Change the ARM fixup code to handle the use of the following

instruction sequence for jumps:

  mov(ip, Operand(target, rmode), LeaveCC, cond);
  bx(ip, cond)

Changed a JS call in the compare stub to a tail call to avoid GC
problems where the pushed return address is not updated on GC.
Review URL: http://codereview.chromium.org/549022

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3582 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/assembler-arm-inl.h

@@ -229,14 +229,24 @@ void Assembler::emit(Instr x) {
 
 
 Address Assembler::target_address_address_at(Address pc) {
-  Instr instr = Memory::int32_at(pc);
-  // Verify that the instruction at pc is a ldr<cond> <Rd>, [pc +/- offset_12].
+  Address target_pc = pc;
+  Instr instr = Memory::int32_at(target_pc);
+  // If we have a bx instruction, the instruction before the bx is
+  // what we need to patch.
+  static const int32_t kBxInstMask = 0x0ffffff0;
+  static const int32_t kBxInstPattern = 0x012fff10;
+  if ((instr & kBxInstMask) == kBxInstPattern) {
+    target_pc -= kInstrSize;
+    instr = Memory::int32_at(target_pc);
+  }
+  // Verify that the instruction to patch is a
+  // ldr<cond> <Rd>, [pc +/- offset_12].
   ASSERT((instr & 0x0f7f0000) == 0x051f0000);
   int offset = instr & 0xfff;  // offset_12 is unsigned
   if ((instr & (1 << 23)) == 0) offset = -offset;  // U bit defines offset sign
   // Verify that the constant pool comes after the instruction referencing it.
   ASSERT(offset >= -4);
-  return pc + offset + 8;
+  return target_pc + offset + 8;
 }
 
 

src/arm/codegen-arm.cc

@@ -5090,12 +5090,10 @@ void CompareStub::Generate(MacroAssembler* masm) {
   }
 
   __ bind(&slow);
-  __ push(lr);
   __ push(r1);
   __ push(r0);
   // Figure out which native to call and setup the arguments.
   Builtins::JavaScript native;
-  int arg_count = 1;  // Not counting receiver.
   if (cc_ == eq) {
     native = strict_ ? Builtins::STRICT_EQUALS : Builtins::EQUALS;
   } else {
@@ -5107,16 +5105,13 @@ void CompareStub::Generate(MacroAssembler* masm) {
       ASSERT(cc_ == gt || cc_ == ge);  // remaining cases
       ncr = LESS;
     }
-    arg_count++;
     __ mov(r0, Operand(Smi::FromInt(ncr)));
     __ push(r0);
   }
 
   // Call the native; it returns -1 (less), 0 (equal), or 1 (greater)
   // tagged as a small integer.
-  __ InvokeBuiltin(native, CALL_JS);
-  __ cmp(r0, Operand(0));
-  __ pop(pc);
+  __ InvokeBuiltin(native, JUMP_JS);
 }