[PATCH 0/1] MR10536: vbscript: Fast-path stack_pop_bool for VT_BOOL.

[Francis De Brabandere (＠francisdb)]

Skip the expensive VariantChangeType call in stack_pop_bool when the
variant is already VT_BOOL, which is the common case after comparison
operators (OP_gt, OP_lt, OP_equal, etc.). Every If, ElseIf, While,
and Do-While condition goes through jmp_false/jmp_true which calls
stack_pop_bool, so this eliminates a redundant VT_BOOL-to-VT_BOOL
conversion on every branch.

This closed the If-condition gap from 1.5–2.1× slower than Windows down to 1.0–1.7× slower, with pure boolean tests reaching parity.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10536

[PATCH 1/1] vbscript: Fast-path stack_pop_bool for VT_BOOL.

[Francis De Brabandere]

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

Skip the expensive VariantChangeType call in stack_pop_bool when the
variant is already VT_BOOL, which is the common case after comparison
operators (OP_gt, OP_lt, OP_equal, etc.). Every If, ElseIf, While,
and Do-While condition goes through jmp_false/jmp_true which calls
stack_pop_bool, so this eliminates a redundant VT_BOOL-to-VT_BOOL
conversion on every branch.
---
 dlls/vbscript/interp.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/dlls/vbscript/interp.c b/dlls/vbscript/interp.c
index ad8ece8605d..07e2a2bd602 100644
--- a/dlls/vbscript/interp.c
+++ b/dlls/vbscript/interp.c
@@ -442,21 +442,26 @@ static HRESULT stack_pop_bool(exec_ctx_t *ctx, BOOL *b)
 {
     variant_val_t val;
     HRESULT hres;
-    VARIANT v;
 
     hres = stack_pop_val(ctx, &val);
     if(FAILED(hres))
         return hres;
 
-    if (V_VT(val.v) == VT_NULL)
-    {
+    switch(V_VT(val.v)) {
+    case VT_BOOL:
+        *b = !!V_BOOL(val.v);
+        break;
+    case VT_NULL:
         *b = FALSE;
-    }
-    else
-    {
+        break;
+    default: {
+        VARIANT v;
         V_VT(&v) = VT_EMPTY;
-        if (SUCCEEDED(hres = VariantChangeType(&v, val.v, VARIANT_LOCALBOOL, VT_BOOL)))
+        hres = VariantChangeType(&v, val.v, VARIANT_LOCALBOOL, VT_BOOL);
+        if(SUCCEEDED(hres))
             *b = !!V_BOOL(&v);
+        break;
+    }
     }
 
     release_val(&val);
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/10536

[Jacek Caban (＠jacek)]

Jacek Caban (@jacek) commented about dlls/vbscript/interp.c:
> -    }
> -    else
> -    {
> +        break;
> +    default: {
> +        VARIANT v;
>          V_VT(&v) = VT_EMPTY;
> -        if (SUCCEEDED(hres = VariantChangeType(&v, val.v, VARIANT_LOCALBOOL, VT_BOOL)))
> +        hres = VariantChangeType(&v, val.v, VARIANT_LOCALBOOL, VT_BOOL);
> +        if(SUCCEEDED(hres))
>              *b = !!V_BOOL(&v);
> +        break;
> +    }
>      }
>
> release_val(&val);
> It is not a big deal, but since this is all about performance, you could move `release_val` to the default case to skip it for fast paths that do not need it.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10536#note_134973

[Francis De Brabandere (＠francisdb)]

On Sat Apr  4 18:19:00 2026 +0000, Jacek Caban wrote:
> It is not a big deal, but since this is all about performance, you could
> move `release_val` to the default case to skip it for fast paths that do
> not need it.
> done

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10536#note_135046