Parsing stack_limit

filetests/parser/preamble.cton

@@ -0,0 +1,18 @@
+test cat
+
+; Verify parsing of stack_limit.
+function %minimal(i64 vmctx) {
+gv0 = vmctx
+; Stack limit
+stack_limit = gv0
+
+ebb0:
+    trap user0
+}
+; sameln: function %minimal(i64 vmctx) fast {
+; nextln: gv0 = vmctx
+; nextln: stack_limit = gv0
+; nextln: 
+; nextln: ebb0:
+; nextln:     trap user0
+; nextln: }

lib/codegen/src/ir/function.rs

@@ -126,6 +126,15 @@ impl Function {
         self.stack_slots.push(data)
     }
 
+    /// Sets the stack limit for the function.
+    ///
+    /// Returns previous one if any.
+    pub fn set_stack_limit(&mut self, stack_limit: Option<GlobalVar>) -> Option<GlobalVar> {
+        let prev = self.stack_limit.take();
+        self.stack_limit = stack_limit;
+        prev
+    }
+
     /// Adds a signature which can later be used to declare an external function import.
     pub fn import_signature(&mut self, signature: Signature) -> SigRef {
         self.dfg.signatures.push(signature)

lib/reader/src/parser.rs

@@ -244,6 +244,15 @@ impl<'a> Context<'a> {
         }
     }
 
+    // Assign the global for the stack limit.
+    fn set_stack_limit(&mut self, gv: GlobalVar, loc: &Location) -> Result<()> {
+        if let Some(_) = self.function.set_stack_limit(Some(gv)) {
+            err!(loc, "multiple stack_limit declarations")
+        } else {
+            Ok(())
+        }
+    }
+
     // Allocate a new EBB.
     fn add_ebb(&mut self, ebb: Ebb, loc: &Location) -> Result<Ebb> {
         while self.function.dfg.num_ebbs() <= ebb.index() {
@@ -973,6 +982,7 @@ impl<'a> Parser<'a> {
     //                   * function-decl
     //                   * signature-decl
     //                   * jump-table-decl
+    //                   * stack-limit-decl
     //
     // The parsed decls are added to `ctx` rather than returned.
     fn parse_preamble(&mut self, ctx: &mut Context) -> Result<()> {
@@ -1009,6 +1019,8 @@ impl<'a> Parser<'a> {
                     self.parse_jump_table_decl()
                         .and_then(|(jt, dat)| ctx.add_jt(jt, dat, &self.loc))
                 }
+                Some(Token::Identifier("stack_limit")) => self.parse_stack_limit_decl()
+                    .and_then(|gv| ctx.set_stack_limit(gv, &self.loc)),
                 // More to come..
                 _ => return Ok(()),
             }?;
@@ -1291,6 +1303,15 @@ impl<'a> Parser<'a> {
         }
     }
 
+    /// stack-limit-decl ::= "stack_limit" "=" GlobalVar(gv)
+    fn parse_stack_limit_decl(&mut self) -> Result<GlobalVar> {
+        self.consume();
+        self.match_token(Token::Equal, "expected '=' in stack limit declaration")?;
+        let gv = self.match_gv("expected global variable")?;
+
+        Ok(gv)
+    }
+
     // Parse a function body, add contents to `ctx`.
     //
     // function-body ::= * { extended-basic-block }