Adds push/pop/peek to VM. Corrects some mistakes in the instructions.
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29bea1a335
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8b84163c56
4 changed files with 88 additions and 3 deletions
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@ -17,6 +17,7 @@ control stack access or control flow.
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|----------|---------------|-------------------------------------------------|
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| SP | Stack Pointer | Stores the current 'top' position of the stack. |
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| BP | Base Pointer | Stores the current stack frame position. |
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| CP | Code Pointer | Stores the instruction which is executed next. |
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| FG | Flag Register | Stores the state of the flags. |
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### Stack Pointer
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@ -3,10 +3,38 @@
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#include <stdlib.h>
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#include <stdio.h>
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Instruction code[] =
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{
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{ VM_EXEC_X, VM_EXEC_X, VM_INPUT_ZERO, VM_INPUT_ZERO, VM_CMD_COPY, 0, VM_FLAG_NO, VM_OUTPUT_DISCARD, 0 },
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};
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void dump_proc(Process *process)
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{
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printf("[ ");
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for(int i = 1; i <= process->stackPointer; i++) {
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printf("%d ", process->stack[i]);
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}
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printf("]\n");
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}
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void vm_assert(int assertion, const char *msg)
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{
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if(assertion != 0)
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return;
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printf("Assertion failed: %s\n", msg);
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exit(1);
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}
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int main(int argc, const char **argv)
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{
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Module module = { code, 1 };
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Process process = { &module, 0, 0, 0, 0 };
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Process *p = &process;
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int stillAlive = vm_step_process(p);
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printf("Process %s.\n", (stillAlive ? "still running" : "terminated"));
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return 0;
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}
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@ -1 +1,34 @@
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#include "vm.h"
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int vm_step_process(Process *process)
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{
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vm_assert(process != NULL, "process must not be NULL.");
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Instruction instr = process->module->code[process->codePointer];
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return 0;
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}
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void vm_push(Process *process, uint32_t value)
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{
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vm_assert(process != NULL, "process must not be NULL.");
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vm_assert(process->stackPointer < VM_STACKSIZE, "Stack overflow");
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process->stack[++process->stackPointer] = value;
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}
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uint32_t vm_pop(Process *process)
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{
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vm_assert(process != NULL, "process must not be NULL.");
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uint32_t psp = process->stackPointer;
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uint32_t val = process->stack[process->stackPointer--];
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// Underflow check works because unsigned overflow is defined ;)
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vm_assert(psp >= process->stackPointer, "Stack underflow");
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return val;
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}
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uint32_t vm_peek(Process *process)
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{
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vm_assert(process != NULL, "process must not be NULL.");
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return process->stack[process->stackPointer];
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}
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@ -74,6 +74,14 @@ _Static_assert(offsetof(Instruction, argument) == 4, "Argument must be must be
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typedef struct
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{
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Instruction *code;
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uint32_t length;
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} Module;
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typedef struct
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{
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Module *module;
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uint32_t codePointer;
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uint32_t stackPointer;
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uint32_t basePointer;
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@ -82,8 +90,23 @@ typedef struct
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uint32_t stack[VM_STACKSIZE];
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} Process;
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/**
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* @brief Steps a given process.
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*
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* Executes a single instruction and processes input and output.
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*
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* @param process The process to be stepped.
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* @returns 1 if the process is still running or 0 if the process is terminated.
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*/
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int vm_step_process(Process *process);
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void vm_push(Process *process, uint32_t value);
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uint32_t vm_pop(Process *process);
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uint32_t vm_peek(Process *process);
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void vm_assert(int assertion, const char *msg);
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#if defined(__cplusplus)
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}
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