RFR: tune native call site check

[yangyongyong]

Roughly there are 3 kinds of native call site checked by nativeCall_before():

1.       Native-Trampoline-Call takes the form of:

add     lr, pc, #4
ldr     pc, [pc, -4]
0x????????    # call_destination
#return_address:
  Some_insn


2.       Native-Imm-Call

bl imm  # call_destination
#return_address:
  Some_insn


3.       Native-Reg-Call


   movw regx, #call_destination

   movt regx, #call_destination
bl regx    # call destination
#return_address:
  Some_insn

Current check logic incurs a problem if the encoding of the call destination of type 1 can by any chance be disassembled as a “bl imm” instruction.
And thus the call address is calculated improperly and then the relocation info will not be found, which causes assert failure in CompiledIC::CompiledIC(nmethod* nm, NativeCall* call):
assert(ret == true, "relocInfo must exist at this address");

This failure can be reproduced simply by “java -Xcomp -XX:ReservedCodeCacheSize=xx”. Please tune xx and make sure some of the JITed code is placed at address 0x?B??????.
The attached patch improves the check logic:
----------------- patch begins ----------------
diff -r 80b7b526cffb src/cpu/aarch32/vm/nativeInst_aarch32.cpp
--- a/src/cpu/aarch32/vm/nativeInst_aarch32.cpp         Sun Sep 04 20:52:43 2016 +0100
+++ b/src/cpu/aarch32/vm/nativeInst_aarch32.cpp      Fri Sep 09 17:38:34 2016 +0800
@@ -132,14 +132,14 @@
}
 bool NativeCall::is_at(address addr) {
-  if (NativeImmCall::is_at(addr)) {
+  if (NativeTrampolineCall::is_at(addr)) {
     return true;
   } else if (NativeMovConstReg::is_at(addr)) {
     NativeMovConstReg *nm = NativeMovConstReg::from(addr);
     address next_instr = nm->next_instruction_address();
     return NativeRegCall::is_at(next_instr) &&
       NativeRegCall::from(next_instr)->destination() == nm->destination();
-  } else if (NativeTrampolineCall::is_at(addr)) {
+  } else if (NativeImmCall::is_at(addr)) {
     return true;
   }
   return false;
diff -r 80b7b526cffb src/cpu/aarch32/vm/nativeInst_aarch32.hpp
--- a/src/cpu/aarch32/vm/nativeInst_aarch32.hpp         Sun Sep 04 20:52:43 2016 +0100
+++ b/src/cpu/aarch32/vm/nativeInst_aarch32.hpp      Fri Sep 09 17:38:34 2016 +0800
@@ -306,10 +306,10 @@
 inline NativeCall* nativeCall_before(address return_address) {
   address call_addr = NULL;
-  if (NativeCall::is_at(return_address - NativeBranchType::instruction_size)) {
+  if (NativeCall::is_at(return_address - NativeCall::instruction_size)) {
+    call_addr = return_address - NativeCall::instruction_size;
+  } else if (NativeCall::is_at(return_address - NativeBranchType::instruction_size)) {
     call_addr = return_address - NativeBranchType::instruction_size;
-  } else if (NativeCall::is_at(return_address - NativeCall::instruction_size)) {
-    call_addr = return_address - NativeCall::instruction_size;
   } else {
     ShouldNotReachHere();
   }
----------------- patch ends ----------------