Small improvement in x64 assembler

src/x64/assembler-x64.cc

Index: src/x64/assembler-x64.cc
===================================================================
--- src/x64/assembler-x64.cc	(revision 13579)
+++ src/x64/assembler-x64.cc	(working copy)
@@ -1505,13 +1505,12 @@
 void Assembler::movq(Register dst, int64_t value, RelocInfo::Mode rmode) {
   // Non-relocatable values might not need a 64-bit representation.
   if (RelocInfo::IsNone(rmode)) {
-    // Sadly, there is no zero or sign extending move for 8-bit immediates.
-    if (is_int32(value)) {
-      movq(dst, Immediate(static_cast<int32_t>(value)));
-      return;
-    } else if (is_uint32(value)) {
+    if (is_uint32(value)) {
       movl(dst, Immediate(static_cast<int32_t>(value)));
       return;
+    } else if (is_int32(value)) {

[Yang, 2013/02/06 10:28:59]

What is the purpose of this change?

[Zheng Liu, 2013/02/06 11:34:08]

Code might be smaller, as [mov r64, imm32] always have a prefix.
MacroAssembler::Set() did similar things.

[Yang, 2013/02/06 11:39:18]

But this change seems to be to the effect of changing

if (A) {
  B;
} else if (C) {
  D;
}

into

if (C) {
  D;
} else if (A) {
  B;
}

I don't see any difference besides changing the order.

+      movq(dst, Immediate(static_cast<int32_t>(value)));
+      return;
     }
     // Value cannot be represented by 32 bits, so do a full 64 bit immediate
     // value.