ARM64: optimize call immediate

src/arm64/macro-assembler-arm64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2006 matching lines @@
   // address is loaded.
   positions_recorder()->WriteRecordedPositions();
 
   // Addresses always have 64 bits, so we shouldn't encounter NONE32.
   ASSERT(rmode != RelocInfo::NONE32);
 
   UseScratchRegisterScope temps(this);
   Register temp = temps.AcquireX();
 
   if (rmode == RelocInfo::NONE64) {
+    // Addresses are 48 bits so we never need to load the upper 16 bits.
     uint64_t imm = reinterpret_cast<uint64_t>(target);
+    // If we don't use ARM tagged addresses, the 16 higher bits must be 0.
+    ASSERT(((imm >> 48) & 0xffff) == 0);
     movz(temp, (imm >> 0) & 0xffff, 0);
     movk(temp, (imm >> 16) & 0xffff, 16);
     movk(temp, (imm >> 32) & 0xffff, 32);
-    movk(temp, (imm >> 48) & 0xffff, 48);
   } else {
     LoadRelocated(temp, Operand(reinterpret_cast<intptr_t>(target), rmode));
   }
   Blr(temp);
 #ifdef DEBUG
   AssertSizeOfCodeGeneratedSince(&start_call, CallSize(target, rmode));
 #endif
 }
 
 
@@ skipping 3120 matching lines @@
   }
 }
 
 
 #undef __
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM64