[716b427f76] Optimize TclStringCatObjv when only one non-empty argument.

2 files changed, 56 insertions, 56 deletions

diff --git a/generic/tclExecute.c b/generic/tclExecute.c
index 30ef536..cfcdd26 100644
--- a/generic/tclExecute.c
+++ b/generic/tclExecute.c
@@ -2685,34 +2685,11 @@ TEBCresume(
 
 	opnd = TclGetUInt1AtPtr(pc+1);
 
-	objv = &OBJ_AT_DEPTH(opnd-1);
-	/* minor optimization in simplest cases */
-	switch (opnd) {
-	case 1: /* only one object */
-	    objResultPtr = *objv;
-	    goto endINST_STR_CONCAT1;
-	case 2: /* two objects - check empty */
-	    if (objv[0]->bytes == &tclEmptyString) {
-		objResultPtr = objv[1];
-		goto endINST_STR_CONCAT1;
-	    }
-	    else
-	    if (objv[1]->bytes == &tclEmptyString) {
-		objResultPtr = objv[0];
-		goto endINST_STR_CONCAT1;
-	    }
-	    break;
-	case 0: /* no objects - use new empty */
-	    TclNewObj(objResultPtr);
-	    goto endINST_STR_CONCAT1;
-	}
-	/* do concat */
 	if (TCL_OK != TclStringCatObjv(interp, /* inPlace */ 1,
-		opnd, objv, &objResultPtr)) {
+		opnd, &OBJ_AT_DEPTH(opnd-1), &objResultPtr)) {
 	    TRACE_ERROR(interp);
 	    goto gotError;
 	}
-      endINST_STR_CONCAT1:
 
 	TRACE_WITH_OBJ(("%u => ", opnd), objResultPtr);
 	NEXT_INST_V(2, opnd, 1);
diff --git a/generic/tclStringObj.c b/generic/tclStringObj.c
index 3478cbb..aae52ba 100644
--- a/generic/tclStringObj.c
+++ b/generic/tclStringObj.c
@@ -2848,10 +2848,18 @@ TclStringCatObjv(
     Tcl_Obj **objPtrPtr)
 {
     Tcl_Obj *objPtr, *objResultPtr, * const *ov;
-    int oc, length = 0, binary = 1, first = 0;
+    int oc, length = 0, binary = 1, first = 0, last = 0;
     int allowUniChar = 1, requestUniChar = 0;
 
-    /* assert (objc >= 2) */
+    /* assert ( objc >= 0 ) */
+
+    if (objc <= 1) {
+	/* Only one or no objects; return first or empty */
+	*objPtrPtr = objc ? objv[0] : Tcl_NewObj();
+	return TCL_OK;
+    }
+
+    /* assert ( objc >= 2 ) */
 
     /*
      * Analyze to determine what representation result should be.
@@ -2861,7 +2869,7 @@ TclStringCatObjv(
      */
 
     ov = objv, oc = objc;
-    while (oc-- && (binary || allowUniChar)) {
+    do {
 	objPtr = *ov++;
 
 	if (objPtr->bytes) {
@@ -2892,72 +2900,79 @@ TclStringCatObjv(
 		}
 	    }
 	}
-    }
+    } while (--oc && (binary || allowUniChar));
 
     if (binary) {
 	/* Result will be pure byte array. Pre-size it */
 	ov = objv; oc = objc;
-	while (oc-- && (length >= 0)) {
+	do {
 	    objPtr = *ov++;
 
 	    if (objPtr->bytes == NULL) {
 		int numBytes;
 
 		Tcl_GetByteArrayFromObj(objPtr, &numBytes); /* PANIC? */
-		if (length == 0) {
-		    first = objc - oc - 1;
+		if (numBytes) {
+		    last = objc - oc;
+		    if (length == 0) {
+			first = last;
+		    }
+		    if ((length += numBytes) < 0) {
+			goto overflow;
+		    }
 		}
-		length += numBytes;
 	    }
-	}
+	} while (--oc);
     } else if (allowUniChar && requestUniChar) {
 	/* Result will be pure Tcl_UniChar array. Pre-size it. */
 	ov = objv; oc = objc;
-	while (oc-- && (length >= 0)) {
+	do {
 	    objPtr = *ov++;
 
 	    if ((objPtr->bytes == NULL) || (objPtr->length)) {
 		int numChars;
 
 		Tcl_GetUnicodeFromObj(objPtr, &numChars); /* PANIC? */
-		if (length == 0) {
-		    first = objc - oc - 1;
+		if (numChars) {
+		    last = objc - oc;
+		    if (length == 0) {
+			first = last;
+		    }
+		    if ((length += numChars) < 0) {
+			goto overflow;
+		    }
 		}
-		length += numChars;
 	    }
-	}
+	} while (--oc);
     } else {
 	/* Result will be concat of string reps. Pre-size it. */
 	ov = objv; oc = objc;
-	while (oc-- && (length >= 0)) {
+	do {
 	    int numBytes;
 
 	    objPtr = *ov++;
 
 	    Tcl_GetStringFromObj(objPtr, &numBytes);	/* PANIC? */
-	    if ((length == 0) && numBytes) {
-		first = objc - oc - 1;
+	    if (numBytes) {
+		last = objc - oc;
+		if (length == 0) {
+		    first = last;
+		}
+		if ((length += numBytes) < 0) {
+		    goto overflow;
+		}
 	    }
-	    length += numBytes;
-	}
+	} while (--oc);
     }
 
-    if (length < 0) {
-	if (interp) {
-	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
-		    "max size for a Tcl value (%d bytes) exceeded", INT_MAX));
-	    Tcl_SetErrorCode(interp, "TCL", "MEMORY", NULL);
-	}
-	return TCL_ERROR;
-    }
-
-    if (length == 0) {
-	/* Total length of zero means every value has length zero */
-	*objPtrPtr = objv[0];
+    if (last == first /*|| length == 0 */) {
+	/* Only one non-empty value or zero length; return first */
+	/* NOTE: (length == 0) implies (last == first) */
+	*objPtrPtr = objv[first];
 	return TCL_OK;
     }
 
-    objv += first; objc -= first;
+    objv += first; objc = (last - first + 1);
 
     if (binary) {
 	/* Efficiently produce a pure byte array result */
@@ -3087,6 +3102,14 @@ TclStringCatObjv(
     }
     *objPtrPtr = objResultPtr;
     return TCL_OK;
+
+  overflow:
+    if (interp) {
+	Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+		    "max size for a Tcl value (%d bytes) exceeded", INT_MAX));
+	Tcl_SetErrorCode(interp, "TCL", "MEMORY", NULL);
+    }
+    return TCL_ERROR;
 }
 
 /*