ARM64: Display method names for indirect calls in JitDisasm output by Copilot · Pull Request #126000 · dotnet/runtime

Copilot · 2026-03-23T23:51:19Z

Description

ARM64 JitDisasm output for indirect calls (blr/br_tail) was missing method name annotations. On x64, indirect calls render as call [addr] ; MethodName, but on ARM64 the equivalent blr x2 had no function name comment.

The method handle is already stored in idMemCookie for all call types. The IF_BR_1B display case in emitDispInsHelp simply never read it.

Before:

            blr     x2

After:

            blr     x2      // code for IndirectCallAnnotation:VirtualCallee():int

Changes

src/coreclr/jit/emitarm64.cpp: In the IF_BR_1B case of emitDispInsHelp, call emitDispCommentForHandle with GTF_ICON_FTN_ADDR to display the method name — matching the format used by movz/movk constant annotations in checked builds and the convention used by other architectures.

Original prompt

This section details on the original issue you should resolve

<issue_title>JIT: Release JitDisasm does not include function names for calls on arm64</issue_title>
<issue_description>E.g. I see
; Assembly listing for method vb_playground.M1:Main() (FullOpts)
; Emitting BLENDED_CODE for arm64 on Apple
; FullOpts code
; optimized code
; fp based frame
; partially interruptible
; No PGO data
; 0 inlinees with PGO data; 2 single block inlinees; 0 inlinees without PGO data

G_M000_IG01:                ;; offset=0x0000
            stp     fp, lr, [sp, #-0x10]!
            mov     fp, sp

G_M000_IG02:                ;; offset=0x0008
            movz    x0, #0x2570
            movk    x0, #0x99F LSL dotnet/runtime#16
            movk    x0, dotnet/runtime#1 LSL dotnet/runtime#32
            bl      CORINFO_HELP_NEWSFAST
            mov     w1, dotnet/runtime#3
            movz    x2, #0x7C00
            movk    x2, dotnet/runtime#590 LSL dotnet/runtime#16
            movk    x2, dotnet/runtime#1 LSL dotnet/runtime#32
            ldr     x2, [x2]
            blr     x2

G_M000_IG03:                ;; offset=0x0030
            ldp     fp, lr, [sp], #0x10
            ret     lr

; Total bytes of code 56
when using JitDisasm on preview3. I would expect a comment with the function name for x2 (IIRC that was the primary reason we did work to store debug info in this case)

cc @dotnet/jit-contrib </issue_description>

<agent_instructions>Please improve JitDisasm for arm64 for Release. Most (if not all) managed-to-managed calls are indirect, but on x64 we render them as call [Foo] while on arm64 we do what is described in the issue with no function name. Please write a small FILECHECK test for arm64 specifically.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

Fixes JIT: Release JitDisasm does not include function names for calls on arm64 #125951

💬 Send tasks to Copilot coding agent from Slack and Teams to turn conversations into code. Copilot posts an update in your thread when it's finished.

dotnet-policy-service · 2026-03-24T00:01:47Z

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

…ail) In the IF_BR_1B case of emitDispInsHelp, after displaying the register, check if idMemCookie is set and display the method name as a comment. This matches x64 behavior where indirect calls show the target method name. Also add a small FileCheck test for ARM64 specifically. Co-authored-by: EgorBo <523221+EgorBo@users.noreply.github.com> Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/b2a47cb3-cb3d-4479-a881-733d20b8576b

Co-authored-by: EgorBo <523221+EgorBo@users.noreply.github.com> Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/b2a47cb3-cb3d-4479-a881-733d20b8576b

Copilot

Pull request overview

This PR updates ARM64 JitDisasm output so indirect calls (blr / br_tail) include a method-name annotation comment, matching the existing behavior on other architectures. It also adds an ARM64 FileCheck-based JIT test to prevent regressions.

Changes:

ARM64: For IF_BR_1B instruction display, print the method name from idMemCookie as a // comment for indirect calls.
Tests: Add a new ARM64 disasm FileCheck test validating blr lines include the target method name annotation.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/coreclr/jit/emitarm64.cpp	Adds method-name comment emission for `IF_BR_1B` (indirect branch/call register format) when `idMemCookie` is present.
src/tests/JIT/opt/Calls/IndirectCallAnnotation.csproj	New JIT disasm/FileCheck-enabled test project configuration.
src/tests/JIT/opt/Calls/IndirectCallAnnotation.cs	New test that forces a virtual call and checks ARM64 disasm contains the callee method name on the `blr` instruction line.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

EgorBo · 2026-03-24T17:06:12Z

@copilot address the feedback.

