A64: Port LSeqStringSetChar optimizations from r16707 and r17521.

src/a64/full-codegen-a64.cc

Index: src/a64/full-codegen-a64.cc
diff --git a/src/a64/full-codegen-a64.cc b/src/a64/full-codegen-a64.cc
index 761e719e932b1c784dc2aadada4c61b296e54a23..05a0dc4f75e2f0ad45532ba2424433bf5501cc5a 100644
--- a/src/a64/full-codegen-a64.cc
+++ b/src/a64/full-codegen-a64.cc
@@ -3224,9 +3224,9 @@ void FullCodeGenerator::EmitOneByteSeqStringSetChar(CallRuntime* expr) {
     __ Throw(kNonSmiValue);
     __ Throw(kNonSmiIndex);
     __ Bind(&both_smis);
-
     static const uint32_t one_byte_seq_type = kSeqStringTag | kOneByteStringTag;
-    __ EmitSeqStringSetCharCheck(string, index, one_byte_seq_type);
+    __ EmitSeqStringSetCharCheck(string, index, kIndexIsSmi, scratch,
+                                 one_byte_seq_type);
   }
 
   __ Add(scratch, string, SeqOneByteString::kHeaderSize - kHeapObjectTag);
@@ -3257,9 +3257,9 @@ void FullCodeGenerator::EmitTwoByteSeqStringSetChar(CallRuntime* expr) {
     __ Throw(kNonSmiValue);
     __ Throw(kNonSmiIndex);
     __ Bind(&both_smis);
-
     static const uint32_t two_byte_seq_type = kSeqStringTag | kTwoByteStringTag;
-    __ EmitSeqStringSetCharCheck(string, index, two_byte_seq_type);
+    __ EmitSeqStringSetCharCheck(string, index, kIndexIsSmi, scratch,
+                                 two_byte_seq_type);
   }
 
   __ Add(scratch, string, SeqTwoByteString::kHeaderSize - kHeapObjectTag);