robust mov situation

2 files changed, 62 insertions, 31 deletions

diff --git a/codegen.c b/codegen.c
index 4e9f63a..6dfaf4a 100644
--- a/codegen.c
+++ b/codegen.c
@@ -30,7 +30,6 @@ static void emit_storage_loc(
         case REGISTER:
             if (sz > 4) fprintf(outfile, "%s", loc->reg->qword);
             else if (sz > 2) fprintf(outfile, "%s", loc->reg->dword);
-            // TODO: for word and byte make sure moving into these zeroes the high register
             else if (sz > 1) fprintf(outfile, "%s", loc->reg->word);
             else fprintf(outfile, "%s", loc->reg->byte);
             break;
@@ -44,19 +43,68 @@ static void emit_storage_loc(
                 fprintf(outfile, "[rbp - %lld]", loc->offset);
             else
                 fprintf(outfile, "[rbp]");
+            break;
+        case IMMEDIATE:
+            fprintf(outfile, "%llu", loc->value);
+            break;
     }
 }
 
+static void emit_mov(
+    FILE* outfile,
+    const struct storage_location* dst,
+    const struct storage_location* src,
+    unsigned long long sz
+) {
+    switch (dst->type) {
+        case REGISTER:
+            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);
+            }
+            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 ");
+            }
+            emit_storage_loc(outfile, dst, sz);
+            fprintf(outfile, ", ");
+            emit_storage_loc(outfile, src, sz);
+            break;
+        case JMP_LABEL:
+            CGEN_PANIC("can't move value into label %s", dst->label);
+        case IMMEDIATE:
+            CGEN_PANIC(
+                "can't move value into immediate value %lld", dst->value);
+    }
+    fprintf(outfile, "\n");
+}
+
 static void emit_int_lit(
     FILE* outfile,
     const struct int_lit_node* node,
     const struct storage_location* storage
 ) {
-    if (storage != NULL) {
-        fprintf(outfile, "\tmov ");
-        emit_storage_loc(outfile, storage, FULL_REG_SZ);
-        fprintf(outfile, ", %lld\n", node->val);
-    }
+    if (storage != NULL)
+        emit_mov(
+            outfile,
+            storage,
+            &(struct storage_location) {
+                .type = IMMEDIATE,
+                .value = node->val,
+            },
+            FULL_REG_SZ);
 }
 
 static void emit_var_ref(
@@ -69,11 +117,7 @@ static void emit_var_ref(
         if (!scope_get_var(scope, &var_def, node->ident))
             CGEN_PANIC("reference to undefined variable %s", node->ident);
 
-        fprintf(outfile, "\tmov ");
-        emit_storage_loc(outfile, storage, var_def.sz);
-        fprintf(outfile, ", ");
-        emit_storage_loc(outfile, &var_def.loc, var_def.sz);
-        fprintf(outfile, "\n");
+        emit_mov(outfile, storage, &var_def.loc, var_def.sz);
     }
 }
 
@@ -142,20 +186,9 @@ static void emit_stmt_group(FILE* outfile, const struct group_node* node) {
 
     emit_group(outfile, node);
 
+    /* don't reset sp because alloca needs to work */
+    scope->next_out->bp_offset = scope->bp_offset;
     scope_pop(&scope);
-    if (scope->bp_offset == 0)
-        fprintf(outfile, "\tmov rsp, rbp\n");
-    else {
-        fprintf(outfile, "\tlea rsp, ");
-        emit_storage_loc(
-            outfile,
-            &(struct storage_location) {
-                .type = BP_OFFSET,
-                .offset = scope->bp_offset,
-            },
-            FULL_REG_SZ);
-        fprintf(outfile, "\n");
-    }
 }
 
 static void emit_stmt(FILE* outfile, const struct stmt_node* node) {
@@ -213,11 +246,7 @@ static void emit_fn_decl(FILE* outfile, const struct fn_decl_node* node) {
             };
             spilled_bp_ofs -= type_sz;
         }
-        fprintf(outfile, "\tmov ");
-        emit_storage_loc(outfile, &var_def.loc, type_sz);
-        fprintf(outfile, ", ");
-        emit_storage_loc(outfile, &arg_src,type_sz);
-        fprintf(outfile, "\n");
+        emit_mov(outfile, &var_def.loc, &arg_src, type_sz);
 
         args_node = args_node->next;
     }
diff --git a/scope.h b/scope.h
index e09e14e..a67c66b 100644
--- a/scope.h
+++ b/scope.h
@@ -6,11 +6,13 @@ struct storage_location {
         REGISTER,
         JMP_LABEL,
         BP_OFFSET,
+        IMMEDIATE,
     } type;
     union {
-        long long offset;
-        const char* label;
         const struct reg* reg;
+        const char* label;
+        long long offset;
+        unsigned long long value;
     };
     unsigned long long sz;
 };