ARM64: optimize call immediate

src/arm64/macro-assembler-arm64.cc

Index: src/arm64/macro-assembler-arm64.cc
diff --git a/src/arm64/macro-assembler-arm64.cc b/src/arm64/macro-assembler-arm64.cc
index d7d0ab7502308f2687beb126076c70e4e3ca1905..a4108410bd837b44ff38524ed48527f95f20ede7 100644
--- a/src/arm64/macro-assembler-arm64.cc
+++ b/src/arm64/macro-assembler-arm64.cc
@@ -2024,11 +2024,13 @@ void MacroAssembler::Call(Address target, RelocInfo::Mode rmode) {
   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));
   }