Ensure that LRandom preserves rsi after call to the C function on x64.

src/x64/lithium-codegen-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2944 matching lines @@
   Register global_object = rcx;
 #else
   ASSERT(ToRegister(instr->InputAt(0)).is(rdi));
   Register global_object = rdi;
 #endif
 
   __ PrepareCallCFunction(1);
   __ movq(global_object,
           FieldOperand(global_object, GlobalObject::kGlobalContextOffset));
   __ CallCFunction(ExternalReference::random_uint32_function(isolate()), 1);
+  __ movq(rsi, Operand(rbp, StandardFrameConstants::kContextOffset));
 
   // 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(xmm2, rcx);
   __ movd(xmm1, rax);
   __ cvtss2sd(xmm2, xmm2);
   __ xorps(xmm1, xmm2);
   __ subsd(xmm1, xmm2);
@@ skipping 1421 matching lines @@
   RegisterEnvironmentForDeoptimization(environment, Safepoint::kNoLazyDeopt);
   ASSERT(osr_pc_offset_ == -1);
   osr_pc_offset_ = masm()->pc_offset();
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64