ssa: emit go semantic metadata by luoliwoshang · Pull Request #1728 · goplus/llgo

luoliwoshang · 2026-03-18T06:54:31Z

Summary

add package-level deadcode metadata emitter infrastructure in SSA
emit !llgo.useiface, !llgo.useifacemethod, and !llgo.methodoff
encode metadata entries by symbol name so emission does not force extra LLVM globals or ABI type descriptors into the module
regenerate existing IR golden files via chore/gentests

Validation

env GOCACHE=/tmp/llgo-gocache go test ./ssa -run '^$'
env GOCACHE=/tmp/llgo-gocache go run ./chore/gentests
env GOCACHE=/tmp/llgo-gocache go test ./cl -run 'TestFromTestgo/(ifaceconv|invoke|abimethod|interface)$' -count=1

gemini-code-assist · 2026-03-18T06:55:16Z

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the LLGo compiler's SSA generation by adding a mechanism to emit semantic metadata. Specifically, it now tracks and annotates instances where concrete types are converted to interface types using !llgo.useiface metadata. This change provides more detailed information in the generated LLVM IR, which can be beneficial for downstream analysis or optimization passes. The update also includes the necessary regeneration of test output files to align with this new metadata emission.

Highlights

Semantic Metadata Emission: Introduced a new package-level semantic metadata emitter infrastructure within the SSA (Static Single Assignment) form generation.
Interface Conversion Metadata: Implemented the emission of !llgo.useiface metadata for non-interface to interface conversions originating from the MakeInterface operation.
Test File Regeneration: Regenerated numerous existing IR golden files to reflect the newly introduced metadata, ensuring consistency and correctness.

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xgopilot · 2026-03-18T06:58:15Z

Overall: Clean, well-scoped PR. The semantic metadata emitter is a solid foundation for recording interface conversions. The golden file updates are consistent. A few items below worth addressing — mainly a redundant abiTypeGlobal call and a missing license header.

xgopilot · 2026-03-18T06:58:17Z

ssa/interface.go

+	if _, ok := types.Unalias(typ.raw.Type).Underlying().(*types.Interface); !ok {
+		b.Pkg.emitUseIface(b.Func.impl, b.abiTypeGlobal(typ.raw.Type).impl)
+	}
 	tabi := b.abiType(typ.raw.Type)


Performance: abiTypeGlobal(typ.raw.Type) is called here at line 121, then called again at line 123 via abiType (which internally calls abiTypeGlobal with the same argument). On first invocation per type this performs TypeName resolution + VarOf map lookup + potentially heavy global construction; on subsequent calls it still does the name computation and lookup.

Consider hoisting the call and reusing the result:

Suggested change

if _, ok := types.Unalias(typ.raw.Type).Underlying().(*types.Interface); !ok {

b.Pkg.emitUseIface(b.Func.impl, b.abiTypeGlobal(typ.raw.Type).impl)

}

tabi := b.abiType(typ.raw.Type)

if _, ok := types.Unalias(typ.raw.Type).Underlying().(*types.Interface); !ok {

b.Pkg.emitUseIface(b.Func.impl, b.abiTypeGlobal(typ.raw.Type).impl)

}

tabi := b.abiType(typ.raw.Type)

→

g := b.abiTypeGlobal(typ.raw.Type) if _, ok := types.Unalias(typ.raw.Type).Underlying().(*types.Interface); !ok { b.Pkg.emitUseIface(b.Func.impl, g.impl) } tabi := Expr{llvm.ConstGEP(g.impl.GlobalValueType(), g.impl, []llvm.Value{...}), prog.AbiTypePtr()}

Or at minimum, ensure abiType can accept a precomputed Global to avoid the double lookup.

xgopilot · 2026-03-18T06:58:19Z

ssa/metadata.go

@@ -0,0 +1,51 @@
+package ssa


Consistency: This file is missing the Apache 2.0 copyright header that every other .go file in ssa/ includes. Please add it for consistency:

/* * Copyright (c) 2024 The XGo Authors (xgo.dev). All rights reserved. * * Licensed under the Apache License, Version 2.0 (the "License"); * ... */

xgopilot · 2026-03-18T06:58:21Z

ssa/metadata.go

+func (p Package) emitUseIface(owner, target llvm.Value) {
+	if owner.IsNil() || target.IsNil() {
+		return


Robustness: The silent nil-guard here may mask bugs upstream. If b.Func.impl or the result of abiTypeGlobal is unexpectedly nil, this silently drops the metadata rather than surfacing the problem. Consider at least a debug-mode log/warning so these cases don't go unnoticed during development.

xgopilot · 2026-03-18T06:58:24Z

ssa/metadata.go

+	p.semMeta.add(
+		p.mod,
+		llgoUseIfaceMetadata,
+		metadataKey(owner.Name(), target.Name()),
+		metadataSymbol(owner),


Clarity / Correctness: The dedup key is built from owner.Name() and target.Name(). Two concerns:

Key collision risk: If two distinct LLVM values share the same name (or both have empty names), the deduplication would incorrectly suppress a legitimate entry.

