ram: integrate OpenSTA for timing and power reporting by tnguy19 · Pull Request #10784 · The-OpenROAD-Project/OpenROAD

tnguy19 · 2026-06-30T18:51:38Z

Summary

Integrates openSTA into the RAM module to display timing and power after RAM generation
Unconstrained worst setup and hold path delays (min clock period and cycle time) and total leakage power are displayed automatically after RAM generation

Type of Change

New feature

Impact

After generating a RAM, user can now see timing and power report numbers

Verification

I have verified that the local build succeeds (./etc/Build.sh).
I have run the relevant tests and they pass.
My code follows the repository's formatting guidelines.
I have included tests to prevent regressions.
I have signed my commits (DCO).

Related Issues

#9392

@rovinski

gemini-code-assist

Code Review

This pull request integrates the Static Timing Analysis (STA) engine into the RAM generator, adding methods to retrieve and report the worst setup slack and total power of the generated RAM. The reviewer recommends adding defensive checks to prevent segmentation faults if these reporting methods are called before a RAM block is generated, as well as handling unconstrained timing values in the Tcl interface to avoid formatting errors.

Signed-off-by: Thinh Nguyen <nguyenthinh19011@gmail.com>

rovinski · 2026-07-01T04:00:10Z

user can now use report_ram_timing to query for worst setup slack number, report_ram_power to query for RAM power, and report_ram_summary to get both numbers

There is no need for a user to manually call these functions. Make them internal functions which are called at the end of the ram generation automatically.

rovinski · 2026-07-01T04:03:05Z

For now, you should assume that no timing constraints have been applied to the RAM. Report the unconstrained worst slack for both hold and setup, as that represents the cycle time of the RAM.

I don't know what STA gives you for the power number if there aren't any activity factors propagated.

… generate, unconstrained worst slack and leakage power is reported Signed-off-by: Thinh Nguyen <nguyenthinh19011@gmail.com>

Signed-off-by: Thinh Nguyen <nguyenthinh19011@gmail.com>

… tidy error Signed-off-by: Thinh Nguyen <nguyenthinh19011@gmail.com>

Signed-off-by: Thinh Nguyen <nguyenthinh19011@gmail.com>

tnguy19 · 2026-07-02T02:09:50Z

I have made the updates to the code, ready for review @rovinski

rovinski

My comment about the power meant that I don't know myself what STA does when you estimate power, but there haven't been any activity factors applied. It might generate them, or it might just give back bogus results. It is worth finding out.

rovinski · 2026-07-02T06:46:41Z

+                  "No Liberty libraries loaded. Please run read_liberty before "
+                  "generate_ram to enable timing and power report.");


If that's the only way this can happen then it shouldn't, because it will crash much earlier without liberty loaded.

rovinski · 2026-07-02T06:49:02Z

+  sta::PathEndSeq setup_ends = sta_->findPathEnds(nullptr,
+                                                  nullptr,
+                                                  nullptr,
+                                                  true,
+                                                  scenes,
+                                                  sta::MinMaxAll::max(),
+                                                  1,
+                                                  1,
+                                                  false,
+                                                  false,
+                                                  -sta::INF,
+                                                  sta::INF,
+                                                  true,
+                                                  group_names,
+                                                  true,
+                                                  false,
+                                                  false,
+                                                  false,
+                                                  false,
+                                                  false);


It's a good idea, and I've seen elsewhere in the code, to put in-line comments with the argument name, e.g.

