Explicitly clear out the IC-data register in ExecuteMatch.

runtime/vm/intrinsifier_arm.cc

Index: runtime/vm/intrinsifier_arm.cc
diff --git a/runtime/vm/intrinsifier_arm.cc b/runtime/vm/intrinsifier_arm.cc
index 342c284652b99cc322c90750898106d7e8df8c71..f608b5a23e16bb6c89455a362372f80057fa6b74 100644
--- a/runtime/vm/intrinsifier_arm.cc
+++ b/runtime/vm/intrinsifier_arm.cc
@@ -1991,7 +1991,7 @@ void Intrinsifier::JSRegExp_ExecuteMatch(Assembler* assembler) {
   // Incoming registers:
   // R0: Function. (Will be reloaded with the specialized matcher function.)
   // R4: Arguments descriptor. (Will be preserved.)
-  // R5: IC-Data. (Will be preserved.)
+  // R5: Unknown. (Must be GC safe on tail call.)
 
   // Load the specialized function pointer into R0. Leverage the fact the
   // string CIDs as well as stored function pointers are in sequence.
@@ -2006,6 +2006,7 @@ void Intrinsifier::JSRegExp_ExecuteMatch(Assembler* assembler) {
   // in R0, the argument descriptor in R4, and IC-Data in R5.
   static const intptr_t arg_count = RegExpMacroAssembler::kParamCount;
   __ LoadObject(R4, Array::Handle(ArgumentsDescriptor::New(arg_count)));
+  __ eor(R5, R5, Operand(R5));
 
   // Tail-call the function.
   __ ldr(R1, FieldAddress(R0, Function::instructions_offset()));