Optimize const_prop mir-opt by accessing local_decls through ecx

[SparrowLii]

From the FIXME in the impl of ConstPropagator. Accessing local_decls and scource_scopes from ecx can reduce clone calls and save compile time.
Besides, according to #96213 , the FIXME about writing layouts to ecx in advance can also be removed.

[rust-highfive]

r? @jackh726

(rust-highfive has picked a reviewer for you, use r? to override)

[wesleywiser]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[bors]

⌛ Trying commit 3d256b3 with merge b5da99ba9e80e1c12cd59707d9f2f96e3458b514...

[bors]

☀️ Try build successful - checks-actions
Build commit: b5da99ba9e80e1c12cd59707d9f2f96e3458b514 (b5da99ba9e80e1c12cd59707d9f2f96e3458b514)

[rust-timer]

Queued b5da99ba9e80e1c12cd59707d9f2f96e3458b514 with parent 3d3dafb, future comparison URL.

[rust-timer]

Finished benchmarking commit (b5da99ba9e80e1c12cd59707d9f2f96e3458b514): comparison url.

Summary:

• Primary benchmarks: 😿 relevant regression found
• Secondary benchmarks: 🎉 relevant improvement found

	Regressions 😿 (primary)	Regressions 😿 (secondary)	Improvements 🎉 (primary)	Improvements 🎉 (secondary)	All 😿 🎉 (primary)
count1	1	0	0	1	1
mean2	2.9%	N/A	N/A	-0.2%	2.9%
max	2.9%	N/A	N/A	-0.2%	2.9%

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression

Footnotes

1. number of relevant changes ↩

2. the arithmetic mean of the percent change ↩

[SparrowLii]

It seems that the call of the methods would be less efficient, so I used references to avoid it.
@wesleywiser Could you help with another perf test?

[jackh726]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[bors]

⌛ Trying commit db23e77 with merge 0c2aa98a8ac3a9726039cc8b380470095e51e1de...

[bors]

☀️ Try build successful - checks-actions
Build commit: 0c2aa98a8ac3a9726039cc8b380470095e51e1de (0c2aa98a8ac3a9726039cc8b380470095e51e1de)

[rust-timer]

Queued 0c2aa98a8ac3a9726039cc8b380470095e51e1de with parent 41ef767, future comparison URL.

[rust-timer]

Finished benchmarking commit (0c2aa98a8ac3a9726039cc8b380470095e51e1de): comparison url.

Summary:

• Primary benchmarks: 🎉 relevant improvement found
• Secondary benchmarks: no relevant changes found

	Regressions 😿 (primary)	Regressions 😿 (secondary)	Improvements 🎉 (primary)	Improvements 🎉 (secondary)	All 😿 🎉 (primary)
count1	0	0	1	0	1
mean2	N/A	N/A	-0.5%	N/A	-0.5%
max	N/A	N/A	-0.5%	N/A	-0.5%

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf -perf-regression

Footnotes

1. number of relevant changes ↩

2. the arithmetic mean of the percent change ↩

[wesleywiser]

Nice!

[wesleywiser]

@bors r+

[bors]

📌 Commit db23e77 has been approved by wesleywiser

[wesleywiser]

r? @wesleywiser

[bors]

⌛ Testing commit db23e77 with merge b21759f...

[bors]

☀️ Test successful - checks-actions
Approved by: wesleywiser
Pushing b21759f to master...

[rust-timer]

Finished benchmarking commit (b21759f): comparison url.

Summary:

• Primary benchmarks: no relevant changes found
• Secondary benchmarks: 🎉 relevant improvements found

	Regressions 😿 (primary)	Regressions 😿 (secondary)	Improvements 🎉 (primary)	Improvements 🎉 (secondary)	All 😿 🎉 (primary)
count1	0	0	0	3	0
mean2	N/A	N/A	N/A	-0.2%	N/A
max	N/A	N/A	N/A	-0.2%	N/A

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression

Footnotes

1. number of relevant changes ↩

2. the arithmetic mean of the percent change ↩