diff --git a/src/hotspot/cpu/riscv/c2_MacroAssembler_riscv.cpp b/src/hotspot/cpu/riscv/c2_MacroAssembler_riscv.cpp
index b3483eca593c7..a45fe0538ea44 100644
--- a/src/hotspot/cpu/riscv/c2_MacroAssembler_riscv.cpp
+++ b/src/hotspot/cpu/riscv/c2_MacroAssembler_riscv.cpp
@@ -1521,26 +1521,39 @@ void C2_MacroAssembler::byte_array_inflate_v(Register src, Register dst, Registe
 
 // Compress char[] array to byte[].
 // result: the array length if every element in array can be encoded; 0, otherwise.
-void C2_MacroAssembler::char_array_compress_v(Register src, Register dst, Register len, Register result, Register tmp) {
+void C2_MacroAssembler::char_array_compress_v(Register src, Register dst, Register len,
+                                              Register result, Register tmp) {
   Label done;
-  encode_iso_array_v(src, dst, len, result, tmp);
+  encode_iso_array_v(src, dst, len, result, tmp, false);
   beqz(len, done);
   mv(result, zr);
   bind(done);
 }
 
-// result: the number of elements had been encoded.
-void C2_MacroAssembler::encode_iso_array_v(Register src, Register dst, Register len, Register result, Register tmp) {
-  Label loop, DIFFERENCE, DONE;
+// Intrinsic for
+//
+// - sun/nio/cs/ISO_8859_1$Encoder.implEncodeISOArray
+//     return the number of characters copied.
+// - java/lang/StringUTF16.compress
+//     return zero (0) if copy fails, otherwise 'len'.
+//
+// This version always returns the number of characters copied. A successful
+// copy will complete with the post-condition: 'res' == 'len', while an
+// unsuccessful copy will exit with the post-condition: 0 <= 'res' < 'len'.
+//
+// Clobbers: src, dst, len, result, t0
+void C2_MacroAssembler::encode_iso_array_v(Register src, Register dst, Register len,
+                                           Register result, Register tmp, bool ascii) {
+  Label loop, fail, done;
 
   BLOCK_COMMENT("encode_iso_array_v {");
   mv(result, 0);
 
   bind(loop);
-  mv(tmp, 0xff);
+  mv(tmp, ascii ? 0x7f : 0xff);
   vsetvli(t0, len, Assembler::e16, Assembler::m2);
   vle16_v(v2, src);
-  // if element > 0xff, stop
+
   vmsgtu_vx(v1, v2, tmp);
   vfirst_m(tmp, v1);
   vmsbf_m(v0, v1);
@@ -1549,18 +1562,19 @@ void C2_MacroAssembler::encode_iso_array_v(Register src, Register dst, Register
   vncvt_x_x_w(v1, v2, Assembler::v0_t);
   vse8_v(v1, dst, Assembler::v0_t);
 
-  bgez(tmp, DIFFERENCE);
+  // fail if char > 0x7f/0xff
+  bgez(tmp, fail);
   add(result, result, t0);
   add(dst, dst, t0);
   sub(len, len, t0);
   shadd(src, t0, src, t0, 1);
   bnez(len, loop);
-  j(DONE);
+  j(done);
 
-  bind(DIFFERENCE);
+  bind(fail);
   add(result, result, tmp);
 
-  bind(DONE);
+  bind(done);
   BLOCK_COMMENT("} encode_iso_array_v");
 }
 
diff --git a/src/hotspot/cpu/riscv/c2_MacroAssembler_riscv.hpp b/src/hotspot/cpu/riscv/c2_MacroAssembler_riscv.hpp
index aabfb8504bdae..5e7a9ffa63ae2 100644
--- a/src/hotspot/cpu/riscv/c2_MacroAssembler_riscv.hpp
+++ b/src/hotspot/cpu/riscv/c2_MacroAssembler_riscv.hpp
@@ -175,7 +175,7 @@
 
  void encode_iso_array_v(Register src, Register dst,
                          Register len, Register result,
-                         Register tmp);
+                         Register tmp, bool ascii);
 
  void count_positives_v(Register ary, Register len,
                         Register result, Register tmp);
diff --git a/src/hotspot/cpu/riscv/matcher_riscv.hpp b/src/hotspot/cpu/riscv/matcher_riscv.hpp
index ab3fca9b003cf..dc1432346f13b 100644
--- a/src/hotspot/cpu/riscv/matcher_riscv.hpp
+++ b/src/hotspot/cpu/riscv/matcher_riscv.hpp
@@ -159,7 +159,7 @@
   }
 
