Run the verifier in the Context methods when it is enabled.

The test drivers can stop calling comp_ctx.verify because legalize() and
regalloc() do it themselves now.

This also makes it possible for those two passes to return other
CtonError codes in the future, not just verifier errors.

lib/cretonne/src/context.rs

@@ -15,6 +15,7 @@ use ir::Function;
 use isa::TargetIsa;
 use legalize_function;
 use regalloc;
+use result::CtonResult;
 use verifier;
 
 /// Persistent data structures and compilation pipeline.
@@ -56,9 +57,19 @@ impl Context {
         verifier::verify_context(self)
     }
 
+    /// Run the verifier only if the `enable_verifier` setting is true.
+    pub fn verify_if(&self, isa: &TargetIsa) -> CtonResult {
+        if isa.flags().enable_verifier() {
+            self.verify(isa).map_err(Into::into)
+        } else {
+            Ok(())
+        }
+    }
+
     /// Run the legalizer for `isa` on the function.
-    pub fn legalize(&mut self, isa: &TargetIsa) {
+    pub fn legalize(&mut self, isa: &TargetIsa) -> CtonResult {
         legalize_function(&mut self.func, &mut self.cfg, isa);
+        self.verify_if(isa)
     }
 
     /// Recompute the control flow graph and dominator tree.
@@ -68,8 +79,9 @@ impl Context {
     }
 
     /// Run the register allocator.
-    pub fn regalloc(&mut self, isa: &TargetIsa) {
+    pub fn regalloc(&mut self, isa: &TargetIsa) -> CtonResult {
         self.regalloc
             .run(isa, &mut self.func, &self.cfg, &self.domtree);
+        self.verify_if(isa)
     }
 }