Implement leaf runtime call stub on ARM and corresponding call redirection

runtime/vm/instructions_arm.cc

Index: runtime/vm/instructions_arm.cc
===================================================================
--- runtime/vm/instructions_arm.cc	(revision 19723)
+++ runtime/vm/instructions_arm.cc	(working copy)
@@ -5,23 +5,25 @@
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_ARM.
 #if defined(TARGET_ARCH_ARM)
 
+#include "vm/constants_arm.h"
+#include "vm/cpu.h"
 #include "vm/instructions.h"
 #include "vm/object.h"
 
 namespace dart {
 
-uword InstructionPattern::Back(int n) const {
+CallPattern::CallPattern(uword pc, const Code& code)
+    : end_(reinterpret_cast<uword*>(pc)),
+      pool_index_(DecodePoolIndex()),
+      object_pool_(Array::Handle(code.ObjectPool())) { }
+
+
+uword CallPattern::Back(int n) const {
   ASSERT(n > 0);
   return *(end_ - n);
 }
 
 
-CallPattern::CallPattern(uword pc, const Code& code)
-    : InstructionPattern(pc),
-      pool_index_(DecodePoolIndex()),
-      object_pool_(Array::Handle(code.ObjectPool())) { }
-
-
 int CallPattern::DecodePoolIndex() {
   ASSERT(Back(1) == 0xe12fff3e);  // Last instruction: blx lr
   // Decode the second to last instruction.
@@ -70,23 +72,40 @@
   // 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);
+  // No need to flush the instruction cache, since the code is not modified.
 }
 
 
+JumpPattern::JumpPattern(uword pc) : pc_(pc) { }
+
+
 bool JumpPattern::IsValid() const {
-  UNIMPLEMENTED();
-  return false;
+  Instr* movw = Instr::At(pc_ + (0 * Instr::kInstrSize));  // movw ip, target_lo
+  Instr* movt = Instr::At(pc_ + (1 * Instr::kInstrSize));  // movw ip, target_lo
+  Instr* bxip = Instr::At(pc_ + (2 * Instr::kInstrSize));  // bx ip
+  return (movw->InstructionBits() & 0xfff0f000) == 0xe300c000 &&
+         (movt->InstructionBits() & 0xfff0f000) == 0xe340c000 &&
+         (bxip->InstructionBits() & 0xffffffff) == 0xe12fff1c;
 }
 
 
 uword JumpPattern::TargetAddress() const {
-  UNIMPLEMENTED();
-  return 0;
+  Instr* movw = Instr::At(pc_ + (0 * Instr::kInstrSize));  // movw ip, target_lo
+  Instr* movt = Instr::At(pc_ + (1 * Instr::kInstrSize));  // movw ip, target_lo
+  uint16_t target_lo = movw->MovwField();
+  uint16_t target_hi = movt->MovwField();
+  return (target_hi << 16) | target_lo;
 }
 
 
-void JumpPattern::SetTargetAddress(uword target) const {
-  UNIMPLEMENTED();
+void JumpPattern::SetTargetAddress(uword target_address) const {
+  uint16_t target_lo = target_address & 0xffff;
+  uint16_t target_hi = target_address >> 16;
+  uword movw = 0xe300c000 | ((target_lo >> 12) << 16) | (target_lo & 0xfff);
+  uword movt = 0xe340c000 | ((target_hi >> 12) << 16) | (target_hi & 0xfff);
+  *reinterpret_cast<uword*>(pc_ + (0 * Instr::kInstrSize)) = movw;
+  *reinterpret_cast<uword*>(pc_ + (1 * Instr::kInstrSize)) = movt;
+  CPU::FlushICache(pc_, 2 * Instr::kInstrSize);
 }
 
 }  // namespace dart