Enhance Verifier error reporting;

cranelift/filetests/verifier/type_check.clif

@@ -44,7 +44,7 @@ function %type_mismatch_controlling_variable() {
 function %fn_call_too_few_args() {
     fn2 = %great_fn(i32, f32)
     ebb0:
-        call fn2() ; error: mismatched argument count, got 0, expected 2
+        call fn2() ; error: mismatched argument count for `call fn2()`: got 0, expected 2
         return
 }
 
@@ -53,7 +53,7 @@ function %fn_call_too_many_args() {
     ebb0:
         v0 = iconst.i64 56
         v1 = f32const 0.0
-        call fn5(v0, v1) ; error: mismatched argument count, got 2, expected 0
+        call fn5(v0, v1) ; error: mismatched argument count for `call fn5(v0, v1)`: got 2, expected 0
         return
 }
 

lib/codegen/src/print_errors.rs

@@ -18,6 +18,16 @@ pub fn pretty_verifier_error(
     err: &VerifierError,
 ) -> String {
     let mut w = String::new();
+
+    match err.location {
+        ir::entities::AnyEntity::Inst(_) => {}
+        _ => {
+            // Print the error, because the pretty_function_error below won't do it since it isn't
+            // tied to an instruction.
+            writeln!(w, "verifier error summary: {}\n", err.to_string()).unwrap();
+        }
+    }
+
     decorate_function(
         &mut |w, func, isa, inst, indent| pretty_function_error(w, func, isa, inst, indent, err),
         &mut w,
@@ -37,8 +47,7 @@ fn pretty_function_error(
     err: &VerifierError,
 ) -> fmt::Result {
     match err.location {
-        ir::entities::AnyEntity::Inst(inst) => {
-            if inst == cur_inst {
+        ir::entities::AnyEntity::Inst(inst) if inst == cur_inst => {
             writeln!(
                 w,
                 "{1:0$}{2}",
@@ -50,18 +59,15 @@ fn pretty_function_error(
             for _c in cur_inst.to_string().chars() {
                 write!(w, "~")?;
             }
-                writeln!(w, "\n\nverifier {}\n", err.to_string())
-            } else {
-                write!(
+            writeln!(w, " verifier {}\n", err.to_string())
+        }
+        _ => writeln!(
             w,
             "{1:0$}{2}",
             indent,
             "",
             func.dfg.display_inst(cur_inst, isa)
-                )
-            }
-        }
-        _ => writeln!(w),
+        ),
     }
 }
 

lib/codegen/src/verifier/mod.rs

@@ -820,7 +820,8 @@ impl<'a> Verifier<'a> {
         if i != variable_args.len() {
             return err!(
                 inst,
-                "mismatched argument count, got {}, expected {}",
+                "mismatched argument count for `{}`: got {}, expected {}",
+                self.func.dfg.display_inst(inst, None),
                 variable_args.len(),
                 i
             );

lib/filetests/src/runone.rs

@@ -135,5 +135,5 @@ fn run_one_test<'a>(
     }
 
     test.run(func, context)
-        .map_err(|e| format!("{}: {}", name, e))
+        .map_err(|e| format!("{}:\n{}", name, e))
 }