[JIT] X64 - Centralize peephole optimization for removing redundant `mov` instructions by TIHan · Pull Request #85780 · dotnet/runtime

TIHan · 2023-05-04T16:52:02Z

Description

This centralizes checking for redundant mov instructions.

Depending on what we do for #85734 , we need to counter some of the regressions that may occur as a result of not removing CAST nodes.

This also includes more peephole optimizations for movzx, movsx and movsxd.

ghost · 2023-05-04T16:52:14Z

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
See info in area-owners.md if you want to be subscribed.

Issue Details

Description

Depending on what we do for #85734 , we need to counter some of the regressions that may occur as a result of not removing CAST nodes. For x64, we can do this by looking for redundant movzx and movsx instructions.

Author:	TIHan
Assignees:	TIHan
Labels:	`area-CodeGen-coreclr`
Milestone:	-

…e optimization to IsRedundantMov.

TIHan · 2023-05-05T01:12:09Z

/azp run runtime-coreclr gcstress0x3-gcstress0xc

TIHan · 2023-05-05T01:12:16Z

/azp run Fuzzlyn

azure-pipelines · 2023-05-05T01:12:20Z

Azure Pipelines successfully started running 1 pipeline(s).

azure-pipelines · 2023-05-05T01:12:25Z

Azure Pipelines successfully started running 1 pipeline(s).

TIHan · 2023-05-05T06:23:02Z

/azp run Fuzzlyn

azure-pipelines · 2023-05-05T06:23:11Z

Azure Pipelines successfully started running 1 pipeline(s).

TIHan · 2023-05-05T18:36:56Z

@dotnet/jit-contrib this is ready. PTAL @BruceForstall - Diffs

All diff improvements, and we get a TP win for x64.
There is a significant TP regression for x86 which is likely because we never actually did any of these optimizations for x86 - we are now eliminating redundant movsx and movzx instructions.

TIHan · 2023-05-05T18:46:34Z

Thinking about it, I'm not sure why there are TP regressions for x86 for MinOpts. These optimizations only kick in when optimizations are on.

BruceForstall · 2023-05-06T01:11:39Z

+ {
+ result = (id->idOpSize() <= size);
+ }
+#ifdef TARGET_64BIT


On 32-bit will EA_4BYTE ever be passed? If not, we don't technically don't need the ifdef?

size can be EA_4BYTE on 32-bit - ifdef'ing this only for 64-bit just does less work on 32-bit.

BruceForstall · 2023-05-06T01:13:38Z

+ result = (id->idOpSize() <= size);
+ }
+#ifdef TARGET_64BIT
+ // movsx/movsxd always sign extends to 8 bytes. W-bit is set.


Why does the W-bit matter here?

W-bit on the encoding is what makes movsx and movsxd sign-extend to 8 bytes. We always default to using the W-bit. Technically, we could have a movsx or movsxd instruction not set the W-bit which would not sign-extend to 8 bytes (that would be a problem and make this optimization not safe), but we never actually emit those instructions that way.

This function cares about instructions and sizes, but not encoding, though.

The comment W-bit is set itself is just meant to inform the reason why this optimization is safe to do. It was already there before.

TIHan · 2023-05-08T18:02:05Z

@BruceForstall This is ready again.

TIHan · 2023-05-10T16:38:10Z

@BruceForstall This is ready again. The optimizations only happen for X64, which was the case before, so no TP regressions for X86.

BruceForstall · 2023-05-10T21:42:08Z

Diffs

Added AreUpperBitsZero and AreUpperBitsSignExtended
d014993

ghost added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label May 4, 2023

ghost assigned TIHan May 4, 2023

TIHan changed the title ~~Added AreUpperBitsZero and AreUpperBitsSignExtended~~[JIT] X64 - Peephole optimization for removing redundant movzx and movsx instructionsMay 4, 2023

TIHan added 4 commits May 4, 2023 11:06

Fix build
ac5764a

Handling sign-extended movs. Centralizing all mov elimination peephol…
a731602
…e optimization to IsRedundantMov.

Minor cleanup
bbb8598

Added JITDUMP calls
c3e79fa

TIHan changed the title ~~[JIT] X64 - Peephole optimization for removing redundant movzx and movsx instructions~~[JIT] X64 - Centralization peephole optimization for removing redundant mov instructionsMay 4, 2023

TIHan changed the title ~~[JIT] X64 - Centralization peephole optimization for removing redundant mov instructions~~[JIT] X64 - Centralize peephole optimization for removing redundant mov instructionsMay 4, 2023

Formatting
2a195e9

TIHan marked this pull request as ready for review May 5, 2023 01:12

Fix sign-extended
9c0c0a0

kunalspathak reviewed May 5, 2023
View reviewed changes

Comment threadsrc/coreclr/jit/emitxarch.h

TIHan mentioned this pull request May 5, 2023
[JIT] Fix - Do not remove CAST nodes on store if the LCL_VAR is address exposed #85734
Merged

BruceForstall suggested changes May 6, 2023
View reviewed changes

ghost added needs-author-action An issue or pull request that requires more info or actions from the author. and removed needs-author-action An issue or pull request that requires more info or actions from the author. labels May 6, 2023

TIHan mentioned this pull request May 8, 2023
Handle different SIMD moves in peephole optimization #85875
Closed

Feedback
4587ac9

Formatting
708ea25

TIHan force-pushed the movzx-movsx-elim branch from 9f90e74 to 708ea25Compare May 10, 2023 03:57

Only do the optimizations for 64-bit
a3e17a0

runfoappBot mentioned this pull request May 10, 2023
Infra improvements for Helix #68176
Closed

BruceForstall approved these changes May 10, 2023
View reviewed changes

TIHan merged commit e87dafa into dotnet:mainMay 11, 2023

JulieLeeMSFT mentioned this pull request Jun 9, 2023
What's new in .NET 8 Preview 5 [WIP] dotnet/core#8436
Closed
3 tasks

ghost locked as resolved and limited conversation to collaborators Jun 10, 2023

Uh oh!

Conversation

TIHan commented May 4, 2023• edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Description

Uh oh!

ghost commented May 4, 2023

Description

Uh oh!

TIHan commented May 5, 2023

Uh oh!

TIHan commented May 5, 2023

Uh oh!

azure-pipelinesBot commented May 5, 2023

Uh oh!

azure-pipelinesBot commented May 5, 2023

Uh oh!

TIHan commented May 5, 2023

Uh oh!

azure-pipelinesBot commented May 5, 2023

Uh oh!

TIHan commented May 5, 2023• edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

TIHan commented May 5, 2023• edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

BruceForstallMay 6, 2023

Choose a reason for hiding this comment

Uh oh!

TIHanMay 6, 2023

Choose a reason for hiding this comment

Uh oh!

BruceForstallMay 6, 2023

Choose a reason for hiding this comment

Uh oh!

TIHanMay 6, 2023• edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

BruceForstallMay 6, 2023

Choose a reason for hiding this comment

Uh oh!

TIHanMay 6, 2023

Choose a reason for hiding this comment

Uh oh!

TIHan commented May 8, 2023

Uh oh!

TIHan commented May 10, 2023

Uh oh!

BruceForstall commented May 10, 2023

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

TIHan commented May 4, 2023•
edited
Loading

TIHan commented May 5, 2023•
edited
Loading

TIHan commented May 5, 2023•
edited
Loading

TIHanMay 6, 2023•
edited
Loading