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

src/arm/full-codegen-arm.cc

Index: src/arm/full-codegen-arm.cc
diff --git a/src/arm/full-codegen-arm.cc b/src/arm/full-codegen-arm.cc
index 4a3997068df1959aa858a99783726d0a42ef5b1a..64a9fdf08bc868101c1ca2c4dc464e852f411742 100644
--- a/src/arm/full-codegen-arm.cc
+++ b/src/arm/full-codegen-arm.cc
@@ -3347,6 +3347,50 @@ void FullCodeGenerator::EmitLog(CallRuntime* expr) {
 }
 
 
+void FullCodeGenerator::EmitRandomHeapNumber(CallRuntime* expr) {
+  ASSERT(expr->arguments()->length() == 0);
+  Label slow_allocate_heapnumber;
+  Label heapnumber_allocated;
+
+  __ LoadRoot(r6, Heap::kHeapNumberMapRootIndex);
+  __ AllocateHeapNumber(r4, r1, r2, r6, &slow_allocate_heapnumber);
+  __ jmp(&heapnumber_allocated);
+
+  __ bind(&slow_allocate_heapnumber);
+  // Allocate a heap number.
+  __ CallRuntime(Runtime::kNumberAlloc, 0);
+  __ mov(r4, Operand(r0));
+
+  __ bind(&heapnumber_allocated);
+
+  // Convert 32 random bits in r0 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, r0);
+  __ ldr(r0,
+         ContextOperand(context_register(), Context::GLOBAL_OBJECT_INDEX));
+  __ ldr(r0, FieldMemOperand(r0, GlobalObject::kNativeContextOffset));
+  __ CallCFunction(ExternalReference::random_uint32_function(isolate()), 1);
+
+  // 0x41300000 is the top half of 1.0 x 2^20 as a double.
+  // Create this constant using mov/orr to avoid PC relative load.
+  __ mov(r1, Operand(0x41000000));
+  __ orr(r1, r1, Operand(0x300000));
+  // Move 0x41300000xxxxxxxx (x = random bits) to VFP.
+  __ vmov(d7, r0, r1);
+  // Move 0x4130000000000000 to VFP.
+  __ mov(r0, Operand::Zero());
+  __ vmov(d8, r0, r1);
+  // Subtract and store the result in the heap number.
+  __ vsub(d7, d7, d8);
+  __ sub(r0, r4, Operand(kHeapObjectTag));
+  __ vstr(d7, r0, HeapNumber::kValueOffset);
+  __ mov(r0, r4);
+
+  context()->Plug(r0);
+}
+
+
 void FullCodeGenerator::EmitSubString(CallRuntime* expr) {
   // Load the arguments on the stack and call the stub.
   SubStringStub stub;