1 files changed, 82 insertions, 33 deletions

diff --git a/codegen.c b/codegen.c
index 6dfaf4a..c8a9933 100644
--- a/codegen.c
+++ b/codegen.c
@@ -61,23 +61,23 @@ static void emit_mov(
             if (src->type == REGISTER && sz < 4) {
                 fprintf(outfile, "\tmovzx ");
                 emit_storage_loc(outfile, dst, FULL_REG_SZ);
-                fprintf(outfile, ", ");
-                emit_storage_loc(outfile, src, sz);
             } else {
                 fprintf(outfile, "\tmov ");
                 emit_storage_loc(outfile, dst, sz);
-                fprintf(outfile, ", ");
-                emit_storage_loc(outfile, src, sz);
             }
+
+            fprintf(outfile, ", ");
+            emit_storage_loc(outfile, src, sz);
             break;
         case BP_OFFSET:
-            fprintf(outfile, "\tmov ");
             if (src->type == BP_OFFSET) {
-                if (sz > 4) fprintf(outfile, "qword ");
-                else if (sz > 2) fprintf(outfile, "dword ");
-                else if (sz > 1) fprintf(outfile, "word ");
-                else fprintf(outfile, "byte ");
+                /* `mov mem, mem` is illegal in x86_64 */
+                emit_mov(outfile, &RV_LOC, src, sz);
+                emit_mov(outfile, dst, &RV_LOC, sz);
+                return;
             }
+
+            fprintf(outfile, "\tmov ");
             emit_storage_loc(outfile, dst, sz);
             fprintf(outfile, ", ");
             emit_storage_loc(outfile, src, sz);
@@ -91,6 +91,12 @@ static void emit_mov(
     fprintf(outfile, "\n");
 }
 
+static void emit_expr(
+    FILE* outfile,
+    const struct expr_node* node,
+    const struct storage_location* storage
+);
+
 static void emit_int_lit(
     FILE* outfile,
     const struct int_lit_node* node,
@@ -107,37 +113,24 @@ static void emit_int_lit(
             FULL_REG_SZ);
 }
 
+static struct var_def get_var(const char* name) {
+    struct var_def var_def;
+    if (!scope_get_var(scope, &var_def, name))
+        CGEN_PANIC("reference to undefined variable %s", name);
+    return var_def;
+}
+
 static void emit_var_ref(
     FILE* outfile,
     const struct var_ref_node* node,
     const struct storage_location* storage
 ) {
     if (storage != NULL) {
-        struct var_def var_def;
-        if (!scope_get_var(scope, &var_def, node->ident))
-            CGEN_PANIC("reference to undefined variable %s", node->ident);
-
+        struct var_def var_def = get_var(node->ident);
         emit_mov(outfile, storage, &var_def.loc, var_def.sz);
     }
 }
 
-static void emit_expr(
-    FILE* outfile,
-    const struct expr_node* node,
-    const struct storage_location* storage
-) {
-    switch (node->type) {
-        case EXPR_EMPTY:
-            break;
-        case EXPR_INT_LIT:
-            emit_int_lit(outfile, &node->as._int_lit, storage);
-            break;
-        case EXPR_VAR_REF:
-            emit_var_ref(outfile, &node->as._var_ref, storage);
-            break;
-    }
-}
-
 static void emit_stmt(FILE* outfile, const struct stmt_node* node);
 
 static unsigned long long get_type_size(const struct type_node* type) {
@@ -150,19 +143,73 @@ static unsigned long long get_type_size(const struct type_node* type) {
     return type_def.size;
 }
 
-static void emit_var_decl(FILE* outfile, const struct var_decl_node* node) {
+static struct var_def emit_var_decl(
+    FILE* outfile,
+    const struct var_decl_node* node
+) {
     unsigned long long type_sz = get_type_size(&node->type);
 
     fprintf(outfile, "\tsub rsp, %llu\n", type_sz);
     scope->bp_offset += type_sz;
-    scope_define_var(scope, (struct var_def) {
+
+    struct var_def var_def = {
         .name = node->ident,
         .loc = {
             .type = BP_OFFSET,
             .offset = scope->bp_offset,
         },
         .sz = type_sz,
-    });
+    };
+    scope_define_var(scope, var_def);
+    return var_def;
+}
+
+struct lval_def {
+    struct storage_location loc;
+    unsigned long long sz;
+};
+
+static struct lval_def emit_lval(
+    FILE* outfile,
+    const struct lval_node* node
+) {
+    struct var_def var_def;
+    switch (node->type) {
+        case LVAL_VAR_DECL:
+            var_def = emit_var_decl(outfile, &node->as._var_decl);
+            return (struct lval_def) {.loc = var_def.loc, .sz = var_def.sz};
+        case LVAL_VAR_REF:
+            var_def = get_var(node->as._var_ref.ident);
+            return (struct lval_def) {.loc = var_def.loc, .sz = var_def.sz};
+    }
+    CGEN_PANIC("unknown lval type: %d", node->type);
+}
+
+static void emit_assignment(
+    FILE* outfile,
+    const struct assign_node* node,
+    const struct storage_location* storage
+) {
+    const struct lval_def lval_def = emit_lval(outfile, &node->lval);
+    emit_expr(outfile, node->rval, &lval_def.loc);
+    if (storage != NULL) emit_mov(outfile, storage, &lval_def.loc, lval_def.sz);
+}
+
+static void emit_expr(
+    FILE* outfile,
+    const struct expr_node* node,
+    const struct storage_location* storage
+) {
+    switch (node->type) {
+        case EXPR_INT_LIT:
+            emit_int_lit(outfile, &node->as._int_lit, storage);
+            break;
+        case EXPR_VAR_REF:
+            emit_var_ref(outfile, &node->as._var_ref, storage);
+            break;
+        case EXPR_ASSIGN:
+            emit_assignment(outfile, &node->as._assign, storage);
+    }
 }
 
 static void emit_return(FILE* outfile, const struct return_node* node) {
@@ -193,6 +240,8 @@ static void emit_stmt_group(FILE* outfile, const struct group_node* node) {
 
 static void emit_stmt(FILE* outfile, const struct stmt_node* node) {
     switch (node->type) {
+        case STMT_EMPTY:
+            break;
         case STMT_VAR_DECL:
             emit_var_decl(outfile, &node->as._var_decl);
             break;