Merge pull request #525 from Marwes/symbol_type

perf: Move the symbol mismatch panic into a colder path
lalrpop · May 2, 2020 · 672716e · 672716e
2 parents 29a4bea + e932f81
commit 672716e
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Showing 3 changed files with 107 additions and 98 deletions.
diff --git a/lalrpop/src/generate.rs b/lalrpop/src/generate.rs
@@ -32,7 +32,7 @@ struct Generator<'grammar> {
     depth: u32,
 }
 
-const MAX_DEPTH: u32 = 10000;
+const MAX_DEPTH: u32 = 7000;
 
 impl<'grammar> Generator<'grammar> {
     fn nonterminal(&mut self, nt: NonterminalString) -> Option<ParseTree> {

diff --git a/lalrpop/src/lr1/codegen/parse_table.rs b/lalrpop/src/lr1/codegen/parse_table.rs
@@ -1175,6 +1175,11 @@ impl<'ascent, 'grammar, W: Write> CodeGenerator<'ascent, 'grammar, W, TableDrive
     }
 
     fn emit_downcast_fns(&mut self) -> io::Result<()> {
+        rust!(self.out, "#[inline(never)]");
+        rust!(self.out, "fn {}symbol_type_mismatch() -> ! {{", self.prefix);
+        rust!(self.out, "panic!(\"symbol type mismatch\")");
+        rust!(self.out, "}}");
+
         for (ty, name) in self.custom.variants.clone() {
             self.emit_downcast_fn(&name, ty)?;
         }
@@ -1224,7 +1229,7 @@ impl<'ascent, 'grammar, W: Write> CodeGenerator<'ascent, 'grammar, W, TableDrive
             self.prefix,
             self.prefix
         );
-        rust!(self.out, "_ => panic!(\"symbol type mismatch\")");
+        rust!(self.out, "_ => {}symbol_type_mismatch()", self.prefix);
         rust!(self.out, "}}");
 
         rust!(self.out, "}}");