Don't cache direct evaluation of patterns with variables

The slow pattern matching path in xsltTestCompMatchDirect caches the
result of evaluating the pattern. But this can't be done if the pattern
contains variables which could evaluate to different values.

Only enable the cache for patterns like template matches that don't
allow variable references. Don't use the cache for "count" and "from"
patterns in xsl:number.

A more fine-grained approach would be nice, but most effort should be
spent on eliminating the slow path completely.

Thanks to Martin Honnen for the report.

Fixes #6.

libxslt/pattern.c

@@ -113,6 +113,7 @@
     xmlNsPtr *nsList;		/* the namespaces in scope */
     int nsNr;			/* the number of namespaces in scope */
     xsltStepOpPtr steps;        /* ops for computation */
+    int novar;                  /* doesn't contain variables */
 };
 
 typedef struct _xsltParserContext xsltParserContext;
@@ -594,7 +595,8 @@
 	}
 	ix = 0;
 
-	if ((parent == NULL) || (node->doc == NULL) || isRVT)
+	if ((parent == NULL) || (node->doc == NULL) || isRVT ||
+            (comp->novar == 0))
 	    nocache = 1;
 
 	if (nocache == 0) {
@@ -1970,6 +1972,7 @@
 		j++;
 	}
 	element->nsNr = j;
+        element->novar = novar;
 
 
 #ifdef WITH_XSLT_DEBUG_PATTERN

tests/docs/bug-214.xml

+<root>
+    <element type="a"/>
+    <element type="b"/>
+    <element type="a"/>
+</root>
+

tests/general/bug-214.out

+<?xml version="1.0"?>
+<root>
+    <element type="a" pos="1"/>
+    <element type="b" pos="1"/>
+    <element type="a" pos="2"/>
+</root>

tests/general/bug-214.xsl

+<xsl:stylesheet
+	xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+	version="1.0">
+
+  <xsl:template match="@* | node()">
+    <xsl:copy>
+      <xsl:apply-templates select="@* | node()"/>
+    </xsl:copy>
+  </xsl:template>
+
+  <xsl:template match="*[@type]">
+      <xsl:copy>
+          <xsl:variable name="type" select="@type"/>
+          <xsl:variable name="pos">
+              <xsl:number count="node()[@type = $type]"/>
+          </xsl:variable>
+          <xsl:apply-templates select="@*"/>
+          <xsl:attribute name="pos">
+              <xsl:value-of select="$pos"/>
+          </xsl:attribute>
+          <xsl:apply-templates/>
+      </xsl:copy>
+  </xsl:template>
+
+</xsl:stylesheet>