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

src/mips/full-codegen-mips.cc

Index: src/mips/full-codegen-mips.cc
diff --git a/src/mips/full-codegen-mips.cc b/src/mips/full-codegen-mips.cc
index 486eb9db2db7a9da86f06f3521a4bf692881a553..6ef871fe669bf66e9d14234c1f72645fb9ca8d7f 100644
--- a/src/mips/full-codegen-mips.cc
+++ b/src/mips/full-codegen-mips.cc
@@ -3378,6 +3378,48 @@ void FullCodeGenerator::EmitLog(CallRuntime* expr) {
 }
 
 
+void FullCodeGenerator::EmitRandomHeapNumber(CallRuntime* expr) {
+  ASSERT(expr->arguments()->length() == 0);
+  Label slow_allocate_heapnumber;
+  Label heapnumber_allocated;
+
+  // Save the new heap number in callee-saved register s0, since
+  // we call out to external C code below.
+  __ LoadRoot(t6, Heap::kHeapNumberMapRootIndex);
+  __ AllocateHeapNumber(s0, a1, a2, t6, &slow_allocate_heapnumber);
+  __ jmp(&heapnumber_allocated);
+
+  __ bind(&slow_allocate_heapnumber);
+
+  // Allocate a heap number.
+  __ CallRuntime(Runtime::kNumberAlloc, 0);
+  __ mov(s0, v0);   // Save result in s0, so it is saved thru CFunc call.
+
+  __ bind(&heapnumber_allocated);
+
+  // Convert 32 random bits in v0 to 0.(32 random bits) in a double
+  // by computing:
+  // ( 1.(20 0s)(32 random bits) x 2^20 ) - (1.0 x 2^20)).
+  __ PrepareCallCFunction(1, a0);
+  __ lw(a0, ContextOperand(cp, Context::GLOBAL_OBJECT_INDEX));
+  __ lw(a0, FieldMemOperand(a0, GlobalObject::kNativeContextOffset));
+  __ CallCFunction(ExternalReference::random_uint32_function(isolate()), 1);
+
+  // 0x41300000 is the top half of 1.0 x 2^20 as a double.
+  __ li(a1, Operand(0x41300000));
+  // Move 0x41300000xxxxxxxx (x = random bits in v0) to FPU.
+  __ Move(f12, v0, a1);
+  // Move 0x4130000000000000 to FPU.
+  __ Move(f14, zero_reg, a1);
+  // Subtract and store the result in the heap number.
+  __ sub_d(f0, f12, f14);
+  __ sdc1(f0, FieldMemOperand(s0, HeapNumber::kValueOffset));
+  __ mov(v0, s0);
+
+  context()->Plug(v0);
+}
+
+
 void FullCodeGenerator::EmitSubString(CallRuntime* expr) {
   // Load the arguments on the stack and call the stub.
   SubStringStub stub;