svec: optimize allocations in debug

The svec set method needs to do a little bit more work (for asserts and
write barriers), which is not necessary if we know it was just allocated.

src/julia.h

@@ -914,7 +914,7 @@ STATIC_INLINE jl_value_t *jl_svecset(
     // TODO: while svec is supposedly immutable, in practice we sometimes publish it first
     // and set the values lazily. Those users should be using jl_atomic_store_release here.
     jl_svec_data(t)[i] = (jl_value_t*)x;
-    if (x) jl_gc_wb(t, x);
+    jl_gc_wb(t, x);
     return (jl_value_t*)x;
 }
 #endif

src/simplevector.c

@@ -13,7 +13,7 @@ JL_DLLEXPORT jl_svec_t *(ijl_svec)(size_t n, ...)
     if (n == 0) return jl_emptysvec;
     va_start(args, n);
     jl_svec_t *jv = jl_alloc_svec_uninit(n);
-    for(size_t i=0; i < n; i++)
+    for (size_t i = 0; i < n; i++)
         jl_svecset(jv, i, va_arg(args, jl_value_t*));
     va_end(args);
     return jv;
@@ -38,7 +38,7 @@ JL_DLLEXPORT jl_svec_t *jl_svec1(void *a)
     jl_svec_t *v = (jl_svec_t*)jl_gc_alloc(ct->ptls, sizeof(void*) * 2,
                                            jl_simplevector_type);
     jl_svec_set_len_unsafe(v, 1);
-    jl_svecset(v, 0, a);
+    jl_svec_data(v)[0] = (jl_value_t*)a;
     return v;
 }
 
@@ -48,8 +48,8 @@ JL_DLLEXPORT jl_svec_t *jl_svec2(void *a, void *b)
     jl_svec_t *v = (jl_svec_t*)jl_gc_alloc(ct->ptls, sizeof(void*) * 3,
                                            jl_simplevector_type);
     jl_svec_set_len_unsafe(v, 2);
-    jl_svecset(v, 0, a);
-    jl_svecset(v, 1, b);
+    jl_svec_data(v)[0] = (jl_value_t*)a;
+    jl_svec_data(v)[1] = (jl_value_t*)b;
     return v;
 }
 
@@ -67,26 +67,24 @@ JL_DLLEXPORT jl_svec_t *jl_alloc_svec(size_t n)
 {
     if (n == 0) return jl_emptysvec;
     jl_svec_t *jv = jl_alloc_svec_uninit(n);
-    for(size_t i=0; i < n; i++)
-        jl_svecset(jv, i, NULL);
+    memset(jl_assume_aligned(jl_svec_data(jv), sizeof(void*)), 0, n * sizeof(void*));
     return jv;
 }
 
 JL_DLLEXPORT jl_svec_t *jl_svec_copy(jl_svec_t *a)
 {
-    size_t i, n=jl_svec_len(a);
+    size_t n = jl_svec_len(a);
     jl_svec_t *c = jl_alloc_svec_uninit(n);
-    for(i=0; i < n; i++)
-        jl_svecset(c, i, jl_svecref(a,i));
+    memmove_refs((void**)jl_svec_data(c), (void**)jl_svec_data(a), n);
     return c;
 }
 
 JL_DLLEXPORT jl_svec_t *jl_svec_fill(size_t n, jl_value_t *x)
 {
-    if (n==0) return jl_emptysvec;
+    if (n == 0) return jl_emptysvec;
     jl_svec_t *v = jl_alloc_svec_uninit(n);
-    for(size_t i=0; i < n; i++)
-        jl_svecset(v, i, x);
+    for (size_t i = 0; i < n; i++)
+        jl_svec_data(v)[i] = x;
     return v;
 }