commit 8a1c728e40813d30a85a1f27afaf16a3f105d32a
author Mark Mendell <mark.p.mendell@intel.com> Mon Jun 29 15:41:28 2015 -0400
committer Mark Mendell <mark.p.mendell@intel.com> Thu Dec 31 12:47:50 2015 -0500
tree 4245fdf57ffa7a1c12b3890bd2f4b1c10c11bf5d
parent 4bb356123b13ec5f41ea80158766df676ae08679

X86_64: Replace x86_64 xchg instruction use

Replacing 'xchg' to exchange two registers with a three instruction move
sequence using the 'TMP' register r10 seems to be a big win.  This is
because xchg is a serializing instruction, even when used on registers.

Change-Id: I1c0f7687630936e7f3d2efc4b30ad11233bd484c
Signed-off-by: Mark Mendell <mark.p.mendell@intel.com>

compiler/optimizing/code_generator_x86_64.cc

diff --git a/compiler/optimizing/code_generator_x86_64.cc b/compiler/optimizing/code_generator_x86_64.cc
index 7c94a8c..c12166e 100644
--- a/compiler/optimizing/code_generator_x86_64.cc
+++ b/compiler/optimizing/code_generator_x86_64.cc
@@ -5232,6 +5232,12 @@
           CpuRegister(ensure_scratch.GetRegister()));
 }
 
+void ParallelMoveResolverX86_64::Exchange64(CpuRegister reg1, CpuRegister reg2) {
+  __ movq(CpuRegister(TMP), reg1);
+  __ movq(reg1, reg2);
+  __ movq(reg2, CpuRegister(TMP));
+}
+
 void ParallelMoveResolverX86_64::Exchange64(CpuRegister reg, int mem) {
   __ movq(CpuRegister(TMP), Address(CpuRegister(RSP), mem));
   __ movq(Address(CpuRegister(RSP), mem), reg);
@@ -5269,7 +5275,7 @@
   Location destination = move->GetDestination();
 
   if (source.IsRegister() && destination.IsRegister()) {
-    __ xchgq(destination.AsRegister<CpuRegister>(), source.AsRegister<CpuRegister>());
+    Exchange64(source.AsRegister<CpuRegister>(), destination.AsRegister<CpuRegister>());
   } else if (source.IsRegister() && destination.IsStackSlot()) {
     Exchange32(source.AsRegister<CpuRegister>(), destination.GetStackIndex());
   } else if (source.IsStackSlot() && destination.IsRegister()) {

compiler/optimizing/code_generator_x86_64.h

diff --git a/compiler/optimizing/code_generator_x86_64.h b/compiler/optimizing/code_generator_x86_64.h
index 9995416..e571138 100644
--- a/compiler/optimizing/code_generator_x86_64.h
+++ b/compiler/optimizing/code_generator_x86_64.h
@@ -142,6 +142,7 @@
   void Exchange32(CpuRegister reg, int mem);
   void Exchange32(XmmRegister reg, int mem);
   void Exchange32(int mem1, int mem2);
+  void Exchange64(CpuRegister reg1, CpuRegister reg2);
   void Exchange64(CpuRegister reg, int mem);
   void Exchange64(XmmRegister reg, int mem);
   void Exchange64(int mem1, int mem2);