8173585: Intrinsify StringLatin1.indexOf(char)

Added new unit test: findOneItem. This will test strings of varying
length ensuring that for all lengths one instance of the search char can
be found. We check what happens when the search character is in each
position of the search string (including first and last positions).

Author: Jason Tatton (AWS)

test/hotspot/jtreg/compiler/intrinsics/string/TestStringLatin1IndexOfChar.java

@@ -12,10 +12,10 @@
  * @library /compiler/patches /test/lib
  * @run main/othervm -Xbatch -XX:Tier4InvocationThreshold=200 -XX:CompileThreshold=100 compiler.intrinsics.string.TestStringLatin1IndexOfChar
  * @run main/othervm -Xbatch -XX:Tier4InvocationThreshold=200 -XX:CompileThreshold=100 -XX:+UnlockDiagnosticVMOptions -XX:DisableIntrinsic=_indexOfL_char compiler.intrinsics.string.TestStringLatin1IndexOfChar
- * @run main/othervm -Xbatch -XX:Tier4InvocationThreshold=200 -XX:CompileThreshold=100 -XX:UseSSE=0 compiler.intrinsics.string.TestStringLatin1IndexOfChar
- * @run main/othervm -Xbatch -XX:Tier4InvocationThreshold=200 -XX:CompileThreshold=100 -XX:UseAVX=1 compiler.intrinsics.string.TestStringLatin1IndexOfChar
- * @run main/othervm -Xbatch -XX:Tier4InvocationThreshold=200 -XX:CompileThreshold=100 -XX:UseAVX=2 compiler.intrinsics.string.TestStringLatin1IndexOfChar
- * @run main/othervm -Xbatch -XX:Tier4InvocationThreshold=200 -XX:CompileThreshold=100 -XX:UseAVX=3 compiler.intrinsics.string.TestStringLatin1IndexOfChar
+ * @run main/othervm -Xbatch -XX:Tier4InvocationThreshold=200 -XX:CompileThreshold=100 -XX:+IgnoreUnrecognizedVMOptions -XX:UseSSE=0 compiler.intrinsics.string.TestStringLatin1IndexOfChar
+ * @run main/othervm -Xbatch -XX:Tier4InvocationThreshold=200 -XX:CompileThreshold=100 -XX:+IgnoreUnrecognizedVMOptions -XX:UseAVX=1 compiler.intrinsics.string.TestStringLatin1IndexOfChar
+ * @run main/othervm -Xbatch -XX:Tier4InvocationThreshold=200 -XX:CompileThreshold=100 -XX:+IgnoreUnrecognizedVMOptions -XX:UseAVX=2 compiler.intrinsics.string.TestStringLatin1IndexOfChar
+ * @run main/othervm -Xbatch -XX:Tier4InvocationThreshold=200 -XX:CompileThreshold=100 -XX:+IgnoreUnrecognizedVMOptions -XX:UseAVX=3 compiler.intrinsics.string.TestStringLatin1IndexOfChar
  */
 
 package compiler.intrinsics.string;
@@ -27,7 +27,8 @@ public class TestStringLatin1IndexOfChar{
 
     public static void main(String[] args) throws Exception {
         for (int i = 0; i < 1_000; ++i) {//repeat such that we enter into C2 code...
-            maintest();
+            findOneItem();
+            withOffsetTest();
             testEmpty();
         }
     }
@@ -40,14 +41,39 @@ private static void testEmpty(){
     private final static char INVERLEAVING_CHAR = 'a';
     private final static char MISSING_CHAR = 'd';
 
-    private static void maintest(){
+    private static void findOneItem(){
+        //test strings of varying length ensuring that for all lengths one instance of the
+        //search char can be found. We check what happens when the search character is in
+        //each position of the search string (including first and last positions)
+        for(int strLength : new int[]{1, 15, 31, 32, 79}){
+            for(int searchPos = 0; searchPos < strLength; searchPos++){
+                String totest = makeOneItemStringLatin1(strLength, searchPos);
+
+                int intri = totest.indexOf(SEARCH_CHAR);
+                int nonintri = indexOfCharNonIntrinsic(totest, SEARCH_CHAR, 0);
+                Asserts.assertEQ(intri, nonintri);
+            }
+        }
+    }
+
+    private static String makeOneItemStringLatin1(int length, int searchPos){
+        StringBuilder sb = new StringBuilder(length);
+
+        for(int n =0; n < length; n++){
+            sb.append(searchPos==n?SEARCH_CHAR:INVERLEAVING_CHAR);
+        }
+
+        return sb.toString();
+    }
+
+    private static void withOffsetTest(){
         //progressivly move through string checking indexes and starting offset correctly processed
         //string is of form azaza, aazaazaa, aaazaaazaaa, etc
         //we find n s.t. maxlength = (n*3) + 2
         int maxaInstances = (MAX_LENGTH-2)/3;
 
         for(int aInstances = 5; aInstances < MAX_LENGTH; aInstances++){
-            String totest = makeCandidateStringLatin1(aInstances);
+            String totest = makeWithOffsetStringLatin1(aInstances);
 
             int startoffset;
             {
@@ -71,7 +97,7 @@ private static void maintest(){
         }
     }
 
-    private static String makeCandidateStringLatin1(int aInstances){
+    private static String makeWithOffsetStringLatin1(int aInstances){
         StringBuilder sb = new StringBuilder((aInstances*3) + 2);
         for(int n =0; n < aInstances; n++){
             sb.append(INVERLEAVING_CHAR);