X5 the values of the registers before on the left and

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x5 . The values of the registers before (on the left) and after (on the right) the execution of this instruction are shown in the corresponding snapshots of the Regs window below. After the execution of this instruction the PC was incremented by 4 to point at address 0x0000000000000004 . If we press the Next button again the following error message will be shown. The message 0x0000000000000004: NO INSTRUCTION indicates that no executable instruction was found at address 0x0000000000000004 so the program was stopped.
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Page 10 of 10 5. Internals The RVS execution of RISC-V programs is based on a Virtual memory (VM) model implemented through hash-based associative memory. In this way the executed code can freely refer and use the entire 64-bit addressing space while the allocated physical memory will be confined only to the necessary minimum. With this model there is no need for an operating system to manage the stack and heap memory allocation. All virtual memory is considered as initialized to 0s so reading from an address without its prior initialization will return 0s without an error while no physical memory will actually be allocated. Writing to an address, however, will lead to actual physical memory allocation (if the memory has not been allocated already.) This is also true for writing 0s, e.g. actual physical memory will be allocated and maintained for storing 0s. Although less efficient, this is a design decision that greatly facilitates the tracking of the memory use by the executed code as shown in the Memory window. The RVS provides bit-accurate representation of the supported RISC-V machine instructions although it uses different data structures for simulating the execution process.
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