X64 Crankshaft: Add DoPower to lithium compiler on x64 platform.

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
===================================================================
--- src/x64/lithium-x64.cc	(revision 6962)
+++ src/x64/lithium-x64.cc	(working copy)
@@ -1436,8 +1436,18 @@
 
 
 LInstruction* LChunkBuilder::DoPower(HPower* instr) {
-  Abort("Unimplemented: %s", "DoPower");
-  return NULL;
+  ASSERT(instr->representation().IsDouble());
+  // We call a C function for double power. It can't trigger a GC.
+  // We need to use fixed result register for the call.
+  Representation exponent_type = instr->right()->representation();
+  ASSERT(instr->left()->representation().IsDouble());
+  LOperand* left = UseFixedDouble(instr->left(), xmm1);
+  LOperand* right = exponent_type.IsDouble() ?
+      UseFixedDouble(instr->right(), xmm2) :
+      UseFixed(instr->right(), rax);
+  LPower* result = new LPower(left, right);
+  return MarkAsCall(DefineFixedDouble(result, xmm3), instr,
+                    CAN_DEOPTIMIZE_EAGERLY);

[Rico, 2011/02/28 19:18:34]

I do not see why we request right to be in xmm2 and rax when we need them in rdi
and xmm1. In addition, is there any reason why we require the result to be in
xmm3?

 }