Revert 17963, 17962 and 17955: Random number generator in JS changes

src/x64/full-codegen-x64.cc

Index: src/x64/full-codegen-x64.cc
diff --git a/src/x64/full-codegen-x64.cc b/src/x64/full-codegen-x64.cc
index a62fde0ee901f4c464f2aab4bc090d61f9c2bf84..71b54680f2035d352122fe631018cdd09b8590cc 100644
--- a/src/x64/full-codegen-x64.cc
+++ b/src/x64/full-codegen-x64.cc
@@ -3271,6 +3271,47 @@ void FullCodeGenerator::EmitLog(CallRuntime* expr) {
 }
 
 
+void FullCodeGenerator::EmitRandomHeapNumber(CallRuntime* expr) {
+  ASSERT(expr->arguments()->length() == 0);
+
+  Label slow_allocate_heapnumber;
+  Label heapnumber_allocated;
+
+  __ AllocateHeapNumber(rbx, rcx, &slow_allocate_heapnumber);
+  __ jmp(&heapnumber_allocated);
+
+  __ bind(&slow_allocate_heapnumber);
+  // Allocate a heap number.
+  __ CallRuntime(Runtime::kNumberAlloc, 0);
+  __ movq(rbx, rax);
+
+  __ bind(&heapnumber_allocated);
+
+  // Return a random uint32 number in rax.
+  // The fresh HeapNumber is in rbx, which is callee-save on both x64 ABIs.
+  __ PrepareCallCFunction(1);
+  __ movq(arg_reg_1,
+          ContextOperand(context_register(), Context::GLOBAL_OBJECT_INDEX));
+  __ movq(arg_reg_1,
+          FieldOperand(arg_reg_1, GlobalObject::kNativeContextOffset));
+  __ CallCFunction(ExternalReference::random_uint32_function(isolate()), 1);
+
+  // Convert 32 random bits in rax to 0.(32 random bits) in a double
+  // by computing:
+  // ( 1.(20 0s)(32 random bits) x 2^20 ) - (1.0 x 2^20)).
+  __ movl(rcx, Immediate(0x49800000));  // 1.0 x 2^20 as single.
+  __ movd(xmm1, rcx);
+  __ movd(xmm0, rax);
+  __ cvtss2sd(xmm1, xmm1);
+  __ xorps(xmm0, xmm1);
+  __ subsd(xmm0, xmm1);
+  __ movsd(FieldOperand(rbx, HeapNumber::kValueOffset), xmm0);
+
+  __ movq(rax, rbx);
+  context()->Plug(rax);
+}
+
+
 void FullCodeGenerator::EmitSubString(CallRuntime* expr) {
   // Load the arguments on the stack and call the stub.
   SubStringStub stub;