Decode ic data and arguments descriptor passed in calls on ARM.

runtime/vm/instructions_arm.cc

Index: runtime/vm/instructions_arm.cc
===================================================================
--- runtime/vm/instructions_arm.cc	(revision 19826)
+++ runtime/vm/instructions_arm.cc	(working copy)
@@ -14,8 +14,19 @@
 
 CallPattern::CallPattern(uword pc, const Code& code)
     : end_(reinterpret_cast<uword*>(pc)),
-      pool_index_(DecodePoolIndex()),
-      object_pool_(Array::Handle(code.ObjectPool())) { }
+      target_address_pool_index_(-1),
+      args_desc_load_end_(-1),
+      args_desc_pool_index_(-1),
+      ic_data_load_end_(-1),
+      ic_data_pool_index_(-1),
+      object_pool_(Array::Handle(code.ObjectPool())) {
+  ASSERT(code.ContainsInstructionAt(pc));
+  ASSERT(Back(1) == 0xe12fff3e);  // Last instruction: blx lr
+  Register reg;
+  args_desc_load_end_ =
+      DecodeLoadWordFromPool(1, &reg, &target_address_pool_index_);
+  ASSERT(reg == LR);
+}
 
 
 uword CallPattern::Back(int n) const {
@@ -24,43 +35,83 @@
 }
 
 
-int CallPattern::DecodePoolIndex() {
-  ASSERT(Back(1) == 0xe12fff3e);  // Last instruction: blx lr
-  // Decode the second to last instruction.
-  uword instr = Back(2);
+// Decodes a load sequence ending at end. Returns the register being loaded and
+// the index in the pool being read from.
+// Returns the location of the load sequence, counting the number of
+// instructions back from the end of the call pattern.
+int CallPattern::DecodeLoadWordFromPool(int end, Register* reg, int* index) {
+  ASSERT(end > 0);
+  uword instr = Back(++end);
   int offset = 0;
-  if ((instr & 0xfffff000) == 0xe59ae000) {  // ldr lr, [pp, #+offset]
+  if ((instr & 0xffff0000) == 0xe59a0000) {  // ldr reg, [pp, #+offset]
     offset = instr & 0xfff;
+    *reg = static_cast<Register>((instr & 0xf000) >> 12);
   } else {
-    ASSERT((instr & 0xfffff000) == 0xe59ee000);  // ldr lr, [lr, #+offset]
+    ASSERT((instr & 0xfff00000) == 0xe5900000);  // ldr reg, [reg, #+offset]
     offset = instr & 0xfff;
-    instr = Back(3);
-    if ((instr & 0xfffff000) == 0xe28ae000) {  // add lr, pp, shifter_op
+    instr = Back(++end);
+    if ((instr & 0xffff0000) == 0xe28a0000) {  // add reg, pp, shifter_op
       const int rot = (instr & 0xf00) * 2;
       const int imm8 = instr & 0xff;
       offset |= (imm8 >> rot) | (imm8 << (32 - rot));
+      *reg = static_cast<Register>((instr & 0xf000) >> 12);
     } else {
-      ASSERT(instr == 0xe08ae00e);  // add lr, pp, lr
-      instr = Back(4);
-      if ((instr & 0xfff0f000) == 0xe340e000) {  // movt lr, offset_hi
+      ASSERT((instr & 0xffff0000) == 0xe08a0000);  // add reg, pp, reg
+      instr = Back(++end);
+      if ((instr & 0xfff00000) == 0xe3400000) {  // movt reg, offset_hi
         offset |= (instr & 0xf0000) << 12;
         offset |= (instr & 0xfff) << 16;
-        instr = Back(5);
+        instr = Back(++end);
       }
-      ASSERT((instr & 0xfff0f000) == 0xe300e000);  // movw lr, offset_lo
+      ASSERT((instr & 0xfff00000) == 0xe3000000);  // movw reg, offset_lo
       ASSERT((offset & 0xffff) == 0);
       offset |= (instr & 0xf0000) >> 4;
       offset |= instr & 0xfff;
+      *reg = static_cast<Register>((instr & 0xf000) >> 12);
     }
   }
   offset += kHeapObjectTag;
   ASSERT(Utils::IsAligned(offset, 4));
-  return (offset - Array::data_offset())/4;
+  *index = (offset - Array::data_offset())/4;
+  return end;
 }
 
 
+RawICData* CallPattern::IcData() {
+  if (ic_data_pool_index_ < 0) {
+    Register reg;
+    // Loading of the argument descriptor must be decoded first, if not already.
+    if (args_desc_pool_index_ < 0) {
+      ic_data_load_end_ = DecodeLoadWordFromPool(
+          args_desc_load_end_, &reg, &args_desc_pool_index_);
+      ASSERT(reg == R4);
+    }
+    DecodeLoadWordFromPool(ic_data_load_end_, &reg, &ic_data_pool_index_);
+    ASSERT(reg == R5);
+  }
+  ICData& ic_data = ICData::Handle();
+  ic_data ^= object_pool_.At(ic_data_pool_index_);
+  return ic_data.raw();
+}
+
+
+RawArray* CallPattern::ArgumentsDescriptor() {
+  if (args_desc_pool_index_ < 0) {
+    Register reg;
+    ic_data_load_end_ = DecodeLoadWordFromPool(
+        args_desc_load_end_, &reg, &args_desc_pool_index_);
+    ASSERT(reg == R4);
+  }
+  Array& args_desc = Array::Handle();
+  args_desc ^= object_pool_.At(args_desc_pool_index_);
+  return args_desc.raw();
+}
+
+
 uword CallPattern::TargetAddress() const {
-  const Object& target_address = Object::Handle(object_pool_.At(pool_index_));
+  ASSERT(target_address_pool_index_ >= 0);
+  const Object& target_address =
+      Object::Handle(object_pool_.At(target_address_pool_index_));
   ASSERT(target_address.IsSmi());
   // The address is stored in the object array as a RawSmi.
   return reinterpret_cast<uword>(target_address.raw());
@@ -71,7 +122,7 @@
   ASSERT(Utils::IsAligned(target_address, 4));
   // The address is stored in the object array as a RawSmi.
   const Smi& smi = Smi::Handle(reinterpret_cast<RawSmi*>(target_address));
-  object_pool_.SetAt(pool_index_, smi);
+  object_pool_.SetAt(target_address_pool_index_, smi);
   // No need to flush the instruction cache, since the code is not modified.
 }