runtime: classify recovered runtime panics

[cpunion]

Summary

• fix recovered runtime panics so recover3.go classifies them as runtime.Error
• add stable test/go coverage for divide-by-zero, nil pointer, bounds, and type assertion recover paths
• remove the now-passing recover3.go darwin/arm64 xfail entry

Coverage

This PR keeps the feature covered under test/go, so it remains checked even when the slow GOROOT workflow is disabled.

Tests

• go test ./test/go -run 'TestRecoverRuntimeErrorClassification' -count=1
• go test ./test/goroot -run TestGoRootRunCases -count=1 -timeout=10m -args -goroot "$(go env GOROOT)" -dirs . -case '^recover3\.go$' -xfail /tmp/llgo-empty-xfail.yaml -run-timeout=60s -build-timeout=3m
• go test ./test/goroot -run TestGoRootRunCases -count=1 -timeout=10m -args -goroot "$(go env GOROOT)" -dirs . -case '^recover3\.go$' -run-timeout=60s -build-timeout=3m
• go test ./ssa -run 'TestTypeAssert|TestMakeInterface|TestBinOp' -count=1
• go run -tags=dev ./cmd/llgo test -run 'TestRecoverRuntimeErrorClassification' -count=1 ./test/go
• (cd runtime && go test ./internal/runtime -count=1)
• git diff --check

CI note

The GOROOT CI workflow is slow and currently disabled. The PR is draft so regular PR CI can run while review stays gated. Manual GOROOT workflow_dispatch cannot resolve fork-only refs unless the branch exists in xgo-dev/llgo; this PR intentionally keeps the branch only in cpunion/llgo.

[cpunion]

Pushed d49f9e4 to cpunion/codex/goroot-recover3-coverage.

Root cause: the recover3 runtime panic changes intentionally lower failed type assertions to runtime.PanicTypeAssert (and nullable array pointer indexing to AssertNilDeref), but several source FileCheck golden comments still expected the old panic-string construction and old IR numbering.

Updated the affected test/go coverage-backed IR checks under cl/_testgo, cl/_testrt, and cl/_testdata. Local verification:

• go test -timeout 20m ./cl -run '^(TestRunAndTestFromTestgo|TestRunAndTestFromTestrt|TestRunAndTestFromTestdata)$/(abimethod|ifaceprom|reader|reflect|tpinst|any|funcdecl|index|makemap|tpabi|typed|vargs)$'\n- go test -timeout 20m ./ssa\n- go test -timeout 20m ./test/go -run '^TestRecoverRuntimeErrorClassification$'\n- go test ./internal/runtime (from runtime/)\n- git diff --check\n\nNote: I did not use xgo-dev as a push target; the PR remains draft.

[cpunion]

Follow-up pushed: ef99d1c39e2a07908d1421390567a0b9f6eed4980 to cpunion/codex/goroot-recover3-coverage.

The d49f9e4 CI failure in Go / test (ubuntu-latest, 19) was not an environment issue. Job 77407357733 failed in ssa/TestFromTestgo/genericembediface because that test arrived from current xgo-dev/main during PR merge testing and still expected the old type assertion panic string. I merged current xgo-dev/main into the branch and updated genericembediface to expect runtime.PanicTypeAssert.

Local verification after the merge:

• go test -timeout 20m ./ssa
• go test -timeout 20m ./cl -run '^(TestRunAndTestFromTestgo|TestRunAndTestFromTestrt|TestRunAndTestFromTestdata)$/(abimethod|genericembediface|ifaceprom|reader|reflect|tpinst|any|funcdecl|index|makemap|tpabi|typed|vargs)$'\n- go test -timeout 20m ./test/go -run '^TestRecoverRuntimeErrorClassification$'\n- (cd runtime && go test ./internal/runtime)\n- git diff --check\n\nPush target was origin (cpunion/llgo) only; PR remains draft.

[cpunion]

Follow-up pushed: 64cbd644a8f9965f0a92f9cb80a880e98f927e68 to cpunion/codex/goroot-recover3-coverage.

The ef99d1c Ubuntu Go failure was not CI/environmental. Job 77411188389 failed in cl/TestRunAndTestFromTestgo/closureall with an undefined symbol for github.com/goplus/llgo/cl/_testgo/closureall.cSqrt. Root cause: the earlier regenerated CHECK-LINE comments sat between //go:linkname cSqrt C.sqrt and func cSqrt, so the Go directive was no longer adjacent to its declaration and linkname was ignored.

Fix: moved the CHECK-LINE comments away from the directive/declaration pair and restored the IR expectation to @sqrt.

Local verification:

• go test -timeout 20m ./cl -run '^(TestRunAndTestFromTestgo|TestRunAndTestFromTestrt|TestRunAndTestFromTestdata)$/(abimethod|closureall|genericembediface|ifaceprom|reader|reflect|tpinst|any|funcdecl|index|makemap|tpabi|typed|vargs)$'\n- go test -timeout 20m ./ssa -run '^(TestFromTestgo|TestFromTestrt|TestFromTestdata)$/(abimethod|closureall|genericembediface|ifaceprom|reader|reflect|tpinst|any|funcdecl|index|makemap|tpabi|typed|vargs)$'\n- go test -timeout 20m ./test/go -run '^TestRecoverRuntimeErrorClassification$'\n- (cd runtime && go test ./internal/runtime)\n- git diff --check\n\nPush target was origin (cpunion/llgo) only; PR remains draft.

[cpunion]

Follow-up CI check for 64cbd644a2ac92382f02312c5b6411198cb7dfa7:

• Go / test (ubuntu-latest, 19) job 77414738781 completed successfully.
• The previously failing Test step passed; embedded emulator env and std symbol coverage steps also passed.
• PR is still draft; remaining macOS jobs are still queued in GitHub Actions at the time of this comment.

[codecov-commenter]

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