diff --git a/stage0/ast.c b/stage0/ast.c
index dd89dda6f3..d67b4881d4 100644
--- a/stage0/ast.c
+++ b/stage0/ast.c
@@ -25,7 +25,8 @@ static void astTokenListEnsureCapacity(
     list->cap = new_cap;
 }
 
-Ast astParse(const char* source, const uint32_t len) {
+static __attribute__((noinline)) AstTokenList tokenize(
+    const char* source, uint32_t len) {
     uint32_t estimated_token_count = len / 8;
 
     AstTokenList tokens = {
@@ -45,6 +46,12 @@ Ast astParse(const char* source, const uint32_t len) {
             break;
     }
 
+    return tokens;
+}
+
+Ast astParse(const char* source, const uint32_t len) {
+    AstTokenList tokens = tokenize(source, len);
+
     uint32_t estimated_node_count = (tokens.len + 2) / 2;
 
     char err_buf[PARSE_ERR_BUF_SIZE];
diff --git a/stage0/astgen.c b/stage0/astgen.c
index 1f4c831e5c..11a5acd58a 100644
--- a/stage0/astgen.c
+++ b/stage0/astgen.c
@@ -1,3 +1,4 @@
+// //
 // astgen.c -- AST to ZIR conversion, ported from lib/std/zig/AstGen.zig.
 //
 // Structural translation of AstGen.zig into C.
@@ -13699,21 +13700,17 @@ static uint32_t lastToken(const Ast* tree, uint32_t node) {
 
         // block (Ast.zig:1085): end_offset += 1 (rbrace), recurse into last.
         case AST_NODE_BLOCK: {
-            uint32_t start = nd.lhs;
-            uint32_t end = nd.rhs;
-            assert(start != end);
+            assert(nd.lhs != nd.rhs);
             end_offset += 1;
-            n = tree->extra_data.arr[end - 1];
+            n = tree->extra_data.arr[nd.rhs - 1];
             continue;
         }
 
         // block_semicolon (Ast.zig:1097): += 2 (semicolon + rbrace).
         case AST_NODE_BLOCK_SEMICOLON: {
-            uint32_t start = nd.lhs;
-            uint32_t end = nd.rhs;
-            assert(start != end);
+            assert(nd.lhs != nd.rhs);
             end_offset += 2;
-            n = tree->extra_data.arr[end - 1];
+            n = tree->extra_data.arr[nd.rhs - 1];
             continue;
         }
 
@@ -13970,9 +13967,8 @@ static uint32_t lastToken(const Ast* tree, uint32_t node) {
         }
         case AST_NODE_SWITCH_COMMA: {
             uint32_t ei = nd.rhs;
-            uint32_t cs = tree->extra_data.arr[ei];
             uint32_t ce = tree->extra_data.arr[ei + 1];
-            assert(cs != ce);
+            assert(tree->extra_data.arr[ei] != ce);
             end_offset += 2; // comma + rbrace
             n = tree->extra_data.arr[ce - 1];
             continue;
@@ -14036,9 +14032,8 @@ static uint32_t lastToken(const Ast* tree, uint32_t node) {
 
         // struct_init: node_and_extra SubRange pattern.
         case AST_NODE_STRUCT_INIT: {
-            uint32_t si = tree->extra_data.arr[nd.rhs];
             uint32_t se = tree->extra_data.arr[nd.rhs + 1];
-            assert(si != se);
+            assert(tree->extra_data.arr[nd.rhs] != se);
             end_offset += 1;
             n = tree->extra_data.arr[se - 1];
             continue;
@@ -14046,17 +14041,15 @@ static uint32_t lastToken(const Ast* tree, uint32_t node) {
 
         // call: SubRange pattern.
         case AST_NODE_CALL: {
-            uint32_t si = tree->extra_data.arr[nd.rhs];
             uint32_t se = tree->extra_data.arr[nd.rhs + 1];
-            assert(si != se);
+            assert(tree->extra_data.arr[nd.rhs] != se);
             end_offset += 1;
             n = tree->extra_data.arr[se - 1];
             continue;
         }
         case AST_NODE_CALL_COMMA: {
-            uint32_t si = tree->extra_data.arr[nd.rhs];
             uint32_t se = tree->extra_data.arr[nd.rhs + 1];
-            assert(si != se);
+            assert(tree->extra_data.arr[nd.rhs] != se);
             end_offset += 2;
             n = tree->extra_data.arr[se - 1];
             continue;
@@ -14147,9 +14140,8 @@ static uint32_t lastToken(const Ast* tree, uint32_t node) {
             continue;
         }
         case AST_NODE_CONTAINER_DECL_ARG_TRAILING: {
-            uint32_t si = tree->extra_data.arr[nd.rhs];
             uint32_t se = tree->extra_data.arr[nd.rhs + 1];
-            assert(si != se);
+            assert(tree->extra_data.arr[nd.rhs] != se);
             end_offset += 2;
             n = tree->extra_data.arr[se - 1];
             continue;
@@ -14214,9 +14206,8 @@ static uint32_t lastToken(const Ast* tree, uint32_t node) {
 
         // struct_init_comma: node_and_extra SubRange.
         case AST_NODE_STRUCT_INIT_COMMA: {
-            uint32_t si = tree->extra_data.arr[nd.rhs];
             uint32_t se = tree->extra_data.arr[nd.rhs + 1];
-            assert(si != se);
+            assert(tree->extra_data.arr[nd.rhs] != se);
             end_offset += 2;
             n = tree->extra_data.arr[se - 1];
             continue;
@@ -14224,17 +14215,15 @@ static uint32_t lastToken(const Ast* tree, uint32_t node) {
 
         // array_init variants.
         case AST_NODE_ARRAY_INIT: {
-            uint32_t si = tree->extra_data.arr[nd.rhs];
             uint32_t se = tree->extra_data.arr[nd.rhs + 1];
-            assert(si != se);
+            assert(tree->extra_data.arr[nd.rhs] != se);
             end_offset += 1;
             n = tree->extra_data.arr[se - 1];
             continue;
         }
         case AST_NODE_ARRAY_INIT_COMMA: {
-            uint32_t si = tree->extra_data.arr[nd.rhs];
             uint32_t se = tree->extra_data.arr[nd.rhs + 1];
-            assert(si != se);
+            assert(tree->extra_data.arr[nd.rhs] != se);
             end_offset += 2;
             n = tree->extra_data.arr[se - 1];
             continue;
@@ -14375,9 +14364,8 @@ static uint32_t lastToken(const Ast* tree, uint32_t node) {
         }
         // tagged_union_enum_tag_trailing (Ast.zig:1022-1030).
         case AST_NODE_TAGGED_UNION_ENUM_TAG_TRAILING: {
-            uint32_t si = tree->extra_data.arr[nd.rhs];
             uint32_t se = tree->extra_data.arr[nd.rhs + 1];
-            assert(si != se);
+            assert(tree->extra_data.arr[nd.rhs] != se);
             end_offset += 2; // comma/semicolon + rbrace
             n = tree->extra_data.arr[se - 1];
             continue;