deps: V8: cherry-pick b66334313c8b

Original commit message:

    [riscv64] use callee save register in regexp

    Bug: v8:12502

    Change-Id: I8d1b599fc945e276b70901953368768594470204
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3343861
    Reviewed-by: ji qiu <qiuji@iscas.ac.cn>
    Commit-Queue: ji qiu <qiuji@iscas.ac.cn>
    Cr-Commit-Position: refs/heads/main@{#78421}

Refs: v8/v8@b663343

PR-URL: #42067
Refs: v8/v8@77d5154
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Mary Marchini <oss@mmarchini.me>
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Stewart X Addison <sxa@redhat.com>

deps/v8/src/regexp/riscv64/regexp-macro-assembler-riscv64.cc

@@ -23,10 +23,10 @@ namespace internal {
  * This assembler uses the following register assignment convention
  * - s3 : kScratchReg. Temporarily stores the index of capture start after a matching pass
  *        for a global regexp.
- * - a5 : Pointer to current Code object including heap object tag.
- * - a6 : Current position in input, as negative offset from end of string.
+ * - s4 : Pointer to current Code object including heap object tag.
+ * - s1 : Current position in input, as negative offset from end of string.
  *        Please notice that this is the byte offset, not the character offset!
- * - a7 : Currently loaded character. Must be loaded using
+ * - s2 : Currently loaded character. Must be loaded using
  *        LoadCurrentCharacter before using any of the dispatch methods.
  * - t0 : Points to tip of backtrack stack
  * - t1 : Unused.

deps/v8/src/regexp/riscv64/regexp-macro-assembler-riscv64.h

@@ -144,10 +144,10 @@ class V8_EXPORT_PRIVATE RegExpMacroAssemblerRISCV
 
   // Register holding the current input position as negative offset from
   // the end of the string.
-  inline Register current_input_offset() { return a6; }
+  inline Register current_input_offset() { return s1; }
 
   // The register containing the current character after LoadCurrentCharacter.
-  inline Register current_character() { return a7; }
+  inline Register current_character() { return s2; }
 
   // Register holding address of the end of the input string.
   inline Register end_of_input_address() { return t2; }
@@ -161,7 +161,7 @@ class V8_EXPORT_PRIVATE RegExpMacroAssemblerRISCV
   inline Register backtrack_stackpointer() { return t0; }
 
   // Register holding pointer to the current code object.
-  inline Register code_pointer() { return a5; }
+  inline Register code_pointer() { return s4; }
 
   // Byte size of chars in the string to match (decided by the Mode argument).
   inline int char_size() { return static_cast<int>(mode_); }