[PATCH v17 9/9] vbscript: Fast-path For-Each iteration over SAFEARRAY.

[Francis De Brabandere]

From: Francis De Brabandere <[e-mail]>

When a For-Each loop iterates over a SAFEARRAY, bypass the
IEnumVARIANT COM vtable dispatch and copy elements directly from
the array data. This eliminates the COM call overhead and one
intermediate VariantCopy per iteration.

For non-refcounted element types (VT_I2, VT_I4, VT_R8, etc.),
also skip VariantCopyInd and VariantClear entirely, replacing them
with a direct struct assignment.

Non-SAFEARRAY iterators (e.g. IDispatch collections) continue to
use the standard IEnumVARIANT_Next path.

For-Each over a 10M-element integer array: 6,339ms -> 58ms (109x faster).
---
 dlls/vbscript/interp.c   | 38 +++++++++++++++++++------------
 dlls/vbscript/utils.c    | 49 ++++++++++++++++++++++++++++++++++++++++
 dlls/vbscript/vbscript.h |  1 +
 3 files changed, 74 insertions(+), 14 deletions(-)

diff --git a/dlls/vbscript/interp.c b/dlls/vbscript/interp.c
index f95db175035..61f4b7a4112 100644
--- a/dlls/vbscript/interp.c
+++ b/dlls/vbscript/interp.c
@@ -1879,11 +1879,16 @@ static HRESULT interp_enumnext(exec_ctx_t *ctx)
     iter = (IEnumVARIANT*)V_UNKNOWN(stack_top(ctx, 0));
 
     V_VT(&v) = VT_EMPTY;
-    hres = IEnumVARIANT_Next(iter, 1, &v, NULL);
-    if(FAILED(hres))
+    hres = safearray_iter_next(iter, &v, &do_continue);
+    if(hres == E_UNEXPECTED) {
+        hres = IEnumVARIANT_Next(iter, 1, &v, NULL);
+        if(FAILED(hres))
+            return hres;
+        do_continue = hres == S_OK;
+    }else if(FAILED(hres)) {
         return hres;
+    }
 
-    do_continue = hres == S_OK;
     hres = assign_ident(ctx, ident, DISPATCH_PROPERTYPUT|DISPATCH_PROPERTYPUTREF, &dp);
     VariantClear(&v);
     if(FAILED(hres))
@@ -1902,7 +1907,6 @@ static HRESULT interp_enumnext_local(exec_ctx_t *ctx)
 {
     const unsigned loop_end = ctx->instr->arg1.uint;
     const int ref = ctx->instr->arg2.lng;
-    VARIANT v;
     IEnumVARIANT *iter;
     VARIANT *local_var;
     BOOL do_continue;
@@ -1917,21 +1921,27 @@ static HRESULT interp_enumnext_local(exec_ctx_t *ctx)
     assert(V_VT(stack_top(ctx, 0)) == VT_UNKNOWN);
     iter = (IEnumVARIANT*)V_UNKNOWN(stack_top(ctx, 0));
 
-    V_VT(&v) = VT_EMPTY;
-    hres = IEnumVARIANT_Next(iter, 1, &v, NULL);
-    if(FAILED(hres))
-        return hres;
-
-    do_continue = hres == S_OK;
-
     local_var = get_local_var(ctx, ref);
     if(V_VT(local_var) == (VT_VARIANT|VT_BYREF))
         local_var = V_VARIANTREF(local_var);
 
-    hres = assign_value(ctx, local_var, &v, DISPATCH_PROPERTYPUT|DISPATCH_PROPERTYPUTREF);
-    VariantClear(&v);
-    if(FAILED(hres))
+    hres = safearray_iter_next(iter, local_var, &do_continue);
+    if(hres == E_UNEXPECTED) {
+        VARIANT v;
+
+        V_VT(&v) = VT_EMPTY;
+        hres = IEnumVARIANT_Next(iter, 1, &v, NULL);
+        if(FAILED(hres))
+            return hres;
+
+        do_continue = hres == S_OK;
+        hres = assign_value(ctx, local_var, &v, DISPATCH_PROPERTYPUT|DISPATCH_PROPERTYPUTREF);
+        VariantClear(&v);
+        if(FAILED(hres))
+            return hres;
+    }else if(FAILED(hres)) {
         return hres;
+    }
 
     if(do_continue) {
         ctx->instr++;
diff --git a/dlls/vbscript/utils.c b/dlls/vbscript/utils.c
index 4bfc2c65a0a..e73495ef3f9 100644
--- a/dlls/vbscript/utils.c
+++ b/dlls/vbscript/utils.c
@@ -196,3 +196,52 @@ HRESULT create_safearray_iter(SAFEARRAY *sa, BOOL owned, IEnumVARIANT **ev)
     *ev = &iter->IEnumVARIANT_iface;
     return S_OK;
 }
+
+HRESULT safearray_iter_next(IEnumVARIANT *iface, VARIANT *dst, BOOL *fetched)
+{
+    safearray_iter *iter;
+    VARIANT *src;
+
+    if(iface->lpVtbl != &safearray_iter_EnumVARIANTVtbl)
+        return E_UNEXPECTED;
+
+    iter = impl_from_IEnumVARIANT(iface);
+
+    if(iter->i >= iter->size) {
+        VariantClear(dst);
+        *fetched = FALSE;
+        return S_OK;
+    }
+
+    src = (VARIANT*)(((BYTE*)iter->sa->pvData) + iter->i * iter->sa->cbElements);
+
+    /* Fast path for non-refcounted types (VT_I2, VT_I4, VT_R8, VT_BOOL, etc.).
+     * SAFEARRAY elements are stored by value (never VT_BYREF), so VariantCopyInd
+     * reduces to VariantCopy, which for simple types is just a struct assignment. */
+    if(!(V_VT(src) & ~VT_TYPEMASK) && V_VT(src) != VT_BSTR
+            && V_VT(src) != VT_DISPATCH && V_VT(src) != VT_UNKNOWN)
+    {
+        if(V_VT(dst) == VT_BSTR || V_VT(dst) == VT_DISPATCH
+                || V_VT(dst) == VT_UNKNOWN || (V_VT(dst) & VT_ARRAY))
+            VariantClear(dst);
+        *dst = *src;
+    }
+    else
+    {
+        VARIANT value;
+        HRESULT hres;
+
+        V_VT(&value) = VT_EMPTY;
+        hres = VariantCopyInd(&value, src);
+        if(FAILED(hres))
+            return hres;
+
+        VariantClear(dst);
+        *dst = value;
+    }
+
+    iter->i++;
+    *fetched = TRUE;
+    return S_OK;
+}
+
diff --git a/dlls/vbscript/vbscript.h b/dlls/vbscript/vbscript.h
index aed2ccaf5e5..b70d5f23324 100644
--- a/dlls/vbscript/vbscript.h
+++ b/dlls/vbscript/vbscript.h
@@ -455,6 +455,7 @@ BSTR string_replace(BSTR,BSTR,BSTR,int,int,int);
 void map_vbs_exception(EXCEPINFO *);
 
 HRESULT create_safearray_iter(SAFEARRAY *sa, BOOL owned, IEnumVARIANT **ev);
+HRESULT safearray_iter_next(IEnumVARIANT *iface, VARIANT *dst, BOOL *fetched);
 
 #define FACILITY_VBS 0xa
 #define MAKE_VBSERROR(code) MAKE_HRESULT(SEVERITY_ERROR, FACILITY_VBS, code)
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/10515