1 files changed, 166 insertions, 0 deletions

diff --git a/vm/src/vm.h b/vm/src/vm.h
new file mode 100644
index 0000000..03dfc88
--- /dev/null
+++ b/vm/src/vm.h
@@ -0,0 +1,166 @@
+#pragma once
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+typedef enum Op {
+  Exit, // Pop value from the stack and return as exit code. Return 0 if the
+        // stack is empty.
+  Push,
+  Pop,
+  Add,
+  Sub,
+  Mul,
+  Div,
+  Dec,   // Decrement the top of the stack by 1.
+  Empty, // Check whether the stack is empty. Pushes a bool.
+  Cmp,   // Pop the top of the stack and compare it with the payload. Pushes a
+         // bool.
+  /* Blocks */
+  End,   // Marks the end of a block.
+  Break, // Exit the current block.
+  Loop,  // Push a loop block. Payload (i32): label.
+  /* Branches */
+  Br, // Branch. Payload (i64): [(i32) conditional? | (i32) label].
+      // A condtional branch pops a bool from the stack and branches if true.
+      // The condition can also be negated. See br_if().
+  /* Functions */
+  Func,
+  Arg,
+  Call,
+  /* Locals */
+  Local,   // Create a local variable.
+  LocalRd, // Load a local variable into the top of the stack.
+  LocalWr, // Pop the top of the stack and store it in a local variable.
+} Op;
+
+typedef enum Type {
+  I32,
+  F32,
+} Type;
+
+// Label type for blocks and locals.
+typedef uint32_t Label;
+
+typedef struct Branch {
+  Label label;
+  bool  conditional : 1; // True for conditional branches.
+  bool  expected    : 1; // Comparison value for conditional branches.
+} Branch;
+
+typedef struct Function {
+  Label label;
+} Function;
+
+typedef struct Value {
+  union {
+    uint64_t u64;
+    int32_t  i32;
+    float    f32;
+    Branch   branch;
+    Label    label;
+  };
+} Value;
+
+typedef struct Inst {
+  Op    op   : 5;
+  Type  type : 2;
+  Value payload;
+} Inst;
+
+typedef struct Vm Vm;
+
+// -----------------------------------------------------------------------------
+// VM API
+
+/// Create a new virtual machine.
+Vm* vm_new();
+
+/// Destroy the virtual machine.
+void vm_del(Vm**);
+
+/// Execute code on the virtual machine.
+///
+/// Returns the program exit code if an exit operation is executed, 0 otherwise.
+int vm_run(Vm*, const Inst[], size_t count);
+
+/// Prints the virtual machine's stack to stdout.
+void vm_print_stack(const Vm*);
+
+// -----------------------------------------------------------------------------
+// Programming API
+
+/// Exit the program.
+static inline Inst vmExit() { return (Inst){.op = Exit}; }
+
+/// Push a value.
+static inline Inst vmPushI32(int32_t value) {
+  return (Inst){.op = Push, .type = I32, .payload = (Value){.i32 = value}};
+}
+
+/// Pop a value.
+static inline Inst vmPop(Type type) { return (Inst){.op = Pop, .type = type}; }
+
+/// Add two values.
+static inline Inst vmAdd(Type type) { return (Inst){.op = Add, .type = type}; }
+
+/// Decrement a value.
+static inline Inst vmDec(Type type) { return (Inst){.op = Dec, .type = type}; }
+
+/// Compare a value.
+static inline Inst vmCmpI32(int32_t value) {
+  return (Inst){.op = Cmp, .type = I32, .payload = (Value){.i32 = value}};
+}
+
+/// End the current block.
+static inline Inst vmEnd() { return (Inst){.op = End}; }
+
+/// Create a loop.
+static inline Inst vmLoop(Label label) {
+  return (Inst){.op = Loop, .payload = (Value){.label = label}};
+}
+
+/// Create the payload of a conditional branch.
+static inline Inst vmBr_if(bool value, Label label) {
+  return (Inst){
+      .op      = Br,
+      .payload = (Value){
+          .branch = {
+              .label       = label,
+              .conditional = 1,
+              .expected    = value,
+          }}};
+}
+
+/// Create a function.
+static inline Inst vmFunc(Label label) {
+  return (Inst){.op = Func, .payload = (Value){.label = label}};
+}
+
+/// Create a function argument.
+static inline Inst vmArg(Type type, Label label) {
+  return (Inst){.op = Arg, .type = type, .payload = (Value){.label = label}};
+}
+
+/// Call a function.
+static inline Inst vmCall(Label label) {
+  return (Inst){.op = Call, .payload = (Value){.label = label}};
+}
+
+/// Create a local variable.
+static inline Inst vmLocal(Type type, Label label) {
+  return (Inst){.op = Local, .type = type, .payload = (Value){.label = label}};
+}
+
+/// Read a local variable.
+static inline Inst vmLocalRd(Type type, Label label) {
+  return (Inst){
+      .op = LocalRd, .type = type, .payload = (Value){.label = label}};
+}
+
+/// Write a local variable.
+static inline Inst vmLocalWr(Type type, Label label) {
+  return (Inst){
+      .op = LocalWr, .type = type, .payload = (Value){.label = label}};
+}