Fix potential overwriting of debug jumps of following code.

src/x64/assembler-x64.cc

Index: src/x64/assembler-x64.cc
diff --git a/src/x64/assembler-x64.cc b/src/x64/assembler-x64.cc
index 999306e37892a434ec19b4e7efb343922d1bb132..16b3fbb3824d3c04a16e0719a580efe3f21a94f5 100644
--- a/src/x64/assembler-x64.cc
+++ b/src/x64/assembler-x64.cc
@@ -916,6 +916,19 @@ void Assembler::call(const Operand& op) {
 }
 
 
+void Assembler::call(Address target) {

[Kevin Millikin (Chromium), 2011/02/04 11:34:54]

Since this function is not entirely safe, the comment from the header should be
repeated here (to guard against someone checking the .cc file, seeing it's
implemented, and using it).

I wonder if we just give it a RelocInfo::Mode so it would generally work?

[Lasse Reichstein, 2011/02/04 12:32:13]

Comment moved.

The RelocInfo::Mode is a little tricky, since we (so far only) use the
instruction during patching, where relocinfo doesn't work anyway.
Suggestions welcome.
Using RelocInfo::INTERNAL_REFERENCE seems the correct thing, but it's used for
absolute references, not relative.

[Kevin Millikin (Chromium), 2011/02/04 12:58:24]

To be clear, I thought the comment should be duplicated so that it occurs in
both places.

[Lasse Reichstein, 2011/02/04 13:04:11]

My bad. That was indeed what I did, but not what I wrote that I had done.

+  positions_recorder()->WriteRecordedPositions();
+  EnsureSpace ensure_space(this);
+  last_pc_ = pc_;
+  // 1110 1000 #32-bit disp.
+  emit(0xE8);
+  Address source = pc_ + 4;
+  intptr_t displacement = target - source;
+  ASSERT(is_int32(displacement));
+  emitl(static_cast<int32_t>(displacement));
+}
+
+
 void Assembler::clc() {
   EnsureSpace ensure_space(this);
   last_pc_ = pc_;