cmd/compile: add ilp pass to help balance commutative expressions aiding in instruction level parallelism

[ryan-berger]

Currently the compiler groups expressions with commutative operations such as a + b + c + d as so: (a + (b + (c + d))) which is suboptimal for CPU instruction pipelining.

This pass balances commutative expressions as shown above to (a + b) + (c + d) to optimally pipeline them.

Below is a benchmark from crypto/md5 on an MacBook Pro M2:

                trunk                 reassociate

Hash1K-8 433.7Mi ± 0% 499.4Mi ± 4% +15.17% (p=0.000 n=10)
Hash8K-8 454.3Mi ± 1% 524.9Mi ± 1% +15.53% (p=0.000 n=10)
....
geomean 284.4Mi 327.5Mi +15.15%

Other CPU architectures tried showed very little change (+/-1%) on this particular benchmark but tight mathematical code stands to gain greatly from this optimization

Fixes #49331

[gopherbot]

This PR (HEAD: e764f20) has been imported to Gerrit for code review.

Please visit https://go-review.googlesource.com/c/go/+/496095 to see it.

Tip: You can toggle comments from me using the comments slash command (e.g. /comments off)
See the Wiki page for more info

[gopherbot]

Message from Wayne Zuo:

Patch Set 1:

(2 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/496095.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Ryan Berger:

Patch Set 1:

(2 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/496095.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Wayne Zuo:

Patch Set 1:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/496095.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Ryan Berger:

Patch Set 1:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/496095.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Keith Randall:

Patch Set 1:

(10 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/496095.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from David Chase:

Patch Set 1:

(2 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/496095.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Ryan Berger:

Patch Set 1:

(12 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/496095.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Ryan Berger:

Patch Set 1:

(2 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/496095.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

This PR (HEAD: cbc1baa) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/496095.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to register for Gerrit.
• To change your code in response to feedback:
  • Push a new commit to the branch used by your GitHub PR.
  • A new "patch set" will then appear in Gerrit.
  • Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
  • Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
  • Multiple commits in the PR will be squashed by GerritBot.
• The title and description of the GitHub PR are used to construct the final commit message.
  • Edit these as needed via the GitHub web interface (not via Gerrit or git).
  • You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

[gopherbot]

Message from tricium-prod@appspot.gserviceaccount.com:

Patch Set 2:

(1 comment)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/496095.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Ryan Berger:

Patch Set 2:

(12 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/496095.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

This PR (HEAD: a79b267) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/496095.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to register for Gerrit.
• To change your code in response to feedback:
  • Push a new commit to the branch used by your GitHub PR.
  • A new "patch set" will then appear in Gerrit.
  • Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
  • Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
  • Multiple commits in the PR will be squashed by GerritBot.
• The title and description of the GitHub PR are used to construct the final commit message.
  • Edit these as needed via the GitHub web interface (not via Gerrit or git).
  • You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

[gopherbot]

Message from Keith Randall:

Patch Set 3:

(4 comments)

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/496095.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

This PR (HEAD: cdffffd) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/496095.

Important tips:

• Don't comment on this PR. All discussion takes place in Gerrit.
• You need a Gmail or other Google account to log in to Gerrit.
• To change your code in response to feedback:
  • Push a new commit to the branch used by your GitHub PR.
  • A new "patch set" will then appear in Gerrit.
  • Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
  • Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
  • Multiple commits in the PR will be squashed by GerritBot.
• The title and description of the GitHub PR are used to construct the final commit message.
  • Edit these as needed via the GitHub web interface (not via Gerrit or git).
  • You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
• See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.