   // Implements a variant of EncodeISOArrayNode that encode ASCII only
-  static const bool supports_encode_ascii_array = false;
+  static const bool supports_encode_ascii_array = true;
 
   // Some architecture needs a helper to check for alltrue vector
   static constexpr bool vectortest_needs_second_argument(bool is_alltrue, bool is_predicate) {
diff --git a/src/hotspot/cpu/riscv/riscv_v.ad b/src/hotspot/cpu/riscv/riscv_v.ad
index e8ea7accdf167..d29616002b812 100644
--- a/src/hotspot/cpu/riscv/riscv_v.ad
+++ b/src/hotspot/cpu/riscv/riscv_v.ad
@@ -2839,15 +2839,31 @@ instruct vstring_inflate(Universe dummy, iRegP_R10 src, iRegP_R11 dst, iRegI_R12
 instruct vencode_iso_array(iRegP_R12 src, iRegP_R11 dst, iRegI_R13 len, iRegI_R10 result,
                            vReg_V1 v1, vReg_V2 v2, vReg_V3 v3, vRegMask_V0 v0, iRegLNoSp tmp)
 %{
-  predicate(UseRVV);
+  predicate(UseRVV && !((EncodeISOArrayNode*)n)->is_ascii());
+  match(Set result (EncodeISOArray src (Binary dst len)));
+  effect(TEMP_DEF result, USE_KILL src, USE_KILL dst, USE_KILL len,
+         TEMP v0, TEMP v1, TEMP v2, TEMP v3, TEMP tmp);
+
+  format %{ "Encode ISO array $src, $dst, $len -> $result # KILL $src, $dst, $len, $tmp, V0-V3" %}
+  ins_encode %{
+    __ encode_iso_array_v($src$$Register, $dst$$Register, $len$$Register,
+                          $result$$Register, $tmp$$Register, false /* ascii */);
+  %}
+  ins_pipe(pipe_class_memory);
+%}
+
+instruct vencode_ascii_array(iRegP_R12 src, iRegP_R11 dst, iRegI_R13 len, iRegI_R10 result,
+                             vReg_V1 v1, vReg_V2 v2, vReg_V3 v3, vRegMask_V0 v0, iRegLNoSp tmp)
+%{
+  predicate(UseRVV && ((EncodeISOArrayNode*)n)->is_ascii());
   match(Set result (EncodeISOArray src (Binary dst len)));
   effect(TEMP_DEF result, USE_KILL src, USE_KILL dst, USE_KILL len,
-         TEMP v1, TEMP v2, TEMP v3, TEMP tmp, TEMP v0);
+         TEMP v0, TEMP v1, TEMP v2, TEMP v3, TEMP tmp);
 
-  format %{ "Encode array $src,$dst,$len -> $result" %}
+  format %{ "Encode ASCII array $src, $dst, $len -> $result # KILL $src, $dst, $len, $tmp, V0-V3" %}
   ins_encode %{
     __ encode_iso_array_v($src$$Register, $dst$$Register, $len$$Register,
-                          $result$$Register, $tmp$$Register);
+                          $result$$Register, $tmp$$Register, true /* ascii */);
   %}
   ins_pipe(pipe_class_memory);
 %}
@@ -2859,7 +2875,7 @@ instruct vstring_compress(iRegP_R12 src, iRegP_R11 dst, iRegI_R13 len, iRegI_R10
   predicate(UseRVV);
   match(Set result (StrCompressedCopy src (Binary dst len)));
   effect(TEMP_DEF result, USE_KILL src, USE_KILL dst, USE_KILL len,
-         TEMP v1, TEMP v2, TEMP v3, TEMP tmp, TEMP v0);
+         TEMP v0, TEMP v1, TEMP v2, TEMP v3, TEMP tmp);
 
   format %{ "String Compress $src,$dst -> $result    // KILL R11, R12, R13" %}
   ins_encode %{