v3: preseed parallel libc helpers

Author: medvednikov

ci/qemu_linux_tests.sh

@@ -203,7 +203,8 @@ if ((sync_checkout)); then
 	ssh "${ssh_options[@]}" "$guest" bash -s -- "$guest_repo" <<'EOF'
 set -Eeuo pipefail
 guest_repo=$1
-manifest=$(git -C "$guest_repo" rev-parse --git-path qemu-linux-tests-untracked)
+git_dir=$(git -C "$guest_repo" rev-parse --absolute-git-dir)
+manifest="${git_dir}/qemu-linux-tests-untracked"
 if [[ -f "$manifest" ]]; then
 	cd "$guest_repo"
 	while IFS= read -r -d '' path; do
@@ -245,7 +246,7 @@ EOF
 			printf '%s\0' "$path"
 		done \
 		| ssh "${ssh_options[@]}" "$guest" \
-			"manifest=\$(git -C ${guest_repo_q} rev-parse --git-path qemu-linux-tests-untracked) && cat > \"\$manifest\""
+			"git_dir=\$(git -C ${guest_repo_q} rev-parse --absolute-git-dir) && cat > \"\${git_dir}/qemu-linux-tests-untracked\""
 fi
 
 if (($# == 0)); then

vlib/v3/gen/c/cleanc.v

@@ -2828,6 +2828,12 @@ pub fn (mut g FlatGen) gen_with_used_options(a &flat.FlatAst, used_fns map[strin
 	} else {
 		g.precompute_consts()
 	}
+	if defer_parallel_support {
+		// The declaration worker emits builtin ABI helpers concurrently with the
+		// function-body workers. Seed compatibility helpers before it starts; body
+		// workers still merge any lowering-only discoveries below.
+		g.preseed_libc_compat_fns()
+	}
 	g.timing_profile('  [ttime] cg precompute      ${f64(cgsw.elapsed().microseconds()) / 1000.0:7.2f} ms')
 	cgsw.restart()
 	orig_sb := g.sb

vlib/v3/gen/c/fn.v

@@ -1402,6 +1402,9 @@ fn (mut g FlatGen) libc_compat_call_name(name string) ?string {
 
 fn (mut g FlatGen) preseed_libc_compat_fns() {
 	refs := g.c_extern_referenced_symbols()
+	if refs['C.syscall'] || refs['syscall'] {
+		g.libc_compat_fns[c_libc_compat_syscall_decl_key] = true
+	}
 	if refs['C.gettid'] || refs['gettid'] {
 		g.libc_compat_fns['gettid'] = true
 	}

vlib/v3/tests/gettid_libc_compat_codegen_test.v

@@ -9,8 +9,10 @@ const gettid_compat_v3_src = os.join_path(gettid_compat_v3_dir, 'v3.v')
 fn gettid_compat_build_v3() string {
 	v3_bin := os.join_path(os.temp_dir(), 'v3_gettid_compat_test_${os.getpid()}')
 	os.rm(v3_bin) or {}
+	// -prealloc enables the parallel declaration worker that must emit the helper
+	// before function bodies can call it.
 	build :=
-		os.execute('${gettid_compat_vexe} -gc none -path "${gettid_compat_vlib_dir}|@vlib|@vmodules" -o ${v3_bin} ${gettid_compat_v3_src}')
+		os.execute('${gettid_compat_vexe} -prealloc -path "${gettid_compat_vlib_dir}|@vlib|@vmodules" -o ${v3_bin} ${gettid_compat_v3_src}')
 	assert build.exit_code == 0, build.output
 	return v3_bin
 }