A brief comment explaining the \x00 separator choice in metadataKey and add would help future maintainers understand this is safe because it cannot appear in symbol names.

gemini-code-assist

Code Review

This pull request introduces an infrastructure for emitting package-level semantic metadata in the SSA backend and uses it to emit !llgo.useiface metadata for non-interface to interface conversions. The implementation includes a new semanticMetadataEmitter to manage and prevent duplicate metadata entries in the LLVM module. The changes are well-structured, with a logical refactoring in abitype.go to support the new functionality in interface.go. The code is clean, correct, and the regenerated golden files confirm the intended behavior. Overall, this is a solid improvement to the compiler's metadata emission capabilities.

codecov · 2026-03-18T09:27:29Z

Codecov Report

❌ Patch coverage is 96.47059% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.19%. Comparing base (aae5e97) to head (d394c0b).

Files with missing lines	Patch %	Lines
ssa/metadata.go	94.36%	2 Missing and 2 partials ⚠️
ssa/mdtest/metadata.go	92.85%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1728      +/-   ##
==========================================
+ Coverage   93.15%   93.19%   +0.03%     
==========================================
  Files          48       50       +2     
  Lines       13352    13511     +159     
==========================================
+ Hits        12438    12591     +153     
- Misses        727      731       +4     
- Partials      187      189       +2

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luoliwoshang · 2026-03-19T09:41:47Z

ssa/mdtest/metadata.go

will use goplus/llvm instead

# Conflicts: # cl/_testgo/abimethod/out.ll # cl/_testgo/embedunexport-1598/out.ll # cl/_testgo/interface/out.ll # cl/_testgo/interface1370/out.ll

…data-producer

luoliwoshang · 2026-03-26T14:22:19Z

cl/_testgo/interface/out.ll

接口方法数组： 0 0 0 0
类型。 1 1 0 1

xgopilot bot reviewed Mar 18, 2026

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luoliwoshang force-pushed the codex/useiface-metadata-producer branch from 1958ac9 to 8e77b05 Compare March 18, 2026 06:58

gemini-code-assist bot reviewed Mar 18, 2026

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luoliwoshang changed the title ~~Add llgo.useiface metadata emission~~ ssa: emit llgo.useiface metadata Mar 18, 2026

luoliwoshang force-pushed the codex/useiface-metadata-producer branch from 57e867d to b0f7c04 Compare March 18, 2026 08:53

luoliwoshang force-pushed the codex/useiface-metadata-producer branch 4 times, most recently from 646581d to 1b2e89b Compare March 18, 2026 10:13

luoliwoshang changed the title ~~ssa: emit llgo.useiface metadata~~ ssa: emit deadcode metadata Mar 18, 2026

luoliwoshang force-pushed the codex/useiface-metadata-producer branch 4 times, most recently from 728feba to a4b76a5 Compare March 19, 2026 02:47

luoliwoshang added 4 commits March 19, 2026 17:39

ssa: emit llgo.useiface metadata

c0efc83

ssa: emit methodoff and useifacemethod metadata

633db7a

ssa: encode metadata owners by symbol name

9e22cde

ssa: add named metadata readback tests

f36871a

luoliwoshang commented Mar 19, 2026

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ssa/mdtest/metadata.go

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luoliwoshang Mar 19, 2026 •

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will use goplus/llvm instead

luoliwoshang force-pushed the codex/useiface-metadata-producer branch 3 times, most recently from 3e35f66 to 7222776 Compare March 19, 2026 11:09

luoliwoshang changed the title ~~ssa: emit deadcode metadata~~ ssa: emit go semantic metadata Mar 19, 2026

luoliwoshang force-pushed the codex/useiface-metadata-producer branch from 7222776 to 146a83e Compare March 20, 2026 01:32

luoliwoshang force-pushed the codex/useiface-metadata-producer branch 2 times, most recently from 3064a49 to b2b62bb Compare March 20, 2026 06:20

ssa: emit reflect method metadata

6cad6b2

luoliwoshang force-pushed the codex/useiface-metadata-producer branch from b2b62bb to 6cad6b2 Compare March 20, 2026 07:14

luoliwoshang mentioned this pull request Mar 20, 2026

build: Go Linktime-like Unreachable Method Pruning #1736

Open

luoliwoshang added 5 commits March 24, 2026 20:40

ssa: inline abi type global helper

cc7eca8

Merge branch 'codex/pr1746-merge' into codex/useiface-metadata-producer

d20b7db

# Conflicts: # cl/_testgo/abimethod/out.ll # cl/_testgo/embedunexport-1598/out.ll # cl/_testgo/interface/out.ll # cl/_testgo/interface1370/out.ll

Merge remote-tracking branch 'upstream/main' into codex/useiface-meta…

4c5c4a4

…data-producer

ssa: preserve abi method string emission order

efdd93f

cl: refresh golden ll outputs

d394c0b

luoliwoshang commented Mar 26, 2026

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cl/_testgo/interface/out.ll

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接口方法数组： 0 0 0 0
类型。 1 1 0 1

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ssa: emit go semantic metadata#1728

ssa: emit go semantic metadata#1728
luoliwoshang wants to merge 10 commits intogoplus:mainfrom
luoliwoshang:codex/useiface-metadata-producer

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