Add support for emitting DW_CFA_restore_extended

This CL enables emitting register codes that are
greater than 6 bits by encoding it as a LEB128.

Change-Id: I35675b5ef6a935f785035aa101ed4ca812af251e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2008305Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#65889}

src/diagnostics/eh-frame.cc

@@ -338,10 +338,14 @@ void EhFrameWriter::RecordRegisterFollowsInitialRule(Register name) {
 
 void EhFrameWriter::RecordRegisterFollowsInitialRule(int dwarf_register_code) {
   DCHECK_EQ(writer_state_, InternalState::kInitialized);
-  DCHECK_LE(dwarf_register_code, EhFrameConstants::kFollowInitialRuleMask);
-  WriteByte((EhFrameConstants::kFollowInitialRuleTag
-             << EhFrameConstants::kFollowInitialRuleMaskSize) |
-            (dwarf_register_code & EhFrameConstants::kFollowInitialRuleMask));
+  if (dwarf_register_code <= EhFrameConstants::kFollowInitialRuleMask) {
+    WriteByte((EhFrameConstants::kFollowInitialRuleTag
+               << EhFrameConstants::kFollowInitialRuleMaskSize) |
+              (dwarf_register_code & EhFrameConstants::kFollowInitialRuleMask));
+  } else {
+    WriteOpcode(EhFrameConstants::DwarfOpcodes::kRestoreExtended);
+    WriteULeb128(dwarf_register_code);
+  }
 }
 
 void EhFrameWriter::Finish(int code_size) {

src/diagnostics/eh-frame.h

@@ -24,6 +24,7 @@ class V8_EXPORT_PRIVATE EhFrameConstants final
     kAdvanceLoc1 = 0x02,
     kAdvanceLoc2 = 0x03,
     kAdvanceLoc4 = 0x04,
+    kRestoreExtended = 0x06,
     kSameValue = 0x08,
     kDefCfa = 0x0c,
     kDefCfaRegister = 0x0d,