Send string concatenation to specialized upcall, shave 17s off librustc compile time.

src/rt/rust_upcall.cpp

@@ -309,6 +309,34 @@ upcall_vec_grow(rust_vec** vp, size_t new_sz) {
     UPCALL_SWITCH_STACK(&args, upcall_s_vec_grow);
 }
 
+struct s_str_concat_args {
+    rust_vec* lhs;
+    rust_vec* rhs;
+    rust_vec* retval;
+};
+
+extern "C" CDECL void
+upcall_s_str_concat(s_str_concat_args *args) {
+    rust_vec *lhs = args->lhs;
+    rust_vec *rhs = args->rhs;
+    rust_task *task = rust_task_thread::get_task();
+    size_t fill = lhs->fill + rhs->fill - 1;
+    rust_vec* v = (rust_vec*)task->kernel->malloc(fill + sizeof(rust_vec),
+                                                  "str_concat");
+    v->fill = v->alloc = fill;
+    memmove(&v->data[0], &lhs->data[0], lhs->fill - 1);
+    memmove(&v->data[lhs->fill - 1], &rhs->data[0], rhs->fill);
+    args->retval = v;
+}
+
+extern "C" CDECL rust_vec*
+upcall_str_concat(rust_vec* lhs, rust_vec* rhs) {
+    s_str_concat_args args = {lhs, rhs, 0};
+    UPCALL_SWITCH_STACK(&args, upcall_s_str_concat);
+    return args.retval;
+}
+
+
 extern "C" _Unwind_Reason_Code
 __gxx_personality_v0(int version,
                      _Unwind_Action actions,

src/rt/rustrt.def.in

@@ -67,6 +67,7 @@ upcall_shared_malloc
 upcall_shared_free
 upcall_shared_realloc
 upcall_vec_grow
+upcall_str_concat
 upcall_call_shim_on_c_stack
 upcall_call_shim_on_rust_stack
 upcall_new_stack

src/rustc/back/upcall.rs

@@ -18,6 +18,7 @@ type upcalls =
      mark: ValueRef,
      vec_grow: ValueRef,
      vec_push: ValueRef,
+     str_concat: ValueRef,
      cmp_type: ValueRef,
      log_type: ValueRef,
      alloc_c_stack: ValueRef,
@@ -69,6 +70,9 @@ fn declare_upcalls(targ_cfg: @session::config,
               dvi("vec_push",
                 [T_ptr(T_ptr(opaque_vec_t)), T_ptr(tydesc_type),
                  T_ptr(T_i8())]),
+          str_concat:
+              d("str_concat", [T_ptr(opaque_vec_t), T_ptr(opaque_vec_t)],
+                T_ptr(opaque_vec_t)),
           cmp_type:
               dv("cmp_type",
                  [T_ptr(T_i1()), T_ptr(tydesc_type),

src/rustc/middle/trans/tvec.rs

@@ -194,15 +194,16 @@ fn trans_append_literal(bcx: block, vptrptr: ValueRef, vec_ty: ty::t,
 fn trans_add(bcx: block, vec_ty: ty::t, lhs: ValueRef,
              rhs: ValueRef, dest: dest) -> block {
     let ccx = bcx.ccx();
-    let strings = alt ty::get(vec_ty).struct {
-      ty::ty_str { true }
-      _ { false }
-    };
+
+    if ty::get(vec_ty).struct == ty::ty_str {
+        let n = Call(bcx, ccx.upcalls.str_concat, [lhs, rhs]);
+        ret base::store_in_dest(bcx, n, dest);
+    }
+
     let unit_ty = ty::sequence_element_type(bcx.tcx(), vec_ty);
     let llunitty = type_of::type_of(ccx, unit_ty);
 
     let lhs_fill = get_fill(bcx, lhs);
-    if strings { lhs_fill = Sub(bcx, lhs_fill, C_int(ccx, 1)); }
     let rhs_fill = get_fill(bcx, rhs);
     let new_fill = Add(bcx, lhs_fill, rhs_fill);
     let {bcx: bcx, val: new_vec_ptr} = alloc_raw(bcx, new_fill, new_fill);