138 lines
3.2 KiB
C
138 lines
3.2 KiB
C
#include "vm.h"
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typedef struct
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{
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uint32_t input0;
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uint32_t input1;
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uint32_t argument;
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uint32_t output;
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} CommandInfo;
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static void cmd_copy(CommandInfo *info)
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{
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info->output = info->input0;
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}
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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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int exec = 1;
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switch(instr.execZ)
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{
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case VM_EXEC_X:
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/* Don't modify execution. */
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break;
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case VM_EXEC_0:
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if((process->flags & VM_FLAG_Z) != 0)
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exec = 0;
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break;
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case VM_EXEC_1:
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if((process->flags & VM_FLAG_Z) == 0)
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exec = 0;
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break;
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default:
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vm_assert(0, "Invalid instruction: execZ undefined.");
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break;
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}
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switch(instr.execN)
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{
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case VM_EXEC_X:
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/* Don't modify execution. */
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break;
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case VM_EXEC_0:
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if((process->flags & VM_FLAG_N) != 0)
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exec = 0;
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break;
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case VM_EXEC_1:
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if((process->flags & VM_FLAG_N) == 0)
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exec = 0;
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break;
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default:
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vm_assert(0, "Invalid instruction: execN undefined.");
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break;
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}
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// Only do further instruction execution when
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// the execution condition is met.
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if(exec)
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{
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CommandInfo info;
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switch(instr.input0)
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{
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case VM_INPUT_ZERO: info.input0 = 0; break;
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case VM_INPUT_POP: info.input0 = vm_pop(process); break;
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case VM_INPUT_PEEK: info.input0 = vm_peek(process); break;
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case VM_INPUT_ARG: info.input0 = instr.argument; break;
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default: vm_assert(0, "Invalid instruction: input0 undefined.");
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}
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switch(instr.input1)
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{
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case VM_INPUT_ZERO: info.input1 = 0; break;
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case VM_INPUT_POP: info.input1 = vm_pop(process); break;
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default: vm_assert(0, "Invalid instruction: input1 undefined.");
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}
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info.argument = instr.argument;
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switch(instr.command)
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{
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case VM_CMD_COPY: cmd_copy(&info); break;
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default: vm_assert(0, "Invalid instruction: command undefined.");
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}
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switch(instr.flags)
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{
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case VM_FLAG_YES:
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process->flags = 0;
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if(info.output == 0)
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process->flags |= VM_FLAG_Z;
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else if((info.output & (1<<31)) != 0)
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process->flags |= VM_FLAG_N;
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break;
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case VM_FLAG_NO: break;
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default:
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vm_assert(0, "Invalid instruction: invalid flags.");
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}
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switch(instr.output)
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{
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case VM_OUTPUT_DISCARD: break;
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case VM_OUTPUT_PUSH: vm_push(process, info.output); break;
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case VM_OUTPUT_JUMP: process->codePointer = info.output; break;
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default:
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vm_assert(0, "Invalid instruction: invalid output.");
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}
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}
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return process->codePointer < process->module->length;
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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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