(nullptr /*arg name 1*/, nullptr /*arg name 2*/, ...

rovinski · 2026-07-02T06:49:35Z

+            : static_cast<float>(setup_ends[0]->dataArrivalTime(sta_));
+
+  // Find worst unconstrained hold path delay/shortest path
+  sta::PathEndSeq hold_ends = sta_->findPathEnds(nullptr,


rovinski · 2026-07-02T06:54:46Z

  FOREIGN RAM8x8 0 0 ;
  CLASS BLOCK ;
-  SIZE 95.68 BY 27.2 ;
+  SIZE 92 BY 27.2 ;


Didn't you deal with this before? Why is it back?

rovinski · 2026-07-02T06:56:31Z

-  -power_pin VPWR \
-  -ground_pin VGND \


It is usually better to do such changes in a separate PR because the downstream LEF changes are distracting from the main purpose of this PR.

rovinski · 2026-07-02T06:59:01Z

+            : static_cast<float>(hold_ends[0]->dataArrivalTime(sta_));
+
+  logger_->info(
+      RAM, 44, "RAM worst setup path delay: {:.6f} ns", setup_delay * 1e9);


"maximum path delay"

Do not hardcode ns, and do not multiply by 1e9. The unit changes depending on the library loaded. Use sta to get the time unit prefix, and use sta to get the timescale factor.

rovinski · 2026-07-02T06:59:40Z

+  logger_->info(
+      RAM, 44, "RAM worst setup path delay: {:.6f} ns", setup_delay * 1e9);
+  logger_->info(
+      RAM, 45, "RAM worst hold path delay: {:.6f} ns", hold_delay * 1e9);


"Minimum path delay"

Same note about time unit

rovinski · 2026-07-02T07:01:44Z

+  sta_->power(
+      sta_->cmdScene(), total, sequential, combinational, clock, macro, pad);
+  logger_->info(
+      RAM, 46, "RAM total power (no activity): {:.6f} W", total.total());


"estimated power:"

Do not hardcode W, get the unit prefix from sta.

github-actions Bot added the size/S label Jun 30, 2026

gemini-code-assist Bot reviewed Jun 30, 2026

View reviewed changes

Comment thread src/ram/src/ram.cpp Outdated

Comment thread src/ram/src/ram.cpp Outdated

Comment thread src/ram/src/ram.tcl Outdated

ram: integrate OpenSTA for timing and power reporting

95c0df8

Signed-off-by: Thinh Nguyen <nguyenthinh19011@gmail.com>

tnguy19 force-pushed the ram-sta-integration branch from 76ee747 to 95c0df8 Compare June 30, 2026 19:20

tnguy19 added 2 commits June 30, 2026 19:57

ram: add dependencies for Bazel checks

c65a580

Signed-off-by: Thinh Nguyen <nguyenthinh19011@gmail.com>

ram: fix buildifier formatting for BUILD file

7c1f48a

Signed-off-by: Thinh Nguyen <nguyenthinh19011@gmail.com>

ram: update so report timing and power called automatically at end of…

ff5ab1a

… generate, unconstrained worst slack and leakage power is reported Signed-off-by: Thinh Nguyen <nguyenthinh19011@gmail.com>

github-actions Bot added size/M and removed size/S labels Jul 1, 2026

tnguy19 added 5 commits July 1, 2026 19:19

ram: fix clang-format in ram.h

9b78de5

Signed-off-by: Thinh Nguyen <nguyenthinh19011@gmail.com>

ram: add includes for sta::StringSeq and sta::PathEndSeq to fix clang…

6564cb4

… tidy error Signed-off-by: Thinh Nguyen <nguyenthinh19011@gmail.com>

ram: update golden .ok files to include timing and power report

9379aaf

Signed-off-by: Thinh Nguyen <nguyenthinh19011@gmail.com>

ram: update golden files and BUILD for all regression tests

b22baf0

Signed-off-by: Thinh Nguyen <nguyenthinh19011@gmail.com>

ram: update BUILD file to fix buildifier lint

4010d4d

Signed-off-by: Thinh Nguyen <nguyenthinh19011@gmail.com>

rovinski reviewed Jul 2, 2026

View reviewed changes

		"No Liberty libraries loaded. Please run read_liberty before "
		"generate_ram to enable timing and power report.");

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rovinski commented Jul 1, 2026

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tnguy19 commented Jun 30, 2026 •

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