Use emitDispCommentForHandle instead of directly calling eeGetMethodFullName and printf, matching the pattern used by movz/movk constant annotations. Remove the FileCheck test since it would only run in checked mode where the method name already appears on the movz/movk constant instructions. Co-authored-by: EgorBo <523221+EgorBo@users.noreply.github.com> Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/84a22a2e-9c3e-40ef-ab3b-97113c002f92

Copilot · 2026-03-24T17:20:58Z

@copilot address the feedback.

Addressed in 43bdb17 — switched to emitDispCommentForHandle and removed the test.

EgorBo · 2026-03-27T19:25:12Z

PTAL @dotnet/jit-contrib fix for JitDisasm

EgorBo · 2026-03-30T14:51:55Z

PTAL @jakobbotsch

EgorBo · 2026-03-30T20:27:38Z

/ba-g "System.Formats.Nrbf.Tests timeout"

Initial plan

56c7f92

Copilot AI assigned Copilot and EgorBo Mar 23, 2026

Copilot started work on behalf of EgorBo March 23, 2026 23:51 View session

github-actions bot added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label Mar 24, 2026

Copilot AI and others added 2 commits March 24, 2026 00:30

Refine test pattern to be more specific about method name match

4915e0f

Co-authored-by: EgorBo <523221+EgorBo@users.noreply.github.com> Agent-Logs-Url: https://github.com/dotnet/runtime/sessions/b2a47cb3-cb3d-4479-a881-733d20b8576b

Copilot AI changed the title ~~[WIP] Fix JIT release to include function names for calls on arm64~~ ARM64: Display method names for indirect calls in JitDisasm output Mar 24, 2026

Copilot AI requested a review from EgorBo March 24, 2026 00:37

Copilot finished work on behalf of EgorBo March 24, 2026 00:37

EgorBo marked this pull request as ready for review March 24, 2026 01:08

Copilot AI review requested due to automatic review settings March 24, 2026 01:08

Copilot started reviewing on behalf of EgorBo March 24, 2026 01:09 View session

Copilot AI reviewed Mar 24, 2026

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Comment thread src/coreclr/jit/emitarm64.cpp Outdated

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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

This was referenced Mar 24, 2026

The Operation will be canceled. The next steps may not contain expected logs. dotnet/dnceng#3008

Open

[android-arm64] The Operation will be canceled. The next steps may not contain expected logs. dotnet/dnceng#6408

Open

Update emitarm64.cpp

4c3d843

jakobbotsch reviewed Mar 24, 2026

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Comment thread src/coreclr/jit/emitarm64.cpp Outdated

jakobbotsch reviewed Mar 24, 2026

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Comment thread src/tests/JIT/opt/Calls/IndirectCallAnnotation.cs Outdated

Copilot started work on behalf of EgorBo March 24, 2026 17:06 View session

Copilot finished work on behalf of EgorBo March 24, 2026 17:22

This was referenced Mar 24, 2026

slow macOS - "##[error]The job running on agent Azure Pipelines 9 ran longer than the maximum time of 60 minutes." dotnet/dnceng#1883

Open

Cannot find 'arm64-v8a' device dotnet/dnceng#2284

Closed

EgorBo requested a review from jakobbotsch March 30, 2026 14:51

jakobbotsch approved these changes Mar 30, 2026

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EgorBo enabled auto-merge (squash) March 30, 2026 20:28

EgorBo merged commit d023efe into main Mar 30, 2026
127 of 129 checks passed

EgorBo deleted the copilot/jit-release-jitdisasm-function-names-arm64 branch March 30, 2026 20:28

dotnet-maestro bot mentioned this pull request Mar 31, 2026

[main] Source code updates from dotnet/runtime dotnet/dotnet#5799

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ARM64: Display method names for indirect calls in JitDisasm output#126000

ARM64: Display method names for indirect calls in JitDisasm output#126000
EgorBo merged 6 commits intomainfrom
copilot/jit-release-jitdisasm-function-names-arm64

Copilot AI commented Mar 23, 2026 •

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Copilot AI commented Mar 23, 2026 •

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