From f0c98e0d590ffae286a8a4847c91212c734be8e3 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@cs.stanford.edu>
Date: Sun, 20 Sep 2020 13:23:53 +0900
Subject: [PATCH] [GNU] Treat labels-as-values as compile-time constant

---
 chibicc.h      |  2 +-
 codegen.c      |  2 +-
 parse.c        | 17 ++++++++++-------
 test/control.c |  4 ++++
 4 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/chibicc.h b/chibicc.h
index 773c7ee..6aa1fc1 100644
--- a/chibicc.h
+++ b/chibicc.h
@@ -169,7 +169,7 @@ typedef struct Relocation Relocation;
 struct Relocation {
   Relocation *next;
   int offset;
-  char *label;
+  char **label;
   long addend;
 };
 
diff --git a/codegen.c b/codegen.c
index f4a93a0..8424c4c 100644
--- a/codegen.c
+++ b/codegen.c
@@ -1338,7 +1338,7 @@ static void emit_data(Obj *prog) {
       int pos = 0;
       while (pos < var->ty->size) {
         if (rel && rel->offset == pos) {
-          println("  .quad %s%+ld", rel->label, rel->addend);
+          println("  .quad %s%+ld", *rel->label, rel->addend);
           rel = rel->next;
           pos += 8;
         } else {
diff --git a/parse.c b/parse.c
index f92a31d..25a9d48 100644
--- a/parse.c
+++ b/parse.c
@@ -136,8 +136,8 @@ static Node *stmt(Token **rest, Token *tok);
 static Node *expr_stmt(Token **rest, Token *tok);
 static Node *expr(Token **rest, Token *tok);
 static int64_t eval(Node *node);
-static int64_t eval2(Node *node, char **label);
-static int64_t eval_rval(Node *node, char **label);
+static int64_t eval2(Node *node, char ***label);
+static int64_t eval_rval(Node *node, char ***label);
 static bool is_const_expr(Node *node);
 static Node *assign(Token **rest, Token *tok);
 static Node *logor(Token **rest, Token *tok);
@@ -1462,7 +1462,7 @@ write_gvar_data(Relocation *cur, Initializer *init, Type *ty, char *buf, int off
     return cur;
   }
 
-  char *label = NULL;
+  char **label = NULL;
   uint64_t val = eval2(init->expr, &label);
 
   if (!label) {
@@ -1830,7 +1830,7 @@ static int64_t eval(Node *node) {
 // is a pointer to a global variable and n is a postiive/negative
 // number. The latter form is accepted only as an initialization
 // expression for a global variable.
-static int64_t eval2(Node *node, char **label) {
+static int64_t eval2(Node *node, char ***label) {
   add_type(node);
 
   if (is_flonum(node->ty))
@@ -1902,6 +1902,9 @@ static int64_t eval2(Node *node, char **label) {
   }
   case ND_ADDR:
     return eval_rval(node->lhs, label);
+  case ND_LABEL_VAL:
+    *label = &node->unique_label;
+    return 0;
   case ND_MEMBER:
     if (!label)
       error_tok(node->tok, "not a compile-time constant");
@@ -1913,7 +1916,7 @@ static int64_t eval2(Node *node, char **label) {
       error_tok(node->tok, "not a compile-time constant");
     if (node->var->ty->kind != TY_ARRAY && node->var->ty->kind != TY_FUNC)
       error_tok(node->tok, "invalid initializer");
-    *label = node->var->name;
+    *label = &node->var->name;
     return 0;
   case ND_NUM:
     return node->val;
@@ -1922,12 +1925,12 @@ static int64_t eval2(Node *node, char **label) {
   error_tok(node->tok, "not a compile-time constant");
 }
 
-static int64_t eval_rval(Node *node, char **label) {
+static int64_t eval_rval(Node *node, char ***label) {
   switch (node->kind) {
   case ND_VAR:
     if (node->var->is_local)
       error_tok(node->tok, "not a compile-time constant");
-    *label = node->var->name;
+    *label = &node->var->name;
     return 0;
   case ND_DEREF:
     return eval2(node->lhs, label);
diff --git a/test/control.c b/test/control.c
index 6ba918c..0a89e3d 100644
--- a/test/control.c
+++ b/test/control.c
@@ -91,6 +91,10 @@ int main() {
   ASSERT(2, ({ void *p = &&v22; int i=0; goto *p; v21:i++; v22:i++; v23:i++; i; }));
   ASSERT(1, ({ void *p = &&v33; int i=0; goto *p; v31:i++; v32:i++; v33:i++; i; }));
 
+  ASSERT(3, ({ static void *p[]={&&v41,&&v42,&&v43}; int i=0; goto *p[0]; v41:i++; v42:i++; v43:i++; i; }));
+  ASSERT(2, ({ static void *p[]={&&v52,&&v52,&&v53}; int i=0; goto *p[1]; v51:i++; v52:i++; v53:i++; i; }));
+  ASSERT(1, ({ static void *p[]={&&v62,&&v62,&&v63}; int i=0; goto *p[2]; v61:i++; v62:i++; v63:i++; i; }));
+
   printf("OK\n");
   return 0;
 }