Implement function calls on ARM using the blx instruction when available. Usi...

src/arm/assembler-arm.h

Index: src/arm/assembler-arm.h
===================================================================
--- src/arm/assembler-arm.h	(revision 4189)
+++ src/arm/assembler-arm.h	(working copy)
@@ -509,7 +509,10 @@
 
 
 extern const Instr kMovLrPc;
+extern const Instr kLdrPCMask;
 extern const Instr kLdrPCPattern;
+extern const Instr kBlxRegMask;
+extern const Instr kBlxRegPattern;
 
 
 class Assembler : public Malloced {
@@ -590,12 +593,34 @@
   static const int kInstrSize = sizeof(Instr);
 
   // Distance between the instruction referring to the address of the call
-  // target (ldr pc, [target addr in const pool]) and the return address
+  // target and the return address.
+#ifdef USE_BLX
+  // Call sequence is:
+  //  ldr  ip, [pc, #...] @ call address
+  //  blx  ip
+  //                      @ return address
+  static const int kCallTargetAddressOffset = 2 * kInstrSize;
+#else
+  // Call sequence is:
+  //  mov  lr, pc
+  //  ldr  pc, [pc, #...] @ call address
+  //                      @ return address
   static const int kCallTargetAddressOffset = kInstrSize;
+#endif
 
   // Distance between start of patched return sequence and the emitted address
   // to jump to.
-  static const int kPatchReturnSequenceAddressOffset = kInstrSize;
+#ifdef USE_BLX
+  // Return sequence is:
+  //  ldr  ip, [pc, #0]   @ emited address and start
+  //  blx  ip
+  static const int kPatchReturnSequenceAddressOffset =  0 * kInstrSize;
+#else
+  // Return sequence is:
+  //  mov  lr, pc         @ start of sequence
+  //  ldr  pc, [pc, #-4]  @ emited address
+  static const int kPatchReturnSequenceAddressOffset =  kInstrSize;
+#endif
 
   // Difference between address of current opcode and value read from pc
   // register.