[flang-commits] [flang] [llvm] [flang] Implement SPLIT intrinsic subroutine with tests (PR #185584)

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@@ -992,6 +992,56 @@ static RT_API_ATTRS void TokenizePositionsImpl(Descriptor &first,
   }
 }
 
+// SPLIT - scans for the next separator character in STRING.
+// When BACK is false (or absent), returns the position of the leftmost
+// character in SET whose position in STRING is greater than POS, or
+// LEN(STRING)+1 if no such character exists.
+// When BACK is true, returns the position of the rightmost character in
+// SET whose position in STRING is less than POS, or 0 if no such
+// character exists.
+template <typename CHAR>
+static RT_API_ATTRS std::size_t SplitImpl(const CHAR *string,
+    std::size_t stringLen, const CHAR *set, std::size_t setLen, std::size_t pos,
+    bool back) {
+  if (back) {
+    // Scan backwards from position pos-1 (1-indexed pos means index pos-2)
+    // looking for the rightmost separator at position < pos.
+    if (pos <= 1) {
+      return 0;
+    }
+    std::size_t scanLen = pos - 1; // number of characters to scan
+    if (scanLen > stringLen) {
+      scanLen = stringLen;
+    }
+    for (std::size_t i = scanLen; i > 0; --i) {
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laoshd wrote:

Re-implemented in terms of SCAN. No need for this nested loops any more.

https://github.com/llvm/llvm-project/pull/185584