checkout 3965

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https://git.openjdk.java.net/jdk/pull/3965.diff

bridgekeeper · 2021-05-11T02:26:12Z

👋 Welcome back yyang! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2021-05-11T02:28:18Z

@kelthuzadx The following label will be automatically applied to this pull request:

hotspot-compiler

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

mlbridge · 2021-05-11T02:33:37Z

Webrevs

01: Full - Incremental (447dc3b3)
00: Full (5690f5cc)

TobiHartmann · 2021-05-11T09:45:05Z

src/hotspot/share/c1/c1_ValueMap.cpp

@@ -585,7 +589,7 @@ void GlobalValueNumbering::substitute(Instruction* instr) {
  if (subst != instr) {
    assert(!subst->has_subst(), "can't have a substitution");

-    TRACE_VALUE_NUMBERING(tty->print_cr("substitution for %d set to %d", instr->id(), subst->id()));
+    TRACE_VALUE_NUMBERING(tty->print_cr("substitution for %c%d set to %c%d", instr->type()->tchar(), instr->id(), subst->id(), subst->type()->tchar()));


Shouldn't the third argument be a char and the fourth an int?

Good catch, fixed.

TobiHartmann

Looks good to me.

openjdk · 2021-05-11T11:04:50Z

@kelthuzadx This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8266798: C1: More types of instruction can also apply LoopInvariantCodeMotion

Reviewed-by: thartmann, neliasso

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 56 new commits pushed to the master branch:

f3b510b: 8266923: [JVMCI] expose StackOverflow::_stack_overflow_limit to JVMCI
548899d: 8266189: Remove C1 "IfInstanceOf" instruction
b46086d: 8266874: Clean up C1 canonicalizer for TableSwitch/LookupSwitch
97367c0: 8266808: Search label still uses old search field id
06d7602: 8261158: JVMState should not be shared between SafePointNodes
476994a: 8266531: ZAddress::address() should be removed from SA
e828a93: 8261395: C1 crash "cannot make java calls from the native compiler"
3c47cab: 8261034: improve jcmd GC.class_histogram to support parallel
ed32e02: 8241187: ToolBox::grep should allow for negative filtering
cc03734: 8266925: Add a test to verify that hidden class's members are not statically invocable
... and 46 more: https://git.openjdk.java.net/jdk/compare/04fad70437a43c0f38fd53414b8eace2eac93509...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@TobiHartmann, @neliasso) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

y1yang0 · 2021-05-11T11:36:41Z

Thank you Tobias for the review!

/integrate

openjdk · 2021-05-11T11:39:27Z

@kelthuzadx
Your change (at version 447dc3b) is now ready to be sponsored by a Committer.

TobiHartmann · 2021-05-12T08:34:14Z

This is non-trivial and requires a second review.

neliasso

Looks good.

TobiHartmann · 2021-05-12T09:07:07Z

/sponsor

openjdk · 2021-05-12T09:08:55Z

@TobiHartmann @kelthuzadx Since your change was applied there have been 57 commits pushed to the master branch:

dcf250d: 8233378: CHT: Fast reset
f3b510b: 8266923: [JVMCI] expose StackOverflow::_stack_overflow_limit to JVMCI
548899d: 8266189: Remove C1 "IfInstanceOf" instruction
b46086d: 8266874: Clean up C1 canonicalizer for TableSwitch/LookupSwitch
97367c0: 8266808: Search label still uses old search field id
06d7602: 8261158: JVMState should not be shared between SafePointNodes
476994a: 8266531: ZAddress::address() should be removed from SA
e828a93: 8261395: C1 crash "cannot make java calls from the native compiler"
3c47cab: 8261034: improve jcmd GC.class_histogram to support parallel
ed32e02: 8241187: ToolBox::grep should allow for negative filtering
... and 47 more: https://git.openjdk.java.net/jdk/compare/04fad70437a43c0f38fd53414b8eace2eac93509...master

Your commit was automatically rebased without conflicts.

Pushed as commit 11759bf.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

y1yang0 · 2021-05-12T09:51:00Z

Thank you Tobias and Nils!

more instructions

5690f5c

openjdk bot added the rfr Pull request is ready for review label May 11, 2021

openjdk bot added the hotspot-compiler hotspot-compiler-dev@openjdk.org label May 11, 2021

TobiHartmann suggested changes May 11, 2021

View reviewed changes

tchar() before id()

447dc3b

TobiHartmann approved these changes May 11, 2021

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openjdk bot added the ready Pull request is ready to be integrated label May 11, 2021

openjdk bot added the sponsor Pull request is ready to be sponsored label May 11, 2021

neliasso approved these changes May 12, 2021

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openjdk bot closed this May 12, 2021

openjdk bot added integrated Pull request has been integrated and removed sponsor Pull request is ready to be sponsored ready Pull request is ready to be integrated rfr Pull request is ready for review labels May 12, 2021

y1yang0 deleted the codemotion_opt branch May 12, 2021 09:51

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8266798: C1: More types of instruction can also apply LoopInvariantCodeMotion #3965

8266798: C1: More types of instruction can also apply LoopInvariantCodeMotion #3965

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8266798: C1: More types of instruction can also apply LoopInvariantCodeMotion #3965

8266798: C1: More types of instruction can also apply LoopInvariantCodeMotion #3965

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