runtime: preserve FuncForPC names for function values

[cpunion]

Summary

• add runtime FuncForPC name lookup backed by debug symbol info
• keep command-line function-value wrappers distinct for FuncForPC so folded functions still report separate names
• cover the issue58300 pattern in test/go and remove issue58300/issue58300b goroot xfails

Tests

• go test ./test/go -run TestRuntimeFuncForPCNamesWithLLGo -count=1
• go test ./test/go -count=1
• go test ./test/goroot -count=1 -run TestGoRootRunCases -args -goroot $(go env GOROOT) -dirs fixedbugs -case '^fixedbugs/issue58300(b)?.go$' -directive-mode=ci -xfail /tmp/llgo-no-xfail.yaml -run-timeout=2m
• go test ./test/goroot -count=1 -run TestGoRootRunCases -args -goroot $(go env GOROOT) -dirs fixedbugs -case '^fixedbugs/issue58300(b)?.go$' -directive-mode=ci -run-timeout=2m
• go test ./ssa -count=1
• go test ./cl -run 'TestRunAndTestFromTestgo|TestRunAndTestFromTestrt|TestRunAndTestFromTestdata' -count=1
• git diff --check

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[cpunion]

Added package-level coverage for the FuncForPC/function-value interface paths that Codecov flagged.

Changes:

• cl: compile-level fixture now asserts reflect.ValueOf(function).Pointer() uses a __llgo_funcpc_stub.* wrapper, with direct helper coverage for reflect, command-line-arguments, ordinary function-to-any, and non-function conversions.
• ssa: MakeInterfaceFuncPC is covered by checking that it creates a FuncForPC-preserving wrapper distinct from the normal closure wrapper path.

Local verification:

• go test ./cl -run 'TestCompileFuncForPCInterfaceUsesFuncPCWrapper|TestMakeInterfaceNeedsFuncPC' -coverprofile=/tmp/llgo-cl-funcpc.cover
• go tool cover -func=/tmp/llgo-cl-funcpc.cover shows makeInterfaceNeedsFuncPC at 100%.
• go test ./ssa -run 'TestMakeInterfaceKinds|TestClosureWrapCache' -coverprofile=/tmp/llgo-ssa-funcpc.cover
• go tool cover -func=/tmp/llgo-ssa-funcpc.cover shows MakeInterfaceFuncPC at 100%.
• go test ./test/go -run TestRuntimeFuncForPCNamesWithLLGo -count=1
• go test ./test/goroot -run TestGoRootRunCases -count=1 -goroot "$(go env GOROOT)" -dirs fixedbugs -case 'fixedbugs/issue58300(b)?\\.go' -progress 30s
• go test ./cl ./ssa -count=1
• git diff --check

Pushed commit: 6aab2c8. CI/Codecov are pending on the new head.

[cpunion]

Fixed the refreshed-head CI build failure.

Changes:

• Merged latest xgo-dev/main into codex/goroot-fixedbugs-funcforpc-names.
• Updated the new ssa/abitype.go closureWrapDecl call to pass keepFuncPC=false, matching the normal ABI method wrapper path.
• Removed the duplicate empty runtime.Func.FileLine stub left after the merge, keeping main's clitedebug implementation.

Validation:

• go test ./ssa -run 'TestMakeInterfaceKinds|TestClosureWrapCache|TestMakeInterfaceFuncPC' -count=1\n- go test ./cl -run 'TestCompileFuncForPCInterfaceUsesFuncPCWrapper|TestMakeInterfaceNeedsFuncPC' -count=1\n- go test ./test/go -run TestRuntimeFuncForPCNamesWithLLGo -count=1\n- git diff --check\n\nCommit: a91f4c8d6f1495b4146227c0c3cda69ddc36068f

[cpunion]

Superseded by #2024 (FuncForPC naming is covered by pc-identity + funcinfo display-name normalization there).